Menp. ECO. MED. 2 - Ecologia Mediterranea
Menp. ECO. MED. 2 - Ecologia Mediterranea
Menp. ECO. MED. 2 - Ecologia Mediterranea
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Tome 28<br />
Fascicule 2, 2002<br />
ISSN 0153-8756<br />
Revue internationale<br />
d’écologie méditerranéenne<br />
International Journal<br />
of <strong>Mediterranea</strong>n Ecology
ecologia<br />
mediterranea<br />
Revue internationale<br />
d’écologie méditerranéenne<br />
International Journal<br />
of <strong>Mediterranea</strong>n Ecology<br />
Tome 28 • Fascicule 2 • 2002
Rédacteur en chef • Managing editor Secrétariat • Secretariat<br />
FRÉDÉRIC MÉDAIL MICHELLE DOUGNY<br />
ARONSON J., CEFE-CNRS, Montpellier<br />
BARBERO M., IMEP, Université Aix-Marseille III<br />
BEAULIEU J.-L. DE, IMEP, Université Aix-Marseille III<br />
BROCK M., University of New England, Armidale, Australie<br />
CHEYLAN M., EPHE, Montpellier<br />
DEBUSSCHE M., CEFE-CNRS, Montpellier<br />
FADY B., INRA, Avignon<br />
GRILLAS P., Station biologique Tour du Valat, Arles<br />
GUIOT J., CEREGE-CNRS, Aix-en-Provence<br />
HOBBS R. J., CSIRO, Midland, Australie<br />
KREITER S., ENSA-M-INRA, Montpellier<br />
LE FLOC’H E., CEFE-CNRS, Montpellier<br />
Rédacteurs • Editors<br />
LAURENCE AFFRE PHILIP ROCHE<br />
THIERRY DUTOIT THIERRY TATONI<br />
JÉRÔME ORGEAS ERIC VIDAL<br />
Fondateur • Founder<br />
PROFESSEUR PIERRE QUÉZEL<br />
Comité de lecture • Advisory board<br />
<strong>Ecologia</strong> mediterranea<br />
MARGARIS N. S., University of the Aegean, Mytilène, Grèce<br />
OVALLE C., CSI-Quilamapu, INIA, Chili<br />
PEDROTTI F.,Universita degli Studi, Camerino, Italie<br />
PLEGUEZUELOS J. M., Université de Grenade, Espagne<br />
PONEL P., IMEP, CNRS, Marseille<br />
PRODON R., Lab. Arago, Université P. & M. Curie, Paris VI<br />
RIDCHARSON D. M., University Cape Town, Afrique du Sud<br />
SANS F. X., Université de Barcelone, Espagne<br />
SHMIDA A., Hebrew University of Jérusalem, Israël<br />
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TROUMBIS A., University of the Aegean Mytilene, Grèce<br />
URBINATI C., Agripolis, Legnaro, Italie<br />
Faculté des sciences et techniques de Saint-Jérôme<br />
Institut méditerranéen d’écologie et de paléoécologie, case 461<br />
F-13997 Marseille, cédex 20, France<br />
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ISSN 0153-8756
ecologia<br />
mediterranea<br />
Revue internationale<br />
d’écologie méditerranéenne<br />
International Journal<br />
of <strong>Mediterranea</strong>n Ecology<br />
Tome 28 • Fascicule 2 • 2002
Belowground traits of mediterranean woody plants<br />
in a Portuguese shrubland<br />
Caractéristiques du système racinaire de ligneux méditerranéens<br />
dans un maquis du Portugal<br />
Joaquim S. Silva 1,Francisco C. Rego 2, Maria A. Martins-Loução 3<br />
1. Escola Superior Agrária de Coimbra, 3040-316 Coimbra, Portugal<br />
2. Instituto Superior de Agronomia, Tapada da Ajuda, 1349-017 Lisboa, Portugal<br />
3. Centro de <strong>Ecologia</strong> e Biologia Vegetal, Faculdade de Ciências de Lisboa, 1749-016 Lisboa, Portugal.<br />
Fax :+ 351 239802979 ; tél. : + 351 802284. email: jss@mail.esac.pt<br />
Abstract<br />
Belowground traits vary widely. Apart from the influence of the<br />
environment both genetic and ontogenic factors are responsible for<br />
this variation. For mediterranean woody plants there is also evidence<br />
of a relationship between regenerative strategies and root system<br />
characteristics. With the general aim of studying these different<br />
aspects, the root systems of seventeen obligate seeders and sixteen<br />
resprouters from ten different species and different developmental<br />
stages were excavated at Tapada Nacional de Mafra in<br />
Central West Portugal. Root systems were photographed, weighted<br />
and measured. Root length and the average root diameter were<br />
determined using digital image software. Root-to-shoot ratio (R/S)<br />
and the specific root length (SRL) were computed for all plants.<br />
Basal section was used as an indicator of plant development. A<br />
principal component analysis (PCA) was performed in order to<br />
study the relationships between variables and between plants. The<br />
analysis showed a clear distinction of plants according to the respective<br />
developmental stage but also according to the regenerative<br />
characteristics of the different species. Allometric relationships were<br />
found between root biomass, shoot biomass and basal section.<br />
Statistical tests showed that resprouters had higher maximum rooting<br />
depth, average root diameter and R/S and lower SRL, than<br />
obligate seeders. A decrease of R/S and SRL with basal section was<br />
verified for a sub-sample of four species.<br />
Key-words<br />
Root development, mediterranean shrublands, regenerative strategies,<br />
root systems, allometric relationships.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 5-13<br />
Résumé<br />
Il existe une grande variabilité associée aux caractéristiques souterraines<br />
des plantes. Outre l’influence de l’environnement, les responsables<br />
en sont les facteurs génétiques et les facteurs ontogéniques.<br />
Dans le cas des plantes ligneuses méditerranéennes, il existe aussi<br />
un rapport entre les stratégies régénératives et les caractéristiques des<br />
systèmes racinaires. En envisageant l’étude de ces différents aspects,<br />
les systèmes racinaires de dix-sept plantes se régénérant par semis et<br />
seize plantes à régénération végétative appartenant à dix espèces<br />
différentes à divers stades de développement, ont été déterrés à<br />
Tapada Nacional de Mafra, dans le Centre-Ouest du Portugal. Les<br />
racines ont été photographiées, pesées et mesurées. La longueur et le<br />
diamètre moyen ont été déterminés en utilisant un programme de<br />
mesure à partir d’images numériques. Le rapport entre la biomasse<br />
des racines et celle de la partie aérienne ainsi que la longueur spécifique<br />
des racines ont été calculés pour toutes les plantes. La section<br />
basale a été utilisée comme un indicateur du développement<br />
de la plante. Une analyse par composantes principales a été utilisée<br />
pour étudier les rapports entre variables et entre plantes. L’analyse<br />
a montré une nette différence des plantes selon leur stade de développement,<br />
mais aussi en fonction des caractéristiques régénératives<br />
des différentes espèces. Des rapports allométriques ont été trouvés<br />
entre la biomasse des racines, la biomasse de la partie aérienne et<br />
la section basale. Des tests statistiques ont montré que les plantes<br />
de régénération végétative présentent un enracinement plus profond,<br />
un diamètre moyen plus important, un plus grand rapport<br />
biomasse racinaire/biomasse aérienne et une longueur racinaire spécifique<br />
plus faible que les plantes de régénération par semis. Une<br />
diminution du rapport biomasse racinaire/biomasse aérienne et de<br />
la longueur racinaire spécifique avec la section basale a été vérifiée<br />
chez un sous-échantillon de quatre espèces.<br />
Mots-clés<br />
Développement racinaire, maquis méditerranéen, stratégies régénératives,<br />
systèmes racinaires, rapports allométriques.<br />
5
6<br />
◆ JOAQUIM S. SILVA, FRANCISCO C. REGO, MARIA A. MARTINS-LOUÇÃO<br />
INTRODUCTION<br />
The origins of the diversity of root systems can be seen<br />
as an optimisation of two primary functions: acquisition<br />
of soil-based resources (water and nutrients) and anchorage<br />
(Fitter, 1996). In the specific case of the <strong>Mediterranea</strong>n<br />
regions of the world, root systems have probably<br />
evolved to deal with the strong spatial and temporal limitations<br />
on availability of water, which are typical of these<br />
regions (Canadell & Zedler, 1995). This evolution has<br />
resulted in various root type morphologies, characteristic<br />
of mediterranean woody species. Several attempts were<br />
made to classify root systems in terms of basic structural<br />
characteristics (Cannon, 1949; Hellmers et al., 1955;<br />
Specht & Rayson, 1957). However the well known plasticity<br />
of root systems as a result of environmental conditions,<br />
has limited the use of these classifications (Fitter,<br />
1996). Bengough et al. (2000) suggested the study of<br />
variability as an alternative to seeking for homogeneous<br />
features. A simple classification of plants into deep rooted<br />
and shallow rooted is generally accepted, although no<br />
strict limits are normally established to define the two<br />
types. These two basic types of root systems correspond<br />
to different adaptations to the highly seasonal water availability<br />
typical of <strong>Mediterranea</strong>n-type climates and have<br />
been associated with the strategy to regenerate after natural<br />
disturbances (fire and grazing). Typical resprouters<br />
normally present deep root systems whereas seeders are<br />
shallow rooted (Keeley, 1986; Correia & Catarino, 1994;<br />
Bell, 2001). In fact, resprouters need to have deep root<br />
systems to supply the growth of new shoots since they<br />
can not rely on a seed bank to regenerate after fire or other<br />
kind of disturbance (Keeley & Zedler, 1978; Clemente et<br />
al., 1996). Although sharing the same climatic conditions<br />
as resprouters, obligate seeders present specific water<br />
saving adaptations such as a higher stomatal control or<br />
leaf hairs, allowing these species to survive in drier conditions<br />
(Keeley, 1986; Correia, 1988; Correia & Catarino;<br />
1994; Silva & Rego, 1998). These water saving mechanisms<br />
partly explain why obligate seeders withstand summer<br />
drought without the use of deep root systems.<br />
The study of root systems have also showed the existence<br />
of different patterns of root development. In the<br />
case of many mediterranean plants it is known the preferential<br />
allocation of resources to roots at early stages<br />
(Canadell & Zedler, 1995) and there is evidence that<br />
woody plants in general present a decreasing trend of rootto-shoot<br />
ratio with age (Kozlowski et al., 1991).The fact<br />
that many species, especially those under dry conditions,<br />
may develop deep tap roots at early stages preceding the<br />
development of lateral roots (Spurr & Barnes, 1980) is<br />
an evidence of the specificity of rooting patterns at different<br />
developmental stages. Ontogeny seems then to be at<br />
least as important as phylogeny to the overall variation of<br />
root systems and the respective traits.<br />
It is an obvious fact that root systems are difficult to<br />
study.These difficulties of root studies increase in the case<br />
of plants from mediterranean ecosystems because soils are<br />
frequently shallow and heterogeneous and also because<br />
many species are growing deep root systems (Kummerow,<br />
1981). Additional problems are found with plants from<br />
dense shrub communities because different individuals<br />
form an intricate root net which makes it extremely difficult<br />
to trace individual root systems. Consequently there<br />
is a considerable lack of knowledge of basic root system<br />
characteristics of mediterranean woody plants, and no<br />
information at all could be found concerning the belowground<br />
traits of the species studied in the present work.<br />
The relative scarcity of root studies in mediterranean ecosystems<br />
is well reflected in the planetary compilation of<br />
root distribution data by Jackson et al. (1996) where the<br />
<strong>Mediterranea</strong>n Region is represented by only 4 studies out<br />
of 250. However it is generally recognised the importance<br />
of obtaining information on root systems for modelling<br />
the functions of ecosystems both at the plant as at the community<br />
level (Caldwell & Richards, 1986; Pagés, 2000) or<br />
even in global scale simulation models (Zeng, 2001).<br />
The general objective of this paper is to assess the existence<br />
of relationships concerning the belowground traits<br />
of mediterranean woody plants. In particular the present<br />
paper is focused on: a) the relationships between different<br />
belowground traits; b) the relationships between plant<br />
development and belowground traits; c) the relationships<br />
between regenerative strategies and belowground traits.<br />
MATERIALS AND METHODS<br />
Plants were collected at Tapada Nacional de Mafra,<br />
a public estate located in the Central West region of<br />
Portugal.Tapada Nacional de Mafra, is a protected area<br />
with 827 ha, about 30 km Northwest of Lisbon and 12<br />
km East from the coast (38º 56’ 37’’ to 38º 58’ 30’’ N<br />
and 9º 15’ 52’’ to 9º 18’ 43’’ W). The lowest altitude is<br />
90 m and the highest is 358 m. Soil is a sandy loam classified<br />
as a humic cambisol (FAO classification) derived<br />
from sandstone. Bedrock is normally located below 2 m.<br />
Mean annual precipitation is 798 mm and mean annual<br />
temperature is 14.6 ºC. Summer precipitation (June,<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
July, August) accounts for only 3.1 % of the total annual<br />
rainfall. Most of the area is constituted by shrublands<br />
dominated by Erica scoparia L. and Erica lusitanica<br />
Rudolphi.<br />
Between September 2000 and April 2001 the complete<br />
root systems of 33 plants from ten woody species<br />
were hydraulically excavated (Böhm, 1979). Although we<br />
have tried to include a wide variety of woody species, our<br />
choice was limited by the floristic composition of the study<br />
area.Within these limits plants were chosen according to<br />
their developmental stage and regenerative characteristics.<br />
From the ensemble of plants, seventeen were obligate<br />
seeders (Lavandula luisieri (Rozeira) Rivas Martinez<br />
(4 plants), Cistus crispus L. (9 plants) and Cistus salviifolius<br />
L. (4 plants) and sixteen were resprouters (Erica scoparia<br />
L. (2 plants), Erica lusitanica Rudolphi (1 plant),<br />
Crataegus monogyna Jacq. (4 plants), Ulex jussiaei Webb<br />
(3 plants), Daphne gnidium L. (4 plants), Pistacia lentiscus<br />
L. (1 plant) and Myrtus communis L.(1 plant)). In<br />
order to obtain four individuals representative of four<br />
classes of basal section, 2 obligate seeders (L. luisieri and<br />
C. crispus) and 2 resprouters (D. gnidium and C. monogyna)<br />
were sampled more intensively, constituting a pooled<br />
sub-sample of sixteen plants.These four species apparently<br />
represented different root system types, within the<br />
obligate seeder and resprouter strategies. Basal section<br />
was used as an indicator of the plants developmental stage.<br />
The four classes of basal section were defined as: class 1<br />
for plants up to 5 mm 2, class 2 from 5 to 25 mm 2, class<br />
3 from 25 to 125 mm 2 and class 4 for plants showing a<br />
basal section higher than 125 mm 2. Despite having sampled<br />
nine C. crispus plants, no plants were collected at<br />
class 4, given the small size of the individuals present at<br />
the excavation site. No replications could be obtained for<br />
each combination species/basal section class due to the<br />
enormous amount of work required for the excavation<br />
and processing of complete root systems. All plants were<br />
excavated in spots where soil depth did not seem to limit<br />
the vertical development of roots, thus allowing the full<br />
expression of potential growth of deep roots. Besides<br />
having observed the plants used in this study, we were<br />
able to observe in the field other partially excavated individuals<br />
from the same species. This allowed to recognise<br />
some basic morphological characteristics, enabling a more<br />
complete description of root systems.<br />
After excavation, the maximum rooting depth, the<br />
maximum average root width and the basal section of<br />
each plant were measured. Maximum rooting depth represents<br />
the depth achieved by the deepest root, maximum<br />
average root width was computed as the average between<br />
ecologia mediterranea, tome 28, fascicule 1, 2002<br />
BELOWGROUND TRAITS OF <strong>MED</strong>ITERRANEAN WOODY PLANTS IN A PORTUGUESE SHRUBLAND ◆<br />
the maximum horizontal width and the respective orthogonal<br />
width and basal section was obtained as the cross<br />
sectional area at the stem base. In the case of plants with<br />
several stems, basal section was obtained by summing all<br />
the stem sections.<br />
In order to obtain the total root length and the average<br />
root diameter, root systems were photographed using a<br />
Fujifilm MX 2900 Zoom (Fuji Photo Film Co., Ltd.,<br />
Tokyo) digital camera, featuring a maximum resolution<br />
of 2.3 millions of pixels. Digital images were analysed<br />
using software WinRhizo 4.1b (Regent Instruments,<br />
Quebec). Some remarks have to be made on the determination<br />
of root length. Root length is difficult to measure<br />
when dealing with extensive root systems. Since most<br />
of the root length is associated with fine roots, it is extremely<br />
difficult to have an accurate estimate of total root<br />
length from shrubs or trees collected in the field.The main<br />
source of errors is the excavation process (Böhm, 1979;<br />
Caldwell & Virginia, 1989), where considerable amounts<br />
of fine roots are inevitably lost.Therefore root length was<br />
determined for comparison purposes only and it should<br />
be strictly interpreted on a relative basis and not as absolute<br />
values.<br />
For biomass determination plants were oven-dried at<br />
85 ºC for 48 hours and weighted, separately for root and<br />
shoot fractions. In addition to these variables the specific<br />
root length (SRL; cm of total root length/g of root dry<br />
weight) and the root-to-shoot ratio (R/S; root dry<br />
weight/shoot dry weight) were computed for each plant.<br />
All root variables (including R/S ratio) were log transformed<br />
and used to perform a principal components analysis<br />
(PCA) for all plants. The principal components<br />
(PC’s) extracted by the analysis were related to the different<br />
individual plants collected, in order to evaluate which<br />
were the main variables responsible for the variation<br />
found and their relationship with species strategies and<br />
plant development. Allometric relationships between<br />
variables were established considering the results obtained<br />
from the PCA.<br />
Given that most variables did not follow a normal distribution<br />
(Shapiro Wilk W test), the Mann-Whitney U test<br />
was used to determine the significance of differences between<br />
obligate seeders and resprouters, for all variables.<br />
Tests were performed both with pooled samples of obligate<br />
seeders and resprouters and within developmental<br />
stages 2 and 3 (not enough plants within stages 1 and 4).<br />
The sub-sample of 16 plants referred above was used<br />
to assess the effect of the developmental stage on R/S and<br />
SRL for the different species.<br />
Species nomenclature followed Castroviejo (1999).<br />
7
8<br />
◆ JOAQUIM S. SILVA, FRANCISCO C. REGO, MARIA A. MARTINS-LOUÇÃO<br />
RESULTS<br />
All C.monogyna plants presented thick, structural roots,<br />
with a smooth pale brownish bark. L. luisieri was characterised<br />
by a fibrous root system composed of an intricate<br />
horizontal network of very thin pale roots. Despite having<br />
only collected young U. jussiaei plants, our observation of<br />
partially excavated roots from adult individuals revealed<br />
that this species presented deep, thick, poorly lignified tap<br />
roots, showing a wrinkled white bark. C. salviifolius and<br />
C.crispus plants showed very similar characteristics. Roots<br />
of both species were relatively simple in terms of branching,<br />
with few dark brown structural roots exploring surface<br />
soil layers.The two Erica species were also very similar<br />
in terms of root system characteristics. Both presented<br />
a lignotuber to which a few deep, black, strongly lignified,<br />
tap roots were connected. Both species were also<br />
showing an intricate network of horizontal, not very<br />
widelly spreading fine roots exploring surface soil layers.<br />
D. gnidium plants showed a rooting pattern similar to the<br />
Erica plants with reddish, deep, tap roots and with only<br />
a few horizontal roots. Root tissues were poorly lignified<br />
which made coarse roots soft and rubber-like, similar to<br />
some succulent shrubs. All D. gnidium plants showed a<br />
swelling region, similar to typical lignotubers, just below<br />
the stem base. M. communis was characterised by the presence<br />
of coarse, pale brown laterally spreading roots,<br />
connected to a main deep reaching root. Given the impossibility<br />
of observing more than one root system in the field<br />
we did not retain the morphological characteristics of<br />
P. lentiscus.<br />
A quantitative description of all plants grouped by species<br />
is presented in table 1. Considering all excavated<br />
plants, root biomass ranged from 111.8 g (E. scoparia) to<br />
0.2 g (C. crispus) and shoot biomass ranged from 141.8 g<br />
(E.scoparia) to 0.3 g (C. crispus). Maximum rooting depth<br />
ranged from 185 cm (D. gnidium) to 12 cm (C. crispus).<br />
Other species, E. lusitanica and E. scoparia, also showed<br />
deep roots (160 cm and 140 cm, respectively). Root system<br />
width ranged from 95 cm (L. luisieri) to 5 cm<br />
(C. monogyna). Total measured root length ranged from<br />
2791.0 cm (L. luisieri) to 65.7 cm (C. monogyna). Another<br />
C. monogyna plant had the second highest length of roots<br />
(1956.8 cm). The average root diameter ranged from<br />
3.6 mm (C. monogyna) to 0.7 mm (C. crispus). R/S ratio<br />
ranged from 3.2 (D. gnidium) to 0.2 (L. luisieri).The three<br />
highest values of R/S ratio were from D. gnidium and the<br />
three lowest were from L. luisieri. Only seven plants pre-<br />
Species n Reg. Basal sect. S. biom. Maxim. root. Root system Root length Aver. root R. biom R/S SRL<br />
strat. (mm2) (g) depth (cm) width (cm) (cm) diam. (mm) (g) (g.g-1) (cm.g-1) C. crispus 9 s 16.7 ± 3.6 2.6 ± 1.0 30.2 ± 5.0 19.1 ± 3.6 302.5 ± 66.1 1.0 ± 0.1 1.4 ± 0.4 0.7 ± 0.1 322.8 ± 88.7<br />
C. salvifolius 4 s 17.0 ± 10.7 3.1 ± 0.9 26.5.0 ± 5.0 15.6 ± 2.2 165.2 ± 29.8 1.4 ± 0.2 1.9 ± 0.9 0.5 ± 0.2 162.6 ± 56.2<br />
C. monogyna 4 r 86.4 ± 51.8 25.3 ± 16.9 45.3 ± 11.9 34.3 ± 15.2 610.7 ± 452.8 2.3 ± 0.3 19.7 ± 12.8 0.9 ± 0.1 51.3 ± 24.4<br />
D. gnidium 4 r 101.8 ± 82.3 31.2 ± 28.5 120.0 ± 36.6 31.8 ± 6.4 652.9 ± 225.7 2.1 ± 0.3 18.3 ± 13.8 1.8 ± 0.6 109.6 ± 41.0<br />
E. lusitanica 1 r 152.1 ± nd 43.1 ± nd 160.0± nd 48.5 ± nd 1738.6 ± nd 1.5 ± nd 36.7 ± nd 0.9 ± nd 47.4 ± nd<br />
E. scoparia 2 r 94.7 ± 78.4 72.9 ± 68.9 90.0 ± 50.0 25.8 ± 11.8 1253.6 ± 494.4 1.5 ± 0.6 57.0 ± 54.8 0.7 ± 0.1 179.6 ± 163.9<br />
L. luisieri 4 s 66.4 ± 51.0 27.6 ± 23.9 28.3 ± 2.3 50.1 ± 16.9 1077.7 ± 585.9 1.2 ± 0.2 5.1 ± 4.1 0.3 ± 0.1 475.1 ± 120.2<br />
M. communis 1 r 41.4 ± nd 8.3 ± nd 120.0 ± nd 73.5 ± nd 676.0 ± nd 2.0 ± nd 11.0 ± nd 1.3 ± nd 61.4 ± nd<br />
P. lentiscus 1 r 19.4 ± nd 2.7 ± nd 50.0 ± nd 20.0 ± nd 393.5 ± nd 1.5 ± nd 2.2 ± nd 0.8 ± nd 176.4 ± nd<br />
U. jussiaei 3 r 11.5 ± 2.9 3.3 ± 1.7 67.7 ± 28.7 14.0 ± 4.5 562.9 ± 212.4 1.1 ± 0.2 2.6 ± 1.5 0.8 ± 0.1 284.3 ± 57.2<br />
Table 1. Descriptive parameters (mean ± SE) of the root systems of 33 plants excavated at Tapada Nacional de Mafra, distributed by species. Legend for abbreviations:<br />
n – number of plants; Reg. strat. – regenerative strategy; Basal sect. – basal section; S. biom. – shoot biomass; Maxim. root. depth – maximum rooting depth; Aver. root<br />
diam. – average root diameter; R. biom. – root biomass; R/S – root-to-shoot ratio; SRL – specific root length; s – obligate seeder; r – resprouter.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
BELOWGROUND TRAITS OF <strong>MED</strong>ITERRANEAN WOODY PLANTS IN A PORTUGUESE SHRUBLAND ◆<br />
sented values of R/S higher than 1. SRL ranged from<br />
848.4 cm.g -1 (C. crispus) to 15.6 cm.g -1 (E. scoparia).The<br />
six highest values of SRL were from three C. crispus plants<br />
and three L. luisieri plants.<br />
The first two principal components extracted by the<br />
PCA (figure 1A) explained 80 % of the total variance.<br />
Root length and root width were best correlated with<br />
Figure 1. PCA diagrams.A represents the components loadings for each variable<br />
and B represents the components scores for each plant individual. Legend for<br />
variables: DIAMETER – Average root diameter; BIOMASS – Root biomass;<br />
DEPTH – Maximum rooting depth;WIDTH – Root system width; LENGTH<br />
– Root length; R/S – Root-to-shoot ratio; SRL – Specific root length. Legend for<br />
species: Cc – Cistus crispus; Cs – Cistus salviifolius; Cm – Crataegus monogyna;<br />
Dg – Daphne gnidium; El – Erica lusitanica; Es – Erica scoparia; Ll –<br />
Lavandula luisieri; Mc – Myrtus communis; Pl – Pistacia lentiscus; Ru –<br />
Rubus ulmifolius; Uj – Ulex jussiaei. Symbols in bold correspond to obligate<br />
seeders. The developmental stage, as obtained by the respective basal section, is<br />
indicated by the number following the species symbol. Stage 1: 0 to 5 mm 2; stage<br />
2: 5 to 25 mm 2; stage 3: 25 to 125 mm 2; stage 4: > 125 mm 2.<br />
ecologia mediterranea, tome 28, fascicule 1, 2002<br />
PC1 (loadings 0.94 and 0.89, respectively). Root diameter<br />
and SRL were best correlated with PC2 (loadings<br />
0.83 and –0.84, respectively). Root biomass was best<br />
correlated with PC1 (loading 0.82) and R/S was best<br />
correlated with PC2 (loading 0.74). Maximum rooting<br />
depth was poorly correlated with both principal components<br />
(loadings 0.69 and 0.44 for PC1 and PC2, respectively).<br />
The plot of component scores (figure 1B)<br />
presented a clear arrangement of plants according to<br />
their developmental stage, as defined by the basal section<br />
classes, with the only exceptions of a C. crispus and<br />
a C. salviifolius plant. Plants were also arranged according<br />
to the respective species and the two regenerative<br />
strategy groups. Most obligate seeders presented lower<br />
scores for PC2 (specially L. luisieri and C. crispus) while<br />
most resprouters presented higher scores for PC2 (specially<br />
D. gnidium and C. monogyna).This pattern was less<br />
evident at developmental stage 2.<br />
Given the results obtained with the PCA, allometric<br />
relationships were established through linear regression<br />
Figure 2.Relationships between Basal Section and two root system indices:Specific<br />
Root Length and Root-Shoot (root-to-shoot ratio),for two obligate seeders (Cistus<br />
crispus and Lavandula luisieri;represented in bold) and two resprouters (Daphne<br />
gnidium and Crataegus monogyna; normal lettering).<br />
9
10<br />
◆ JOAQUIM S. SILVA, FRANCISCO C. REGO, MARIA A. MARTINS-LOUÇÃO<br />
Variables a b r 2 p<br />
Root biomass (0.1 g) 0.335 1.003 0,79 < 0.001<br />
Shoot biomass (0.1 g) 0.615 1.046 0.83 < 0.001<br />
Root system length (cm) 4.383 0.528 0.61 < 0.001<br />
Root system width (cm) 2.059 0.357 0.55 < 0.001<br />
Table 2.Allometric relationships obtained by linear regression between basal section<br />
(mm 2) and four different root variables: root biomass, shoot biomass, root<br />
system length and root system width.All variables were log-transformed.Biomass<br />
data is indicated in decigrams in order to obtain only positive values. For each<br />
linear regression it is indicated the intercept (a), the slope (b), the coefficient of<br />
determination (r 2) and the associated probability (p).<br />
using the log-transformed values of root biomass, shoot<br />
biomass, root system length and root system width as<br />
independent variables and the log-transformed values of<br />
basal section as the dependent variable (table 2). The<br />
linear regressions for root and shoot biomass presented<br />
coefficients of determination of 0.79 and 0.83 (p < 0.001<br />
for both regressions), respectively. The linear regression<br />
slopes were very similar (1.003 and 1.046, respectively).<br />
In the cases of root system length and root system width<br />
the relationships were still highly significant (p < 0.001)<br />
showing coefficients of determination of 0.61 and 0.55,<br />
respectively.<br />
Figure 3. Images of 16 plants representing<br />
different developmental stages (as defined in figure 1)<br />
of two resprouters:<br />
A – Daphne gnidium (stages 1,2,3 and 4),<br />
B – Crataegus monogyna (stages 1,2,3 and 4);<br />
and two obligate seeders:<br />
C – Lavandula luisieri (stages 1,2,3 and 4),<br />
D – Cistus crispus (stages 1,2,2 and 3).<br />
The vertical bars represent 0.5 m.<br />
Arrows indicate the ground surface.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
ecologia mediterranea, tome 28, fascicule 1, 2002<br />
BELOWGROUND TRAITS OF <strong>MED</strong>ITERRANEAN WOODY PLANTS IN A PORTUGUESE SHRUBLAND ◆<br />
According to the Mann-Whitney U test the ensemble<br />
of obligate seeders presented significantly lower values<br />
than the ensemble of resprouters for maximum rooting<br />
depth (p < 0.001), average root diameter (p < 0.01), root<br />
biomass (p < 0.01) and R/S (p < 0.01). Resprouters presented<br />
significantly lower values than obligate seeders for<br />
SRL (p< 0.01). Basal section, shoot biomass, root width<br />
and root length were not significantly different. Due to<br />
the smaller number of individuals, these differences could<br />
be only partially confirmed within developmental stages<br />
2 (maximum rooting depth, p < 0.05; root biomass,<br />
p
12<br />
◆ JOAQUIM S. SILVA, FRANCISCO C. REGO, MARIA A. MARTINS-LOUÇÃO<br />
roots may be critical for surviving the first dry season after<br />
germination. The expected decreasing trend observed for<br />
SRL (Fitter, 1985) was much more marked for the two<br />
obligate seeder species, which may hint at different strategies<br />
of root growth. Apparently, differences are due to the<br />
preferential investment on structural roots and storage tissues<br />
of the two resprouters at early developmental stages,<br />
contrasting with the preferential investment on fine roots<br />
of the two obligate seeders at similar developmental stages.<br />
Despite the existence of a broad range of R/S ratios<br />
corresponding to different species and different developmental<br />
stages, root biomass and shoot biomass were similarly<br />
and consistently correlated with basal section. This<br />
was confirmed by both the linear regressions and the PCA.<br />
The existence of close relationships between stem variables<br />
(diameter and/or basal section) and root biomass, has been<br />
found in different studies on tree species ( e.g. Santantonio<br />
et al., 1977; Drexhage & Colin, 2001; Hoffmann &<br />
Usoltsev, 2001; Ranger & Gelhaye, 2001). The establishment<br />
of a single consistent allometric relationship for different<br />
species between root biomass and stem variables<br />
(Santantonio et al., 1977), is in accordance with the widespread<br />
pipe model theory, (Shinozaki et al., 1964). Stem<br />
section seems to limit root and shoot development in a<br />
similar way for different species and different developmental<br />
stages. Given the different sample sizes of each<br />
developmental stages and each species, it must be pointed<br />
out that the allometric relationships found are only<br />
valid within the scope of the present work. Sampling limitations<br />
have also to be kept in mind when interpreting the<br />
differences obtained between regenerative strategies. The<br />
similarity of belowground traits among obligate seeders<br />
certainly reflected the phylogenetic relationships between<br />
plants since only two genera could be sampled.Thus, the<br />
existence of common traits can be associated to a common<br />
regenerative strategy, or just simply to the fact that<br />
part of the plants were closely related in terms of phylogeny.<br />
Special sampling designs have been established to<br />
overcome this difficulty (Nicotra et al., 2002) but they are<br />
not always applicable within a single plant community as<br />
in our case. Therefore, the significant differences found<br />
between the two regenerative groups have to be interpreted<br />
also in view of the role of phylogeny. However our<br />
results are supported by similar findings (Hellmers et al.,<br />
1955; Higgins et al., 1987; Bell, 2001) in other <strong>Mediterranea</strong>n-type<br />
regions, which lead us to assume that the same<br />
adaptive mechanisms existing elsewhere are also valid in<br />
the plant community where this study was undertaken.<br />
One of the aspects lacking in our study was the assessment<br />
of the influence of site conditions on belowground<br />
traits. Most authors agree on the fundamental influence<br />
of environmental factors on root systems characteristics<br />
(e.g. Spurr & Barnes, 1980; Kummerow, 1981; Fitter,<br />
1996; Atkinson, 2000). In our case the absence of evident<br />
soil constraints for the development of roots and the proximity<br />
of the excavation sites, lead us to assume the existence<br />
of relatively homogeneous environmental conditions<br />
allowing the comparison of root systems on a genetic and<br />
an ontogenic basis. Nevertheless we have to admit that<br />
the existence of differences in plant density or micro-relief<br />
may have definitely contributed to the overall variance of<br />
belowground traits.<br />
AKNOWLEDGMENTS<br />
We thank the Director of Tapada Nacional de Mafra,<br />
Ricardo Paiva, for making the plant excavation possible,<br />
and two referees for comments on this paper.This study<br />
was supported by EU funds from the research project<br />
Mod<strong>MED</strong> III-Modelling <strong>Mediterranea</strong>n Ecosystem<br />
Dynamics (contract ENV4-CT97-0680).<br />
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13
Above-ground phytomass and below-ground biomass<br />
production of Salvia verbenaca Linné<br />
Production de phytomasse et biomasse racinaire<br />
chez Salvia verbenaca Linné<br />
M. Conceição Castro 1, Carlos Roquete 2, Luís Gazarini 3<br />
1. Dep. Planeamento Biofísico e Paisagístico, Univ. Évora, Edif. António Verney, Apartado 94, 7002-554 Évora, Portugal;<br />
Fax: + 351 266 744968; email: mccastro@uevora.pt (correspondence)<br />
2. Dep. Zootecnia, Univ. Évora, Núcleo da Mitra, 7002-554 Évora, Portugal<br />
3. Dep. Biologia, Univ. Évora, Núcleo da Mitra, 7002-554 Évora, Portugal<br />
Abstract<br />
Salvia verbenaca L. is a ruderal herbaceous plant, very common<br />
in the <strong>Mediterranea</strong>n region. Its flowers are prized for their appearance,<br />
and it displays a high degree of adaptability in relation to<br />
habitat sites with a paucity of resources.<br />
The objective of this study was to obtain data about the production<br />
of phytomass and root biomass, with a view to the probable<br />
use of this species in urban green spaces. A two-year field experiment<br />
was undertaken, comprising four treatments of eight randomly<br />
selected plots, four being used in each year. This species was<br />
manual seed broadcast at the following densities: 20 000, 15 000,<br />
10 000 and 5 000 viable seeds m 2.<br />
The production of phytomass and root biomass was assessed through<br />
periodic collections, during the seasonal cycle of the species under<br />
study. In the first year there appears to have been a tendency for an<br />
increase in seed density to cause an increase in phytomass production.<br />
In the second year, by which time the plants had settled, when<br />
seed density rose from 5 000 to 10 000, a slight increase in phytomass<br />
production occurred. However, when the seed density rose from<br />
10 000 to 20 000 seeds m -2, a decrease in phytomass production<br />
was observed. Root biomass, in the first year, had minimum value<br />
in January and a maximum value in June-July. In the second year,<br />
the highest values were observed in May. The relationship between<br />
above and below ground biomass, for the first-year experiment,<br />
decreased over the cutting dates. However, an inverse behaviour<br />
occurred in the second year. Although the values of the phytomass<br />
obtained did not reveal statistically significant differences between<br />
treatments, when the plants were found already established, they<br />
appeared to indicate that densities of seeding between 5 000 and<br />
10 000 m 2 could be more advantageous.<br />
Key-words<br />
Phytomass, seed density, root biomass, shoot/root ratio.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 15-22<br />
Résumé<br />
Salvia verbenaca L. est une herbacée rudérale très commune dans<br />
la région méditerranéenne. Ses fleurs sont très prisées pour des raisons<br />
esthétiques. Cette espèce présente un degré d’adaptation important<br />
pour des habitats pauvres en ressources. L’objectif de cette étude<br />
a consisté à analyser la production de la phytomasse et de la biomasse<br />
racinaire dans l’optique d’utiliser cette espèce dans les espaces<br />
verts des villes. Durant deux ans, une expérience a été réalisée, comprenant<br />
quatre traitements avec huit plots aléatoires ; quatre plots<br />
étant utilisés chaque année. Les graines ont été semées selon les densités<br />
suivantes : 20 000, 15 000, 10 000 et 5 000 graines/m2. La production de la phytomasse et de la biomasse racinaires a été<br />
mesurée suite à des récoltes périodiques pendant la durée du cycle<br />
saisonnier. Dans la première année, il semble que l’augmentation de<br />
la densité des semis a conduit à un accroissement de la production de<br />
phytomasse.<br />
Dans la deuxième année, lorsque la plante était déjà installée, l’augmentation<br />
de la densité des graines de 5 000 à 10 000 a entraîné une<br />
légère croissance de la production de phytomasse. Cependant, lorsque<br />
la densité des graines a augmenté de 10 000 à 20 000 graines/m2, une réduction de la production de phytomasse a été observée. Dans la<br />
première année, la biomasse racinaire a présenté une valeur minimum<br />
en janvier et une valeur maximum en juin-juillet. Dans la<br />
deuxième année, les valeurs les plus hautes ont été observées en mai.<br />
La relation entre la phytomasse et la biomasse racinaire, pour la première<br />
année, diminue au fil des dates de coupe. Cependant, un phénomène<br />
inverse s’est produit au cours de la deuxième année. Bien que<br />
les valeurs de la phytomasse n’aient pas révélé de différences significatives<br />
entre les traitements, lorsque les plantes sont déjà établies, elles<br />
indiquent que les densités de graines comprises entre 5 000 et<br />
10 000/m2 pourraient être plus avantageuses.<br />
Mots-clés<br />
Phytomasse, densité des graines, biomasse racinaire, ratio tige/racine.<br />
15
16<br />
◆ M. CONCEIÇÃO CASTRO, CARLOS ROQUETE, LUÍS GAZARINI<br />
INTRODUCTION<br />
The importance of studying spontaneous herbaceous<br />
species from the point of view of their use in urban green<br />
spaces has been approached by various authors, due to<br />
the difficulty that certain exotic species have in adapting<br />
to places with a paucity of resources, and thus making<br />
them unable to survive in adverse conditions. (Cole &<br />
Keen, 1976;Wells, 1987; Brown, 1989; Clément, 1990).<br />
The spatial and temporal distribution of photosynthesis-active<br />
organs plays an important role in determining<br />
the quantity of sunlight which is captured by the<br />
plant, thus contributing towards an increase in the quantity<br />
of elements assimilated (Norman & Campbell, 1992).<br />
Root biomass, expressed in dry weight, reflects the<br />
effort of the plant to distribute the products of photosynthesis.<br />
The thickest roots have a greater capacity for<br />
penetrating more compact soils, are more durable and<br />
contribute over the long term to the development of the<br />
root system (Oliveira et al., 2000).<br />
The partial or total removal of the aerial part of the<br />
plant is invariably followed by compensatory growth, that<br />
is, distributed assimilated elements or reserves of carbohydrates<br />
in the root system are channelled towards the<br />
formation of leaf tissue, and away from root formation,<br />
in such a way that the equilibrium between the two systems<br />
is restored (Troughton, 1977).<br />
There is an interactive relationship between aerial and<br />
root biomass, which is reflected in the level of distribution<br />
of photosynthesised products between the above and below<br />
ground systems, which have simultaneously different and<br />
complementary functions.While the aerial part of the plant<br />
depends on the absorption capacity of the root system for<br />
its growth, the root system needs the carbohydrates pro-<br />
duced by the organs of photosynthesis. Thus, there is an<br />
interdependent relationship between them (Troughton,<br />
1977; Bohm, 1979 cit. in Oliveira, 1988; Klepper, 1991).<br />
In zones with a <strong>Mediterranea</strong>n climate, the amount<br />
and timing of rainfall is often the limiting factor in the<br />
choice of species, the choice being those preferring dry<br />
land to meadowland, having originating in the different<br />
climatic conditions of the <strong>Mediterranea</strong>n.Thus, the objective<br />
of this study was to evaluate the production of phytomass<br />
and root biomass, using four densities of seeding,<br />
with a view to the probable use of the species under study<br />
in urban green spaces.<br />
MATERIALS AND METHODS<br />
Salvia verbenaca (Labiatae) is a herbaceous plant, growing<br />
on uncultivated land, which is very commonly found<br />
in the <strong>Mediterranea</strong>n region, Southern and Western<br />
Europe and Northern Scotland (Tutin et al., 1972). It<br />
produces lilac flowers, with spring blooming (March to<br />
April). The aerial part of the plant ages and dies in early<br />
summer. After the fall of the first autumn rains, the vegetative<br />
stage begins, with the emergence of the first leaves.<br />
Study site<br />
The study was carried out at the University of Évora<br />
in the Alentejo region of Portugal (38º 32’ N; 8º 01’ W;<br />
200 m altitude).The soils were classified as alfisoils (SSS,<br />
1992) or luvisoils according to the FAO/UNESCO (1988).<br />
The climate is an oceanic <strong>Mediterranea</strong>n pluvial-seasonal<br />
bio-climate (MPO), according to Rivas Martínez<br />
(1995). Figure 1 shows climate data for the study period<br />
Figure 1.Thermo-pluviometric chart<br />
referring to Évora -Malagueira Meteorological<br />
Station (1993-1995).<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
ABOVE-GROUND PHYTOMASS AND BELOW-GROUND BIOMASS PRODUCTION OF SALVIA VERBENACA LINNÉ ◆<br />
(1993 to 1995). A two-year field experiment was performed<br />
comprising four treatments of eight randomly selected<br />
plots, four being used in each year. Each plot, sited<br />
30 cm apart, had an area of 1 m 2. Seeding was carried<br />
out by manual seed broadcast, using the following densities:<br />
20 000, 15 000, 10 000 and 5 000 viable seeds<br />
(Germination capacity: 65 %; Degree of purity: 99 %;<br />
Field losses: 78.7 %;Weight of 1,000 seeds: 2.643 g). Seed<br />
densities were selected in accordance with the work carried<br />
out by Harper & Gajic, 1961; Ross & Harper, 1972;<br />
Sheldon, 1974;Weaver & Cavers, 1979; Gross & Werner,<br />
1982; Shaw & Antonovics, 1986. The study was performed<br />
in field conditions. In the first year, only four plots<br />
were used. The other four were used in the second year,<br />
when plants were already settled. At the end of the first<br />
year, when the plants reached the stage of senescence, the<br />
above-ground material was removed.<br />
Determination of phytomass<br />
Sampling sites with an area of 625 cm 2 (25 cm x<br />
25 cm) were randomly selected in each plot. A border of<br />
15 cm width was set between each site. Phytomass was<br />
divided into vegetative, support and reproductive structures.<br />
The dry matter weight was recorded from the<br />
samples which were oven-dried at 80 ºC until constant<br />
weight was achieved, after approximately 48 hours (Milner<br />
& Hughes, 1968).The dry weight of the structures, which<br />
included some ash, was related to soil surface unit. Total<br />
phytomass was obtained from the sum of the weight of<br />
all the structures, and calculated per soil surface unit.<br />
Determination of root biomass<br />
At the site where the above-ground material of plants<br />
was removed, four soil samples per layer were extracted<br />
using a hand auger, comprising a cylindrical tube 10 cm<br />
long, with an inside diameter of 7 cm (Oliveira et al., 2000).<br />
Roots were extracted from the soil sample by a hydropneumatic<br />
elutriation system (Smucker et al., 1982;<br />
Oliveira et al., 2000).<br />
Soil samples, containing roots for each depth and each<br />
sampling event, were placed in individual plastic bags,<br />
which were labelled and frozen awaiting laboratory treatment<br />
(Oliveira et al., 2000).<br />
The root dry weight was recorded for root samples,<br />
which were oven-dried at 70 ºC until there was no further<br />
change in weight, after approximately 48 hours<br />
(Böhm, 1979; Schuurman & Goedewaagen, 1971 cit. in<br />
Oliveira et al., 2000).<br />
ecologia mediterranea, tome 28, fascicule 1, 2002, p. 15-22<br />
In accordance with Gregory (1988) and Oliveira et al.<br />
(2000) among others, the root dry weight was related to<br />
soil volume unit.<br />
The relationship between above<br />
and below ground biomass<br />
In order to evaluate the relationship between above<br />
and below ground biomass, the shoot-root ratio was estimated<br />
(Böhm, 1979; Pagès et al., 2000; Atkinson, 2000).<br />
Data Analysis<br />
The data recorded were analysed by descriptive statistics<br />
and analysis of variance (ANOVA), followed by<br />
comparison of means among treatments, using Newman/<br />
Keul’s test.<br />
RESULTS AND DISCUSSION<br />
Phytomass production<br />
The mean values of phytomass dry weight, in the first<br />
year of the study, varied from 141.9±79.9 g.m -2 (seed<br />
density 5 000) to 189.6±89.6 g.m -2 (seed density 20 000).<br />
Table 1 shows that there was a tendency for an<br />
increase in phytomass up until June (223 days after seeding),<br />
when production peaked. In the second year<br />
(table 2), there was a tendency for production to peak<br />
in May, 212 days after the emergence of the first leaves.<br />
Average annual values varied from 502.3±230.7 g.m -2<br />
(seed density 20 000) to 554.3±290.1 g.m -2 (seed density<br />
10 000).Thus, in the first year, there seems to have<br />
been a tendency for the increase in seed density to cause<br />
an increase in phytomass production. In the second year,<br />
a time by which the plants had settled, when seed density<br />
rose from 5 000 to 10 000, an increase in phytomass<br />
production occurred. However, when the seed density<br />
rose from 15 000 to 20 000, a decrease in phytomass<br />
production was observed. According to Harper<br />
(1961), the above ground weight of the plant may not<br />
initially be influenced by seed density but, at high seed<br />
densities, the competition between individual plants leads<br />
to a reduction in individual plant weight.The behaviour<br />
of the species observed in this study may be explained<br />
by competition being less when there are fewer plants<br />
per soil surface unit, with these plants taking the opportunity<br />
to increase phytomass production.<br />
17
18<br />
◆ M. CONCEIÇÃO CASTRO, CARLOS ROQUETE, LUÍS GAZARINI<br />
Treatments<br />
Cutting date Sv 20 000 Sv 15 000 Sv 10 000 Sv 5 000<br />
17/01/94 51.0 ± 7.6 54.7 ± 7.4 37.3 ± 11.0 18.6 ± 6.8<br />
c c b a<br />
07/03/94 199.7 ± 99.6 134.9 ± 31.8 143.6 ± 34.8 80.9 ± 5.3<br />
b ab ab a<br />
11/04/94 176.3 ± 58.9 154.7 ± 24.8 192.2 ± 35.8 156.8 ± 38.6<br />
a a a a<br />
09/05/94 224.4 ± 61.3 155.6 ± 25.4 158.9 ± 23.1 169.6 ± 25.3<br />
a a a a<br />
06/06/94 271.4 ± 30.4 222.9 ± 29.7 240.9 ± 51.3 270.6 ± 14.7<br />
a a a a<br />
11/07/94 223.0 ± 81.5 165.4 ± 19.5 185.9 ± 46.9 170.7 ± 18.0<br />
a a a a<br />
Annual average 189.6 ± 89.6 148.0 ± 55.3 156.9 ± 70.8 141.9 ± 79.9<br />
b a a a<br />
Different letters note significant differences (P
ABOVE-GROUND PHYTOMASS AND BELOW-GROUND BIOMASS PRODUCTION OF SALVIA VERBENACA LINNÉ ◆<br />
Table 3. Salvia verbenaca L. (Sv)<br />
average dry weight<br />
of root bomass (mg.m -3),<br />
for periodic cuttings and treatments.<br />
Table 4. Salvia verbenaca L. (Sv)<br />
average dry weight<br />
of root bomass (mg.m -3),<br />
for periodic cuttings and treatments.<br />
Table 5. Shoot and root ratio (s/r)<br />
of Salvia verbenaca L. (Sv),<br />
for periodic cuttings and treatments.<br />
ecologia mediterranea, tome 28, fascicule 1, 2002, p. 15-22<br />
Treatments<br />
Cutting date Sv 20 000 Sv 15 000 Sv 10 000 Sv 5 000<br />
17/01/94 0.14 ± 0.04 0.12 ± 0.03 0.12 ± 0.02 0.05 ± 0.01<br />
a a a b<br />
07/03/94 0.24 ± 0.19 0.24 ± 0.19 0.28 ± 0.19 0.15 ± 0.12<br />
a a a a<br />
11/04/94 0.42 ± 0.39 0.43 ± 0.35 0.48 ± 0.42 0.36 ± 0.26<br />
a a a a<br />
09/05/94 0.58 ± 0.50 0.52 ± 0.43 0.52 ± 0.41 0.50 ± 0.45<br />
a a a a<br />
06/06/94 0.58 ± 0.58 0.55 ± 0.58 0.57 ± 0.60 0.65 ± 0.49<br />
a a a a<br />
11/07/94 0.75 ± 0.80 0.60 ± 0.65 0.70 ± 0.63 0.47 ± 0.53<br />
a a a a<br />
Annual average 0.54 ± 0.58 0.49 ± 0.50 0.53 ± 0.51 0.45 ± 0.45<br />
a a a a<br />
Different letters note significant differences (P
20<br />
◆ M. CONCEIÇÃO CASTRO, CARLOS ROQUETE, LUÍS GAZARINI<br />
Treatments<br />
Cutting date Sv 20 000 Sv 15 000 Sv 10 000 Sv 5 000<br />
19/12/94 1.32 1.08 1.02 1.31<br />
31/03/95 2.92 2.44 2.10 3.78<br />
23/05/95 2.64 2.72 2.97 2.72<br />
10/07/95 3.12 1.99 2.01 3.60<br />
Annual average 2.50 ± 0.81 2.06 ± 0.72 2.02 ± 0.80 2.85 ± 1.13<br />
Different letters note significant differences (P
According to Davidson (1969), a plant constitutes a<br />
“whole”, although the absorption of water and nutrients<br />
is carried out by the roots in distinct edaphic conditions<br />
from those in which photosynthesis occurs. As the difference<br />
of temperature between leaves and roots changes,<br />
there seems to be a tendency for the plant to compensate<br />
for this by means of changes in root activity, increasing<br />
or decreasing the relative size of the root system. In field<br />
conditions, according to Davidson, there is great degree<br />
of disparity between root activity and photosynthesis activity<br />
as days decrease in length and summer progresses<br />
towards winter, in which the drop in soil temperature is<br />
higher than the drop in air temperature, and thus root<br />
growth is limited. This may provide a possible explanation<br />
for the seasonal variation of the patterns of growth<br />
observed in this study.<br />
When either the root or the aerial part of the plant is<br />
removed, a compensatory process is activated in the plant<br />
which restores the s/r ratio which is characteristic of the<br />
species. Brouwer and De Wit (1969 cit. in Klepper, 1991)<br />
state that when they removed half of the aerial part of<br />
bean plants they found that, later, the growth of the aerial<br />
part was faster than that of the roots until the initial r/s<br />
ratio was attained. This could contribute to an understanding<br />
of the evolution of the s/r relationship in the<br />
second year of this study, by virtue of the fact that, at the<br />
end of the first year, the aerial part of the plants on the<br />
plots which were the object of study in the second year<br />
was removed in its entirety.<br />
CONCLUSION<br />
ABOVE-GROUND PHYTOMASS AND BELOW-GROUND BIOMASS PRODUCTION OF SALVIA VERBENACA LINNÉ ◆<br />
The levels of production for each of the two years of<br />
the study were not compared statistically, because the first<br />
year was for seeding. However it was an evidently lower<br />
level of production in the first year. In the second year,<br />
by which time the plants had settled, there seems to have<br />
been a tendency for the increase in seed density to cause<br />
a decrease in phytomass production.This behaviour may<br />
be explained by possible competition between individuals,<br />
at high seed densities.<br />
Assuming the above and below ground system interdependency,<br />
shoot/root ratio provided some indications<br />
as to the changes occurring in growth in these systems.<br />
In the first year of the study, s/r values progressively<br />
decreased throughout the cutting dates, which could be<br />
interpreted as a greater increase in the below ground than<br />
in the above ground system. In the second year, the oppo-<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 15-22<br />
site occurred. Probably, due to the low levels of precipitation,<br />
which occurred in the first year of the study, root<br />
system development predominated, allowing deeper soil<br />
layers to be explored. In the second year, the plants produced<br />
more aboveground biomass, probably using the<br />
reserves stored in the root system. Nonetheless, the removal<br />
of the entirety of the aboveground biomass of the existing<br />
plants, at the end of the first year, after senescence,<br />
could also have contributed to the plants attempting to<br />
adjust in the following year to the s/r relationship, which<br />
is characteristic of the species.<br />
The results seem to indicate that biomass production<br />
was more sensitive to environmental or seasonal changes<br />
than to seed densities.<br />
Nowadays, in Portugal, the seeds from wild plants are<br />
collected by hand in its habitat.Timing seed collection is<br />
one of the most crucial and difficult steps in the process<br />
as flowers and fruits are produced in succession. Thus,<br />
the seed collector has either to select only mature seeds<br />
or to wait until the whole inflorescence will be ripen, losing<br />
seeds from the earliest ripened fruits.Therefore, this is an<br />
expensive method of obtaining large quantities of seeds.<br />
Although the values of the phytomass obtained did not<br />
reveal statistically significant differences between treatments,<br />
when the plants were found already established,<br />
they appeared to indicate that densities of seeding between<br />
5 000 and 10 000 m -2 could be more advantageous,<br />
reducing seed collection.<br />
References<br />
ANTEN N.P.R. & HIROE T., 1999. Interspecific differences in<br />
above-ground growth patterns resulting in spatial and temporal<br />
partitioning of light among species in a tall meadow<br />
grass. J. Ecol. 87: 583-597.<br />
ATKINSON D., 2000. Root characteristics: why and what to measure.<br />
In: Smit et al. (eds), Root methods:a handbook. Springer-<br />
Verlag, Berlin, 1-32.<br />
BÖHM W., 1979. Methods of studying root systems. Springer-Verlag,<br />
New York.<br />
BROWN R. J., 1989. Seeds of success. Lands. Design 181: 34-36.<br />
CLÉMENT G., 1990. Le Jardin en mouvement. Pandora Éditions,<br />
Paris.<br />
COLE L. & KEEEN C., 1976. Dutch techniques for the establishment<br />
of natural plant communities in urban areas. Lands.<br />
Design 116: 31-34.<br />
DAVIDSON R. L., 1969. The effect of root/leaf temperature differentials<br />
on root/shoot ratios in some pasture grasses and<br />
clover. Ann. Bot. 33: 561-569.<br />
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22<br />
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FAO/UNESCO, 1988. Soil map of the world. Food and<br />
Agriculture Organization of the United Nations, Rome.<br />
GREGORY P. J., 1988. Growth and functioning of plant root. In:<br />
Wild A. (ed.), Russel’s soil conditions and plant growth. Bath.<br />
Press, Avon, 113-167.<br />
GROSS K. J. & WERNER P., 1982.The colonizing abilities of biennial<br />
plant species in relation to ground cover: implications<br />
for their distributions in a successional series. Ecology 63:<br />
921-931.<br />
HARPER J. L. & GAJIC D., 1961. Experimental studies of the mortality<br />
and plasticity of a weed. Weed Res. 1: 91-104.<br />
HARPER J. L., 1961. Approaches to the study of plant competition.<br />
Symposia of the society for Exp. Biol. 15: 1-39.<br />
KLEPPER B., 1991. Root-shoot relationships. In:Waisel,Y., Eshel,<br />
A. & Kafkafi, U. (eds.), Plant Roots.The hidden half. Marcel<br />
Dekker Inc., New York, 265-286.<br />
KUIPER D., 1992. Phenotypic plasticity in Plantago species. In:<br />
Kuiper, P. J. C. & Bos, M. (eds.), Plantago:A Multidisciplinary<br />
study. Springer-Verlag, New York, 169-183.<br />
MILNER C. & HUGHES R. E., 1968. Methods for measurement of<br />
the primary production of grassland. IBP Handbook. Blackwell<br />
Scientific Publications, Oxford.<br />
NORMAN J. M. & CAMPBEL G. S, 1992. Canopy structure. In:<br />
Pearcy R. W., Ehleringer J., Mooney H. A. & Rundel P. W.<br />
(eds). Plant physiological ecology. Field methods and instrumentation.<br />
Chapman & Hall, London, 301-325.<br />
OLIVEIRA M. R. G., 1988. Comportamento do sistema radical de<br />
algumas espécies forrageiras e pratenses com interesse para a<br />
modernização dos sistemas de agricultura no Alentejo. PhD<br />
Universidade de Évora.<br />
OLIVEIRA M. R., NOORDWIJK M.VAN,GAZE S. R., BROUWER G.,<br />
BONA S., MOSCA G. & HAIRIAH K, 2000. Auger sampling, in<br />
growth cores and pinboard methods. In: Smit et al. (eds.),<br />
Root methods: a handbook. Springer-Verlag, Berlin, 175-210.<br />
PAGÈS L., ASSENG S., PELLERIN S. & DIGGLE A., 2000. Modelling<br />
root system growth and architecture. In: Smit et al. (eds.),<br />
Root methods: a handbook. Springer-Verlag, Berlin, 113-146.<br />
RIVAS-MARTÍNEZ S., 1995. Classificación bioclimática de la tierra.<br />
Folia Bot. Madritensis 16: 1-32.<br />
ROSS M. A. & HARPER J., 1972. Occupation of biological space<br />
during seedling establishment. J. Ecol. 60: 77-88.<br />
SHAW R. G. & ANTONOVICS J., 1986. Density in Salvia lyrata, a<br />
herbaceous perennial: the effects of the experimental alteration<br />
of seed densities. J. Ecol. 74: 797-813.<br />
SHELDON J. C., 1974. The behaviour of seeds in soil. I - The<br />
influence of seed morphology and the behaviour of seedlings<br />
on the establishment of plants from surface-lying seeds.<br />
J. Ecol. 62: 47-66.<br />
SMUKER A. J. M., MC BURNEY S. L. & SRIVASTAVA A. K., 1982.<br />
Quantitative separation of root from compacted soil profiles<br />
by hidropneumatic elutriation system. Agron. J. 74:<br />
500-503.<br />
SOIL SURVEY STAFF (SSS), 1992. Key to soil taxonomy. 5th ed.,<br />
Pocohontas Press, Virginia.<br />
TAPPEINER U. & CERNUSCA A., 1996, Microclimate and fluxes<br />
of water vapour, sensible heat and carbon dioxide in structurally<br />
differing sub-alpine plant communities in the Central<br />
Caucasus. Plant Cell Envir. 19: 403-417.<br />
TAPPEINER U. & CERNUSCA A., 1998. Model simulation of spatial<br />
distribution of photosynthesis in structurally differing<br />
plant communities in the central Caucasus. Ecol. Model. 113:<br />
201-223.<br />
TROUGHTON 1977. Relationship between the root and shoot systems<br />
of grasses. In: Marshall (ed.), The below ground ecosystem:<br />
a synthesis of plant-associated processes. Colorado State<br />
University, 26: 39-51.<br />
TUTIN T. G., HEYWOOD V. H., BURGES N. H., MOORE D. M.,<br />
VALENTINE D. H.,WALTERS S. M. & WEB D. A. (EDS.), 1972.<br />
Flora Europaea. Cambridge University Press, Cambridge,<br />
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WEAVER S. E. & CAVERS P. B., 1979.The effects of date of emergence<br />
and emergence order on seedling survival rates in<br />
Rumex crispus and Rumex obtusifolius.Can.J.Bot.57: 730-738.<br />
WELLS T. C. E., 1987. The establishment of floral grasslands.<br />
Acta Horticulturae 195: 59-67.<br />
ZELLER V., BAHN M., AICHNER M. & TAPPEINER U., 2000. Impact<br />
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ecologia mediterranea, tome 28, fascicule 2, 2002
Diversité génétique des populations naturelles<br />
de l’Argyrolobium uniflorum Jaub. et Spach. (Fabaceae) en Tunisie<br />
Genetic diversity in Tunisian populations<br />
of Argyrolobium uniflorum Jaub. et Spach. (Fabaceae)<br />
Zaouali Yosr, Ben Fadhel Najeh, Boussaid Mohamed<br />
Laboratoire de biotechnologie végétale, Institut national des sciences appliquées et de technologie, BP 676, 1080 Tunis Cedex, Tunisie<br />
email : bossdmohd@insat.rnu.tn – Tél. : (216) 71 703 829 (929) – Fax : (216) 1 71704 329<br />
Résumé<br />
Argyrolobium uniflorum Jaub. et Spach., est une Fabacée pastorale,<br />
diploïde (2n=2x=16) et cléistogame, qui pousse spontanément<br />
dans les parcours steppiques de la Tunisie centrale et méridionale.<br />
Les populations de cette espèce disparaissent progressivement sous l’influence<br />
continue du surpâturage et du défrichement des parcours.<br />
Les mesures de sauvegarde de l’espèce doivent passer au préalable par<br />
l’analyse de la diversité génétique des populations naturelles.<br />
Douze populations d’Argyrolobium uniflorum, collectées dans différentes<br />
régions de la Tunisie, ont fait l’objet d’une analyse du polymorphisme<br />
de six systèmes enzymatiques.<br />
Vingt-quatre loci, dont douze se sont avérés polymorphes, ont été<br />
détectés. La diversité génétique intrapopulation, estimée par le<br />
nombre moyen d’allèles par locus polymorphe, le pourcentage de<br />
loci polymorphes et les taux moyens d’hétérozygotie, est importante.<br />
Elle résulterait d’une forte hétérogénéité des populations ancestrales<br />
et de migration de graines à partir de populations adjacentes.<br />
La différenciation des populations, estimée par les indices de fixation<br />
de Wright et par une analyse en composantes principales effectuée sur<br />
les fréquences alléliques, est assez forte. La perturbation des sites et la<br />
cléistogamie de l’espèce joueraient un rôle primordial dans cette structuration.<br />
L’indice d’identité génétique de Nei (1978) entre les populations<br />
est élevé. La faible divergence génétique entre les populations<br />
et leur forte différenciation témoigneraient de leur fragmentation<br />
récente, essentiellement sous l’influence des pressions anthropiques. Le<br />
dendrogramme établi à partir des indices d’identité génétique de Nei<br />
(UPGMA) fait ressortir deux groupes de populations. Au sein de<br />
chaque ensemble, l’agrégation des populations selon leur proximité<br />
géographique ou bioclimatique ne s’est opérée que pour un nombre<br />
limité d’entre elles. La conservation de l’espèce doit intégrer dans un<br />
premier temps la collecte d’un maximum d’individus à l’intérieur<br />
des populations et préserver celles ayant présenté un niveau élevé de<br />
polymorphisme, particulièrement celles à allèles rares.<br />
Mots-clés<br />
Argyrolobium uniflorum, cléistogamie, conservation, diversité<br />
génétique, isozymes, Tunisie.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 23-37<br />
Abstract<br />
Argyrolobium uniflorum Jaub. et Spach., is a pasture legume,<br />
diploid (2n=2x=16) and cleistogamous which grows in the Central<br />
and the Southern rangelands of Tunisia. Natural populations are<br />
endangered by overgrazing and clearing. Conservation actions of<br />
the species require knowledge of the genetic diversity of populations.<br />
Twelve Tunisian Argyrolobium uniflorum populations collected<br />
in different parts of Tunisia, were assessed by the analysis of six<br />
isozymes.<br />
The enzymes analyzed were encoded by 24 loci and 12 out of them<br />
were polymorphic.<br />
The mean number of alleles per polymorphic locus, the percentage<br />
of loci polymorphic and the observed and the expected heterozygotities<br />
were very high. They indicate a high level of genetic diversity<br />
within populations as a result both of a high diversity of genets<br />
within the former populations and the seed recruitment from adjacent<br />
populations. A high genetic differentiation of populations, estimated<br />
by Wright’s indices and a principal component analysis performed<br />
on allelic frequencies, was detected. The species mating system<br />
and site perturbances may play great roles in population differentiation.<br />
The genetic divergence between populations estimated<br />
by Nei’s (1978) genetic identity was globally low. The high level<br />
of similarities between populations and their substantial differentiation<br />
might indicate recent population isolation dictated essentially<br />
by anthropic pressures.<br />
The UPGMA, established through genetic Nei’s genetic identities,<br />
revealed two groups of populations. Within each group, populations<br />
from the same bioclimatic stage or geographically near were not<br />
clustered obligatory together.<br />
Preservation of populations with high levels of polymorphism and<br />
exhibiting unique alleles, and the collect of a high number of individuals<br />
within populations may constitute the starting point for<br />
the species conservation program.<br />
Key-words<br />
Argyrolobium uniflorum, cleistogamy, conservation, genetic diversity,<br />
isozymes, Tunisia.<br />
23
24<br />
◆ ZAOULI YOSR, BEN FADHEL NAJEH, BOUSSAID MOHA<strong>MED</strong><br />
ABREGED ENGLISH VERSION<br />
Argyrolobium uniflorum Jaub. et Spach. (Fabaceae) is<br />
a pasture legume growing spontaneously in Tunisian arid<br />
rangelands. The species is diploid (2n=2x=16), strongly<br />
and even strictly cleistogamous. It produces a high number<br />
of pods with numerous small seeds which are dispersed<br />
by wind and streaming.<br />
Overgrazing and human activities (farming, clearing<br />
of rangelands) in Tunisian arid areas had led to habitat<br />
destruction and to the reduction of the number and size<br />
of populations. At present, populations were restricted to<br />
limited perturbed lands (cultivated and abandoned cereal<br />
fields) and to some recent protected pasture areas.<br />
Rangeland management programs and conservation<br />
actions that will promote adapted Argyrolobium uniflorum<br />
genotypes require knowledge of the genetic variability of<br />
the species first.<br />
In this study, we investigated the genetic diversity of<br />
twelve populations representing the geographic area of the<br />
species using 13 % starch horizontal gel electrophoresis.<br />
Six isozymes (PGI, MDH, PGM, ADH, 6PGD and ICD)<br />
were analyzed to assess genetic variations within and among<br />
populations.Twenty individuals per population were sampled<br />
at random. Electrophoresis protocols (protein extraction,<br />
buffer preparation, gel staining…) were taken from<br />
Pasteur et al. (1987), and Wendel and Weeden, (1989).The<br />
computer program Biosys 1 (Swofford & Selander, 1981)<br />
was used to calculate standard parameters in order to assess<br />
the levels of genetic variation (number of alleles per polymorphic<br />
locus, percentage of polymorphic loci, observed<br />
and expected heterozygosities). Wright’s F statistics and<br />
deviation from Hardy-Weinberg expectations were calculated<br />
to estimate the level of heterozygosity and population<br />
differentiation. A principal component analysis, performed<br />
on allelic frequencies, was also used to estimate the differentiation<br />
of populations. Genetic divergence between<br />
populations was estimated using Nei’s (1978) unbiased<br />
genetic identity. A hierarchical cluster analysis of genetic<br />
identity values was performed using the UPGMA method.<br />
The species maintains high levels of genetic diversity<br />
within populations. Genetic measure parameter values<br />
were higher than those reported for cleistogamous or autogamous<br />
species (57.64 % of polymorphic loci, 1.62 alleles<br />
per polymorphic locus, and 0.103 and 0.207 respectively<br />
observed and expected heterozygosities).The high levels<br />
of variation within populations might result from the high<br />
diversity of genets at the starting population and the<br />
recruitment of new genets via seed migration from adjacent<br />
populations by wind and streaming.<br />
A deficiency of heterozygosity for the majority of loci<br />
for most of the populations and a high level of inbreeding<br />
(F IS = 0,488) were detected as a result of the species<br />
mating system.<br />
Estimated values of Wright’s F indexes indicated a substantial<br />
structuration among populations (F ST = 0,163).<br />
The number of migrants per generation is low (Nm =<br />
1.28). The high genetic differentiation and the low gene<br />
flow may be the result of both site perturbance by human<br />
activities and the species mating system. Plots derived<br />
from the ACP analysis showed also a large separation between<br />
populations.<br />
The average of Nei’s (1978) genetic identity values (I)<br />
was high (0.917 to 1.000), and reflected the paucity of<br />
genetic divergence between populations.The high similarities<br />
between populations and the high level of their genetic<br />
differentiation were indicators of their recent isolation.<br />
UPGMA analysis showed at I = 0.940 two aggregates<br />
of populations. In each subgroup, there is no evident relationship<br />
between population neighboring, bioclimatic<br />
stage population belonging and clustering.<br />
Conservation implications of our survey are still fragmentary.<br />
Other studies including molecular and demographic<br />
estimates are necessary to elaborate an appropriate<br />
population preservation program. However, our<br />
study showed that some populations exhibited high levels<br />
of polymorphism and some of them have particular alleles.<br />
The conservation of these populations and the collect of<br />
a high number of individuals within populations may<br />
constitute a starting step for conservation programs.<br />
INTRODUCTION<br />
Les parcours naturels de la Tunisie présentent une<br />
diversité floristique spécifique et infraspécifique importante<br />
(Gounot, 1995 ; Le Houérou, 1969 ; Le Floc’h,<br />
1995 ; Thiault, 1995 ; Waechter, 1995).<br />
Le défrichement des parcours (au profit de la céréaliculture<br />
et l’arboriculture) et le surpâturage, en Tunisie centrale<br />
et méridionale, ont conduit à une dégradation des<br />
habitats et à un appauvrissement de leur diversité floristique<br />
(Boussaid et al., 1998). Un nombre élevé d’espèces,<br />
à bonne valeur pastorale, se raréfient progressivement et<br />
sont remplacées par des espèces peu ou pas palatables<br />
(Boussaid et al., 1998 ; Ben Fadhel et al., 2000). Medicago<br />
sativa L. ssp. tunetana Murb. (Fabaceae), Cenchrus ciliaris<br />
L. (Poaceae),Tricholaena teneriffae Link. (Poaceae),<br />
Tetrapogon villosus L. (Poaceae) et Hedysarum carnosum<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
DIVERSITÉ GÉNÉTIQUE DES POPULATIONS NATURELLES DE L’ARGYROLOBIUM UNIFLORUM JAUB. ET SPACH… ◆<br />
Desf. (Fabaceae), ne sont actuellement représentés que<br />
par de petites populations dans des sites refuges (parcelles<br />
mises en défens, parcs nationaux…). La présence<br />
d’Hedysarum flexuosum Desf. et H. humile L. n’est attestée<br />
que par des listes d’herborisation fort anciennes (Quézel,<br />
1991 ; Schoenenberger, 1995 ; Boussaid et al., 1998).<br />
Argyrolobium uniflorum Jaub. et Spach., Fabaceae pastorale<br />
diploïde (2n=2x=16), à port prostré et appartenant<br />
à la tribu des Génistées (Raynaud, 1974) est bien<br />
représentée dans les parcours steppiques de la Tunisie<br />
centrale et méridionale. Elle est considérée, comme les<br />
autres espèces du même genre [A. abissynicum Jaub. et<br />
Spach., A. arabicum (Desf.) Jaub. et Spach., A. zanonii<br />
(Turra) Ball. et A. saharaea (Pomel)], comme une bonne<br />
espèce pastorale pouvant intervenir dans la réhabilitation<br />
des parcours en milieux arides de l’Afrique du Nord<br />
(Raynaud, 1974 ; Lwogo, 1984 ; Attia, 1986 ; Ben Fadhel<br />
et al., 2000). Elle est très appréciée par le bétail, présente<br />
une bonne valeur nutritive et a une production de matière<br />
verte étalée dans le temps (de septembre à juillet). Elle<br />
résiste au piétinement et au surpâturage (développement<br />
de bourgeons végétatifs latents à tous les niveaux de la<br />
plante, port prostré…) et produit un nombre élevé de<br />
gousses (plus de 50 par individu) (Le Houérou & Ionsco,<br />
1973 ; Floret & Pontanier, 1982 ; Zaouali, 1999 ; Ben<br />
Fadhel et al., 2000). La déhiscence des gousses est échelonnée<br />
dans le temps et une à cinq graines restent souvent<br />
conservées dans la partie proximale de la gousse,<br />
proche du pédoncule (Zaouali, 1999). Les graines (8 à<br />
15 par gousse) sont ovoïdes, de très petite taille (1,5-<br />
3 mm) et de couleur variable (jaune, brun et orange).<br />
Elles sont dispersées par le vent et les eaux de ruissellement<br />
(Zaouali, 1999 ; Ben Fadhel et al., 2000). L’espèce<br />
se reproduit sous un régime très fortement, sinon exclusivement,<br />
cléistogame (Abdelkefi et al., 1990). Les fleurs,<br />
axillaires, sont jaunâtres et de petite taille (4 à 6 mm de<br />
longueur). La déhiscence des anthères et la formation<br />
des graines s’opèrent avant l’épanouissement de la fleur<br />
(Dardour et al., 1989 ; Abdelkefi et al., 1990). Ce n’est<br />
que dans de très rares cas que nous avons pu observer<br />
une émergence du stigmate en dehors du bouton floral<br />
(3 fleurs sur 600 individus d’origine géographique<br />
diverse). Cette situation favoriserait des allofécondations<br />
à condition que le stigmate soit encore réceptif, que les<br />
ovules (ou une bonne proportion d’entre eux) ne soient<br />
pas fécondés par l’autopollen, et qu’il n’y ait pas des phénomènes<br />
d’allo-incompatibilité.<br />
L’espèce est décrite dans les flores comme étant une<br />
chaméphyte pérenne pouvant se reproduire aussi bien par<br />
graine que par drageon (Quézel & Santa, 1962 ; Ozenda,<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 23-37<br />
1977 ; Pottier Alapetite, 1979). Toutefois, en Tunisie et<br />
dans les conditions naturelles, l’espèce se comporte<br />
comme une annuelle, ne se multipliant le plus souvent<br />
que par graine. En effet, la production de drageons est<br />
faible et le développement de ces structures est très limité<br />
(1 à 2 cm) suite au dessèchement estival des plantes<br />
(observations personnelles).<br />
En Tunisie, les populations d’Argyrolobium uniflorum<br />
se raréfient progressivement sous l’influence du surpâturage<br />
et du défrichement des parcours. Des mesures de<br />
sauvegarde s’imposent pour assurer la diversité floristique<br />
des parcours steppiques, préserver la diversité génétique<br />
de l’espèce et promouvoir sa gestion durable. La mise en<br />
œuvre de stratégies efficaces de conservation nécessite au<br />
préalable une évaluation de la diversité génétique des<br />
populations par des marqueurs génétiques efficaces<br />
(isoenzymatiques et moléculaires particulièrement). Cette<br />
étude, chez des espèces menacées d’extinction telles que<br />
l’Argyrolobium uniflorum, devrait permettre d’estimer la<br />
taille effective des populations, d’évaluer leur dépression<br />
de consanguïnité, d’analyser leur structuration génétique<br />
et de mesurer les flux géniques entre elles (Batista et al.,<br />
2001 ; Hedrick, 2001). L’importance relative de ces paramètres,<br />
associée à la connaissance de la biologie de l’espèce<br />
(régime de reproduction notamment) et des facteurs<br />
du milieu environnant, doit contribuer à évaluer l’organisation<br />
de la variabilité à l’intérieur et entre les populations,<br />
et à orienter efficacement les programmes de restauration<br />
des populations naturelles.<br />
L’analyse du polymorphisme isoenzymatique, en dépit<br />
de ses limites (détection d’une faible proportion de variations<br />
pour existence d’enzymes multigéniques, redondance<br />
du code génétique, modifications post transcriptionnelles…),<br />
constitue actuellement un moyen utile et<br />
relativement peu coûteux pour évaluer la variabilité génétique<br />
et le degré de différenciation des populations, et<br />
mesurer les flux géniques entre elles afin de mieux étayer<br />
les stratégies de conservation (Pernès, 1984).<br />
MATÉRIELS ET MÉTHODES<br />
Populations analysées<br />
Douze populations d’Argyrolobium uniflorum, représentatives<br />
de l’aire géographique de l’espèce en Tunisie,<br />
ont été analysées. Les populations se développent dans les<br />
étages bioclimatiques aride inférieur et aride supérieur<br />
(Emberger, 1955) sous des pluviométries qui varient de<br />
25
26<br />
◆ ZAOULI YOSR, BEN FADHEL NAJEH, BOUSSAID MOHA<strong>MED</strong><br />
Figure 1. Localisation<br />
géographique et bioclimatique<br />
des douze populations<br />
d’Argyrolobium uniflorum<br />
analysées en Tunisie.<br />
Figure 1. Geographic<br />
and bioclimatic situation<br />
of the twelve<br />
Argyrolobium uniflorum<br />
populations analyzed in Tunisia.<br />
1, 2, 3… : populations analysées<br />
Hi : humide inférieur,<br />
Sh : subhumide,<br />
Sas : semi-aride supérieur,<br />
Sam : semi-aride moyen,<br />
Sai : semi-aride inférieur,<br />
As : aride supérieur,<br />
Ai : aride inférieur,<br />
S:saharien.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
DIVERSITÉ GÉNÉTIQUE DES POPULATIONS NATURELLES DE L’ARGYROLOBIUM UNIFLORUM JAUB. ET SPACH… ◆<br />
150 à 300 mm/an. Les populations se rencontrent dans<br />
les lits et sur les berges d’oueds temporaires et sur des terrains<br />
sableux dérivant de steppes primaires à chaméphytes<br />
pérennes (Rhanterium suaveolens (Desf.) Q. et S., Artemisia<br />
campestris L. et A.herba-alba Asso.,Stipa tenacissima L.,etc.)<br />
défrichées récemment au profit de la céréaliculture et la<br />
création de réserves fourragères (Opuntia ficus-indica L.,<br />
Acacia L. ssp.). La localisation géographique des populations<br />
est représentée dans la figure 1. Les caractéristiques<br />
écologiques essentielles des sites figurent dans le tableau 1.<br />
Vingt individus pourvus de gousses mûres ont été collectés<br />
au hasard, dans chaque population, dans une superficie<br />
qui varie de 2 à 7 ha. Les plantes ont été prélevées<br />
à des distances supérieures à 10 m pour éviter la collecte<br />
d’individus issus d’une même plante mère.<br />
Sur chaque plante, nous avons prélevé une gousse.<br />
Une graine par gousse, représentant un individu par population,<br />
a été mise en germination dans une boîte de Pétri<br />
sur papier filtre imbibé d’eau pendant une semaine.<br />
Electrophorèse et systèmes<br />
enzymatiques analysés<br />
Six systèmes enzymatiques : la malate déshydrogénase<br />
(MDH ; EC 1.1.1.37), l’alcool déshydrogénase (ADH ;<br />
EC 1.1.1.1), la 6 phosphogluconate déshydrogénase<br />
(6PGD ; EC 1.1.1.44), l’isocitrate déshydrogénase (ICD ;<br />
EC 1.1.1.42), la phosphoglucoisomérase (PGI ; EC<br />
5.3.1.9), et la phosphoglucomutase (PGM ; EC 2.7.5.1),<br />
ont été analysés par électrophorèse horizontale sur gel<br />
Population Code Étages Pluviométrie Nature des sites<br />
population bioclimatiques annuelle<br />
et variantes* (mm/an)<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 23-37<br />
d’amidon à 13 % (Pasteur et al., 1987). Ces enzymes interviennent<br />
dans les voies métaboliques primaires chez les<br />
végétaux (voie des pentoses, cycles de Krebs et de<br />
Calvin…).<br />
Les protéines enzymatiques sont extraites à partir de<br />
chaque germination par broyage à froid (4 °C) dans<br />
100 ml de tampon ascorbate de sodium (0,1 mol.L-1 ;<br />
pH 8,4) additionné de 5 mM de ß mercaptoéthanol<br />
(0,035 %) et 8,35 % de saccharose. L’homogénat est centrifugé<br />
à 4 °C à 13 500 tours/mn pendant 30 mn.<br />
Les extraits sont déposés dans les puits du gel à l’aide<br />
de papier Wateman (1 x 0,5 cm) imbibé d’extrait. Un bac<br />
de glace est déposé sur le gel pour éviter la dénaturation<br />
des protéines. La migration, anodique, se déroule dans<br />
une chambre froide (4 °C) à ampérage constant (20 mA)<br />
et dure 12 heures. Le tampon de migration est à base<br />
d’histidine (0,065 mol.L-1 L-histidine et 0,02 mol.L-1 d’acide citrique, pH 6,8). L’intensité du courant et la durée<br />
de migration ont été fixées suite à des essais préliminaires<br />
pour optimiser la résolution des bandes électrophoriques.<br />
Dans ces manipulations nous avons fait varier l’ampérage<br />
(de 20 à 40 mA) et la durée de migration (de 6 à 12 h).<br />
La meilleure résolution des zymogrammes, dans nos<br />
conditions de travail, a été obtenue pour 20 mA et 12 h<br />
de migration.<br />
La révélation des isozymes a été effectuée selon les<br />
procédures préconisées par Stuber et al. (1988) et Wendel<br />
et Weeden (1989).<br />
Mazzouna 1 AI (hd) 197 steppe défrichée et replantée en cactus inerme.<br />
Skira 1 2 AI (hd) 180 champ abandonné et réservé à des cultures céréalières (orge).<br />
Skira 2 3 AI (hd) 180 champ abandonné et réservé à des cultures céréalières (orge).<br />
Mareth 4 AI (hd) 190 steppe à Lygeum spartum dégradée par érosion éolienne et hydrique.<br />
Ben Guerdene 5 AI (hd) 181 terrain reboisé en Acacia ssp. et Prosposis ssp.<br />
Sidi Maklouf 6 AI (hd) 152 champ cultivé en céréales (orge) et Lathyrus ssp.<br />
Skira 3 7 AI (hd) 175 champ abandonné, réservé à des cultures céréalières (orge).<br />
El Houareb 1 8 AS (htd) 286 berges et lit d’oued.<br />
El Houareb 2 9 AS (hd) 286 terrain reboisé en Acacia ssp et Atriplex nummularia.<br />
Sbeitla 10 AS (hf) 282 ravins et lit d’oued.<br />
Sidi Bouzid 11 AS (hd) 247 steppe à Rantherium suavelens défrichée et replantée en cactus inerme.<br />
Baten 12 AS (hd) 254 terrain abandonné, réservé pour des cultures céréalières (orge).<br />
AI : Aride inférieur; AS : Aride supérieur; hd : Hiver doux ; htd : Hiver tempéré à doux ; hf : Hiver frais<br />
* Les étages et les variantes bioclimatiques ainsi que la pluviométrie sont issus de la carte bioclimatique de la Tunisie. Echelle 1/1 000 000 (Nabli, 1995).<br />
Tableau 1. Caractéristiques écologiques principales des 12 populations d’Argyrolobium uniflorum analysées en Tunisie.<br />
Table 1. Main ecological traits of the twelve Tunisian Argyrolobium uniflorum population analyzed.<br />
27
28<br />
◆ ZAOULI YOSR, BEN FADHEL NAJEH, BOUSSAID MOHA<strong>MED</strong><br />
Méthodes d’analyse des résultats<br />
Dans notre travail l’interprétation des zymogrammes<br />
n’a pas été confrontée à une analyse de génétique formelle.<br />
Pour chaque système isoenzymatique et par comparaison<br />
de tous les zymogrammes, nous avons émis des<br />
hypothèses sur le contrôle génétique de chaque isozyme<br />
selon les principes avancés par Pernès (1984), Pasteur et<br />
al. (1987),Wendel et Weeden (1989) et Hannan et Orick<br />
(2000). Nos interprétations génétiques ont également tenu<br />
compte de travaux antérieurs effectués sur des Fabaceaes<br />
fourragères et pastorales allogames telles que Hedysarum<br />
coronarium L. (Trifi et al., 1989), H. carnosum Desf.<br />
(Chatti, 1987) ou autogames telles que Medicago polymorpha<br />
L. (Salhi-Hanachi et al., 1998).<br />
Pour chaque système enzymatique, les locus identifiés<br />
sont désignés successivement par les chiffres 1,2,3..., selon<br />
leur vitesse de migration anodique. Les allèles, pour<br />
chaque locus, sont désignés par des lettres a, b, c…. selon<br />
leur vitesse de migration vers l’anode.<br />
Pour chaque population, les fréquences génotypiques<br />
ont été calculées. La matrice des données a été traitée par<br />
le programme informatique Biosys1 (Swofford &<br />
Selander, 1981). Pour chaque population nous avons<br />
estimé : les fréquences alléliques ; le nombre moyen d’allèles<br />
par locus polymorphe (Ap)<br />
1 L<br />
Ap = — ∑ ni<br />
L i=1<br />
où ni est le nombre d’allèles par locus polymorphe, et L<br />
le nombre total de loci polymorphes) ;<br />
le pourcentage de loci polymorphes (P)<br />
np<br />
P = — x 10<br />
Nt<br />
où np est le nombre de loci polymorphes et Nt le nombre<br />
total des loci) ;<br />
le taux moyen d’hétérozygotie observée (Ho) et attendue<br />
(He) sous l’équilibre de Hardy-Weinberg<br />
L<br />
H o = ∑ H ok<br />
i=1<br />
————<br />
L<br />
où H ok, le taux d’hétérozygotes au locus k, est égal à<br />
n<br />
∑P ij (i≠j),<br />
i, j=1<br />
L = le nombre des loci, n= nombre d’allèles et P ij = fréquence<br />
du génotype ij au locus k.<br />
La déviation par rapport à la panmixie pour chaque<br />
locus a été évaluée par un test χ 2 de Pearson (Dagnellie,<br />
1974). L’excès ou le déficit d’hétérozygotie ont été testés<br />
par les indices de fixation F de Wright (Wright, 1965).<br />
La structuration des populations est estimée par le calcul<br />
des indices de subdivision de Wright (1978). La formule<br />
de base utilisée pour le calcul des valeurs des différents<br />
indices, est 1-F IT = (1-F IS) (1-F ST) où F IT est le paramètre<br />
de différenciation globale de toutes les subdivisions,<br />
F IS (F IS=1-H o/H e) est le paramètre de différenciation dans<br />
les populations et F ST est le paramètre de différenciation<br />
entre les populations<br />
k 1 S 2<br />
F ST = ∑ — ∑ [qx(i) – ¯q (i)]<br />
i=1 S X=1<br />
où qx(i) est la fréquence relative de l’allèle i dans les subdivisions<br />
; ¯q (i) est la moyenne des fréquences alléliques<br />
de i ; k est le nombre d’allèles ; S est le nombre de subdivisions.<br />
Un test χ2 a été utilisé pour juger de la signification<br />
des différences des valeurs de FST.Pour chaque locus,<br />
la valeur du χ2 est calculée par la formule χ2 = 2N FST (K-<br />
1) à (K-1)(S-1) degrés de liberté ; N est le nombre total<br />
des individus, K est le nombre d’allèles par locus et S est<br />
le nombre des populations (Workman & Niswander,<br />
1970 ; Gao et al., 2000). Le nombre de migrants (Nm)<br />
par génération entre les populations est estimé par la formule<br />
Nm=[(1-FST)]/4 FST (Wright, 1951).<br />
Pour mieux visualiser la différenciation des populations,<br />
nous avons effectué, par le programme informatique<br />
SAS (SAS, 1990) une analyse en composantes principales<br />
(ACP) sur les fréquences alléliques au niveau des<br />
loci polymorphes chez toutes les populations.<br />
La divergence génétique entre les populations est estimée<br />
à travers les indices d’identité (I) non biaisées de Nei<br />
(1978)<br />
¯J xy<br />
I = ———<br />
√¯J x • ¯J y<br />
où ¯J x et ¯J y sont les moyennes arithmétiques de J x et J y probabilités<br />
d’identité de deux allèles tirés au hasard dans la<br />
même population et ¯J xy moyenne arithmétique de J xy probabilité<br />
d’identité de deux allèles pris au hasard dans la<br />
population x et l’autre dans la population y (Pernès, 1984).<br />
Un dendrogramme (UPGMA ; Unweighted Pair Group<br />
Method Using Arithmetic Averages), établi à partir de ces<br />
indices, a été construit pour l’ensemble des populations<br />
pour juger de leur similarité génétique.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
DIVERSITÉ GÉNÉTIQUE DES POPULATIONS NATURELLES DE L’ARGYROLOBIUM UNIFLORUM JAUB. ET SPACH… ◆<br />
RÉSULTATS<br />
Variabilité génétique intrapopulation<br />
Pour les six systèmes enzymatiques analysés, 24 loci<br />
ont été détectés. Douze d’entre-deux (Adh-1, Icd-2, Icd-3,<br />
Mdh-1, Mdh-2, Mdh-3, Pgm-1, Pgm-2, Pgi-1, Pgi-2, Pgi-<br />
3 et Pgi-8) se sont avérés polymorphes (tableau 2). Chaque<br />
locus, excepté le Pgi-3 (à 3 allèles) comporte deux allèles.<br />
Les fréquences alléliques sont variables selon les populations<br />
(tableau 2). Des allèles particuliers n’ont été détectés<br />
que dans un petit nombre de populations. C’est le cas des<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 23-37<br />
Populations<br />
allèles Adh1-b, Pgi 8-a et Pgm1-b. La présence de ces allèles<br />
(à des fréquences souvent supérieures à 15 %) n’est pas liée<br />
à des zones géographiques ou bioclimatiques données. En<br />
effet, des populations proches géographiquement et se développant<br />
dans la même zone bioclimatique peuvent présenter<br />
des allèles uniques différents (tableaux 1 et 2).<br />
Le nombre moyen d’allèles par locus polymorphe (Ap)<br />
varie de 1,4 (populations 2, 3 et 8) à 1,8 (populations 5,<br />
7, 11 et 12) (tableau 3). Les pourcentages de loci polymorphes<br />
sont relativement élevés. Ils varient de 41,7<br />
(populations 2, 3 et 8) à 75 % (populations 5, 7 et 12).<br />
Le pourcentage moyen de loci polymorphes est de<br />
Locus 1 2 3 4 5 6 7 8 9 10 11 12<br />
Adh-1<br />
a 0,700 1,000 1,000 1,000 1,000 0,500 1,000 0,500 1,000 1,000 1,000 0,850<br />
b 0,300 0,000 0,000 0,000 0,000 0,500 0,000 0,500 0,000 0,000 0,000 0,150<br />
Icd-2<br />
a 1,000 0,850 0,850 0,850 0,900 1,000 1,000 1,000 1,000 0,950 1,000 0,900<br />
b 0,000 0,150 0,150 0,150 0,100 0,000 0,000 0,000 0,000 0,050 0,000 0,100<br />
Icd-3<br />
a 0,000 0,250 0,150 0,150 0,150 0,000 0,250 0,200 0,000 0,050 0,050 0,100<br />
b 1,000 0,750 0,850 0,850 0,850 1,000 0,750 0,800 1,000 0,950 0,950 0,900<br />
Mdh-1<br />
a 0,200 0,000 0,000 0,000 0,000 0,150 0,100 0,000 0,050 0,000 0,000 0,250<br />
b 0,800 1,000 1,000 1,000 1,000 0,850 0,900 1,000 0,950 1,000 1,000 0,750<br />
Mdh-2<br />
a 0,500 0,100 0,350 0,850 0,300 0,550 0,850 0,450 0,350 0,650 0,600 0,550<br />
b 0,500 0,900 0,650 0,150 0,700 0,450 0,150 0,550 0,650 0,350 0,400 0,450<br />
Mdh-3<br />
a 0,300 0,100 0,350 0,850 0,300 0,400 0,750 0,450 0,300 0,650 0,600 0,300<br />
b 0,700 0,900 0,650 0,150 0,700 0,600 0,250 0,550 0,700 0,350 0,400 0,700<br />
Pgm-1<br />
a 1,000 1,000 1,000 0,700 0,900 1,000 0,900 1,000 0,450 1,000 0,550 1,000<br />
b 0,000 0,000 0,000 0,300 0,100 0,000 0,100 0,000 0,550 0,000 0,450 0,000<br />
Pgm-2<br />
a 0,000 0,000 0,000 0,300 0,100 0,000 0,100 0,000 0,550 0,000 0,450 0,000<br />
b 1,000 1,000 1,000 0,700 0,900 1,000 0,900 1,000 0,450 1,000 0,550 1,000<br />
Pgi-1<br />
a 0,150 0,000 0,000 0,000 0,250 0,000 0,050 0,000 0,000 0,150 0,050 0,150<br />
b 0,850 1,000 1,000 1,000 0,750 1,000 0,950 1,000 1,000 0,850 0,950 0,850<br />
Pgi-2<br />
a 0,850 1,000 1,000 1,000 0,750 1,000 0,950 1,000 1,000 0,850 0,950 0,850<br />
b 0,150 0,000 0,000 0,000 0,250 0,000 0,050 0,000 0,000 0,150 0,050 0,150<br />
Pgi-3<br />
a 0,150 0,000 0,000 0,000 0,125 0,000 0,025 0,000 0,000 0,075 0,025 0,075<br />
b 0,425 0,500 0,500 0,500 0,500 0,500 0,500 0,500 0,500 0,500 0,500 0,500<br />
c 0,425 0,500 0,500 0,500 0,375 0,500 0,475 0,500 0,500 0,425 0,475 0,425<br />
Pgi-8<br />
a 0,000 0,000 0,025 0,000 0,000 0,250 0,000 0,000 0,000 0,000 0,000 0,000<br />
b 1,000 1,000 0,975 1,000 1,000 0,750 1,000 1,000 1,000 1,000 1,000 1,000<br />
Tableau 2. Fréquences alléliques des 12 loci polymorphes détectés chez les 12 populations d’Argyrolobium uniflorum analysées.<br />
Table 2. Allelic frequencies of the 12 polymorphic loci detected in the twelve Argyrolobium uniflorum populations analyzed.<br />
29
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◆ ZAOULI YOSR, BEN FADHEL NAJEH, BOUSSAID MOHA<strong>MED</strong><br />
Moyenne d’hétérozygotie<br />
Populations Code Nomb. moyen Nomb. moyen % loci<br />
individus / allèles / locus polymorphes (P) Obs.* Att.**<br />
population polymorphe (Ap) (Ho) (He)<br />
Mazzouna 1 20 1,7 58,3 0,121 0,238<br />
(0,2) (0,083) (0,067)<br />
Skira 1 2 20 1,4 41,7 0,083 0,127<br />
(0,1) (0,083) (0,052)<br />
Skira 2 3 20 1,5 41,7 0,087 0,168<br />
(0,2) (0,083) (0,061)<br />
Mareth 4 20 1,6 58,3 0,083 0,202<br />
(0,1) (0,083) (0,056)<br />
Ben Guerdene 5 20 1,8 75,0 0,083 0,255<br />
(0,2) (0,083) (0,057)<br />
Sidi Maklouf 6 20 1,5 50 0,175 0,223<br />
(0,2) (0,112) (0,070)<br />
Skira 3 7 20 1,8 75,0 0,083 0,193<br />
(0,2) (0,083) (0,050)<br />
Houareb 1 8 20 1,4 41,7 0,167 0,197<br />
(0,1) (0,112) (0,072)<br />
Houareb 2 9 20 1,5 50,0 0,083 0,210<br />
(0,2) (0,083) (0,071)<br />
Sbitla 10 20 1,7 58,3 0,083 0,186<br />
(0,2) (0,083) (0,062)<br />
Sidi Bouzid 11 20 1,8 66,7 0,083 0,236<br />
(0,2) (0,083) (0,070)<br />
Baten 12 20 1,8 75,0 0,108 0,255<br />
(0,2) (0,085) (0,056)<br />
Moyenne 20 1,625 57,64 0,103 0,207<br />
* obs : moyenne d’hétérozygotie observée<br />
** att : moyenne d’hétérozygotie attendue sous l’équilibre de Hardy-Weinberg<br />
Tableau 3. Nombre moyen d’allèles par locus polymorphe (Ap), pourcentage de loci polymorphes (P) et taux d’hétérozygotie (Ho et He)<br />
chez les 12 populations d’Argyrolobium uniflorum analysées. Les écarts types figurent entre parenthèse.<br />
Table 3. Mean number of alleles by polymorphic locus (Ap), percentage of polymorphic loci (P) and observed (Ho) and expected (He) heterozygosities<br />
in Argyrolobium uniflorum populations. Standard deviations were indicated within parenthesis.<br />
57,64 % (tableau 3). Les moyennes d’hétérozygotie observée<br />
(Ho) et attendue (He) sous l’équilibre de Hardy-<br />
Weinberg sont respectivement 0,103 et 0,207. Les populations,<br />
considérées dans leur ensemble, ne sont pas à<br />
l’équilibre de Hardy-Weinberg (Ho 0,05) (tableau 4). La majorité<br />
des valeurs de F (indice de fixation de Wright pour<br />
chaque locus) sont supérieures à zéro, témoignant d’une<br />
proportion observée en hétérozygotes inférieure à l’attendue.<br />
L’excès d’hétérozygotie n’a été observé que pour<br />
les loci Pgi-3 (chez toutes les populations) et Adh-1<br />
(populations 6 et 8).<br />
La valeur moyenne de FIS (indice de fixation de Wright<br />
décrivant la subdivision à l’intérieur des populations) pour<br />
l’ensemble des populations et pour tous les loci est de<br />
0,488. Pour la majorité des loci (9/12), les valeurs de FIS sont positives et égales à 1 (absence totale d’hétérozygotes)<br />
(tableau 5).Trois valeurs fortement négatives dénotant<br />
d’un excès en héterozygotes ont été observées pour<br />
les loci Adh-1 (-0,731), Pgi-3 (-0,856) et Pgi-8 (-0,646).<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
DIVERSITÉ GÉNÉTIQUE DES POPULATIONS NATURELLES DE L’ARGYROLOBIUM UNIFLORUM JAUB. ET SPACH… ◆<br />
Pop. 1 2 3 4 5 6 7 8 9 10 11 12<br />
Locus<br />
Adh-1 ns - - - - -1,00*** - -1,00*** - - - ns<br />
Icd-2 - 1,00*** 1,00*** 1,00*** 1,00*** - - - - 1,00*** - 1,00***<br />
Icd-3 - 1,00*** 1,00*** 1,00*** 1,00*** - 1,00*** 1,00*** - 1,00*** 1,00** 1,00***<br />
Mdh-1 1,00*** - - - - 1,00*** 1,00*** - 1,00*** - - 1,00***<br />
Mdh-2 1,00*** 1,00*** 1,00*** 1,00*** 1,00*** 1,00*** 1,00*** 1,00*** 1,00*** 1,00*** 1,00*** 1,00***<br />
Mdh-3 1,00*** 1,00*** 1,00*** 1,00*** 1,00*** 1,00*** 1,00*** 1,00*** 1,00*** 1,00*** 1,00*** 1,00***<br />
Pgm-1 - - - 1,00*** 1,00*** - 1,00*** - 1,00*** - 1,00*** -<br />
Pgm-2 - - - 1,00*** 1,00*** - 1,00*** - 1,00*** - 1,00*** -<br />
Pgi-1 1,00*** - - - 1,00*** - 1,00** - - 1,00*** 1,00** 1,00***<br />
Pgi-2 1,00*** - - - 1,00*** - 1,00** - - 1,00*** 1,00** 1,00***<br />
Pgi-3 -0,38*** -1,00*** -1,00*** -1,00*** -0,69*** -1,00*** -0,91*** -1,00*** -1,00*** -0,77*** -0,91*** -0,77***<br />
Pgi-8 - - ns - - 0,73*** - - - - - -<br />
***. Significatif à P
32<br />
◆ ZAOULI YOSR, BEN FADHEL NAJEH, BOUSSAID MOHA<strong>MED</strong><br />
Pour mieux expliquer l’origine de ce déficit en hétérozygotes,<br />
nous avons calculé des indices de fixation<br />
moyen par population et dans trois régions géographiques<br />
(R1 : région de Gabès, R2 : région de Kairouan et R3 :<br />
région de Médenine). Chaque région regroupe des populations<br />
peu éloignées (sur un rayon de 20 km). En outre,<br />
le F ST pour l’ensemble des populations subdivisées en six<br />
sous-groupes [(populations 2, 3 et 7), (populations 4, 5<br />
et 6), (populations 8, 9 et 12), (population 1), (population<br />
10), (population 11)] a été également calculé. Au sein<br />
de chaque sous-groupe, les populations ont été rassemblées<br />
arbitrairement selon leur proximité géographique<br />
(figure 1 et tableau 5).<br />
Le FIS moyen par population (FIS= 1 – Ho/He) est élevé<br />
pour la majorité des populations et varie de 0,416 à 0,674.<br />
Deux valeurs, 0,215 et 0,152, relativement faibles, ont été<br />
observées respectivement pour les populations 6 et 8. Les<br />
FST moyens, selon les régions géographiques, sont de<br />
0,162 pour R1 (populations 2, 3 et 7), 0,147 pour R2<br />
(populations 8, 9 et 12) et 0,161 pour R3 (populations<br />
Axes Valeur propre Proportion (%) cumulé (%) Variables les plus corrélées aux axes de l’ACP<br />
Axe 1 6,913 27,65 27,65 Pgi-1a, Pgi-1b, Pgi-2a, Pgi-2b,<br />
Axe 2 6,118 24,47 52,13 Adh-1a, Adh-1b, Pgm-1b, Pgm-2a, Pgm-2b, Pgi-8a, Pgi-8b<br />
Axe 3 5,052 20,20 72,33 Icd-2a, Icd-2b, Icd-3a, Icd-3b, Mdh-1a, Mdh-1b, Mdh-2a,<br />
Mdh-3a, Mdh-3b<br />
Tableau 6. Analyse en composantes principales (ACP) : absorption de la variabilité et définition des trois premiers axes de l’ACP.<br />
Table 6. Principal component analysis: eigenvalues, proportions and axis definition.<br />
Figure 2. Analyse en composantes principales effectuée sur les fréquences alléliques des 12 loci polymorphes chez toutes les populations.<br />
A. Analyse selon le plan défini par les axes 1-2 ; B. Analyse selon le plan défini par les axes 1-3 (* = populations).<br />
Figure 2. Principal component analysis performed on allelic frequencies for the twelve populations for the 12 polymorphic loci<br />
A. Plot according to axis 1-2 ; B. Plot according to axis 1-3 (* = populations).<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
DIVERSITÉ GÉNÉTIQUE DES POPULATIONS NATURELLES DE L’ARGYROLOBIUM UNIFLORUM JAUB. ET SPACH… ◆<br />
Populations code 1 2 3 4 5 6 7 8 9 10 11 12<br />
Mazzouna 1 **** 0,959 0,980 0,917 0,981 0,988 0,950 0,985 0,921 0,977 0,935 1,000<br />
Skira 1 2 **** 0,991 0,875 0,983 0,935 0,902 0,954 0,927 0,935 0,908 0,967<br />
Skira 2 3 **** 0,936 0,990 0,964 0,957 0,976 0,939 0,980 0,948 0,989<br />
Mareth 4 **** 0,919 0,917 0,992 0,926 0,930 0,972 0,985 0,931<br />
Ben Guerdene 5 **** 0,942 0,941 0,958 0,945 0,976 0,949 0,987<br />
Sidi Maklouf 6 **** 0,942 0,992 0,903 0,958 0,922 0,978<br />
Skira 3 7 **** 0,950 0,909 0,991 0,967 0,964<br />
Houareb 1 8 **** 0,909 0,964 0,930 0,977<br />
Houareb 2 9 **** 0,915 0,988 0,923<br />
Sbitla 10 **** 0,961 0,984<br />
Sidi Bouzid 11 **** 0,940<br />
Baten 12 ****<br />
Tableau 7. Indices de similarité de Nei (1978) pour l'ensemble des populations d’Argyrolobium uniflorum analysées.<br />
Table 7. Nei’s (1978) unbiased genetic identity calculated among populations of Argyrolobium uniflorum.<br />
4, 5 et 6). Elles indiquent une structuration substantielle<br />
entre les populations dans chaque région (tableau 5). Le<br />
F ST moyen pour les 6 sous-groupes de populations est<br />
faible (F ST = 0,073) et témoigne d’une faible structuration<br />
régionale de la variabilité.<br />
La structuration des populations, évaluée par l’indice<br />
de subdivision de Wright F ST calculé toutes les populations<br />
(12 populations), est significative. Pour tous les locus<br />
les valeurs de F ST sont significativement différentes de<br />
zéro (tableau 5). La valeur moyenne de F ST est de 0,163,<br />
c’est-à-dire que 16,3 % de la variance génétique se trouve<br />
entre les populations.<br />
L’analyse en composantes principales (ACP), effectuée<br />
sur les fréquences alléliques pour tous les loci au niveau<br />
de l’ensemble des populations, a montré que les trois premières<br />
composantes absorbant 72,33 % de l’inertie totale<br />
(tableau 6). L’axe 1 (27,65 % de la variation) est défini<br />
par les locus Pgi-1 et Pgi-2. L’axe 2 (24,47 % de la variation)<br />
est corrélé aux loci Adh-1, Pgm-1, Pgm-2 et Pgi-8.<br />
L’axe 3 (20,20 % de la variation) est défini par les loci Icd-<br />
2, Icd-3 Mdh-1, Mdh-2 et Mdh-3. La projection des populations,<br />
sur le plan défini par les axes 1 et 2, révèle une<br />
forte structuration des populations selon l’axe 1 (figure<br />
2A). Le regroupement des populations selon leur proximité<br />
géographique ou leur appartenance à un même étage<br />
bioclimatique n’est observée que pour un nombre limité<br />
d’entre elles. La projection des populations selon le plan<br />
défini par les composantes 1 et 3 montre une structuration<br />
des populations globalement similaire à celle obtenue<br />
précédemment selon les axes 1-2, avec toutefois un regrou-<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 23-37<br />
pement préférentiel de quatre populations (7, 11, 4, 9) de<br />
l’aride supérieur du côté négatif de l’axe 2 (figure 2B).<br />
Les indices d’identité génétique de Nei (1978) (I) entre<br />
les populations varient de 0,917 (populations 1 et 11) à<br />
1,000 (populations 1 et 12) (tableau 7). Toutefois, il n’y<br />
a pas de corrélation évidente entre ces valeurs, la proximité<br />
géographique des populations (cas des populations<br />
1-12, 8-9) ou l’étage bioclimatique (populations 1, 7 et<br />
11 par exemple). Le dendrogramme (figure 3) établi à<br />
partir de ces indices fait ressortir, à I = 0,940, deux grands<br />
groupes de populations :<br />
— le premier agrégat réunit des populations d’origines<br />
géographique et bioclimatique variables. Il peut être subdivisé<br />
(à I = 0,970) en deux sous-ensembles, comprenant<br />
respectivement quatre (1,12, 6 et 8) et trois (2, 3 et 5)<br />
populations (figure 3). Les populations du premier sousensemble<br />
se développent dans des sites très perturbés<br />
(terres de culture, oueds) et n’appartiennent pas au même<br />
étage bioclimatique. Celles du second sous-ensemble, géographiquement<br />
proches, appartiennent toutes à l’étage<br />
aride inférieur.<br />
— le second groupe est formé de 5 populations rassemblées<br />
en deux sous-groupes. Le premier est constitué<br />
de trois populations (4, 7 et 10) dont deux appartiennent<br />
à l’étage aride inférieur tandis que le second est formé de<br />
deux populations de l’aride supérieur (9 et 11).<br />
Au sein de chaque agrégation (premier ou second agrégat),<br />
l’éloignement géographique des populations ne<br />
semble pas jouer un rôle prédominant dans le regroupement<br />
des populations.<br />
33
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◆ ZAOULI YOSR, BEN FADHEL NAJEH, BOUSSAID MOHA<strong>MED</strong><br />
DISCUSSION<br />
L’analyse du polymorphisme isoenzymatique chez<br />
l’Argyrolobium uniflorum, espèce cléistogame, a révélé une<br />
diversité génétique intrapopulation importante. Le nombre<br />
moyen d’allèles par locus polymorphe (Ap = 1,625), le<br />
pourcentage de loci polymorphes (P = 57,64) et les taux<br />
d’hétérozygotie observée (H o = 0,103) et attendue (He =<br />
0,207) sous l’équilibre de Hardy-Weinberg sont plus élevés<br />
que ceux rapportés classiquement chez des taxons<br />
autogames voire cléistogames (Ap = 1,31 ; P = 20 % ;<br />
H e = 0,074 ; Ho = 0,159) (Hamrick & Godt, 1989 ;<br />
Matolweni et al., 2000 ; Linert et al., 2002). L’importante<br />
diversité intrapopulation indiquerait que la dégradation<br />
des sites n’a pas encore diminué la variabilité de l’espèce.<br />
Cette forte variation résulterait à la fois du niveau élevé<br />
de la diversité des populations ancestrales et de migration<br />
de graines (pouvant être faible mais continue au cours du<br />
temps) à partir de populations adjacentes. Aucune de ces<br />
hypothèses ne peut être rejetée pour le moment. Un marquage<br />
moléculaire (par des microsatellites, par exemple)<br />
de populations de petite taille (source et puits) (Wright,<br />
1978 ; Pernès, 1984), des mesures des flux potentiel et<br />
efficace des graines entre elles, et un suivi de la prolifération<br />
de la descendance au cours du temps devraient être<br />
réalisés pour tester ces hypothèses. Une grande variabilité<br />
génétique intrapopulation a été rapportée chez des<br />
espèces autogames, voire cléistogames, se développant sur<br />
des sites perturbés (Lewis & Crawford, 1995 ; Mc Donald<br />
& Hamrick, 1996 ; Evans et al., 2000 ; Linert et al., 2002).<br />
Figure 3. Dendrogramme établi à partir des indices<br />
d'identité génétique de Nei (1978) pour l'ensemble<br />
des populations analysées.<br />
Figure 3. Dendrogram based on Nei's (1978)<br />
unbiased genetic identities for all populations.<br />
* Populations<br />
** Étages bioclimatiques<br />
AI : aride inférieur,<br />
AS : aride supérieur<br />
Les populations d’Argyrolobium uniflorum se reproduisent<br />
sous un régime non panmictique (H o < H e). Le<br />
F IS moyen au sein des populations est élevé. Pour la majorité<br />
des loci polymorphes détectés (9/12), les valeurs des<br />
indices de fixation F de Wright sont égales à 1,000, indiquant<br />
une déviation totale par rapport à l’équilibre de<br />
Hardy-Weinberg par absence d’hétérozygotes (tableau 4).<br />
Le test χ 2 appliqué à ces indices révèle des différences<br />
hautement significatives (P < 0,001) par rapport à l’équilibre<br />
panmictique. Seuls trois loci Adh-1 (populations 1,<br />
6 et 8), Pgi-3 (pour toutes les populations) et Pgi-8 (populations<br />
3 et 6) ont montré une présence et un excès en<br />
hétérozygotes.<br />
Le niveau élevé d’homozygotie observé ne peut résulter<br />
d’un biais d’échantillonnage parce qu’il est révélé chez<br />
toutes les populations, en dépit de leur éloignement géographique<br />
et que notre analyse, pour une population donnée,<br />
a porté sur des individus collectés loin les uns des<br />
autres et dans une grande aire (> 3 ha). Il est dû au mode<br />
de reproduction cléistogame de l’espèce puisque le F ST<br />
calculé pour l’ensemble des populations subdivisées en<br />
six sous-groupes est faible (0,073). Nos résultats rappellent<br />
ceux observés par Tarayre et Thompsom (1997) chez<br />
Thymus vulgaris L. (espèce gynodioïque). La faible différenciation<br />
entre les subdivisions et la forte consanguinité<br />
des populations résulteraient du régime de reproduction<br />
de l’espèce.<br />
L’existence d’hétérozygotie chez Argyrolobium uniflorum,<br />
pour certains loci (3/12), peut trouver son origine<br />
suite à des mutations ayant affecté certains loci. L’excès<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
DIVERSITÉ GÉNÉTIQUE DES POPULATIONS NATURELLES DE L’ARGYROLOBIUM UNIFLORUM JAUB. ET SPACH… ◆<br />
d’hétérozygotes observé pour les loci Adh-1, Pgi-3 et Pgi-<br />
8 pourrait correspondre à un équilibre sélectif pour promouvoir<br />
certains loci afin de maintenir une hétérozygotie<br />
adaptative à certaines pressions du milieu (surpâturage,<br />
par exemple) (Falk & Holsinger, 1991).<br />
La cléistogamie de l’Argyrolobium uniflorum assure non<br />
seulement le maintien de la stabilité de la structure génétique<br />
des populations, mais permet aussi la pérennité des<br />
populations par la production des graines en dépit des<br />
conditions défavorables du milieu aride (irrégularité des<br />
facteurs physiques, rareté des pollinisateurs, etc.).<br />
Toutefois, l’homozygotie contribue à diminuer l’aptitude<br />
de résistance des individus aux variations du milieu et<br />
augmenterait le risque d’extinction des populations<br />
(Ellstrand & Elam, 1993 ;Young et al., 1996). Le maintien<br />
d’un niveau suffisant de variabilité génétique à l’intérieur<br />
des populations serait donc tributaire de l’ampleur<br />
du flux migratoire des graines et de la survie de leur descendance.<br />
Il est important de signaler qu’en milieu aride<br />
très perturbé de nombreux facteurs, dont le défrichement<br />
des parcours par des labours profonds, le surpâturage et<br />
les fortes érosions éolienne et hydrique, favorisent la dispersion<br />
des graines. Ces facteurs sont paradoxalement<br />
néfastes pour le milieu physique et l’installation des populations.<br />
Une différenciation substantielle entre les populations<br />
(F ST = 0,163) et une faible structuration régionale (F ST =<br />
0,073) sont observées. La différenciation des populations<br />
résulterait donc de la cléistogamie de l’espèce. La destruction<br />
continuelle des habitats contribue à réduire les<br />
flux géniques entre les populations. Saunders et al. (1999),<br />
Evans et al. (2000), Matolweni et al. (2000), Linert et al.<br />
(2002) ont rapporté des résultats similaires chez des<br />
espèces cléistogames ou autogames dont les populations<br />
ont été perturbées par les pressions anthropiques. L’analyse<br />
en composantes principales illustre bien la différenciation<br />
des populations. Celles-ci, selon les deux types de<br />
représentation (axes 1-2 ou axes 1-3), sont fortement dispersées<br />
sur les plans définis par les trois premiers axes de<br />
l’ACP. Leur regroupement selon la proximité géographique<br />
ou l’étage bioclimatique ne s’est opéré que pour<br />
un nombre limité d’entre elles.<br />
Une grande similarité génétique entre les populations<br />
d’Argyrolobium uniflorum est observée. Les indices d’identité<br />
génétique de Nei (I) sont très élevés et la plus faible<br />
valeur de I est de 0,915 entre les populations 9 (Houareb<br />
2) et 10 (Sbeitla) distantes de 70 km. Ceci indique une<br />
grande similarité génétique entre les populations tunisiennes<br />
d’Argyrolobium uniflorum. La variation des valeurs<br />
de I n’est pas toujours corrélée à la proximité géogra-<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 23-37<br />
phique des populations (cas des populations 3 et 7 ; 8 et<br />
9). Ceci veut dire que ce critère ne doit pas toujours être<br />
considéré comme un bon prédicateur de la diversité génétique<br />
interpopulations (Godt & Hamrick, 1993 ;<br />
Mc Donald & Hamrick, 1996). Des faibles divergences<br />
génétiques, entre populations d’espèces cléistogames ou<br />
autogames, à habitats peu ou pas perturbés, sont rarement<br />
rapportées dans la littérature. En effet, ces caractéristiques<br />
semblent plutôt caractériser des espèces allogames<br />
(Bartlett et al., 2002).<br />
Le dendrogramme, établi à partir des indices d’identité<br />
génétique de Nei, a montré que le regroupement des<br />
populations s’opère avec des indices élevés (I comprise<br />
entre 0,930 et 1,000). Il peut être subdivisé à I = 0,940<br />
en deux sous-ensembles, sans corrélation franche entre le<br />
regroupement des populations, l’étage bioclimatique et la<br />
proximité géographique. En effet, l’agrégation des populations<br />
selon ces deux facteurs n’a été réalisé que pour un<br />
nombre limité d’entre elles.<br />
CONCLUSION<br />
L’analyse de la diversité génétique chez Argyrolobium<br />
uniflorum a montré que le polymorphisme intrapopulation<br />
est élevé et que certaines populations possèdent des<br />
allèles rares. Les populations sont fortement différenciées<br />
et présentent de faibles divergences génétiques entre elles.<br />
La forte structuration des populations et le niveau élevé<br />
de leur similarité génétique témoigneraient d’une fragmentation<br />
récente des populations sous l’influence des<br />
pressions anthropiques (surpâturage et défrichement).<br />
Ces facteurs, en milieu aride, jouent des rôles antagonistes<br />
mais importants dans la dynamique des populations. Le<br />
défrichement et le surpâturage détruisent le milieu et isolent<br />
progressivement les populations. Toutefois, la détérioration<br />
des habitats favorise l’action du vent et des eaux<br />
de ruissellement qui dispersent les graines. La migration<br />
des graines contribuerait à élever le niveau du polymorphisme<br />
intrapopulation.<br />
Les programmes de conservation de l’espèce ne peuvent<br />
s’appuyer uniquement sur l’analyse du polymorphisme<br />
isoenzymatique qui peut masquer d’autres variations<br />
pouvant être liées à des adaptations spécifiques à<br />
certaines conditions du milieu (physiologiques, morphologique<br />
et autres). Une estimation du polymorphisme<br />
moléculaire (AFLP, microsatellites, etc.) et une analyse<br />
plus précise de la dynamique des populations (distances<br />
de dispersion de semences, estimation de la taille effec-<br />
35
36<br />
◆ ZAOULI YOSR, BEN FADHEL NAJEH, BOUSSAID MOHA<strong>MED</strong><br />
tive des populations…) permettraient d’affiner notre<br />
étude.Toutefois, notre travail sur le polymorphisme enzymatique<br />
de l’Argyrolobium uniflorum constitue déjà un<br />
point de départ en vue de la conservation de l’espèce. Une<br />
priorité doit être accordée à la préservation des populations<br />
ayant présenté un niveau élevé de polymorphisme<br />
et des allèles rares. La conservation, ex-situ, doit s’appuyer<br />
sur la collecte d’un maximum d’individus à l’intérieur<br />
des populations et non entre les populations.<br />
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37
Browsing and nutritive value of the most common range species<br />
in Matruh area, a coastal <strong>Mediterranea</strong>n region, Egypt<br />
Broutage et valeur nutritive des espèces<br />
de parcours les plus communes dans la région de Matruh,<br />
une zone côtière méditerranéenne en Égypte<br />
S. Z. Heneidy<br />
Botany Department, Faculty of Science, University of Alexandria, Egypt.<br />
Abstract<br />
The grazing system in Matruh area is studied during the wet and<br />
dry seasons during two years. The study reveals that the area is occupied<br />
with 39 perennial and 43 annual species, Chamaephytes are<br />
the most dominant life-forms. The area (which include 32 sampling<br />
sites) composed of 5 different habitats. About 38 % of the<br />
studied sites are suffering from high grazing pressure. In addition<br />
66% of the habitats are found to be good pastures. Moreover, based<br />
on abundance and palatability, 5 to 7 species are considered as<br />
indicator (key) species in each site. Atriplex halimus and<br />
Asphodelus ramosus are the most common ones. Further about<br />
51 % of the perennial species are highly palatable.<br />
Grazing value was high for 69 and 49 % for the perennials and<br />
annuals species respectively. Therefore, the pasture condition and<br />
the quality in the studied area can be considered good. The average<br />
level of the digestible crude protein (DCP, 5.7 %), total digestible<br />
nutrients (TDN, 67 %), gross energy (GE, 3,976 kcal<br />
kg -1DM), digestible energy (DE, 3,274 kcal kg -1DM), and metabolizable<br />
energy (ME, 2,824 kcal kg -1DM), indicates that the present<br />
pasture is able to meet the feed demands of the grazing animals<br />
and these animals receive most of their energy requirements.<br />
The energy content is however equivalent 0.84 of the Scandinavian<br />
feed unit.<br />
Key-words<br />
Nutritive value, indicator species, pasture condition, Matruh area,<br />
Egypt.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 39-49<br />
Résumé<br />
Le système de pâturage a été étudié durant les périodes humides et<br />
sèches, pendant deux années, dans la zone de Matruh, en Égypte.<br />
Notre travail montre que cette zone est occupée par trente-neuf<br />
espèces pérennes et quarante-trois annuelles. Les chaméphytes sont<br />
les types biologiques dominants. La zone (qui comprend trente-deux<br />
sites d’échantillonnage) est composée de cinq habitats différents.<br />
38 % du site d’étude souffrent de surpâturage, mais 66 % des habitats<br />
peuvent être considérés comme de bonnes pâtures, 51 % des<br />
espèces pérennes sont fortement consommables. À partir de leur<br />
abondance et de leur appétence, 5 à 7 espèces ont été considérées<br />
comme espèces indicatrices (espèces clés) pour chaque site. Atriplex<br />
halimus et Asphodelus ramosus en sont les plus communes.<br />
La valeur nutritive pour le pâturage est forte, avec respectivement<br />
69 % et 49 % pour les espèces pérennes et les annuelles. Par conséquent,<br />
les conditions de pâturage et la qualité alimentaire de la<br />
zone étudiée peuvent être considérées comme bonnes. Le niveau<br />
moyen de digestibilité des matières azotées totales (DCP, 5.7 %),<br />
des cendres solubles (TDN, 67 %), de l’énergie totale (GE,<br />
3.976 Kcal kg -1 DM), de l’énergie digestible (DE 3.274 Kcal<br />
kg -1DM) et de l’énergie métabolisable (ME, 2.824 Kcal kg -1 DM),<br />
indique que l’état actuel des pâtures est capable de satisfaire la<br />
demande alimentaire des animaux au pâturage et que ces animaux<br />
reçoivent la plupart de leurs besoins énergétiques. La teneur en énergie<br />
est cependant équivalente à 0.84 de l’unité scandinave d’alimentation.<br />
Mots-clés<br />
Valeur nutritive, espèces indicatrices, conditions de pâturage, région<br />
de Matruh, Égypte.<br />
39
40<br />
◆ S. Z. HENEIDY<br />
INTRODUCTION<br />
The coastal <strong>Mediterranea</strong>n region, particularly the arid<br />
and semi-arid parts of Africa, has a long history of intensive<br />
land-use, mainly for grazing and rainfed farming.<br />
According to Duivenbooden (1985), rangeland, the major<br />
feed resources, occupies an estimated 90 % of the total<br />
area of such coastal zone. In this zone many areas are<br />
dominated by shrubs and sub-shrubs.The annuals occur<br />
only in a limited extent because of weather conditions and<br />
the increased animal density. According to Le Houérou<br />
(1980a), about 1.5 million heads of animals are normally<br />
present, and rangeland vegetation is insufficient throughout<br />
the year and therefore supplementary feed is a must.<br />
Subsequently sustainable development and improvement<br />
of the grazing system (including biomass, and nutritive<br />
values) are very important for continuity, particularly in<br />
the present <strong>Mediterranea</strong>n coastal area (e.g. Matruh).<br />
The present study is initiated to collect information<br />
about pasture in Matruh area which is one of the most<br />
richest area for grazing in the Egyptian coastal region. It<br />
is worthy to mention that in Egypt there are about 2.5<br />
million hectares of arid rangelands of the chamaephytic<br />
steppe type (Le Houérou, 1980a), 50 % of this area occured<br />
in its North west of the coastal region on the<br />
<strong>Mediterranea</strong>n sea.<br />
The objectives of this study are: (1) identification of<br />
range species and their life-forms, (2) estimation of the<br />
physical grazing characters of the rangeland species and<br />
assessment to their grazing value, and palatability (3)<br />
determination of the nutritive value of the plants in a purpose<br />
to evaluate the quality and quantity of the forage,<br />
and (4) focusing or throwing light on the role of the<br />
browse species in the grazing system (these species which<br />
are most effective in the range system, called key species).<br />
Key management species are however those on which the<br />
grazing management of a specific range is based.<br />
THE STUDY AREA<br />
The studied area is located about 200 km west of<br />
Alexandria. Its area extends to about 30 km southwords<br />
in the inland plateau and transversally to about 10 km<br />
from west to east parallel to the sea shore. It lies between<br />
the following longitudes and latitudes (30 o 30 - – 31 o 10 -N,<br />
27 o 30 - – 28 oE). The area includes different physiographic<br />
units leading to variety of habitats. Geomorphologically,<br />
it is a part of the Egyptian western desert and it<br />
is a plateau with numerous large and deep topographic<br />
depressions. Its soil is young, and essentially alluvial<br />
(Kamal, 1988).They are derived from two main sources<br />
(a)- the table land (inland plateau) composed essentially<br />
of limestone alternating with strata and shale; and (b)beach<br />
deposits composed of calcareous oolitic grains.The<br />
dominating land use is grazing by domestic animals.<br />
Climatologically, this area is classified as arid with mild<br />
winters and warm summers (UNESCO, 1977).<br />
METHODS<br />
The present study was carried out during the two climatic<br />
conditions (during two successive years) characterizing<br />
this area of the <strong>Mediterranea</strong>n region, the wet season<br />
(winter and spring) and dry season (summer and<br />
autumn).The study area was classified into five habitats:<br />
rocky plateau, flat plateau, rocky ridge, non-saline depression,<br />
and saline depression. At the beginning of the study<br />
several flocks of grazing animals (sheep, goats and camels)<br />
were observed several times in the studied sites (32 sites),<br />
to explore which species is preferred following the<br />
methods applied by Abdel-Razik et al. (1988a, b), Genin<br />
and Badan-Dangon (1989) and Heneidy (1992, 1996).<br />
The grazing pressure was assessed by determination of<br />
the stocking rate in each site, and according to the status<br />
and abundance of the vegetation (palatable species and<br />
its rate of consumption). These parameter were taken to<br />
estimate the grazing pressure and the pasture condition<br />
(El-Kady, 1983; Heneidy & Bidak, 1998). Floristic identification<br />
are according to Täckholm (1974) and the Latin<br />
names of species were updated following Boulos (1995).<br />
Pasture condition based on the distribution and the<br />
valuable of rangeland species were recorded in each site.<br />
Selection of the indicator (key) species<br />
The key-plant and key-area concepts have proven<br />
highly useful to managers in evaluating grazing effects on<br />
range vegetation (Holechek, 1988). A key species is one<br />
whose use indicates the degree of use of associated species<br />
and is important in the management program for<br />
study. The key species in the study area can withstand<br />
relative higher utilization level during the dry period.They<br />
also provide the bulk of the forage for the grazing animals<br />
within the pasture. They are abundant, productive, and<br />
palatable. In the present study the key species have been<br />
considered palatable for all types of livestock, and are<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
considered as a leading dominant species among the perenials.<br />
However, in each habitat, the key species (indicator<br />
species) are selected according to their abundance<br />
(cover and biomass) and palatability beside the above characters.<br />
In each site from five to seven species are recorded<br />
as key species (ranges from six to twenty species in<br />
the saline depression and in the flat plateau habitats respectively).<br />
Key management species are those on which<br />
the grazing management of a specific range is based.These<br />
species are ligneous plants and are considered as a<br />
constant biological resource, i.e. they are the main feeding<br />
source throughout the year (Holechek, 1988). The<br />
key species are also serve as indicators of management<br />
effectiveness. Generally, when the key species are considered<br />
properly used, the entire pasture is considered correctly<br />
used.<br />
Chemical analysis<br />
BROWSING AND NUTRITIVE VALUE OF THE MOST COMMON RANGE SPECIES IN COASTAL EGYPT ◆<br />
Chemical analysis were carried out on the samples collected<br />
during the wet season (the growing season) at the<br />
time of maximum consumption.These samples are eaten<br />
parts (grazeable parts) of each indicator species in each<br />
site. Before analysis the samples were cleaned and dried<br />
(carefully rinsed several times with tap and distilled water,<br />
then air dried and oven dried at 70 oC to constant weight).<br />
The analyses were to performed determine the following<br />
parameters: (a) total carbohydrates (nitrogen free extract,<br />
(NFE) according to Murata et al. (1968); (b) Crude protein<br />
CP; (c) ether extract (EE) and ash content according<br />
to Allen et al. (1974); (d) Crude fiber (CF) using the formula<br />
[CF = 100 – (CP + EE + NFE + ash)] after Le<br />
Houérou (1980b); (e) Digestible crude protein (DCP)<br />
using Demarquilly’s equations DCP = 0.93 CP – 3.52<br />
after De Ridder et. al. (1982).This equation is only valid<br />
in the case of nitrogen concentration among 3 to 0.61%<br />
(or CP > 3.81 %).TDN was calculated according to Abu-<br />
El-Naga and El Shazly (1971); (f) Energy contained in<br />
food (gross energy, or energy intake, GE) was determined<br />
according to Petrusewicz (1976); (g) The diet gross<br />
energy was calculated from its chemical analysis components<br />
multiplied by their average of heat of combustion<br />
(Lofgreen, 1951); (h) Digestible and metabolizable energy<br />
(DE and ME) were calculated according to Crampton<br />
and Harris (1969).<br />
Direct observation of animal behaviour, such as counting<br />
the number of bites from each plant species is a practical<br />
way of collecting dietary data in open pastures<br />
(Abdel-Razik et al., 1988a; Heneidy, 1992). In the present<br />
study numerous factors were considered when clas-<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 39-49<br />
sifying a plant as palatable or not. Phenological stage, morphological<br />
form, odour, taste, chemical composition and<br />
its abundance were the main factors taken as the major<br />
effective parameters on the dietary data. However, through<br />
the long and continuous field observations, the degree of<br />
preference and the consumption rate were assessed. After<br />
getting the results of the above mentioned parameters<br />
palatability can be assessed (Heneidy, 1992, 1996;<br />
Heneidy & Bidak, 1996).<br />
RESULTS<br />
Palatability and pasture condition<br />
Eighty-two species were investigated in the study area<br />
(39 perennial and 43 annual species). Families, life-forms,<br />
palatability rate, grazing value, consumed parts, and types<br />
of livestock are represented in table 1. The most abundant<br />
life-forms of the species under study are chamaephytes.<br />
About 51 % of the perennial species are highly<br />
palatable, 38 % are palatable and about 10 % has shown<br />
low palatable. For annual species about thirty are highly<br />
palatable, 44 % palatable, 16 % are low palatability, and<br />
9% are unpalatable species for livestock.The grazing value<br />
is mostly dependent upon the high percentage of crude<br />
protein, mineral nutrients and low concentration of crude<br />
fibers. About 51 % of the perennial species have very high<br />
grazing value, 31 % attained high grazing value, and 18%<br />
have low grazing value. For annuals about 49 % attained<br />
high grazing value (5 % very highly grazing value), while<br />
the rest 51 % attained low grazing value.<br />
Table 2 shows the perennial indicator species, their<br />
habitats and their frequency in each site of the study area.<br />
The woody species Atriplex halimus is the most frequent<br />
indicator species (found in 59 % of the sites) in the study<br />
area. It is followed by Asphodelus ramosus and Salsola<br />
tetrandra in 56 and 50 % of the total sites respectively.<br />
Table 3 shows pasture condition (good, fair and poor),<br />
grazing pressure and local rainfall in different sites. About<br />
59 % of all sites are generally good pasture, depending<br />
upon the type of vegetation, (vegetation composition), the<br />
dry matter production, and the contribution of the palatable<br />
species. In the mean time twenty-two percent of the<br />
total sites are fair in pasture condition while 19 % are poor<br />
pastures. Generally, on habitat level, about 38 % of all<br />
habitats are suffering from highly grazing pressure while,<br />
34 % and 28 % are under moderate and low grazing pressure<br />
respectively. Fifty-nine percent of habitats are good<br />
41
42<br />
◆ S. Z. HENEIDY<br />
Species Family Life-form Palata-Bility Grazing Stock Consumed<br />
value type part<br />
Perennials<br />
Anabasis articulata (Forssk.) Moq Chenopodiaceae Ch. P VH CSG Yb, F<br />
Anabasis oropediorum Maire Chenopodiaceae Ch. VHP VH CSG Yb, F<br />
Artemisia herba-alba Asso. Compositae Ch. VHP VH SGC Yb, F<br />
Argyrolobium uniflorum (Decne.) Jaub & Spach Leguminosae Ch. VHP VH SGC Yb<br />
Asphodelus ramosus L. Liliaceae G. HP VH GS Yl,Dl,I<br />
Astragalus sieberi DC Leguminosae Ch. HP VH CGS Yb. Fl<br />
Astragalus spinosus (Forssk.) Muschl Leguminosae Ch. VHP VH CGS Yb, Fl<br />
Atriplex halimus L. Chenopodiaceae Ch/Ph HP H CSG Yb. L<br />
Carthamus lanatus L. Compositae Ch. P H CGS I,L<br />
Centaurea alexandrina Descr & Delile Compositae Ch. LP L1 CGS I<br />
Deverra tortuosa (Desf.) DC., Prodr Caryophyllaceae Ch. VHP L1 SGC Yb<br />
Echiochilon fruticosum Desf. Boraginaceae Ch. VHP VH SGC Yb, L<br />
Echinops spinosissimus Turra. Compositae Ch. P H CGS I,Yb<br />
Gymnocarpos decandrum Frossk. Caryophyllaceae Ch. VHP H SGC Yb, L<br />
Haloxylon scoparia Pomel Noum. Chenopodiaceae Ch. P VH CSG Yb, L<br />
Helianthemum kahiricum Del. Cistaceae Ch. HP VH SG Yb. L<br />
Helianthemum lippii (L.) Pres. Cistaceae Ch. VHP VH SG Yb, L<br />
Kickxia aegyptica Dumart. Scrophulariaceae Ch. P H CGS Yb, L<br />
Launaea nudicaulis (L.) Hook. Compositae Hc VHP VH SG Ab.Gr<br />
Lygeum spartum Loefl. Ex. L. Gramineae Hc P H SG Ab.Gr<br />
Lycium shawii Roem & Schult. Solanaceae Ch. HP VH SGC Yb, L<br />
Noaea mucronata (Frossk.) Asch.&Schwei. Chenopodiaceae Ch. HP VH CSG Yb, L<br />
Periploca angustifolia Labill. Asclepiadaceae Ch. VHP VH SGC Yb, L<br />
Plantago albicans L. Plantaginaceae Hc. VHP L1 SG Ab.Gr<br />
Polygonum equisetiforme Sm. Polygonaceae Ch. P H SG Ab. Gr<br />
Salvia aegyptiaca L. Labiatae Ch. P VH SG Yb, L<br />
Salvia lanigera L. Labiatae Ch. P VH SG Yb, L<br />
Salsola tetrandra Forssk. Chenopodiaceae Ch. P VH CGS Yb<br />
Salsola tetragona Del. Chenopodiaceae Ch. VHP VH SGC Br, L<br />
Salsola vermiculata Poir Chenopodiaceae Ch. P H CGS Yb, L<br />
Scorzonera undulata Vahl. Compositae G. VHP VH SG Ab. Gr<br />
Stipa parviflora Desf. Gramineae Hc. VHP VH SG Ab, Gr<br />
Suaeda pruinosa Lange. Chenopodiaceae Ch. P H CGS Yb, L<br />
Suaeda vermiculata Forssk. Ex. J. F. Gmel Chenopodiaceae Ch. P H CGS Yb, L<br />
Suaeda volkensii C.B.Clarke Chenopodiaceae Ch. P H CGS Yb<br />
Teucrium polium L. Labiatae Ch. LP L1 GS Yb, Fl<br />
Thymelaea hirsuta (L.) End. Thymelaeaceae Ch. P L1 GS Yb, Dbr<br />
Verbascum letourneuxii Asch.&Schwei. Scrophulariaceae Ch. LP L1 GSC Yb, L<br />
Zilla spinosa (Turra) Prantl. Cruciferae Ch. LP L1 CG Yb, L<br />
Annuals<br />
Adonis dentata Delile Compositae Th. LP L1 SG Fl.<br />
Aegilops bicornis (Forssk.) Jaub& Spach. Gramineae Th. VHP H SG +<br />
Aizoon canariense L. Aizoaceae Th. NP L1 -- --<br />
Anacyclus alexandrinus Willd. Compositae Th. P H GCS Fl.<br />
Anchusa aegyptiaca (L.) ADC. Boraginaceae Th. P H SG +<br />
Anthemis microsperma Boiss & Kotschy Compositae Th. P H SG Fl.<br />
Beta vulgaris L. Chenopodiaceae Th. P H GS +<br />
Brassica tournefortii Gouan. Cruciferae Th. P L1 CG +<br />
Bromus rubens L. Gramineae Th. HP H SG +<br />
Bupleurum semicompositum L. Umbelliferae Th. P L1 SG +<br />
Calendula arvensis L. Compositae Th. P L1 GS Fl.<br />
Carrichtera annua (L.) DC Cruciferae Th. P L1 SG +<br />
Centaurea glomerata Vahl. Compositae Th. P L1 SG +<br />
Chenopodium murale L. Chenopodiaceae Th. NP L1 -- --<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
BROWSING AND NUTRITIVE VALUE OF THE MOST COMMON RANGE SPECIES IN COASTAL EGYPT ◆<br />
Chrysanthemum coronarium L. Compositae Th. NP L1 -- --<br />
Cutandia dichotoma (Forssk.) Trab. Gramineae Th. VHP H SG +<br />
Didesmus aegyptius (L.) Desv. Cruciferae Th. LP L1 SG +<br />
Filago desertorum Pomel. Compositae Th. P L1 SG +<br />
Herniaria hirsuta L. Caryophyllaceae Th. LP L1 SG +<br />
Hippocrepis areolata Desv. Leguminosae Th. HP H SG +<br />
Hordeum leporinum (Link.) Arcong. Gramineae Th. HP H SGC +<br />
Ifloga spicata (Forssk.) Sch. Compositae Th. P L1 GS +<br />
Lobularia arabica (Boiss) Musch. Cruciferae Th. P H SG +<br />
Malva parviflora L. Malvaceae Th. P L1 SG +<br />
Matthiola livida (Delile) Maire Cruciferae Th. P L1 SG +<br />
Medicago laciniata (L.) Mill. Leguminosae Th. HP H SG +<br />
Medicago truncatula Gaertm. Leguminosae Th. HP H SG +<br />
Onobrychis crysta-galli (L.) Lam. Leguminosae Th. HP H SG +<br />
Ononis serrata Forssk. Leguminosae Th. LP H SG +<br />
Paronychia arabica (L.) DC. Caryophyllaceae Th. LP L1 GS +<br />
Phalaris minor Retz. Gramineae Th. HP H SG +<br />
Picris radicata (Frossk.) Less. Compositae Th. P L1 GS Fl.<br />
Plantago crypsoides Boiss. Plantaginaceae Th. HP H SG +<br />
Plantago ovata Frossk. Plantaginaceae Th. P H SG +<br />
Pseudorlaya pumila (L.) Grande Umbelliferae Th. P L1 SG +<br />
Reichardia tingitana (L.) Roth. Compositae Th. P L1 SG I<br />
Scabiosa rhizantha Viv. Dipsacaceae Th. LP L1 SG +<br />
Schismus barbatus (L.) Thell. Gramineae Th. HP H SG +<br />
Silene villosa Forssk. Caryophyllaceae Th. NP L1 -- --<br />
Spergularia marina (L.) Griseb. Caryophyllaceae Th. LP L1 SGC +<br />
Trifolium resupin atum L. Leguminosae Th. VHP VH SGC +<br />
Trigonella stellata Forssk. Leguminosae Th. VHP VH SGC +<br />
Valantia hispida L. Rubiaceae Th. LP H SG --<br />
Ch. = Chamaephytes, G. = Geophytes, Hc. = Hemicryptophytes, Ph. = Phanerophytes, Th. = Therophytes, VHP. = Very highly palatable, Hp. = Highly palatable,<br />
P. = Palatable, L.P = Low palatability, NP. = Unpalatable, VH.= Very high, H.= High, L1. = Low, S = Sheep, G. = Goats, C.= Camels, and + = Whole<br />
plant (annual species),Yb, = Young branch, Fl. = Flowers (without peduncle), L.= Leaves, Br.= Branch, I. = Inflorescence, Dl = Dead leaves, D br. = Dead<br />
branch, Ab. Gr. = Above-ground. (perennial herb species).<br />
Table 1. List of plant species, families, life-forms, palatability, grazing value, stock type, and consumed part in Matruh area.<br />
pastures while, 22 and 19 % may be considered to have<br />
fair and poor pasture condition respectively. The maximum<br />
rainfall is attained in site number 16 (173.3 mm),<br />
while the minimum rainfall is attained in site number 26<br />
(6.4 mm). On the other hand, the maximum average rainfall<br />
is observed in saline depression 107.3 ± 9.2 mm, followed<br />
by 77.8 ± 13.7 mm in the rocky plateau habitat<br />
(local meterological stations). Amount of rainfall is the<br />
most effective factors on the plant composition and the<br />
pasture condition, especially in the desert ecosystem where<br />
the growth of plant species is completely dependant of<br />
the amount and distribution of rainfall.<br />
Chemical analysis and nutritive value<br />
The individual indicator species in all sites were difficult<br />
to organize for chemical analysis so that all individuals<br />
at each habitat were pooled together in a compo-<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 39-49<br />
site sample (different individuals of the same species) for<br />
chemical analysis as a habitat indicator species. Results of<br />
the chemical composition of the indicator species (grazeable<br />
parts) of each habitats (means and standard errors)<br />
during the season of maximum consumption are shown<br />
in table 4. Obviously the numbers of indicators species<br />
differs from one habitat to another.The table shows that<br />
the values of NFE ranges from a maximum of 34.1 ±<br />
3.9 % in the flat plateau to a minimum of 30.9 ± 4.7% in<br />
the non-saline depression. Also, the indicator species of<br />
the flat plateau attained the maximum ash content (14.2<br />
± 8.2 %). In addition the species of the non-saline depression<br />
attained the maximum of CP, CF, DCP, and GE (10.7<br />
± 4.3, 36.9 ± 9.4, 6.4 ± 4.0 % and 4.1 ± 0.23 Mcal kg -1<br />
respectively). Moreover, TDN values are the highest in<br />
the species of saline depression (67.2 ± 2.9 %). However,<br />
there was little variability in the percentages of chemical<br />
43
44<br />
◆ S. Z. HENEIDY<br />
Species Site number which species present Habitat* Total number % (from<br />
of sites all sites)<br />
Anabasis articulata 1,5,19,25 R.Pl.,F.Pl. 4 13<br />
Anabasis oropediorum 2,8,9,14,19,24,30 R.Pl.,F.Pl.,R.R. 7 22<br />
Artemisia herba-alba 3,25,27 R.Pl.,F.Pl. 3 9<br />
Argyrolobium uniflorum 22,31 N.Sal.Dep. 2 6<br />
Asphodelus ramosus 1,2,3,4,5,7,9,13,14,15,16,18,21,22,23,26,29,31 R.Pl.,F.Pl.,R.R.,N.Sal.Dep.,Sal.Dep. 18 56<br />
Atriplex halimus 6,7,8,10,11,12,13,15,16,17,19,20,21,23,26,28,29,30,32 R.Pl.,F.Pl.,R.R.,Sal.Dep. 19 59<br />
Carthamus lanatus 2,3,6,11,13,16,17,20 R.Pl.,F.Pl.,R.R.,N.Sal.Dep.,Sal.Dep. 8 25<br />
Deverra tortuosa 2,3,4,8,10,12,13,14,18,26,30,31,32 R.Pl.,F.Pl.,N.Sal.Dep. 13 41<br />
Echinops spinosissimus 1,2,5,6,9,14,21,23,31 R.Pl.,F.Pl.,R.R.,N.Sal.Dep. 9 28<br />
Gymnocarpos decandrum 2,4,6,7,8,9,14,23,24,25,29,32 R.Pl.,F.Pl.,R.R.,N.Sal.Dep. 12 38<br />
Haloxylon scoparia 1,3,5,6,7,13 R.Pl.,F.Pl.,R.R.,N.Sal.Dep. 6 19<br />
Helianthemum kahiricum 27 F.Pl. 1 3<br />
Helianthemum lippii 7 F.Pl. 1 3<br />
Lycium shawii 4,22,23,28 R.Pl.,F.Pl.N.Sal.Dep. 4 13<br />
Noaea mucronata 5,9,10,12,16,18,26 R.Pl.,F.Pl.,R.R. 7 22<br />
Periploca angustifolia 20,25,32 R.Pl.,R.R. 3 9<br />
Salvia aegyptiaca 6,11,12,22 F.Pl.,N.Sal.Dep. 4 13<br />
Salsola tetrandra 8,9,10,11,12,15,17,18,19,20, 21,24,25,26,27,30 R.Pl.,F.Pl.,R.R.,N.Sal.Dep.Sal.Dep. 16 50<br />
Salsola tetragona 2,10,11,15,17,21,24,25,26,27,29,30,32 R.Pl.,F.Pl.,Sal.Dep. 13 41<br />
Salsola vermiculata 10,28 F.Pl. 2 6<br />
Stipa parviflora 29 F.Pl. 1 3<br />
Suaeda pruinosa 8,19,20,28 R.Pl.,F.Pl.,R.R. 4 13<br />
Suaeda vermiculata 8 Sal.Dep. 1 3<br />
Thymelaea hirsuta 1,3,4,15,16,18,31 R.Pl.,N.Sal.Dep.,Sal.Dep 7 22<br />
Zilla spinosa 24 R.Pl. 1 3<br />
* R. Pl. = Rocky plateau, F.Pl. = Flat plateau, R. R. = Rocky ridge, N. Sal. Dep. = Non-saline depression, and Sal. Dep. = Saline depression.<br />
composition within different habitats. On the other hand,<br />
chemical analysis may differ from one habitat to another<br />
for the same species. For example A. ramosus (perennial<br />
herb) is common in all habitats, where the NFE content<br />
was high (31.3 %) in the rocky- plateau species, and low<br />
(29.4 %) in the flat plateau.<br />
Averages of digestible (DE) and metabolizable energy<br />
(ME) contents (Mcal kg -1 ) of the indicator species of different<br />
habitats of the study area are shown in table 5.The<br />
highest DE and ME values was attained by the grazeable<br />
parts of Periploca angustifolia (3.84 and 3.32 Mcal kg -1<br />
respectively) in the rocky ridge habitat while, the lowest<br />
contents were attained by Salsola tetragona from the saline<br />
depression and Salvia aegyptiaca in the non- saline depression<br />
habitats.<br />
DISCUSSION<br />
Table 2. Indicator species (perennial), the frequency, habitats and percentage of each species at the sampling sites of study area.<br />
Livestock of the study area is constituted by sheep,<br />
goats and camels, which have different behaviour and pre-<br />
ferences for plant species.Young branches and leaves are<br />
prefered but sometimes dead parts and inflorescences are<br />
also consumed by such livestock (Heneidy, 1992).<br />
Palatability of range plant species is a very complex notion.<br />
Moreover, it is difficult to generalize as it is linked to many<br />
factors that vary in time and space and is relative to what<br />
other alternative are available. Some of these variables are<br />
linked to the plant, others to the animals while a third<br />
category depends on various environmental factors (Le<br />
Houérou, 1980a; Heneidy, 1996; Heneidy & Bidak, 1996).<br />
As a rule, the palatability of a given taxon would<br />
increase with environmental aridity (Le Houérou, 1992).<br />
However, the same species may be palatable in some<br />
places and unpalatable in the others (Le Houérou, 1992;<br />
Heneidy, 1996). Palatable species typically put all their<br />
energy from photosynthesis into growth and reproduction,<br />
while unpalatable species put part of their energy<br />
into compounds that discourage defoliations. So the more<br />
productive and desirable vegetation decreased with an<br />
increase in the less palatable and poisonous plant species<br />
(Taylor & Ralphs, 1992). Most of the species in the study<br />
area are highly palatable (about 87% of perennials and<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
BROWSING AND NUTRITIVE VALUE OF THE MOST COMMON RANGE SPECIES IN COASTAL EGYPT ◆<br />
Site number Pasture condition Grazing pressure Habitat Mean of rainfall (mm)<br />
4 Low Non-saline depression 110<br />
5 Moderate Flat plateau 10<br />
6 Low Flat plateau 20<br />
8 Low Rocky ridge 74<br />
10 Moderate Flat plateau 87<br />
12 High Flat plateau 87<br />
14 Moderate Rocky plateau 102<br />
18 High Non-saline depression 97<br />
21 Low Rocky plateau 66<br />
22 Good Low Non-saline depression 84<br />
23 Moderate Rocky plateau 30<br />
24 Moderate Rocky plateau 55<br />
25 Low Rocky plateau 116<br />
26 Low Flat plateau 6<br />
27 Moderate Flat plateau 51<br />
29 Moderate Flat plateau 28<br />
30 Low Rocky plateau 30<br />
31 Moderate Non-saline depression 17<br />
32 Low Rocky ridge 42<br />
2 Moderate Rocky plateau 31<br />
7 High Flat plateau 62<br />
11 Moderate Flat plateau 78<br />
13 Fair High Rocky ridge 105<br />
15 High Saline depression 120<br />
19 High Flat plateau 162<br />
28 Moderate Flat plateau 28<br />
1 High Rocky plateau 90<br />
3 High Non-saline depression 67<br />
9 Poor High Rocky ridge 80<br />
16 High Rocky plateau 173<br />
17 High Saline depression 84<br />
20 High Rocky plateau 85<br />
Table 3.The pasture condition, [grazing pressure, habitats and average of rainfall (mm)] at the different sites of Matruh area.<br />
74% of annuals), which is consistent with the results recorded<br />
by Heneidy (1992) and Heneidy and Bidak (1998)<br />
in other grazing areas.<br />
The present study area is considered as one of the<br />
richest area for its forage resources and for the livestock<br />
on the coastal region. The most common life-forms are<br />
shrubby species (browse species) which are the skeleton<br />
part of this system.The contribution of the shrubby species<br />
is about 30% of perennial species some of them are<br />
woody, their heights reach to 3m, while about 41% of them<br />
are sub-shrubs (dwarf shrubs). However, the propagation<br />
of woody species in the study area is very important for<br />
improvement the present pasture. Where the fodder<br />
shrubs are essentially a supplementary or emergency feed<br />
(85% of shrubby species are highly palatable) for periods<br />
of grazing shortage that may occur in the dry season and/<br />
or prolonged droughts (Le Houérou, 1989).<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 39-49<br />
The contribution of shrubby species is about 80% of<br />
the total rangeland production in the study area Heneidy<br />
(under publication). Shrubby species also play an important<br />
role in the protection of catchement basins, erosion<br />
control, fuel wood, and the strategy against desertification.<br />
Some of the shrubby species are able to improve the<br />
soil fertility and to increase the crop yield owing to the<br />
organic matter and nutrients, windbreak, to bring to the<br />
topsoil from deep layers of the subsoil and to smooth off<br />
the microclimatic condition (Le Houérou, 1989).<br />
The pasture condition is based on many factors, some<br />
of them are biomass, and accessible parts (actual production)<br />
for the livestock (Heneidy, 2000). On the other<br />
hand, there are factors like palatability, life-forms, performance,<br />
of plant species, nutritive value, topographic<br />
factor and soil type. However, the field observation is one<br />
of the main criteria to justify the status of the pasture.<br />
45
46<br />
◆ S. Z. HENEIDY<br />
According to Le Houérou (1993) the pasture conditions<br />
can be distinguished into three categories (good, fair, and<br />
poor). However, the pasture condition in the study area<br />
is generally good, as 59% of the sites is good pasture and<br />
about 22% is fair.<br />
The grazing value of the plant species is influenced by<br />
many factors. The main factors are chemical composition,<br />
morphology and floristic composition. However, in<br />
the present study, grazing value is mainly based on chemical<br />
composition especially, i.e. where the pasture has<br />
Percentage Mcal kg- 1<br />
Habitat NFE CP CF EE Ash DCP TDN GE<br />
Rocky plateau (18 species) 33.98 ± 4.32 9.6 ± 2.9 32.4± 10.2 8.0 ± 2.7 16.8 ± 8.1 5.4 ± 2.5 67.2 ± 1.9 4.0 ± 0.37<br />
Flat plateau (20 species) 34.1 ± 3.9 10.1± 2.5 30.2± 9.2 7.1 ± 1.9 19.2 ± 8.2 5.9 ± 2.3 66.6 ± 1.5 3.9 ± 0.39<br />
Rocky ridge (12 species) 33.7 ± 5.0 10.4± 2.7 32.2± 4.7 7.1 ± 1.5 16.9 ± 6.2 6.1 ± 2.5 66.7 ± 1.4 3.9 ± 0.32<br />
Non-saline depression (13 species) 30.9 ± 4.7 10.7 ± 4.3 36.9 ± 9.4 6.9 ± 2.5 13.7 ± 5.4 6.4 ± 4.0 66.4 ± 1.9 4.1 ± 0.23<br />
Saline depression (6 species) 31.6 ± 5.8 9.2±1.9 33.2 ± 13.4 7.6 ± 2.4 18.6 ± 6.9 4.9 ± 1.1 67.2 ± 1.9 3.9 ± 0.26<br />
Table 4. Means and standard error of chemical composition {percentage of nitrogen free extract (NFE), crude protein (CP), ether extract (EE), crude fibre (CF), ash, digistable<br />
crude protein (DCP), total digistable nutrients (TDN), and gross energy (GE Mcal kg-1)} of the grazeable parts of the indicator species at the different habitats of<br />
Matruh area.<br />
Habitats<br />
Species Non-saline depression Flat plateau Rocky plateau Rocky ridge Saline depression<br />
DE ME DE ME DE ME DE ME DE ME<br />
Anabasis articulta -- -- 3.1 2.7 3.3 2.8 -- -- -- --<br />
Anabasis oropediorum -- -- 2.7 2.3 2.9 2.5 2.9 2.5 -- --<br />
Artemisia herba-alba 3.5 3.0 3.5 3.0 3.7 3.2 -- -- -- --<br />
Asphodelus ramosus 3.2 2.8 3.4 2.9 3.5 3.0 3.3 2.8 3.4 2.9<br />
Atriplex halimus -- -- 3.1 2.7 3.1 2.7 3.1 2.7 3.1 2.6<br />
Carthamus lanatus 3.3 2.8 3.5 3.0 3.4 2.9 3.3 2.8 3.4 3.0<br />
Deverra tortuosa 3.5 3.0 3.4 2.9 3.6 3.1 3.4 2.9 -- --<br />
Echinops spinosissimus 3.5 3.0 3.6 3.1 3.1 2.7 3.0 2.6 -- --<br />
Gymnocarpos decandrum 3.2 2.8 3.2 2.8 3.5 3.1 3.5 3.0 -- --<br />
Haloxylon scoparia 3.5 3.0 3.4 2.9 3.4 2.9 3.0 2.6 -- --<br />
Helianthemum kahiricum -- -- 3.6 3.1 -- -- -- -- -- --<br />
Helianthemum lippii -- -- 3.0 2.6 -- -- -- -- -- --<br />
Lycium shawii 3.4 2.9 3.3 2.8 3.7 3.2 -- -- -- --<br />
Noaea mucronata 3.4 2.9 3.5 3.0 3.2 2.8 3.4 2.9 -- --<br />
Periploca angustifolia -- -- -- -- 3.7 3.2 3.8 3.3 -- --<br />
Salvia aegyptiaca 3.5 3.0 3.5 3.0 -- -- -- -- -- --<br />
Salsola tetrandra 2.9 2.5 2.9 2.5 2.8 2.4 3.4 2.9 3.0 2.6<br />
Salsola tetragona -- -- 2.7 2.3 2.9 2.5 -- -- 2.9 2.5<br />
Stipa parviflora -- -- 3.4 2.9 -- -- -- -- -- --<br />
Suaeda pruinosa -- -- 2.7 2.3 2.7 2.3 2.9 2.5 -- --<br />
Suaeda vermiculata -- -- 2.8 2.4 -- -- -- -- -- --<br />
Thymelaea hirsuta 3.4 2.9 -- -- 3.5 3.0 -- -- 3.5 3.0<br />
Zilla spinosa -- -- -- -- 3.3 2.8 -- -- -- --<br />
Table 5. Average of digestible energy (DE), and metabolizable energy (ME) (Mcal kg-1) in the indicator species in each habitat of Matruh area.<br />
higher CP content and minerals, and lower CF content.<br />
Eighty-two percent of the perennial species and 44% of<br />
the annual species in the present study have high grazing<br />
value.<br />
Overgrazing is one of the most important issue of arid<br />
land especially in rangeland areas (Ayyad, 1978; Abdel-<br />
Razik et al. 1988a,b; Le Houérou, 1989; Heneidy, 1992).<br />
Based on the long field observation of different flocks in<br />
each site, the degree of consumption of plant species,<br />
topography of the site, the ratio of unpalatable species<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
BROWSING AND NUTRITIVE VALUE OF THE MOST COMMON RANGE SPECIES IN COASTAL EGYPT ◆<br />
and the position of the settlements (i.e. whether they inhabit<br />
near by or far from the pasture), it is possible to estimate<br />
the grazing pressure in the different sites (El-Kady,<br />
1983; Heneidy, 1992; Heneidy & Bidak, 1998). In the present<br />
study 38 % of the sites have high grazing pressure,<br />
34 % have moderate and 28 % have low grazing pressure.<br />
Rangeland under high grazing pressure needs rotational<br />
grazing management to reduce the grazing intensity<br />
(depend on the status of the pasture). Actually, destocking<br />
deferred grazing and reduction of stocking rates are<br />
also effective means to regenerate these rangelands.<br />
The present study indicates that the indicator species<br />
have relatively high content of CP and low content of CF<br />
compared with many desert plants (Le Houérou, 1980b).<br />
CP and CF are viewed classically as an indicator of the<br />
nutritional value of plant as feed for ruminants (Bryant<br />
& Kuropat, 1983; Heneidy, 1992). In all habitats of the<br />
study area about 75% of the indicator species contained<br />
more than 8% CP and 50% of them contained less than<br />
30% CF. According to the percentage of CP the sites could<br />
be ranked into three groups.The first group includes 47%<br />
(15 sites) of the sites where CP > 10%, the second group<br />
includes 31% (10 sites) of the sites where CP > 8%, while<br />
the third group includes 22% (7 sites) of the sites where<br />
CP < 8%.The maximum average of CP is attained by the<br />
indicator plant species in the non-saline depression habitat<br />
(10.7 ± 4.3 %), while the minimum is attained by the<br />
indicator plant species in the saline depression (9.2 ±<br />
1.9 %).<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 39-49<br />
% Kcal kg -1<br />
Fodder References DCP TDN GE DE ME<br />
Supplementary feed Soliman & El-Shazly, 1978<br />
berseem -- 56 -- -- -barley<br />
-- 64 -- -- -corn<br />
-- 68 -- -- --<br />
Western <strong>Mediterranea</strong>n Abdel-Salam, 1985 -- 66 -- -- --<br />
Desert Pasture (Omayed) Abdel-Razik et al., 1988 5.4 75 -- -- --<br />
Heneidy, 1992 4.9 72 3,606 2,610 2,278<br />
Aqaba Gulf Area Pasture (Sinai) Heneidy, 1996 4.6 66.5 4,100 2,650 2,200<br />
Bisha area (Saudi Arabia) Heneidy, 2000 8.8 74.8 3,974 3,292 2,874<br />
Tunisia (as arid zone) Sarson & El-Hamrouni, 1974 4-20 -- -- -- --<br />
East of Matruh Present study 5.7 67.0 3,993 3,274 2.824<br />
Table 6. A comparison between the present annual average percentage of total digestible nutrients (TDN), digestible crude protein (DCP), gross energy (GE), digestible<br />
energy (DE) and metabolizable energy (ME) in Kcal kg -1 with those supplementary feed and other pastures.<br />
The DCP percentage in the present study varied from<br />
a minimum 4.9 (as an average) in the saline depression<br />
habitat to a maximum 6.4 in the non-saline depression.<br />
This however is comparable with that recorded in the saltmarshes<br />
area of the <strong>Mediterranea</strong>n region where values<br />
ranged from 5.8 to 7.5 (Heneidy & Bidak, 1996), and<br />
with the values recorded by Heneidy (1992) in Omayed<br />
area 4.9 (table 6). This Table also contained the annual<br />
average DCP% in supplementary feed and other pastures.<br />
The mean DCP% in the study area (5.7) is slightly higher<br />
than that recorded in the plants of Aqaba Gulf in Sinai<br />
area by Heneidy (1996). But it is within the range 4 -20%<br />
of the dry matter of DCP% for woody steppe in arid zone<br />
(Sarson & El-Hamrouni, 1974).<br />
The term TDN (total digestible nutrients) is only an<br />
approximate measure of the food energy available to animal<br />
after the digestion losses have been deducted<br />
(Lofgreen, 1951).Therefore,TDN is a measure of energy<br />
requirement of animals and energy value of feeds. TDN<br />
values in the study area ranges from 66.4 ± 0.6% in the<br />
non-saline depression to 67.6 ± 1.1% in the flat plateau.<br />
The annual average percentage of TDN found in the present<br />
study is compared with that of the supplementary<br />
feed and other pastures as also shown in table 6.The TDN<br />
value in the study area is 67.0% comparing with that recorded<br />
in the natural forage from Aqaba Gulf of Sinai region<br />
(e.g. 66.5%) (Heneidy, 1996) and 66.2% in the halophytes<br />
of the <strong>Mediterranea</strong>n region (Heneidy & Bidak, 1996).<br />
The obtained results of TDN in the present study is also<br />
47
48<br />
◆ S. Z. HENEIDY<br />
higher than the average TDN (62.7%) in the supplementary<br />
feed (berseem, barley and corn) reported by<br />
Soliman & El-Shazly (1978). However, Abdel-Salam<br />
(1985) and Abdel-Razik et al. (1988a) reported that the<br />
average of TDN ranges from 66 to 75% in the coastal<br />
region.<br />
The average GE in the study area ranges from 3.9 ±<br />
0.1 Mcal kg -1 in the habitat of the rocky ridge, to 4.1 ±<br />
0.1 Mcal kg -1 in the non-saline depression. Lower GE<br />
values (3.6 and 3.5 Mcal kg -1 ) were recorded by Heneidy<br />
(1992) and Heneidy and Bidak (1996) in the western<br />
coastal region and in the halophytic species of the<br />
<strong>Mediterranea</strong>n region respectively.The average of DE in<br />
the study area was 3.3 ± 0.02 Mcal kg -1 which is less than<br />
2.6 Mcal kg -1 calculated by Heneidy (1992) in Omayed<br />
area of the coastal region.<br />
Generally the average of ME was 2.88 ± 0.04 in the<br />
non-saline depression, 2.8 ± 0.07 in the flat plateau, 2.84<br />
± 0.06 in rocky plateau, 2.79 ± 0.06 in the rocky ridge,<br />
and 2.81 ± 0.08 Mcal kg -1 in the saline depression habitat.<br />
Consequently, the average of ME in the whole study<br />
area was 2.82 ± 0.01 Mcal kg -1 which is compareable with<br />
2.2 Mcal kg -1 recorded by Heneidy (1996) in the natural<br />
forage in Aqaba Gulf.<br />
Le Houérou and Hoste (1977) reported that 1 SFU<br />
(Scandinavian Feed Unit) = 1,650 Kcal. Accordingly, the<br />
energy content in the study aera is equivalent to 0.84 SFU.<br />
Comparing with the energy content of forage in Aqaba<br />
Gulf pasture was 0.66 SFU (Heneidy, 1996), and 0.76<br />
SFU Heneidy and Bidak (1996) in halophytic pasture.<br />
Le Houérou et al. (1982) reported the energy content of<br />
one kg dry matter of the best fodder roughage and good<br />
fodder crops (alfalfa) was 0.8 and 0.6 SFU, respectively.<br />
It seems that the energy content of the pasture in the study<br />
area is higher than the good fodder crops and close to the<br />
best fodder roughage. However, this area is considered<br />
good pasture if compared with other pastures.<br />
CONCLUSION<br />
The problem which faces the pastoralists in range lands<br />
areas is low rainfall and how to prevent or reduced the<br />
land degradation.This is a matter of adjustment of stock<br />
numbers to the natural feed resources. Increasing the grazing<br />
pressure beyond the limits set by dry seasons reduces<br />
fodder resources and leads to depletion in forage<br />
resources. It is therefore appropriate to manage vegetation<br />
properly and to think in terms of encouraging or pro-<br />
pagation of the native species by using techniques which<br />
still have to be established. In particular the following<br />
points should be considered: 1- propagation of the palatable<br />
and high grazing value species (specially woody species<br />
) which produce quantity of seeds (e.g. Artemisia<br />
herba-alba, Anabasis oropediorum, Anabasis articulata,<br />
Atriplex halimus, Argyrolobium uniflorum, Gymnocarpos<br />
decandrum, Helianthemum lippii, Deverra tortuosa, Lycium<br />
shawii and Periploca angustifolia), 2- establishment of the<br />
shrub-land species (especially legume species), 3constructing<br />
a good policy to manage the use of grazing<br />
lands as a purpose to reduce the supplementary feed cost.<br />
AKNOWLEDGEMENTS<br />
The author wish to thank to Prof. F. Abdel-Khader,<br />
(the principal investigator of the Project of Water/Land<br />
Management Northwest Coast of Egypt), for facilitating<br />
during the field work.<br />
Sincere thanks are due to Professor K. H. Shaltout,<br />
and Professor El-Rayis, O. A. for their careful revision the<br />
manuscript although I should emphasize that outstanding<br />
errors are mine.<br />
References<br />
ABDEL-RAZIK M., AYYAD M. A. & HENEIDY S. Z., 1988a. Preference<br />
of grazing mammals for forage species and their nutritive<br />
value in a <strong>Mediterranea</strong>n desert ecosystem (Egypt). J.<br />
Arid Environ. 15: 297-300.<br />
ABDEL-RAZIK M.,AYYAD M.A. & HENEIDY S. Z., 1988b. Phytomass<br />
and mineral composition in range biomass of a <strong>Mediterranea</strong>n<br />
arid ecosystem (Egypt). Œcol. Plant. 9: 359-370.<br />
ABDEL-SALAM H., 1985. Grazing Capacity per Feddan at<br />
Omayed Grazing area “The Northern Coastal Zone”Western<br />
to Alexandria Ph. D.Thesis University of Alexandria. 166 p.<br />
ABU-EL-NAGA M. A. & EL-SHAZLY K., 1971.The prediction of<br />
the nutritive value of animal feeds from chemical analysis. J.<br />
Agric. Sci. 77: 25-37.<br />
ALLEN S. E., GRIMSHAY H. M., PARKINSON T. A. & QUARMBY,<br />
C., 1974. Analysis of Ecology Materials. Oxford, London:<br />
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AYYAD M. A., 1978. A preliminary assessment of the effect of<br />
protection on the vegetation of the <strong>Mediterranea</strong>n desert ecosystems.<br />
Tackholmia 9:85-101.<br />
BOULOS L., 1995. Flora of Egypt:Checklist. Al-Hadra Publishing,<br />
Cairo, 286 p.<br />
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BROWSING AND NUTRITIVE VALUE OF THE MOST COMMON RANGE SPECIES IN COASTAL EGYPT ◆<br />
BRYANT J. P. & KUROPAT P. J., 1983. Selection of winter forage<br />
by sub-arctic browsing vertebrates: the role of plant chemistry.<br />
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CRAMPTON E.W. & HARRIS L. E., 1969. Applied Animal Nutrition<br />
(2 nd ed.). San Francisco: W. H. Freeman, 753 p.<br />
DE RIDDER N., SROOSIJDER L., CISSE A. M. & VAN KEULEN H.,<br />
1982. A Study of the Soils, the Vegetation and the Exploitation<br />
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Agriculturral University, 231 p.<br />
DUIVENBOODEN N. VEN, 1985. Animal Husbandry in the Northwestern<br />
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EL-KADY H.F., 1983. Animal Resources. In: AYYAD M. A. & LE<br />
FLOC’H E. (eds.). An Ecological Assessment of Renewable<br />
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<strong>Mediterranea</strong>n Coastal Region of Egypt. Mapping Workshop<br />
of CNRS/CEPE: CNRS, p. 77-79.<br />
GENIN D. & BADAN-DANGON A., 1989. Rapport d’activites agropastorales<br />
en République du Niger. IEMVT Paris, 140 p.<br />
HENEIDY S. Z., 1992. An Ecological Study of the Grazing Systems<br />
of Mariut, Egypt. Submitted to UNESCO, 51 p.<br />
HENEIDY S. Z., 1996. Palatability and nutritive value of some<br />
common plant species from the Aqaba Gulf area of Sinai,<br />
Egypt. J. Arid Environ. 34: 115-123.<br />
HENEIDY S. Z., 2000. Palatability, chemical composition and<br />
nutritive value of some common range plants from Bisha,<br />
assir region, southwestern of Saudi Arabia. Desert Inst. Bull.,<br />
Egypt.<br />
HENEIDY S. Z. & BIDAK, L.M., 1996. Halophytes as a forage<br />
source in the western <strong>Mediterranea</strong>n coastal region of Egypt.<br />
Desert Inst. Bull., Egypt. (49), 2: 283-304.<br />
HENEIDY S. Z. & BIDAK L. M., 1998. Diversity of wadi vegetation<br />
in Matrouh region, Egypt. J. Union Arab.Biol.Cairo 6(B).<br />
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49
Epiphytic lichen vegetation<br />
of the Cedrus atlantica forests (Morocco)<br />
La végétation des lichens épiphytes<br />
des cédraies à Cedrus atlantica du Maroc<br />
Giuseppe Massari, Sonia Ravera<br />
Dipartimento di Biologia Vegetale. Università di Roma “La Sapienza”<br />
Piazzale Aldo Moro 5, 00185 Roma, Italia – email: giuseppe.massari@uniroma1.it<br />
Summary<br />
In Morocco, human influence induces actually transformation and<br />
destruction of forests. We conducted a three-year study (1998-2000)<br />
on the epiphytic lichen vegetation of the Cedrus atlantica forests<br />
of the mountain ranges of Rif and Central Atlas, comparing our<br />
findings with the syntaxonomical position of the syntaxa described<br />
in Europe and using, as reference, the epiphytic acidophilous communities<br />
of Hypogymnietea physodis Follm. 1974.<br />
Although most of the lichen species observed are common in the<br />
mountains of Europe, the Moroccan communities show substantial<br />
differences. These differences depend on climatic, ecological,<br />
and phytogeographic factors, which are strictly related to the<br />
<strong>Mediterranea</strong>n character of the Cedrus atlantica forests.<br />
The specificity of the epiphytic lichen vegetation of Moroccan Cedrus<br />
atlantica forests is represented by Pseudevernio-Hypogymnietum<br />
laminisorediatae ass. nov. which replaces the Pseudevernietum<br />
furfuraceae occurring in European coniferous woods.<br />
Key-words<br />
Phytosociology, epiphytic lichen vegetation, Morocco, Cedrus atlantica<br />
forests, syntaxonomy.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 51-57<br />
Résumé<br />
L’activité humaine et la dégradation sont en train de transformer<br />
la végétation forestière du Maroc. Pour étudier les communautés<br />
de lichens épiphytes qui présentent encore leur structure originale,<br />
nous avons entrepris une étude sur trois ans (1998-2000) de la<br />
végétation lichénique des forêts à Cedrus atlantica du Rif et de<br />
l’Atlas central. Les données marocaines ont été comparées aux unités<br />
syntaxonomiques des forêts à Larix decidua et Pinus cembra<br />
des montagnes européennes et, en particulier, aux communautés<br />
acidophyles épiphytiques de l’ Hypogymnietea physodis Follm.<br />
1974.<br />
Malgré une certaine similitude floristique, les communautés des<br />
lichens des cédraies marocaines diffèrent de celles des montagnes<br />
européennes : les différences dépendent surtout des facteurs climatiques,<br />
écologiques et phytogéographiques qui marquent les limites<br />
de la végétation épiphytique oroboréale avec la végétation oroméditerranéenne.<br />
La spécificité des communautés épiphytiques des cédraies du Maroc<br />
est représentée par le Pseudevernio-Hypogymnietum laminisorediatae<br />
ass. nov., vicariante du Pseudevernietum furfuraceae des<br />
montagnes européennes.<br />
Mots-clés<br />
Phytosociologie, végétation lichénique épiphytique, Maroc, forêts à<br />
Cedrus atlantica, syntaxonomie.<br />
51
52<br />
◆ GIUSEPPE MASSARI, SONIA RAVERA<br />
INTRODUCTION<br />
The lichen flora of the Cedrus atlantica forests of<br />
Morocco is apparently similar to that of the coniferous<br />
woods of the mountains of Europe. However, the epiphytic<br />
lichen vegetation of the Moroccan forests has never<br />
been thoroughly studied, a fact which is becoming of<br />
increasing importance in that these old forms are rapidly<br />
being eliminated or transformed by human influence and<br />
deforestation.<br />
To acquire knowledge on the lichen communities of<br />
the Moroccan cedar forests that still conserve traces of<br />
the original elements, we conducted a three-year study<br />
(1998-2000) on the epiphytic lichen vegetation of the<br />
Cedrus atlantica forests of the mountain ranges of Rif and<br />
Central Atlas, comparing our findings with the syntaxonomical<br />
position of the syntaxa described in Europe, using<br />
as reference the epiphytic acidophilous communities of<br />
Hypogymnietea physodis Follm. 1974 that have a subartic,<br />
subalpine and euatlantic distribution.<br />
We also aimed to expand the knowledge obtained from<br />
Morocco to the Taurus, Cyprus and West Himalayan<br />
forests of Cedrus libani, C. brevifolia and C. deodara,given<br />
that these forests are similar to those of Morocco in terms<br />
of flora and silviculture, and in light of the theory that all<br />
of these forests have a single common origin (Meusel,<br />
1971; Meusel & Schubert, 1971; Quézel 1978).<br />
STUDY AREA<br />
The study area is illustrated in figure 1. The lichen<br />
vegetation of the Cedrus atlantica forests of the Rif mountains<br />
was studied in the area surrounding the cities of Bab-<br />
Besen and Ketama, specifically, in snow stands located<br />
downwind from the principal mountain summits at altitudes<br />
ranging from 1,660m to 1,840m above sea level.<br />
The forests in this area grow on siliceous and marly-schistose<br />
substrata.<br />
The study areas in the Central Atlas mountains are<br />
located near the cities of Azrou (altitude: 1,270m),<br />
Michliffen (approximately 2,000m), and Ifrane (approximately<br />
2,000m), in areas exposed to prevalently oceanic<br />
winds. The forests grow on a calcareous substratum.<br />
The climate of these mountain ranges was described<br />
by Emberger (1939) with the apparently contradictory<br />
term “humid <strong>Mediterranea</strong>n”, with cold winters and a<br />
relatively continental climate. The rainfall varies from<br />
600mm to 1,000mm per year (Despois & Raynal, 1975),<br />
and summers are dry and brief, as observed in those areas<br />
of the <strong>Mediterranea</strong>n Basin with the highest rainfall.<br />
METHODS<br />
The epiphytic lichens were identified both on the<br />
cedars and in laboratory on fragments of bark which were<br />
collected, such as the unknown thalli, using the method<br />
of the “prélèvement partiel” (Clauzade & Roux, 1975;<br />
Roux, 1990).The cover-abundance indices were attributed<br />
according Braun-Blanquet’s scale, modified by Pignatti<br />
(1959), also used by Nimis (1981, 1985) in Canada. Other<br />
indices were integrated after identification of the collected<br />
samples in the laboratory, according to the method.<br />
Most of the relevés were of a qualitative type, both in<br />
order to make comparisons with the works on lichen sociology<br />
used as reference and because the epiphytic cedar<br />
communities consist of fruticose lichens too, which makes<br />
quantitative analysis difficult.<br />
We studied those Cedrus atlantica forests with large,<br />
centuries-old cedars, which were apparently suffering less<br />
from anthropic impact.<br />
Taxonomic references: the nomenclature used was that<br />
of Egea (1996) and Nimis (2000). Pertusaria was identified<br />
in accordance with Sipman (2000); Usnea lapponica<br />
was identified by Clerc, Lepraria elobata by Tønsberg.<br />
Authors’ abbreviations are according to Brummitt and<br />
Powell (1992), phytosociological nomenclature to<br />
Barkman et al. (1976). All samples are preserved in the<br />
Herbarium of the University of Rome “La Sapienza”<br />
(RO).<br />
Syntaxonomical position and phytogeographical references:<br />
we followed the system of Wirth (1995), proposed<br />
for Baden-Württembergs (Austria) and adopted in<br />
Spain by Sarriòn and Burgaz (1995) and Fos (1998).<br />
The syntaxonomic units of Hypogymnietalia that we<br />
used as reference were as follows. At the level of alliance,<br />
Hypogymnion physodis Beschel 1958 also referred to as<br />
Pseudevernion furfuraceae (Barkm.) James et al. 1977, first<br />
described in Great Britain, and to as Parmelion saxatilis<br />
Barkm. 1958 em. Delzenne & Géhu 1997 for France,<br />
rejected by Van Haluwyn & Schumacker (1988). At the<br />
level of association, Pseudevernietum furfuraceae (Hil.) Kalb<br />
1970, which is present throughout Europe, where it characterises<br />
the epiphytic vegetation of both coniferous and<br />
other types of woods of the montane subalpine belt.The<br />
typical association is a community with a central-<br />
European distribution that is non-aerohygrophilous and<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
which requires periods of drought.This syntaxon is common<br />
in the Italian Alps and Apennines; on the Iberian<br />
Peninsula, it has occasionally been found in the subhumid<br />
mesomediterranean belt (Atienza, 1990; Giralt,<br />
1996). At the level of association, we also used Letharietum<br />
vulpinae Gams 1927 as reference; this syntaxon occurs in<br />
subalpine woods of Larix decidua and Pinus cembra with<br />
high continental climate.<br />
All of these communities are acidophilous, and most<br />
of them are nitrophobous, toxiphobous, photophytic and<br />
ombrophilous. In terms of floristic composition, these<br />
communities are characterised by the dominance of the<br />
genera Parmelia s.l., Hypogymnia, Pseudevernia, Usnea,<br />
Alectoria, and Bryoria and by the presence of Letharia,<br />
Evernia, Cetraria, Platismatia, and Parmeliopsis.<br />
RESULTS<br />
We selected 55 relevés from the study areas of the Rif<br />
and Central Atlas mountains, which include a total of 47<br />
taxa, a low number in comparison by European Hypogymnietalia<br />
communities.<br />
The lichen species identified are common in the mountains<br />
of Europe, with the exception of, for example,<br />
Evernia illyrica, Lethariella intricata, Pertusaria multipunctoides,<br />
Hypogymnia laminisorediata, and Pertusaria tazzakensis,<br />
which is only known in Morocco. Nonetheless,<br />
the Moroccan communities are substantially different<br />
from those of Europe, in part for the lack of certain elements<br />
that are typical in the European communities, as<br />
described below.<br />
Hypogymnietalia:The following elements are absent in<br />
the Moroccan forests: i) the montane species with a typically<br />
arctic-alpine and circumboreal distribution, such as<br />
the epiphytic species of the Cetraria genus; ii) the species<br />
Imshaugia aleurites and Parmeliopsis hyperopta, which are<br />
diagnostic of Cetrario pinastri-Parmeliopsidetum ambiguae<br />
(Hil.) Van Haluwyn & Schumacker, 1988; and iii) Hypogymnia<br />
farinacea, H. bitteri, and H. physodes, which represent<br />
important elements of the order Hypogymnietalia.<br />
The finding that these species are lacking throughout the<br />
entire country of Morocco (Egea, 1996) could signify that<br />
there exists a climatic boundary between the oroboreal<br />
and the oromediterranean zone.<br />
Hypogymnion: All of the species of this alliance are present,<br />
obviously with the exception of Cetraria clorophylla.<br />
Pseudevernietum furfuraceae: Certain species that are<br />
faithful and characteristic of Pseudevernia communities<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 51-57<br />
EPIPHYTIC LICHEN VEGETATION OF THE CEDRUS ATLANTICA FORESTS (MOROCCO) ◆<br />
are lacking (e.g. Usnea hirta and the above-mentioned<br />
Hypogymnia).<br />
Letharietum vulpinae:With regard to the definition of<br />
Letharia communities, in accordance with Barkman<br />
(1954), we defined a community as such only when<br />
Letharia vulpina was dominant. In our relevés, various<br />
species that Frey (1952) and Kalb (1970) consider as<br />
characteristic and as companions of Letharietum vulpinae<br />
were missing.<br />
The most interesting lichens for the syntaxonomy of<br />
the cedar forests of Morocco can be summarised as follows:<br />
Hypogymnia laminisorediata, Pseudevernia furfuracea,<br />
and Parmelia saxatilis are the dominant species.<br />
Hypogymnia laminisorediata,whose distribution is limited<br />
to the Balkan mountains and the mountains of North<br />
Africa and Macaronesian region, belongs to the oromediterranean<br />
zone.<br />
Parmelia submontana is associated with Hypogymnia<br />
tubulosa, Phlyctis argena, Anaptychia ciliaris and Usnea lapponica<br />
in the forests of the Central Atlas mountains, which<br />
are humid and dense and where foliose and fruticose<br />
growth-forms prevail.The light is diffuse, despite the fact<br />
that the density of the tree foliage does not allow direct<br />
sunlight to reach the forest floor. Sexual reproduction is<br />
common, even among species that are generally sterile in<br />
Europe, such as Pseudevernia furfuracea, Hypogymnia laminisorediata,<br />
Parmelia saxatilis, and Parmelia submontana.<br />
Pertusaria tazzakensis was found in all of the relevés<br />
from the Rif mountains. A characteristic species combination<br />
of this forest is: Pertusaria tazzakensis associated<br />
with P. multipunctoides, Evernia illyrica, and Lethariella<br />
intricata.<br />
Letharia vulpina, which is easily recognised for its<br />
bright yellow colour, is present in the mountains at low<br />
altitudes, although it has a low degree of cover. In the<br />
Central Atlas mountains, for example in the cedar forests<br />
of Jebel Hebri near Azrou, there exist true communities<br />
of this lichen at 2,000 m, where there is a more marked<br />
continental climate.<br />
Table 1 shows the groups of relevés with the species,<br />
and in particular 21 taxa that are the most representative<br />
of the epiphytic lichen vegetation.<br />
Vegetation types<br />
(relevé type in table 2)<br />
Pseudevernio-Hypogymnietum laminisorediatae ass. nov.<br />
Association characterised by species that prefer an<br />
oceanic climate and by the dominance of Hypogymnia<br />
53
54<br />
◆ GIUSEPPE MASSARI, SONIA RAVERA<br />
Relevés group 1 2 3 4 5 6<br />
typical form var. with Pertusaria var. with Parmelia subass. letharietosum<br />
tazzakensis submontana<br />
Mean circumference of cedars (cm) 400 260 190 210 360 320 440<br />
Mean surface (m 2) 0.6 0.5 0.4 0.4 0.5 0.4 0.6<br />
Height above ground (cm) 100-130 110-140 100-150 90-100 90-120 80-100 90-110<br />
Prevailing exposure N NE NE N NE ENE-NE N-NE<br />
Mean coverage (%) 75 90 70 80 90 70 70<br />
Character-taxon of the association<br />
Pseudevernio-Hypogymnietum laminisorediatae ass. nov.<br />
Hypogymnia laminisorediata D. Hawksw. & Poelt V 1-3 V 2 IV 1-2 V +-2 IV 1-2 V +-2 V +-2<br />
Character-taxa of higher units<br />
Pseudevernia furfuracea (L.) Zopf V1-2 III +-1 V +-2 V1-3 V1-2 V +-3 V1-2 Parmelia saxatilis (L.) Ach. V +-3 IV +-1 IV +-1 V +-1 V1-3 IV + IV +-1<br />
Bryoria fuscescens (Gyeln.) Brodo & D. Hawksw. I + IIr II + III + IIIr-+ IV +-1<br />
Platismatia glauca (L.) W. L. Culb. & C. F. Culb. II1-3 V2-4 V1-3 III +-2<br />
Ochrolechia androgyna (Hoffm.) Arnold I + V +-1 V + IIr-+ III +<br />
Parmelia sulcata Taylor in J. Mackay I + I +<br />
Hypogymnia tubulosa (Schaer.) Hav. V +-1 V +-2<br />
Parmeliopsis ambigua (Wulfen) Nyl. II +<br />
Companions<br />
Lepraria elobata Tønsberg V + II + II + III + IV +<br />
Usnea lapponica Vainio II + III +<br />
var. with Pertusaria tazzakensis<br />
Pertusaria tazzakensis (Werner) Werner V + IV +-1<br />
Evernia illyrica Zahlbr. II r<br />
Lethariella intricata (Moris) Krog II r<br />
Pertusaria multipunctoides Dibben II +<br />
var. with Parmelia submontana<br />
Parmelia submontana Nadv. ex Hale IV +-1 V 1<br />
Phlyctis argena (Spreng.) Flot. V +-1 V +-1<br />
Anaptychia ciliaris (L.) A. Massal. V +-1 IV +-1 I r<br />
Pseudevernio-Hypogymnietum laminisorediatae letharietosum subass. nov.<br />
Letharia vulpina (L.) Hue V r-1 V 1-4 V 2<br />
Hypocenomyce scalaris (Liljeblad) M. Choisy V +-1 V +-2<br />
Lecanora varia (Hoffm.) Ach. I + V + I +<br />
Other taxa. Cladonia fimbriata (L.) Fr. +, Dendriscocaulon umhausense (Auersw.) Degel. +, Rinodina sp. +, Thelenella modesta (Nyl.) Nyl. +, in typicum. Candelariella xanthostigma<br />
(Ach.) Lettau +, in 1. Calicium trabinellum (Ach.) Ach. +, in 2. Ramalina fraxinea (L.) Ach. +, Lecanora albella (Pers.) Ach. +, Buellia griseovirens (Sm.) Almb. +, in 3. Cladonia<br />
fimbriata (L.) Fr. +, Physcia semipinnata (J.F. Gmel.) Moberg +, Candelariella xanthostigma (Ach.) Lettau +, Ramalina fraxinea (L.) Ach. +, Buellia griseovirens (Sm.) Almb. +,<br />
Trapeliopsis granulosa (Hoffm.) Lumbsch +, Lecanora chlarotera Nyl. +, Ramalina farinacea (L.) Ach. 1, Diplotomma alboatrum (Hoffm.) Flot. +, Physconia distorta (With.) J.R.<br />
Laundon +, Physconia perisidiosa (Erichsen) Moberg +, Parmelia glabra (Schaer.) Nyl. 1, Parmelia tiliacea (Hoffm.) Ach. 2, in 4. Parmelia exasperatula Nyl. 1, Xanthoria parietina<br />
(L.) Th. Fr r, Lecanora hagenii (Ach.) Ach +, Calicium trabinellum (Ach.) Ach. +, Lecanora albella (Pers.) Ach. +, Catillaria chalybeia (Borrer) A. Massal. +, Lecidella elaeochroma<br />
(Ach.) Haslz. +, Caloplaca cerinelloides (Erichsen) Poelt r, Physcia semipinnata (J.F. Gmel.) Moberg +, in 5. Chaenothecopsis pusilla (Ach.) A.F.W. Schmidt +, Lepraria sp. +, Cladonia<br />
fimbriata (L.) Fr. +, in 6.<br />
Localities. 1. BAB-BESEN, 1.750-1.840 m, exp. N, slope (°) 10; 2. KETAMA, 1.660-1.720, N, 40; 3. IFRANE, 1.750-1.800, 0; 4. AZROU, 1.750-1.800, 0; 5. JEBEL HEBRI,<br />
1.980-2.010, WSW, 10; 6. MICHLIFFEN, 1.960-2.040, NNW, 40.<br />
Table 1. Synthesis table (55 relevés) of the epiphytic lichen vegetation of the Rif and Central Atlas.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 51-57<br />
EPIPHYTIC LICHEN VEGETATION OF THE CEDRUS ATLANTICA FORESTS (MOROCCO) ◆<br />
Pseudevernio-Hypogymnietum laminisorediatae typicum subass.<br />
var. with var. with letharietosum<br />
typical form P. tazzakensis P. submontana<br />
Stand Azrou Michliffen Bab-Besen Ketama Ifrane Azrou Michliffen Jebel Hebri<br />
UTM 50 zone 30, coordinates E 2 96 762 3 12 167 3 47 875 3 54 248 3 05 617 2 99 480 3 12 278 2 99 915<br />
N 36 99 913 37 06 118 38 70 051 38 65 423 37 10 633 36 99 784 37 06 229 36 94 280<br />
Altitude above sea level (m) 1 775 2 040 1 840 1 660 1 755 1 755 2 010 2 010<br />
Stand exposure 0 NNW N N 0 0 NNW WSW<br />
Slope (°) 0 40 10 40 0 0 40 10<br />
Canopy coverage (%) 50 100 40 100 60 90 50 50<br />
Number of relevé 29 53 8 5 12 40 42 16<br />
Date of relevé 2/01/99 31/12/00 2/01/98 2/01/98 7/01/98 6/01/00 27/12/00 28/12/98<br />
Circumference (cm) 555 340 245 180 190 385 435 258<br />
Surface (m 2) 0.63 0.42 0.49 0.48 0.42 0.49 0.5 0.63<br />
Height above ground (cm) 100 100 110 100 100 110 90 80<br />
Exposure N NW N ENE N NNW NNW ENE<br />
Coverage (%) 70 70 100 50 70 100 70 50<br />
Character-taxon of the association<br />
Hypogymnia laminisorediata 2 3 2 + + 1 1 +<br />
Character-taxa of higher units<br />
Pseudevernia furfuracea 1 1 • + 2 2 1 1<br />
Parmelia saxatilis 2 + + 1 1 2 • +<br />
Platismatia glauca • 1 4 2 • • 1 •<br />
Ochrolechia androgyna • + + + • • + +<br />
Bryoria fuscescens • • • • • + + r<br />
Parmelia sulcata • • • • • + • •<br />
Hypogymnia tubulosa • • • • + + • •<br />
Parmeliopsis ambigua • • • • • • + •<br />
Companions<br />
Lepraria elobata + + + • • • + •<br />
Usnea lapponica + • • • • + • •<br />
var. with Pertusaria tazzakensis<br />
Pertusaria tazzakensis • • + + • • • •<br />
Evernia illyrica • • r • • • • •<br />
Lethariella intricata • • r • • • • •<br />
Pertusaria multipunctoides • • + • • • • •<br />
var. with Parmelia submontana<br />
Parmelia submontana • • • • 1 1 • •<br />
Phlyctis argena • • • • 1 1 • •<br />
Anaptychia ciliaris • • • • 1 • • •<br />
Differential-taxa<br />
of the subassociation<br />
Letharia vulpina • • • 1 • • 2 2<br />
Hypocenomyce scalaris • • • • • • 1 1<br />
Lecanora varia • • • • • • • +<br />
Other taxa<br />
Dendriscocaulon umhausense + • • • • • • •<br />
Thelenella modesta + • • • • • • •<br />
Cladonia fimbriata + • • • • • • •<br />
Candelariella xanthostigma • • + • • • •<br />
Calicium trabinellum • • • + • • • +<br />
Ramalina fraxinea • • • • + r • •<br />
Buellia griseovirens • • • • + • • •<br />
Ramalina farinacea • • • • • 1 • •<br />
Chaenothecopsis pusilla • • • • • • + •<br />
Lecanora albella • • • • • • • +<br />
Catillaria chalybeia • • • • • • • +<br />
Table 2. Relevé type of the syntaxa.<br />
55
56<br />
◆ GIUSEPPE MASSARI, SONIA RAVERA<br />
laminisorediata which replaces in cedars forest the<br />
Hypogymnia species of the montane and subalpine coniferous<br />
woods. The community is a phytoclimatic indicator<br />
of the humid montane forests of Cedrus atlantica in<br />
the Central Atlas and Rif mountains, with a relatively<br />
continental climate.<br />
var. with Pertusaria tazzakensis. Geographic variant<br />
characterised by the endemic Pertusaria tazzakensis, by<br />
Platismatia glauca with a high degree of cover, by the<br />
dominance of Ochrolechia androgyna, and by the sporadic<br />
Evernia illyrica and Lethariella intricata, which are rare<br />
suboceanic species. It is present in the cedar forests of the<br />
Rif mountains, at an altitude of 1,660-1,840 m, on the<br />
northern slopes of the mountains.<br />
The aerohygrophilous aspect of the Pseudevernia communities<br />
of Ochrolechia androgyna and Platismatia glauca<br />
has been well documented for Central Europe and has<br />
been described as a distinct association [Ochrolechio<br />
androgynae-Platismatietum glaucae (Hil.) Delzenne et al.,<br />
1978] and subassociation (Parmelietum furfuraceae Hil.<br />
1925, sensu Ochsner 1928, ochrolechietosum androgynae<br />
Barkm. 1958). The combination of these species on<br />
cedars is typical; thus they cannot be categorised into<br />
these syntaxa.<br />
var. with Parmelia submontana. Geographic variant of<br />
the dense cedar forests with thick ground cover found in<br />
the Central Atlas mountains, characterised by the dominance<br />
of Parmelia submontana, Phlyctis argena, and<br />
Hypogymnia tubulosa, found at lower altitudes with respect<br />
to the communities of Letharia vulpina, in habitats<br />
in which certain species of Ramalina, Physconia and<br />
Parmelia, are present, most of which are nitrophilous.<br />
Pseudevernio-Hypogymnietum<br />
laminisorediatae letharietosum subass. nov.<br />
Stable subassociation, with a continental, xerophile,<br />
and heliophile affinity. This subassociation characterises<br />
the lower-cover and luminous cedar forests which are prevalently<br />
at the top of the mountains, at altitudes of<br />
2,000 m, on cedars with a mean circumference of 380 cm.<br />
The erosion caused by wind results in the fragmentation<br />
of the thalli and favours the growth of Hypocenomyce<br />
scalaris, which firmly adheres to bark, and the vegetative<br />
propagation of Letharia vulpina.<br />
Those species that are characteristic of higher units,<br />
which require greater humidity, are missing.<br />
Class: Hypogymnietea physodis Follm. 1974<br />
Order: Hypogymnietalia physodo-tubulosae Barkm. 1958 (!Parmelietalia<br />
physodo-tubulosae) / syn.: Alectorietalia (Dahl & Hada÷, 1944)<br />
Alliance: Pseudevernion furfuraceae (Barkm.) (James et al., 1977) / syn.:<br />
Hypogymnion physodis Beschel 1958 (!Parmelion physodis)<br />
Association: Pseudevernio-Hypogymnietum laminisorediatae ass. nov.<br />
var. with Pertusaria tazzakensis<br />
var. with Parmelia submontana<br />
subassociation: Pseudevernio-Hypogymnietum laminisorediatae letharietosum<br />
subass. nov.<br />
Figure 1. Study<br />
area in Morocco.<br />
Geographical locations:<br />
1. Azrou,<br />
2. Michliffen,<br />
3. Jebel Hebri,<br />
4. Ifrane,<br />
5. Bab-Besen,<br />
6. Ketama.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
CONCLUSION<br />
This analysis of the epiphytic lichen vegetation of the<br />
Moroccan cedar forests, together with the comparison<br />
with the floristically similar communities of the European<br />
mountains, allowed us to identify vegetation that is both<br />
original and specific. In particular, we observed a new<br />
association, Pseudevernio-Hypogymnietum laminisorediatae,<br />
a first variant with Pertusaria tazzakensis on the Rif<br />
mountains, a second variant with Parmelia submontana on<br />
the Central Atlas mountains, and the subassociation<br />
Pseudevernio-Hypogymnietum laminisorediatae letharietosum<br />
in the forests at high altitudes, with continental climate,<br />
where Letharia vulpina is the differential species<br />
with respect to the European Letharia communities.<br />
The differences between the Moroccan and the<br />
European communities obviously depend on climatic,<br />
ecological, and phytogeographic factors, which are strictly<br />
related to the <strong>Mediterranea</strong>n character of the Cedrus atlantica<br />
forests.These forests, although reduced to fragments<br />
and surrounded by areas where human activity is quite<br />
intense, constitute extremely interesting conserved habitats,<br />
which need to be actively protected.<br />
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EPIPHYTIC LICHEN VEGETATION OF THE CEDRUS ATLANTICA FORESTS (MOROCCO) ◆<br />
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Strauchflechten. Ergebn. wiss. Untersuch. schweiz. Nat.-Parks<br />
3: 361-504.<br />
GIRALT M., 1996. Líquens epífits i contaminació atmosfèrica a la<br />
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Catalans. ASC, 113. Barcelona. 525 p.<br />
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of the West Himalayas. In: Davis P.H., Plant Life of<br />
South-West Asia. Edinburgh.<br />
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GmbHr & Co., Stuttgart. 1006 p.<br />
57
Population structure and habitat use in relation<br />
to body size in the grass snake (Natrix natrix) from<br />
a fragmented habitat of <strong>Mediterranea</strong>n central Italy<br />
Structure des populations et utilisation de l’habitat en relation<br />
avec la masse corporelle chez la couleuvre à collier (Natrix natrix)<br />
dans un habitat fragmenté d’Italie centrale méditerranéenne<br />
Lorenzo Rugiero 1, Massimo Capula 2, Luca Luiselli 3-4<br />
1. FIZV, via Domenico Cimarosa 13, I-00198 Roma, Italy<br />
2. Museo Civico di Zoologia, via Ulisse Aldrovandi 18, I-00197 Roma, Italy – email: m.capula@comune.roma.it<br />
3. Environmental Studies Centre Demetra and FIZV, via dei Cochi 48/B, I-00133 Roma, Italy<br />
4. Ecology Research Group, TSKJ Nigeria Ltd, 172 A Aba Road, Port Harcourt, Rivers State, Federal Republic of Nigeria<br />
Abstract<br />
Annual variation of the population structure and habitat use in<br />
relation to sex and body size of the grass snake, Natrix natrix, were<br />
studied in a fragmented agro-forest habitat of <strong>Mediterranea</strong>n central<br />
Italy. The study was carried out in two years (1995 and 1998).<br />
The population structure was different in the two years, as the proportion<br />
of subadults was much higher in 1995 than in 1998. Males<br />
were captured slightly more frequently than females, but the adult<br />
sex-ratio was similar in the two study years. The density of snakes<br />
felt dramatically of nearly 40% in the second study year, due to a<br />
clear decrement in the number of captured subadults. No specimen<br />
firstly marked in 1995 was recaptured in 1998. Natrix natrix<br />
individuals used the various basking sites available in the study<br />
area in a different way, depending on their body size. Some hypotheses<br />
to explain the size-based partitioning of the available habitat<br />
are presented and discussed.<br />
Key-words<br />
Natrix natrix, snakes, habitat fragmentation, population structure,<br />
sex-ratio, Italy<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 59-64<br />
Résumé<br />
Les variations annuelles dans la structure de population et l’utilisation<br />
de l’habitat en relation avec le sexe et la taille corporelle des<br />
individus ont été étudiées chez la couleuvre à collier Natrix natrix<br />
dans un milieu agro-forestier d’Italie centrale méditerranéenne.<br />
Cette étude a été conduite sur deux années de comparaison (1995<br />
et 1998). Les structures de population se sont avérées différentes<br />
entre les deux années, avec une proportion de subadultes nettement<br />
plus élevée en 1995 qu’en 1998. Les mâles ont globalement été capturés<br />
plus fréquemment que les femelles, mais le sex-ratio des adultes<br />
n’a pas varié entre les deux années d’étude. La densité des serpents<br />
a chuté de près de 40 % en 1998 du fait de la diminution nette<br />
des captures de subadultes. Aucun individu initialement marqué<br />
en 1995 n’a pu être recapturé en 1998. La fréquentation des sites<br />
de thermo-régulation disponibles dans la zone d’étude est variable<br />
en fonction de la taille corporelle des différents individus de Natrix<br />
natrix. Plusieurs hypothèses susceptibles d’expliquer le patron observé<br />
sont présentées et discutées.<br />
Mots-clés<br />
Natrix natrix, serpents, fragmentation de l’habitat, structure de<br />
population, sex-ratio, Italie<br />
59
60<br />
◆ LORENZO RUGIERO, MASSIMO CAPULA, LUCA LUISELLI<br />
INTRODUCTION<br />
In the last fifty years, enormous modifications of the<br />
pristine <strong>Mediterranea</strong>n landscape have been produced<br />
in the Italian peninsula, in particular by fragmenting the<br />
pristine wooded surface into a patchy mosaic of “wooded<br />
islands” interspersed inside a “sea” of areas modified<br />
by human impact (Mazzoleni & Spada, 1992). The<br />
extensive fragmentation of the natural landscape caused<br />
catastrophic consequences on several species of the vertebrate<br />
fauna, including several reptiles (see Andreone &<br />
Sindaco, 1998; Bologna et al., 2000). With regard to<br />
snakes, Filippi and Luiselli (2000) have pointed out that<br />
distribution-related factors, i.e. habitat loss and fragmentation,<br />
are the prevailing threats in Italy for more<br />
than 50% of the species.<br />
Since several years, we are studying the effects of habitat<br />
fragmentation both on the ecology of snakes of<br />
<strong>Mediterranea</strong>n central Italy (Luiselli & Capizzi, 1997)<br />
and the extinction risk of the various species (Filippi &<br />
Luiselli, 2000). In this paper, we analyse variation of some<br />
aspects of the population structure and habitat use of a<br />
population of grass snake (Natrix natrix Laurenti) inhabiting<br />
a typically fragmented and disturbed agro-forest<br />
habitat of <strong>Mediterranea</strong>n central Italy, in two different<br />
non-consecutive years. Our study aims to verify whether<br />
the population structure and the habitat use of Natrix<br />
natrix may vary substantially from year to year in a fragmented<br />
habitat. Natrix natrix was chosen as model species<br />
because (i) it is still relatively abundant in the study<br />
area despite the high levels of habitat disturbance, (ii) it<br />
is well known as a very adaptable species (Bruno &<br />
Maugeri, 1990; Luiselli & Capizzi, 1997), and (iii) it is<br />
one of the best known species of snakes in terms of ethoecology<br />
either in Italy (Luiselli & Rugiero, 1991; Gentilli<br />
& Zuffi, 1995; Luiselli, 1996; Luiselli et al., 1997) or in<br />
other European countries (Madsen, 1983, 1984; Madsen<br />
& Shine, 1993).<br />
MATERIALS AND METHODS<br />
The field study was carried out at an agro-forest area<br />
of central Italy (Vejo, province of Rome, approximately<br />
70 m a.s.l), that was also used by us for other snake studies<br />
(Capula et al., 2000). We investigated the structure<br />
of a Natrix natrix population by capture-mark-recapture<br />
procedure, in 1995 and 1998. In total, 166 days were spent<br />
in the field.<br />
The area inhabited by Natrix natrix was about 8.75<br />
ha. The area is sited inside a suburban sector of the city<br />
of Rome, and it is characterized by fragments of mixed<br />
oak forests surrounded by roads, houses, cultivations and<br />
grasslands. Natrix natrix occurs in a remnant thick oak<br />
forest, growing along the banks of a small stream. Inside<br />
this area, Natrix natrix individuals were constrained to<br />
bask only in five small sites (we named clearing “A”, “B”,<br />
“C”, “D”, “E”), that were subject to strong disturbance<br />
by humans and cars, especially at night.The general habitat<br />
conditions did not vary between the two study years.<br />
The five basking clearings had an almost identical grassy<br />
vegetation structure, but the clearings “A” and “B” were<br />
more wet than the clearings “C”, “D”, and “E”. This is<br />
clearly explained by the different average linear distance<br />
(m) between the various clearings and the stream banks<br />
(figure 1; one-way ANOVA: F = 8.710, d.f. = 4, 50, P =<br />
0.00002). Four clearings (“A”, “B”, “C”, “D”) were surveyed<br />
in both the study years, while the clearing “E” was<br />
surveyed only in 1998.<br />
Natrix natrix individuals were searched for by standardized<br />
routes conducted throughout each microhabitat<br />
type available in the study area.When captured, each<br />
individual was permanently marked by ventral scale-clipping<br />
(Brown & Parker, 1976). Then, it was painted with<br />
a white number on the back for easy individual identification<br />
within short timespans without necessity to further<br />
recapture it (see Luiselli, 1995; Luiselli et al., 1996, 1997).<br />
The captured individuals were routinarily measured to<br />
snout-vent length (SVL, to ± 0.5 cm precision) and sexed.<br />
For each capture event we recorded the exact spot of capture,<br />
the time of observation (Rome local time), and the<br />
type of activity exhibited by the snake.<br />
Population size was estimated, independently for the<br />
two study years, by using two different indexes, in a way<br />
to give a better approximation, according to Seber (1982).<br />
The two indexes are the following:<br />
[1] N = A x n / a (Lincoln-Petersen index);<br />
[2] N = A (n + 1) / (a + 1);<br />
where N is the population size, A is the total number<br />
of marked individuals, n is the total number of observed<br />
individuals, and a is the total number of recaptured individuals.<br />
Statistical analyses (χ2 test, ANOVAs followed by Tukey<br />
HSD post-hoc tests to identify direction trends of multiple<br />
comparisons) were performed using SPSS and STA-<br />
TISTICA for Windows PC package (version 4.3B). All<br />
tests were two-tailed, with alpha set at 5 %.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
POPULATION STUCTURE AND HABITAT USE IN RELATION TO BODY SIZE IN THE GRASS SNAKE (NATRIX NATRIX)… ◆<br />
RESULTS<br />
Population size, density and sex-ratio<br />
In 1995, 45 individuals were captured and marked (11<br />
males, 6 females, 28 subadults), 20 were observed and<br />
not captured, and 8 individuals were recaptured. In 1998,<br />
33 individuals were captured and marked (16 males, 8<br />
females, 9 subadults), 20 were observed, and 10 recaptured.<br />
Pooling data from the two years, the number of<br />
males exceeded that of females, but not at a statistically<br />
significant level (χ 2 = 3.12, d.f. = 1, P= 0.06).The apparent<br />
sex-ratio was similar in the two study years (1.8:1 in<br />
1995, 2:1 in 1998).The frequency of subadults was significantly<br />
higher in 1995 than in 1998 (χ 2= 27.58, d.f. = 1,<br />
P = 0.00001).<br />
The estimated rough population size was similar using<br />
both the indexes 1 and 2 ([1], N = 112 individuals in<br />
1995; N = 66 individuals in 1998; [2], N = 105 individuals<br />
in 1995; N = 63 individuals in 1998). From these<br />
estimates it seems that the Natrix natrix population experienced<br />
a very serious decline between 1995 and 1998<br />
(about 41% following the index [1], and 40% following<br />
the index [2]).<br />
The estimated rough density was 12-13 individuals ×<br />
ha -1 in 1995, and 7.2-7.5 individuals × ha -1 in 1998. If we<br />
consider only the adult specimens, the density was about<br />
5 individuals × ha -1 in 1995, and 4.5-5 individuals × ha -1<br />
in 1998. No specimen marked in 1995 was recaptured in<br />
1998.<br />
Habitat use in relation to sex and body size<br />
The frequencies of observation of males and females<br />
Natrix natrix in the five basking sites surveyed during the<br />
present study are presented in table 1. The inter-sexual<br />
difference in clearing utilization was not statistically significant<br />
in 1995 (χ 2 = 7.13, d.f. = 3, P = 0.068), while it<br />
Basking clearing 1995 1995 1998 1998<br />
males females males females<br />
A 9 (30%) 6 (35.3%) 2 (9.5%) 3 (21.4%)<br />
B 8 (26.7%) 6 (35.3%) 2 (9.5%) 3 (21.4%)<br />
C 5 (16.7%) 1 (5.9%) 6 (28.6%) 1 (7.1%)<br />
D 8 (26.7%) 4 (23.5%) 7 (33.3%) 6 (42.8%)<br />
E - - 4 (19%) 1 (7.1%)<br />
Table 1. Frequency of observation of Natrix natrix males and females<br />
in the five basking clearings in 1995 and in 1998.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 59-64<br />
was significant in 1998 (χ 2 = 27.2, d.f. = 4, P < 0.001).<br />
In the latter year, males especially used as basking sites<br />
the clearings “C” and “D”, while females the clearing “D”<br />
(table 1).<br />
The mean snout-vent length of the Natrix natrix individuals<br />
differed at a statistically significant level among<br />
the various basking clearings either in 1995 (Kruskal-<br />
Wallis ANOVA, P < 0.05) or in 1998 (Kruskal-Wallis<br />
ANOVA, P < 0.001; figure 2). A Tukey HSD post-hoc<br />
test revealed that (i) in 1995 we captured mainly large<br />
sized specimens at the clearing “D”, and (ii) in 1998 the<br />
large sized specimens were again captured frequently at<br />
the clearing “D”, but also at the clearing “E”.<br />
DISCUSSION<br />
Important aspects highlighted by our study are (i) the<br />
drastic decrement in the Natrix natrix population size<br />
from 1995 to 1998, and (ii) the remarkable inter-annual<br />
variation in the juvenile portion of the marked population.<br />
The drastic decrement of the population size<br />
(approximately 40%) was almost exclusively due to the<br />
latter factor, as the number of marked adults remained<br />
more or less constant in the two study years.<br />
Two years without surveys (i.e. 1996, 1997) were<br />
enough to have a complete turnover of the individuals, as<br />
no specimen captured in 1995 was recaptured three years<br />
later. This may be due (i) to the dispersal tendency and<br />
the wide home-range of the species (Madsen, 1984), (ii)<br />
to the regeneration of the “marked” ventral scales, that<br />
may confound identification of recaptured specimens<br />
when a long timespan passes throughout two capture<br />
events (Luiselli & Capula, unpublished data), (iii) to the<br />
different rate of birth in the years without surveys (1996,<br />
1997), and (iv) to unusually higher mortality rates due to<br />
habitat disturbance by man in the study area.<br />
Density of the Natrix natrix population was intermediate<br />
between that observed in populations from northwestern<br />
Italy (Gentilli & Zuffi, 1995) and that recorded<br />
in populations from central Germany (Mertens, 1995).<br />
The adult sex-ratio was similar to that observed in conspecific<br />
populations by other Authors (see, e.g., Gentilli &<br />
Zuffi, 1995; Mertens, 1995; Luiselli, 1996; Luiselli et al.,<br />
1997). It was also in good agreement with the adult sexratio<br />
expected in a species with an operational sex-ratio<br />
skewed towards males (see, e.g., Madsen & Shine, 1993;<br />
Luiselli, 1996). Considering that in both the study years<br />
we surveyed the area along the whole activity period of<br />
61
62<br />
◆ LORENZO RUGIERO, MASSIMO CAPULA, LUCA LUISELLI<br />
Figure 2. Averages (and dispersion measures)<br />
of the Natrix natrix snout-vent length (SVL)<br />
in the five basking clearings,<br />
in 1995 (A) and in 1998 (B).<br />
For statistical details, see text.<br />
Figure 1. Averages (and dispersion measures)<br />
of the linear distance (in m) between the five basking<br />
clearings and the banks of a stream.<br />
For statistical details, see text.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
POPULATION STUCTURE AND HABITAT USE IN RELATION TO BODY SIZE IN THE GRASS SNAKE (NATRIX NATRIX)… ◆<br />
the snakes, it is likely that the observed adult sex-ratio is<br />
a true reflection of the actual population structure (Parker<br />
& Plummer, 1987).<br />
The tendency toward a snake-size based selection of<br />
basking clearings is noteworthy and deserves further<br />
research.This trend was consistent in both the study years,<br />
which means that a given category of individuals tended<br />
to select a given clearing in both years. Apart for differences<br />
in mean humidity, the vegetation structure of the<br />
five basking clearings was practically identical, which led<br />
us to reject the possibility that the snake-size based habitat<br />
partitioning was simply the effect of diverging catchability<br />
patterns among snake body size classes.We can<br />
put forward the hypothesis that the different size categories<br />
of snakes selected different basking clearings in relation<br />
to their ecological needs, i.e. the need of encountering<br />
precise prey types (e.g., adults of Bufo bufo for the<br />
larger specimens, juveniles Bufo bufo and Rana italica for<br />
young individuals and smaller adults), and the need of<br />
finding good oviposition sites by the gravid females.The<br />
evidence for this hypothesis is that in the basking clearings<br />
“D” and “E”, where the larger Natrix natrix individuals<br />
were captured, adult specimens of Bufo bufo were<br />
much more common than in the other three clearings. On<br />
the other hand, Rana italica and newly metamorphosed<br />
Bufo bufo were especially abundant in the clearings “A”,<br />
“B” and “C” (Rugiero, unpublished data). At this regard,<br />
it must be stressed that the Italian Natrix natrix populations<br />
investigated to date are known to feed on tadpoles<br />
and small frogs during the first years of life, and on adult<br />
toads during the late maturity years (Luiselli et al., 1997).<br />
Concerning the inter-sexual differences in the utilization<br />
of the five basking clearings, the pattern emerging<br />
from our data is less obvious. In one of the study years<br />
(1995) the two sexes exhibited similar basking clearing<br />
selection, while in the other study year (1998) there was<br />
a significant inter-sexual difference in basking clearing<br />
utilization. We think that further research is necessary in<br />
order to give firm conclusions, especially in consideration<br />
of the fact that inter-sexual variation in life-history traits<br />
is one of the major problems in contemporary snake<br />
research (see, e.g., Shine, 1986, 1991, 1994; Parker &<br />
Plummer, 1987; Houston & Shine, 1993).<br />
ACKNOWLEDGEMENTS<br />
We thank Dr Dario Capizzi (Roma) and Dr Francesco<br />
M. Angelici (Roma) for helpful discussion on several<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 59-64<br />
issues of this paper. Dr Marco A.L. Zuffi (Pisa) kindly<br />
revised the final version of the manuscript. The field<br />
research was supported by a grant (X98NNP) by<br />
“Demetra SpA” and by MURST 40% funds (grant<br />
‘Variazione geografica e diversità a livello di specie, faune<br />
e zoocenosi: cause storiche ed ecologiche’).<br />
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Seigel R.A., Collins J.T. & Novak S.S. (eds.), Snakes:<br />
Ecology and Evolutionary Biology, MacMillan, New York:<br />
253-301.<br />
SEBER G.A.F., 1982. The Estimation of Animal Abundance and<br />
Related Parameters. Charles Griffin & Co. Ltd., London.<br />
SHINE R., 1986. Sexual differences in morphology and niche utilization<br />
in an aquatic snake, Acrochordus arafurae. Œcologia<br />
69: 260-267.<br />
SHINE R., 1991. Intersexual dietary divergence and the evolution<br />
of sexual dimorphism in snakes. Am. Nat. 138: 103-122.<br />
SHINE R., 1994. Sexual size dimorphism in snakes revisited.<br />
Copeia 1994: 326-346.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
The colonisation of the Great Spotted Woodpecker<br />
(Picoides major L.) in Eucalypt woods<br />
and Popular Cultivations in Sicily 1<br />
La colonisation des plantations d’eucalyptus et de peupliers<br />
en Sicile par le pic épeiche (Picoides major L.)<br />
Tommaso La Mantia 1, Michele Spoto 2,Bruno Massa 3<br />
1. Dipartimento di Colture Arboree, Universit degli Studi, Viale delle Scienze 11, 90128 Palermo I; email: lamantia@unipa.it<br />
2. Stazione di Inalellamento, c/o Dipartimento Senfimizo, Vialle delle Scienze 13, 90128 Palermo I<br />
3. Entomologia, Acarologia and Zoologia, Dipartimento Senfimizo, Vialle delle Scienze 13, 90128 Palermo I; email: zoolappl@unipa.it<br />
Summary<br />
Thank to the forestry activity, in the last half of the century the<br />
wood surface in Sicily has increased. The species planted were<br />
<strong>Mediterranea</strong>n pine and Eucalyptus spp., the latter were used<br />
because considered more adapted to marginal soils. In comparison<br />
with some natural formations, Eucalyptus plantations appear quite<br />
poor either from floristic and faunistic point of view. Nevertheless,<br />
in the last years, some Australian species of insects, linked to<br />
Eucalyptus, colonised the European continent, contributing to<br />
increase the biodiversity of Eucalypt afforestations. The recent diffusion<br />
of the Great Spotted Woodpecker (Picoides major L.) in<br />
these woods is part of this process, which involved also other types<br />
of wood plantations, like poplar cultivation. In the Eucalypt afforestations,<br />
the Great Spotted Woodpecker exploits Eucalyptus, both<br />
extracting from them larvae of the Cerambycidae beetle Phoracantha<br />
semipunctata and drinking the sap oozing out through holes made<br />
along the trunk. This bird species is actually spreading in Pinus,<br />
Eucalytpus and Populus woods close to natural and semi-natural<br />
formations, as well as in isolated woods, using almond and olive<br />
orchards as biocorridors.<br />
Key-words<br />
Eucalyptus, Populus, Picoides major, Phoracantha semipunctata,<br />
Sicily<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 65-73<br />
Résumé<br />
Du fait d’une importante activité de reboisement durant la dernière<br />
moitié du siècle passé, la superficie des forêts en Sicile a considérablement<br />
augmenté. Les espèces utilisées pour le reboisement ont<br />
surtout été des pins méditerranéens et différentes espèces d’eucalyptus<br />
; ces dernières ayant souvent été préférées car considérées comme<br />
mieux adaptées à des conditions de sol difficiles. Comparées aux<br />
formations forestières naturelles, les plantations d’eucalyptus sont<br />
généralement plus pauvres tant d’un point de vue floristique que<br />
faunistique. Néanmoins, quelques espèces d’insectes australiens inféodés<br />
aux eucalyptus ont également colonisé le continent européen,<br />
contribuant ainsi à l’augmentation de la biodiversité de ces boisements.<br />
La colonisation récente de ces boisements d’eucalyptus ainsi<br />
que des plantations de peupliers par le pic épeiche (Picoides<br />
major L.) fait partie du même processus. Les facteurs qui ont favorisé<br />
cette colonisation du pic sont d’une part, la présence du coléoptère<br />
cérambycide Phoracantha semipunctata, dont les larves vivant<br />
dans les troncs des eucalyptus sont particulièrement recherchées par<br />
le Pic et, d’autre part, la consommation de la sève d’eucalyptus qui<br />
suinte au travers des trous creusés par l’oiseau le long du tronc. Cette<br />
espèce est actuellement en expansion dans les boisements de Pinus,<br />
Eucalyptus et Populus, à proximité de formations naturelles ainsi<br />
qu’au niveau de bosquets isolés où les vergers d’amandiers et d’oliviers<br />
servent de corridors biologiques.<br />
Mots-clés<br />
Eucalyptus, Populus, Picoides major, Phoracantha semipunctata,<br />
Sicile<br />
1. Paper carried out within the research program “Programma Operativo Multiregionale – Misura 2 – Innovazioni tecnologiche e trasferimento dei risultati<br />
della ricerca – Progetto B28: Nuove metodologie per la gestione sostenibile dei sistemi forestali complessi nell’Italia Meridionale”. Authors took equal parts<br />
in its fulfillment.<br />
65
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◆ TOMMASO LA MANTIA, MICHELE SPOTO, BRUNO MASSA<br />
Riassunto<br />
Nell’ultima metà del secolo scorso, la superficie forestale in Sicilia<br />
ha avuto un discreto incremento determinato dall’opera di rimboschimento.<br />
Le specie utilizzate sono state soprattutto pini mediterranei<br />
ed eucalitti. Questi ultimi sono stati utilizzati per la presunta<br />
elevata produttività e della effettiva capacità di adattamento alle<br />
situazioni pedologiche più difficili. I nuovi boschi di eucalitto hanno<br />
mostrato tutti i loro limiti in termini ecologici, non consentendo<br />
un’elevata diversità floro-faunistica. In questi ultimi anni, grazie<br />
anche alla colonizzazione da parte di specie di insetti proprie dell’eucalitto,<br />
è in atto un processo di naturalizzazione, che precorre una<br />
Photos 1 and 1bis. During the winter some Eucalyptus camaldulensis show a series of regularly spaced holes<br />
from which the Great Spotted Woodpecker obtain the sugary sap.<br />
probabile diversificazione dell’habitat. La diffusione del Picchio<br />
rosso maggiore negli eucalitteti si inserisce in questo processo; esso è<br />
stato osservato anche in altri tipi di rimboschimenti, come i pioppeti,<br />
la cui finalità è del tutto differente. Negli eucalitteti, il Picchio<br />
si nutre delle larve della Phoracantha semipunctata e della linfa<br />
ottenuta effettuando numerosi fori nel tronco di alcune piante. La<br />
specie si è diffusa in boschi di pini ed eucalitti, contigui a formazioni<br />
naturali e seminaturali ma anche in boschi isolati dimostrando<br />
una capacità dispersiva inattesa. Le osservazioni hanno<br />
accertato il ruolo di corridoi ecologici svolto dagli arboreti come<br />
mandorleti ed oliveti nel consentire questa espansione.<br />
Photo 2. Holes made by woodpeckers<br />
on a telephone pole, probably with<br />
the aim to excavate a nesting hole.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
THE COLONISATION OF THE GREAT SPOTTED WOODPECKER (PICOIDES MAJOR L.) IN EUCALYPT WOODS… ◆<br />
INTRODUCTION<br />
One of the main causes of the massive use of Eucalyptus<br />
species in the past decades has been the total absence of<br />
specific pests interfering significantly with the production<br />
processes. Nevertheless, in the last years, as international<br />
woody exotic species trade became more and more<br />
intense, the increasing import of entire trees and vegetative<br />
propagules enhanced the dispersal opportunities for<br />
a high number of insects linked to Eucalyptus species in<br />
their original country. As matter of the fact, the australian<br />
beetle Phoracantha semipunctata Fabricius became<br />
almost cosmopolite. In Europe it was recorded firstly in<br />
Sardinia (Tassi 1969; Piras et al., 1970) where, according<br />
to Cavalcaselle and Contini (1973) about 100,000 trees<br />
were already attacked in 1971; in the following years it<br />
was also reported from Sicily (Romano & Carapezza,<br />
1975) and Central-South Italy (Parenzan, 1976; Longo<br />
et al., 1993; Rastelli et al., 2001).<br />
Additionally, due to hazelnut economical crisis (Clerici<br />
& Asciuto, 1991), many poplars took the place of hazel<br />
orchards, or, in some pedologically favourable territories,<br />
previously uncultivated, a productive poplar cultivation<br />
started. Actually the surface of poplar in this area is about<br />
300 ha.<br />
Generally, Eucalypt plantations are very poor in bird<br />
species, but in the last ten years in Sicily they were colonised<br />
by the Great Spotted Woodpecker (Picoides major<br />
L.). Aims of this research were to ascertain the actual diffusion<br />
of this species into Sicilian Eucalypt and poplar<br />
plantations and its behavioural relationships with these<br />
trees.<br />
MATERIALS AND METHODS<br />
Between 1995 and 2001 all Eucalyptus woods of Sicily<br />
were visited to record: a) the possible presence of the<br />
Australian xylophagous Phoracantha semipunctata by its<br />
typical emerging holes or the presence of adults or larvae<br />
under the bark; b) the possible presence of the Great<br />
Spotted Woodpecker (Picoides major L.) by its calls, its<br />
typical druming (mechanical sound made by resonance<br />
of dead branches under rapid blows from bill) or other<br />
evidences of its activity on tree bark. Abundance of some<br />
woodpecker populations was estimated by the IKA<br />
method (Ferry & Frochot, 1958), which gives linear values<br />
of abundance referred to a measure unit (number of individuals<br />
per km). Holes were inspected to ascertain if used<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 65-73<br />
by woodpeckers to nest, drum or feed. Some data on its<br />
feeding habits were obtained through observations in the<br />
field with the aid of a 10 x 40 binocular.<br />
In the years 1999-2000 in five eucalypt forests seven<br />
sample areas (0.5 ha) were established, where the diameter<br />
of all trees (n = 1119) was measured by a calliper,<br />
and evidences of the woodpecker presence (nests, druming<br />
and feeding holes) were recorded.<br />
The main features of the studied Eucalyptus plantations<br />
are reported in table 1. Mustigarufi is the largest<br />
one, with three species of Eucalyptus (E. camaldulensis,<br />
E. occidentalis and E. globulus) mixed at patch. The plots<br />
have been selected within two homogeneous areas but the<br />
observations were carried out in the entire wood. Reina,<br />
Torretta and Cannatello woods are homogeneous and<br />
similar according to species, surface and age on the<br />
contrary Spagnolo wood shows some differences in species<br />
utilisation and plant size.<br />
Additionally, in the years 1999-2000, in the poplar cultivation<br />
of Piazza Armerina (Enna) some observations<br />
were carried out to ascertain which clones are preferred<br />
by woodpeckers for feeding and nesting; three sample<br />
areas 40 x 40 m were established to gather some biometrical<br />
parameters and to evaluate the percentage of trees<br />
(n = 206) exploited by woodpeckers.<br />
RESULTS AND DISCUSSION<br />
Spreading of the Great Spotted Woodpecker<br />
in eucalypt wood: toward<br />
a new association woodpecker-eucalypt?<br />
Woodpeckers are a bird group clearly defined and<br />
homogeneous, highly specialized for the arboreal life,<br />
widespread all over the world, with the exception of<br />
Australia, New Zealand and Madagascar. The Great<br />
Spotted Woodpecker (Picoides major) constitutes a superspecies<br />
with P. leucopterus, P. assimilis, P. himalayensis and<br />
P. syriacus and is well diffused in the Palearctic Region, in<br />
woodland, plantations and some urban parks (Del Hoyo<br />
et al., 2002). In Sicily it was known as uncommon and<br />
local resident breeder (Iapichino & Massa, 1989), living<br />
in all the naturally wooded areas. Lo Valvo et al. (1993)<br />
recorded it on 19.9 % of UTM 10 x 10 km sicilian<br />
squares; more recently, presumably from nearby natural<br />
woods, it colonized some woods, including Eucalyptus<br />
woods, poplar afforestations and riparian woods, with an<br />
67
68<br />
◆ TOMMASO LA MANTIA, MICHELE SPOTO, BRUNO MASSA<br />
Wood, Municipality Area Plants/ha Occurrence (%) Mean Ø Plants with holes made by woodpeckers for drinking sap Plants with holes for nests<br />
(Province) (in ha) of different species (± s.d.) in cm<br />
in the sample area<br />
n/ha % Mean Ø % of Eucalyptus species nests/ha Mean Ø % of Eucalyptus species with<br />
(± s.d.) in cm with woodpecker holes woodpecker holes<br />
Mustigarufi, 3,252 289 100 E. camaldulensis 24.3 ± 5.5 11 3.8 19.3 ± 4.3 100 E. camaldulensis* 2 29.2 100 E.camaldulensis*<br />
San Cataldo (CL)<br />
Reina, 210 350 95 E. camaldulensis 16.4 ± 4.4 13 3.7 15.6 ± 3.5 100 E. camaldulensis 3 24.7 100 E.camaldulensis<br />
Mussomeli (CL) 5 E. occidentalis<br />
Torretta, 76 750 95 E. camaldulensis 15.8 ± 4.4 10 1.5 17.0 ± 2.4 100 E. camaldulensis 2 28.6 100 E.camaldulensis<br />
Mussomeli (CL) 5 E. occidentalis<br />
Cannatello, 137 500 95 E. camaldulensis 16.5 ± 4.7 8 1.6 16.0 ± 2.2 100 E. camaldulensis 2 22,0 75 E.camaldulensis<br />
Mussomeli (CL) 5 E. occidentalis 17.0 ± 4.2 25 E.occidentalis 32,0<br />
Spagnolo, 226 350 56 E. occidentalis 11.1 ± 4.88 10 2.9 10.3 ± 2.3 100 E. camaldulensis 2 11,0 75 E. camaldulensis<br />
Milena (CL) 44 E. camaldulensis 10.8 ± 4.2 12,0 25 E. occidentalis<br />
* Outside sample areas some specimens of E. occidentalis with presence signs of woodpeckers were observed.<br />
Table 1. Some parameters of Sicilian Eucalyptus woods where woodpecker activity was observed and characteristics of plants where woodpeckers carried out their activity.<br />
amount of variation of another 6.4%, totally covering<br />
26.3% of UTM squares (fig. 1 and 2).<br />
This was unexpected, particularly because Eucalyptus<br />
afforestations are generally considered very poor in fauna<br />
and flora (La Mantia & Pasta, 2001); additionally, as<br />
reported by some authors (e.g. Hinsley et al.,1995), this<br />
woodpecker is usually lacking in small woods, like most<br />
Sicilian afforestations.<br />
Censuses of woodpeckers carried out in Sicilian natural<br />
woods let us to obtain densities remarkably higher than in<br />
afforestations, particularly of Eucalyptus. In oakwoods and<br />
beechwoods we found as much as 3-5 individuals/10 km,<br />
while in Eucalyptus afforestations only 0.5-1 individuals/10<br />
km; the difference was significant (Wilcoxon test: Z 8=1.94,<br />
P=0.05). During the winter we found many small holes<br />
(mean width 1.5 cm, depth 0,5 cm) on scattered trees; the<br />
result of its activity is a very high number of rings of holes<br />
around the trunk trees. Following its behaviour, we assumed<br />
that the food source was the sap and that the woodpecker<br />
used to exploit many times the same tree for this<br />
reason.<br />
Many species of woodpeckers, Great Spotted Woodpecker<br />
included, cover the bark of living trees with series<br />
of regularly spaced holes from which they obtain the<br />
sugary sap (Del Hoyo et al., 2002). Typically, the holes,<br />
known as “sap wells”, are arranged in horizontal rows,<br />
which, together with those made in previous years, can<br />
extend over rather distinctly large parts of a tree.<br />
Tree sap may be the key resource for survival in arid<br />
habitats.<br />
This behaviour indicates that the sap was not randomly<br />
searched for, but the same tree was exploited for a long<br />
time. Previously, other authors highlighted the importance<br />
of sap as food of P. major (cf. Cramp, 1985 and<br />
references therein); the rings of holes are made by woodpeckers<br />
to drink sap oozing out or, possibly, also to eat<br />
exposed cambium of tree. Similar situation were observed<br />
an individual tree of Ulmus glabra, showing over 400<br />
holes for sap extraction, thus certainly used for many<br />
years (Gatter, 1972).<br />
As regards the size of trees concerned by woodpecker<br />
activity it is variable. Woodpeckers seem to prefer trees<br />
characterized by a small trunk diameter (table 1 and fig. 3).<br />
The mean diameter of trees where woodpeckers excavated<br />
nesting holes resulted a bit larger, and dependent again<br />
on the mean size of trees (table 1 and fig. 3), but the scarce<br />
number of trees did not allowed a statistic test.<br />
Xylophagous larvae of P. semipunctata are also an<br />
important prey in winter. In Eucalyptus afforestations<br />
insects are scarce and uncommon, and larvae of P. semi-<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
THE COLONISATION OF THE GREAT SPOTTED WOODPECKER (PICOIDES MAJOR L.) IN EUCALYPT WOODS… ◆<br />
Fig. 2. Map of Sicilian wood in Sicily<br />
(after Lo Valvo et al., 1993).<br />
punctata may provide an important part of the woodpecker’s<br />
diet (as reported by Mendel et al. (1984) for P. syriacus<br />
in Israel).We observed woodpeckers capturing insects<br />
living under bark in dead trees and in dead wood in the<br />
ground during the winter, and insects living on the surface<br />
of trees and on foliage in spring and summer.There<br />
are also consistent data reporting seeds, bird eggs and<br />
chicks as food of this woodpecker (Cuisin & Pesson, 1980;<br />
Cramp, 1985). Also Amat and Soriguer (1983) and Zenatello<br />
(1995) report as food of P. major in spring both xylophagous<br />
insects and other species collected on the leaves<br />
(particularly on the lower surface). Different authors have<br />
stressed the importance of xylophagous larvae in the diet<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 65-73<br />
Fig. 1. Map of distribution of the Great Spotted Woodpecker<br />
(Picoides major L.) in Sicily.<br />
In black the 10 x 10 km UTM squares where<br />
the woodpecker was present in 1979-93<br />
(after Lo Valvo et al., 1993), in white newly colonised areas.<br />
of this woodpecker, mostly in winter. Woodpeckers are<br />
efficient predators of overwintering moth larvae, frequently<br />
reducing the pest population in orchards to a level<br />
where other natural control agents were able to prevent<br />
the succeeding generation from damaging the fruit to an<br />
uneconomical degree (Mac Lellan, 1959).<br />
Adult and larvae of bark beetles form 67-99 % of the<br />
winter diet of woodpeckers in infected areas, and their<br />
activity results in 45-98 % decrease in beetle survival<br />
(Crockett & Hanoley, 1978). Woodpeckers have been<br />
recognized for many years as a major factor in the natural<br />
reduction of Engelmann spruce beetle populations<br />
(Knight, 1958). P. major is considered an important pre-<br />
69
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◆ TOMMASO LA MANTIA, MICHELE SPOTO, BRUNO MASSA<br />
Fig. 3. Mean diameter of trees in different Eucalypt woods (c = Eucalyptus camaldulensis;o=Eucalyptus occidentalis)<br />
and mean diameter of trees used by woodpeckers for nesting and for drinking sap.<br />
dator of overwintering larvae of Scolytus intricatus, being<br />
responsible of capturing up to 62.6 % of them (Pavlik,<br />
1999). Related species are also considered important predators<br />
of xylophagous insects. Mendel et al. (1984) observed<br />
that hole density of P. syriacus on Eucalyptus increase<br />
during the spring and summer, and that the average larval<br />
mortality of P. semipunctata due to predation of this<br />
woodpecker may reach as much as 29 %. They consider<br />
P. syriacus an efficient natural enemy of P. semipunctata,<br />
destroying larvae and consuming the eggs on standing<br />
trees.<br />
We dissected some trees bearing a high number of<br />
rings of holes (testifying the woodpecker activity for drinking<br />
sap), without finding any evidence of the presence<br />
of xylophagous insects. Conversely, only removing the<br />
bark of trees with wide and irregular woodpecker holes,<br />
we found the typical galleries of P. semipunctata.Thus, we<br />
may assume that woodpeckers excavate on the plant regu-<br />
lar and horizontal small holes to drink sap. As a matter of<br />
fact, only from parts of trees bearing wide and irregular<br />
woodpecker holes, preserved in laboratory, adults of<br />
P. semipunctata emerged.<br />
As regards eucalypt species, when woodpecker is searching<br />
for sap, it prefers Eucalyptus camaldulensis and E.globulus,<br />
probably because these species have a gum type<br />
deciduous bark (Moggi, 1964); species, with persistent<br />
bark, like E. occidentalis which present Stringybark type<br />
(Moggi, 1964), are not interested by woodpecker drinking<br />
activity. Conversely, the woodpecker activity for extracting<br />
larvae of P. semipunctata is independent from the<br />
eucalypt species and the bark type.<br />
During our research, we found rings of holes made by<br />
woodpeckers also on some Aleppo Pine (Pinus halepensis),<br />
Cypress (Cupressus sempervirens) and Elm (Ulmus<br />
minor) and, exceptionally, also on a telephone pole, probably<br />
with the aim to excavate the nesting hole. Several<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
THE COLONISATION OF THE GREAT SPOTTED WOODPECKER (PICOIDES MAJOR L.) IN EUCALYPT WOODS… ◆<br />
Clones plants/ha Mean diameter Height Plants bearing Nesting or resting holes<br />
% n (cm) (m) woodpecker Plants with holes Mean N. Height range of<br />
feeding holes (%) of holes per plant holes (m)<br />
I 614 12 50 41 30.0 25* 63** 3.5 5-7<br />
Armerino 88 381 24 25.7 – – – –<br />
* feeding holes and nesting or resting holes were found in different plants<br />
** % is referred to the total number of plants of the clone<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 65-73<br />
Table 2. Characteristics of poplar cultivations and woodpecker activity at Piazza Armerina (Enna).<br />
authors have reported damages caused by woodpeckers.<br />
Evers (1982) noticed in Germany and Norway some cases<br />
of Norway Spruce power line poles (preserved with carbolineum),<br />
exploited as sites for the excavation of nesting<br />
holes by P. major, while Moran (1977) reported cases of<br />
attack to polyethylene irrigation pipes in Israel orchards<br />
by P. syriacus. According to Allegro (1993), the benefits<br />
of P. major (which feeds on a wide range of insect pests)<br />
outweigh any damage to the tree bark and stems which<br />
may be caused. As regards eucalypt woods, probably trees<br />
injured by woodpecker activity are more easily submitted<br />
to pathogen and P. semipunctata attacks, but certainly the<br />
woodpecker results to be an important natural enemy of<br />
the xylophagous insect. Indeed, we found many trees killed<br />
by the attacks of P. semipunctata, while we did not find<br />
dead trees, bearing typical rings of holes caused by woodpecker<br />
searching for sap.<br />
In the wood of Mustigarufi we observed the highest<br />
activity of the woodpecker against larvae of P. semipunctata<br />
in plots where trees, according to Fierotti et al. (1995),<br />
grow under very unfavourable conditions. Evidence of its<br />
activity was the presence of irregular holes spread on the<br />
bark. On the contrary, in plots where trees grow under<br />
quite favourable conditions, we mostly observed the typical<br />
woodpecker activity for extracting sap, testified by the<br />
presence of small regular rings of holes.<br />
Concerning sampled eucalypt woods, they (with the<br />
exception of Mustigarufi) are small sized and well isolated<br />
from other woods. It seems that P. major has colonised<br />
these woods through areas with scattered trees, like<br />
almond orchards, that it exploits in autumn-winter for<br />
feeding reasons (A. Cairone, pers. comm.) and suggests<br />
the important role of small woods and biocorridors. At<br />
local scale, some studies (La Mantia 1997; Massa & La<br />
Mantia, 1997) have already highlighted the key-role played<br />
in Sicily by biocorridors and hedgerows-windbreaks in<br />
conserving and increasing species richness.<br />
Colonisation of the poplar cultivation<br />
of Piazza Armerina by the Great Spotted<br />
Woodpecker<br />
Recently, the Great Spotted Woodpecker has colonised<br />
the poplar cultivations of Piazza Armerina, in central<br />
Sicily (fig. 2).This area has been cultivated with a mosaic<br />
distribution of Eucalyptus, poplar, Pinus pinea, and riparial<br />
vegetation which increased the diversity. Nowadays,<br />
at Piazza Armerina the following poplar clones are cultivated<br />
(Garfì & La Mantia, unpublished data): 1)<br />
‘Armerino’, now naturalised, which is a hybrid of uncertain<br />
origin between Populus nigra and euroamerican<br />
hybrids introduced to Piazza Armerina. Despite its lower<br />
productivity in comparison with other clones, it shows a<br />
higher fitness to the environment and very good technological<br />
characteristics to produce matches that are the<br />
main local product; 2) ‘I 214’, an euroamerican clone very<br />
diffused in the modern poplar cultivation for its high productivity,<br />
at Piazza Armerina it has been decreasing<br />
because its wood is not suitable for matches production;<br />
3) ‘Luisa Avanzo’, also introduced for its high productivity,<br />
but, for the same reasons of ‘I 214’, has become rare.<br />
As a consequence of the availability of newly afforested<br />
territories (both of eucalypts and poplars), the Great<br />
Spotted Woodpecker has recently colonised the above<br />
cited poplar plantations, showing evident preferences for<br />
some clones. In particular, in poplar stands with mixed<br />
clones, it does not excavate holes in trees of ‘Armerino’,<br />
while it does in ‘Luisa Avanzo’ and ‘I 214’ clones, both<br />
for feeding and nesting. Our observations (table 2) let us<br />
to conclude that the presence of few trees of ‘I 214’ or<br />
‘Luisa Avanzo’ (preferred by woodpeckers) possibly<br />
consents to protect them from xylophagous attacks,<br />
without be detrimental to technological characteristics of<br />
‘Armerino’ trees. Some farmers report negative effects of<br />
woodpeckers on poplars, but scattered ‘I 214’ and ‘Luisa<br />
71
72<br />
◆ TOMMASO LA MANTIA, MICHELE SPOTO, BRUNO MASSA<br />
Avanzo’ clones may play the same role of dead trees and<br />
natural woods bordering poplar cultivations of North Italy<br />
(Allegro, 1991). Concerning the positive role of this woodpecker<br />
within poplar stands, Camerini & Quadrelli (1991)<br />
report the interesting observation of its active predation<br />
on Ostrinia nubilalis living within stems of corn that area<br />
cultivated at the edge of a young poplar, where it regularly<br />
preyed the xylophagous Cossus cossus, Saperda carcharias<br />
and Paranthrene tabaniformis (cf. also Allegro 1991,<br />
1993). In winter, in riparian forests of poplar this woodpecker<br />
may destroy about 10-50% of larvae of Saperda<br />
carcharias by pecking them out of their galleries (Srot,<br />
1983; Allegro, 1991 and 1996). According to Quadrelli<br />
(1984), in poplars of North Italy it removes about 20%<br />
of larvae of Cossus cossus, showing a higher foraging activity<br />
in trees with diameter between 40-50 and 80-90 cm.<br />
CONCLUSIONS<br />
The recent diffusion of the Great Spotted Woodpecker<br />
suggests the important role of small woods and biocorridors.Their<br />
function has been recognised at an international<br />
level and led to the realisation of the “European Ecological<br />
Network” (E<strong>ECO</strong>NET) (Benett, 1991, 1994).<br />
The results of this work, focusing on the role of great<br />
spotted woodpecker and Phoracantha semipunctata, show<br />
an increase of ecological interactions within these artificial<br />
woods. For this reasons several researches are now<br />
involved in the identification of the best approach to<br />
increase their naturalisation process (La Mantia et al.,<br />
2000). In particular, the adoption of more adequate selvicultural<br />
techniques should enhance the diffusion of<br />
many autochthonous trees and berry-producing shrubs.<br />
The so-called “re-naturalisation actions” (La Mantia &<br />
Pasta, 2001) could be applied in different ways, depending<br />
on the wood-type; besides, they should allow an<br />
increase and a maintainance of species-richness (Ciancio,<br />
2000).Thus, it is necessary to fit wood implantation and<br />
management techniques to the new role that wood itself<br />
plays in the western countries.<br />
AKNOWLEDGEMENTS<br />
We thank the staff of the Forestry Office of Sutera and<br />
Mustigarufi, and particularly Mr. S. Butera, Mr. G. Farina<br />
and Mr. C. Platania (ISFA Catania), who allowed and<br />
facilitated our investigations in the poplar implantation of<br />
Piazza Armerina; Mr. P. Colina for his kind help,<br />
A. Cairone, V. Di Dio, R. Ientile, M. Lo Valvo and<br />
O. Vitrano for providing their personal data on Great<br />
Spotted Woodpecker. Thanks to I. Sparacio for bibliographic<br />
researches, G. Garfì and M. Cassarà for field<br />
investigations at Piazza Armerina.We are grateful to Miss<br />
N. Callea, for maps’ editing. This research was partially<br />
funded by the Assessorato Agricoltura e Foreste Regione<br />
Sicilia to Stazione di Inanellamento.<br />
The authors are thankful to P. Villard for the critical<br />
and careful reading of this paper.<br />
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THE COLONISATION OF THE GREAT SPOTTED WOODPECKER (PICOIDES MAJOR L.) IN EUCALYPT WOODS… ◆<br />
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73
Interactions between sympatric snakes, Coluber viridiflavus<br />
and Elaphe longissima: are there significant inter-annual<br />
differences in coexistence patterns?<br />
Interactions entre deux serpents sympatriques,<br />
Coluber viridiflavus et Elaphe longissima :existe-t-il<br />
des variations dans les modalités de coexistence inter-annuelles ?<br />
Lorenzo Rugiero 1, Dario Capizzi 2, Luca Luiselli 3<br />
1. FIZV, via Domenico Cimarosa 13, I-00198 Rome, Italy; email: lrugiero@hotmail.com<br />
2. INFS, via Ca’Fornacetta 14, Ozzano Emilia (Bologna), Italy; email: dario.capizzi@tin.it<br />
3. FIZV, via Olona 7, I-00198 Rome, Italy, and Institute of Environmental Studies “Demetra”,<br />
Largo Rina Morelli 15/III, I-00139 Rome, Italy; email: lucamlu@tin.it<br />
Abstract<br />
The dynamics of coexistence between two large-sized colubrid snakes<br />
(Elaphe longissima and Coluber viridiflavus) were studied in a<br />
mixed-oak forest in central Italy during eleven consecutive years<br />
(1986-1996). 511 adult C. viridiflavus (270 males, 241 females)<br />
and 294 adult E. longissima (153 males, 141 females) were captured<br />
and marked. Adult sex-ratio did not depart significantly from<br />
equality in either species. Males of both species were significantly<br />
larger (snout-vent-length) than females. The abundance ratio between<br />
the two species was always skewed towards C. viridiflavus<br />
(mean ratio: 1.65: 1, Standard Deviation = 0.32), although there<br />
were some annual fluctuations and inter-habitat differences in<br />
abundance patterns. Mean adult densities were 2.32 ± 1.05 specimens<br />
for C. viridiflavus and 1.34 ± 0.89 specimens x ha -1 for<br />
E. longissima. C. viridiflavus was abundant in sunny habitats<br />
and tended to avoid habitats with closed canopy, which were clearly<br />
preferred by E. longissima. Both species were, however, generalists<br />
in terms of macro-habitat preferences. There were no major interannual<br />
differences in the patterns observed. At all ages, the dietary<br />
spectrum of C. viridiflavus was wider than that of E. longissima<br />
and included rodents, lizards and birds (common prey for both species)<br />
as well as frogs and invertebrates, which were not taken at all<br />
by E. longissima. In addition, C. viridiflavus more often preyed<br />
upon Clethrionomys glareolus than on Apodemus flavicollis,<br />
whereas the reverse was true for E. longissima. Male C. viridiflavus<br />
consumed a significantly higher number of lacertids than rodents<br />
but females consumed an almost identical number of each; no such<br />
inter-sexual differences occurred in E. longissima. The diet composition<br />
of the juveniles of the two species essentially consisted of<br />
lacertid lizards, but C. viridiflavus also ate invertebrates. ‘Preysize-predator-size’<br />
relationships were similar in the two species. Body<br />
temperature (T b) was higher in C. viridiflavus (x = 25.4 ± 3.1 °C)<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 75-91<br />
than in E. longissima (x = 23.4 ± 1.8 °C), but in both species T b<br />
was positively correlated with air temperature (T a), and the regressions<br />
T a-T b were similar and both differed significantly from ideal<br />
poikilothermy. Body temperature did not correlate with snout-vent<br />
length in either species. The relative stability shown across years in<br />
this study system is likely to be due to the mature and stable conditions<br />
of the environment, the low level of habitat fragmentation<br />
and the high quality of habitat along the buffer zones. Species-specific<br />
eco-physiological requirements appear to explain the coexistence<br />
patterns of the two species better than any community-based<br />
synecological factors.<br />
Key-words<br />
Colubridae, Coluber viridiflavus, Elaphe longissima, Interspecific<br />
relationships, Ecology, Population biology, Italy<br />
Résumé<br />
La dynamique de coexistence entre deux espèces de serpents colubridés<br />
de grande taille (Elaphe longissima et Coluber viridiflavus)<br />
a fait l’objet d’un suivi, onze années durant (1986-1996), dans une<br />
forêt mixte de chênes en Italie centrale. 511 individus adultes de C.<br />
viridiflavus (270 mâles, 241 femelles) et 294 individus adultes de<br />
E. longissima (153 males et 141 femelles) ont ainsi été capturés, et<br />
marqués. Le sex-ratio des adultes ne diffère pas significativement de<br />
l’égalité pour les deux espèces. Les mâles des deux espèces se sont avérés<br />
être significativement plus gros que les femelles.<br />
Le rapport d’abondance entre les deux espèces a toujours été en<br />
faveur de C. viridiflavus (taux moyen : 1.65 :1, écart-type = 0.32)<br />
malgré quelques fluctuations annuelles et des différences inter-habitat<br />
dans les patrons d’abondance. Les densités moyennes d’individus<br />
adultes furent 2.32 ± 1.05 spécimens pour C. viridiflavus et<br />
1.34 ± 0.89 spécimens x ha-1 pour E. longissima. C. viridiflavus<br />
75
76<br />
◆ LORENZO RUGIERO, DARIO CAPIZZI, LUCA LUISELLI<br />
est une espèce particulièrement abondante dans les habitats ensoleillés<br />
qui tend à éviter les milieux trop fermés, lesquels sont clairement<br />
préférés par E. longissima. Les deux espèces se sont cependant<br />
avérées être relativement généralistes en termes de macro-habitats.<br />
Quel que soit l’âge, le spectre alimentaire de C. viridiflavus<br />
est apparu plus large que celui de E. longissima et inclut des rongeurs,<br />
des lézards et des oiseaux (proies communes pour les deux<br />
espèces) ainsi que des amphibiens et des invertébrés (chez E. longissima<br />
seulement). En outre, C. viridiflavus prédate plus fréquemment<br />
Cle-thrionomys glareolus que Apodemus flavicollis<br />
alors que c’est l’inverse pour E. longissima. Les mâles de C. viridiflavus<br />
consomment un nombre significativement plus élevé de<br />
lézards que de rongeurs alors que les femelles en consomment un<br />
nombre identique. Une telle différence entre les sexes n’a pas été<br />
mise en évidence chez E. longissima. Le régime alimentaire des<br />
juvéniles des deux espèces est essentiellement composé de lézards<br />
Lacertidés, mais C. viridiflavus consomme également des invertébrés.<br />
La relation “taille des proies-taille des prédateurs” est simi-<br />
laire chez les deux espèces. La température corporelle (T b) est plus<br />
élevée chez C. viridiflavus (x = 25.4 ± 3.1 °C) que chez E. longissima<br />
(x = 23.4 ± 1.8 °C), mais chez les deux espèces, T b est<br />
positivement corrélée avec la température de l’air (T a), et les régressions<br />
T a-T b présentent des valeurs identiques et différent de la poïkilothermie<br />
idéale. La température du corps n’est corrélée avec la<br />
longueur du corps chez aucune des deux espèces. La relative stabilité<br />
au cours des années est probablement due aux conditions stables<br />
et matures de l’environnement, le faible degré de fragmentation et<br />
la qualité de l’habitat le long des zones-tampons. Les besoins écophysiologiques<br />
spécifiques de chaque espèce semblent mieux expliquer<br />
leurs patrons de coexistence que l’ensemble des paramètres synécologiques<br />
des communautés.<br />
Mots-clés<br />
Colubridae, Coluber viridiflavus, Elaphe longissima, relations<br />
inter-spécifiques, écologie, biologie des populations, Italie<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
INTRODUCTION<br />
INTERACTIONS BETWEEN SYMPATRIC SNAKES, COLUBER VIRIDIFLAVUS AND ELAPHE LONGISSIMA… ◆<br />
The study of community organization and species’<br />
interactions is one of the prominent issues of modern ecology.<br />
It has for a long time been dominated by an “epistemiological<br />
misdirection” towards equilibrium hypotheses<br />
(sensu Barbault, 1991), where snapshots in space and time<br />
of given assemblages have been considered as reliable indicators<br />
of that community’s organization, i.e. with an underestimation<br />
of the role of physical factors and of spatial<br />
and temporal variability in the dynamics of natural communities<br />
(e.g., see Wiens, 1977; Schoener, 1986; Barbault,<br />
1991). Considering that spatial and temporal variability<br />
no doubt exists in most (all?)natural systems (e.g., see<br />
Blondel, 1990), it is evident that the data-sets best suited<br />
to interpret ecological patterns and processes should come<br />
from long-term studies (Magnuson, 1990) and / or from<br />
comparative studies of the same ecological system (i.e.<br />
the interaction between the same species) under different<br />
environmental conditions (e.g., different habitat types; see<br />
Harvey & Pagel, 1991). Both these approaches, however,<br />
are time consuming and logistically difficult and have only<br />
infrequently been used to study species’ interaction dynamics<br />
in the field (Schoener, 1983); this shortfall is especially<br />
true of snake studies (but see Luiselli et al., 2002).<br />
In the present paper, we use a long-term approach to<br />
study the interaction dynamics of two large-sized colubrid<br />
snakes from the <strong>Mediterranea</strong>n region of central Italy<br />
(Coluber viridiflavus and Elaphe longissima). We investigated<br />
whether the mechanisms of coexistence of these<br />
two species show any notable variation across years and<br />
whether coexistence dynamics are maintained through<br />
competitive relationships or via species-specific eco-physiological<br />
constraints (see Barbault, 1991; Barbault &<br />
Stearns, 1991). We address these issues using data collected<br />
over 11 consecutive years in a mature Oak forest<br />
in central Italy.This long-term approach permits a much<br />
deeper analysis of the ecological relationships between<br />
these two species than has previously been possible. It is<br />
noteworthy that both these species have been subject to<br />
detailed auto-ecological studies (e.g., see Naulleau, 1984,<br />
1987, 1989, 1992a, 1992b; Ciofi & Chelazzi, 1991, 1994;<br />
Luiselli & Rugiero, 1993; Bonnet & Naulleau, 1996a,<br />
1996b; Capula & Luiselli, 1995, 2002; Capula et al.,1995,<br />
1997, 2000; Filippi, 1995; Naulleau & Bonnet, 1995;<br />
Rugiero & Luiselli, 1995; Capizzi et al., 1996; Pillet, 1997;<br />
Bonnet et al., 1999; Kammel, 1999; Najbar, 1999a, 1999b,<br />
2000a, 2000b; Springolo & Scali, 1999; Agrimi, 2000;<br />
Cattaneo & Capula, 2000; Hofer, 2001a, 2001b; Zuffi,<br />
2001; Gomille, 2002), but their synecological relation-<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 75-91<br />
ships have been studied in less detail (but see Scali & Zuffi,<br />
1994; Capizzi & Luiselli, 1996a; Luiselli & Capizzi, 1997;<br />
Bretscher, 1999; Filippi & Luiselli, 2001, 2002; Hofer,<br />
2001a, 2001b).<br />
Here, we attempt to address the following main questions<br />
concerning sympatric populations of C. viridiflavus<br />
and E. longissima:<br />
1. Do the populations of these snakes exhibit annual<br />
fluctuations in <strong>Mediterranea</strong>n habitats? If so, to what<br />
extent, i.e. within what range do these fluctuations<br />
occur?<br />
2. Do these species exhibit any resource partitioning<br />
in terms of a) habitat utilization and b) dietary habits,<br />
and do any patterns occur consistently among years<br />
over a long-term period?<br />
3. Given that differences in thermal ecology may<br />
constitute niche differences among sympatric populations<br />
of different species (Avery, 1979), do these snakes<br />
differ each from the other in terms of thermal ecology<br />
attributes?<br />
4. Can the eventual interspecific differences observed<br />
be interpreted as a result of competitive relationships<br />
or via species-specific eco-physiological constraints?<br />
These questions are crucial to understanding the proper<br />
structure of species’ interaction because they link<br />
population dynamics with community structure (Strong<br />
et al., 1984).<br />
MATERIALS AND METHODS<br />
Study area<br />
Data presented in this paper were gathered from the<br />
“Bosco Macchia Grande di Manziana” (province of<br />
Rome, approx. 300-350 m a.s.l.), which is situated<br />
approximately 5 km west-northwest of Bracciano, and 2<br />
km south-west of Manziana.The study area, which has a<br />
surface of approximately 530 ha, is the last remnant piece<br />
of the ancient Sylva Mantiana, an enormous mixed forest<br />
(with oaks, lime-trees and maples) which previously covered<br />
the whole territory of the Sabatini, Ceriti, and Tolfa<br />
Mountains.The study area is situated inside the sub-montane<br />
deciduous oak forest climatic region, and is dominated<br />
by Quercus cerris, Q. frainetto, Acer campestre and<br />
Tilia sp., and has populations of Carpinus betulus and C.<br />
orientalis in cooler parts. Populations of Q. ilex are present<br />
in the drier and sunny sites, and populations of<br />
77
78<br />
◆ LORENZO RUGIERO, DARIO CAPIZZI, LUCA LUISELLI<br />
Corylus avellana, Fraxinus ornus, and Ulmus minor, are<br />
present in a few spots with optimal humidity conditions.<br />
The borders of the woodlot are colonized by <strong>Mediterranea</strong>n<br />
macchia vegetation with Cytisus scoparius, whereas<br />
the typical undergrowth consists of species of central-european<br />
origin (Sorbus domestica, S. aucuparia,<br />
Mespilus germanica,Crataegus monogyna,Rubus caesius,R.<br />
ulmifolius, Prunella vulgaris, Prunus spinosa, Ruscus aculeatus,Ilex<br />
aquifolium,Rosa canina,R.arvensis,Hedera helix,<br />
Daphne laureola, Pteridium aquilinum, etc.). Grassy areas<br />
are dominated by Dactylis glomerata, Luzula forsteri, Poa<br />
trivialis, Lolium perenne,Trifolium repens, Plantago lanceolata,<br />
and Galium vernum. Further details of the vegetation<br />
of the area are published elsewhere (e.g., Montelucci,<br />
1977; Spada, 1977).<br />
The fauna is rich and diverse. Among reptiles, apart<br />
from the two species studied here, the following species<br />
are found: Vipera aspis,Natrix natrix,N.tessellata,Coronella<br />
austriaca, Elaphe quatuorlineata, Lacerta bilineata, Podarcis<br />
sicula, P. muralis, Chalcides chalcides,Anguis fragilis,Testudo<br />
hermanni (Bruno, 1977; Luiselli et al., unpublished observations;<br />
Filippi, 1995).<br />
General methods<br />
Most of the data are original, apart from some of the<br />
dietary data, which the authors have published elsewhere<br />
(Luiselli & Rugiero, 1993; Capula & Luiselli, 2002).<br />
Snakes were searched along standardized routes<br />
conducted throughout the study area. Each snake was<br />
measured for snout-vent length (SVL, to the nearest ±<br />
0.1, cm) and body mass (to ± 0.1 g precision by an electronic<br />
balance), and individually marked by ventral scale<br />
clipping. Snakes were palpated in the abdomen until<br />
regurgitation of ingested food or defecation occurred, and<br />
prey items were identified to the lowest taxon possible.<br />
Female pregnancy status and numbers of eggs were determined<br />
by abdominal palpation. Subadults (which were<br />
discriminated from the adults by their different dorsal<br />
livery; see Bruno & Maugeri, 1977) were included in our<br />
dietary analyses, but were excluded from our analyses of<br />
population abundance.This was because their frequency<br />
appeared to be very different between sites and years and<br />
it was impossible to establish whether this occurred<br />
because of true site- or year-specific differences in abundance,<br />
or because of observer bias resulting from differences<br />
in vegetation and habitat structure among sites.<br />
Each year, from 1986 to 1996, a total of 21 to 32 man/<br />
days was spent in the field surveying the study area. We<br />
attempted to standardise effort as much as possible year-<br />
by-year and between macro-habitat types. Four well-separates<br />
snake macro-habitats were surveyed within the study<br />
area:<br />
1. Forest clearings with grassy-sandy soil (CLR).The<br />
typical phytosociological communities are included in<br />
the Thero-Brachypodetalia Br.-Bl. (1931) 1936 and the<br />
Brometalia Br.-Bl. (1936);<br />
2. Dense oak forest (OAK) (mainly Quercus cerris,<br />
Q. pubescens, Ostrya carpinifolia and Carpinus orientalis<br />
(canopy approx. > 70 %);<br />
3. Sparse oak forest (ROV) (mainly Quercus cerris,<br />
Q. frainetto and also Acer monspessulanum, Cercis siliquastrum<br />
and Paliurus spina-christi) with bushes (Rubus<br />
ulmifolius and Cytisus scoparius) (canopy approx.<br />
of the number of captured specimens of one species and<br />
of the number of captured specimens of the other species.<br />
Each snake was counted only once within each year,<br />
regardless of whether it was recaptured in subsequent<br />
years. By applying this procedure, a total number of 730<br />
data entries for C. viridiflavus and 448 for E. longissima<br />
were obtained. In order to evaluate yearly variations in<br />
habitat use of the two species, we used data only from the<br />
first capture of each specimen within each year under the<br />
assumption that records of habitat usage from recaptures<br />
within short-time spans could be biased by the disturbance<br />
effect of previous captures.<br />
All statistical tests, using SPSS and STATISTICA<br />
(versions for Windows), were two-tailed and alpha was<br />
set at 5 %. Means are presented followed by ± one standard<br />
deviation.<br />
RESULTS<br />
INTERACTIONS BETWEEN SYMPATRIC SNAKES, COLUBER VIRIDIFLAVUS AND ELAPHE LONGISSIMA… ◆<br />
● Do the populations of Coluber viridiflavus and Elaphe<br />
longissima exhibit annual fluctuations in <strong>Mediterranea</strong>n<br />
habitats?<br />
▲ In total, 511 adult C. viridiflavus (270 males, 241<br />
females) and 294 adult E. longissima (153 males, 141<br />
females) were captured. Adult sex-ratio did not depart<br />
significantly from equality in either species (Fisher exact<br />
test, NS). Males attained significantly larger SVL than<br />
females in both species (C. viridiflavus: males, x = 83.8<br />
± 11.1 cm, N = 254; females, x = 74.3 ± 9.1 cm, N =<br />
233; differences significant at P < 0.000001, t-test with<br />
df = 485; — E. longissima: males, x = 95.8 ± 15.2 cm,<br />
N = 149; females, x = 73.8 ± 14.4 cm, N = 140; differences<br />
significant at P < 0.000001, t-test with df = 287).<br />
The yearly ratio between captured specimens of the two<br />
species was always skewed towards C. viridiflavus, and<br />
was relatively stable across years at a value > 1.5: 1 (mean<br />
ratio: 1.65: 1, Standard Deviation = 0.32). However, in<br />
1991 there was a considerable excess of C. viridiflavus<br />
versus E. longissima (2.49: 1), and in 1994 and 1996 the<br />
number of C. viridiflavus was just slightly higher than<br />
that of E. longissima (1.37: 1, and 1.29: 1, respectively).<br />
If we pool data for four habitat types, the mean density<br />
per year of C. viridiflavus adults was 2.32 ± 1.05 specimens<br />
x ha -1, and the mean density of E. longissima<br />
adults was 1.34 ± 0.89 specimens x ha -1.<br />
● Do Coluber viridiflavus and Elaphe longissima exhibit<br />
any resource partitioning in terms of habitat utilization,<br />
and any patterns occur consistently among years over a<br />
long-term period?<br />
▲ The numbers of snake sightings in the various macrohabitats,<br />
year-by-year from 1986 to 1996, are presented<br />
in table 1. Coluber viridiflavus was observed essentially<br />
in habitats CLR (31.6 % of the total observations,<br />
N = 730) and CUL (45.1 %), whereas E.longissima were<br />
found in CLR (31.6 %, N = 448) and OAK (38.4 %).<br />
YEAR CLR CLR OAK OAK ROV ROV CUL CUL<br />
E.l. C.v. E.l. C.v. E.l. C.v. E.l. C.v.<br />
1986 11 23 14 6 10 7 7 33<br />
1987 16 28 13 3 13 18 8 38<br />
1988 18 21 19 5 8 13 4 36<br />
1989 9 19 12 7 7 12 8 31<br />
1990 14 22 17 3 4 6 4 35<br />
1991 7 26 16 4 2 15 4 27<br />
1992 13 17 13 1 6 16 5 23<br />
1993 20 20 14 1 2 11 2 30<br />
1994 15 24 19 4 7 13 7 25<br />
1995 10 16 17 3 5 10 7 29<br />
1996 13 15 18 4 6 8 4 22<br />
Total 146 231 172 41 70 129 60 329<br />
% Total 32.6 31.6 38.4 5.6 15.6 17.7 13.4 45.1<br />
Table 1. Number of snake sightings in the various macro-habitats of the “Macchia di Manziana” area, year-by-year from 1986 to 1996.<br />
Symbols: C.v. = Coluber viridiflavus; E.l. = Elaphe longissima; CLR = Forest clearings; OAK = Dense oak forest;<br />
ROV = Sparse oak forest with bushes (Rubus, Cytisus); CUL = Cultivations with bushes.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 75-91<br />
79
80<br />
◆ LORENZO RUGIERO, DARIO CAPIZZI, LUCA LUISELLI<br />
A factorial General Linear Model (GLM) with year as<br />
the fixed factor, habitat types as random factors, and the<br />
ratio ‘numbers of C. viridiflavus / numbers of E. longissima’<br />
as the dependent variable, revealed a significant<br />
effect for habitat type (F3,30 = 21.389, P < 0.0001), but<br />
not for year (F3,10 = 1.594, P = 0.156; intercept: F1,3 =<br />
4.294, P = 0.130). When applying the same GLM to<br />
E. longissima as the dependent variable, with year as the<br />
fixed factor, and habitat types as random factors, we obtained<br />
the same result, i.e. the frequency of the study species<br />
did not vary among years (F10,30 = 1.121, P = 0.379)<br />
but depended upon the habitat type (F3,30 = 31.649,<br />
P < 0.0001; intercept: F1,3 = 12.191, P = 0.026).<br />
Repeating the same statistical model for C. viridiflavus,<br />
we obtained an almost identical result, i.e. the year did<br />
not have any statistically significant effect (F10,30 = 2.048,<br />
P = 0.063), whereas the habitat type did (F3,30 = 113.169,<br />
P < 0.000001; intercept: F1,3 = 8.559, P = 0.061).<br />
The general patterns were:<br />
(i) C. viridiflavus was abundant in sunny habitats and<br />
tended to avoid habitats with closed canopy (OAK);<br />
(ii) E. longissima clearly preferred habitats with closed<br />
canopy (OAK);<br />
(iii) both species were generalists, as they were found<br />
in all the macro-habitats available at the study area and<br />
exhibited values of habitat niche breadth typical for<br />
generalist species, when a series of four habitat types<br />
are available (table 2);<br />
(iv) the values of habitat niche breadth did not differ<br />
significantly either between species (one-way ANOVA:<br />
F1,20 = 2.054, P = 0.167), or among years (F10,11 =<br />
1.193, P = 0.385);<br />
(v) the proportion of snakes observed in the various<br />
macro-habitats was not significantly related to the field<br />
effort performed in each macro-habitat type, either<br />
considering year-by-year separately (C. viridiflavus:<br />
Spearman’s r = 0.218, N = 44, P > 0.532; E. longissima:<br />
r = 0.313, N = 44, P > 0.455) or pooling all the years<br />
together (C. viridiflavus: r = 0.795, N = 4, P = 0.205;<br />
E. longissima: r = 0.698, N = 4, P = 0.302).<br />
The values of habitat niche overlap (table 2) indicated<br />
a clear-cut habitat partitioning between species (0.5<br />
< O jk < 0.72) in most years, although in 1989 the interspecific<br />
habitat overlap was relatively high (O jk = 0.822),<br />
and in 1996 it was extremely low (O jk = 0.240).<br />
● Do Coluber viridiflavus and Elaphe longissima exhibit<br />
any resource partitioning in terms of food preferences?<br />
▲ Prey type. — The food items recorded from the two<br />
species at the study area are presented in tables 3 and<br />
4. Data are expressed on the basis of the sex and the<br />
age (juveniles or adults) of the specimens examined.<br />
Concerning C. viridiflavus, 211 prey items were recorded.The<br />
bulk of the diet of juveniles consisted of lacertid<br />
lizards, with invertebrates and newborn rodents also<br />
occasionally eaten. Adults of both sexes preyed mainly<br />
upon small sized vertebrates, i.e. lacertids, rodents, and<br />
birds. Nonetheless, there were remarkable inter-sexual<br />
differences (c 2 test with df = 2, P < 0.001), in that males<br />
consumed a significantly higher amount of lacertids than<br />
rodents, whereas females consumed an almost identical<br />
amount of rodents and lacertids. Birds were also<br />
preyed upon in similar rates by the two sexes (fig. 2A,<br />
p. 82). Frogs were occasionally consumed.<br />
127 prey items were recorded from E. longissima specimens<br />
(table 4).The bulk of the diet of juveniles consisted<br />
of lacertid lizards, but newborn rodents were also<br />
occasionally consumed. Adults of both sexes preyed only<br />
upon small sized vertebrates, mainly rodents, birds, and<br />
lacertid lizards.The ontogenetic change in dietary composition<br />
was very significant (c 2 test with df = 1,<br />
P < 0.00001), with juveniles taking more lizards and<br />
less mammals and birds than adults of both sexes. If we<br />
consider the adults, there were no statistically significant<br />
inter-sexual differences in dietary composition<br />
(c 2 test with df = 2, P > 0.05), although males tended<br />
to consume more lacertids than females. Birds were also<br />
1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996<br />
C.v. = B s 1.672 1.718 1.706 1.776 1.578 1.778 1.739 1.645 1.773 1.633 1.745<br />
E.l. = B s 1.946 1.949 1.776 1.961 1.715 1.608 1.855 1.481 1.834 1.814 1.629<br />
O (C.v.-E.l.) 0.718 0.792 0.617 0.822 0.523 0.526 0.680 0.535 0.720 0.710 0.240<br />
Table 2.Values of macro-habitat niche breadth (Bs) and niche overlap (O) between Coluber viridiflavus (C.v.) and Elaphe longissima (E.l.),<br />
at a mature Oak Forest in central Italy (“Macchia di Manziana”).Values are calculated, year-by-year between 1986 and 1996, by Simpson’s (1949)<br />
diversity index (niche breadth values) and by Pianka’s (1986) symmetric equation (niche overlap values).<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
INTERACTIONS BETWEEN SYMPATRIC SNAKES, COLUBER VIRIDIFLAVUS AND ELAPHE LONGISSIMA… ◆<br />
PREY TYPE JUVENILES ADULT ADULT<br />
MALES FEMALES<br />
Oligochaeta<br />
Lumbricus sp.<br />
Arthropoda<br />
1 (1) – –<br />
Lithobius sp. 1 (1)<br />
Orthoptera<br />
Amphibia<br />
4 (3) 1 (1) 1 (1)<br />
Rana italica<br />
Reptilia<br />
– – 1 (1)<br />
Elaphe longissima (juv.) – – 1 (1)<br />
Anguis fragilis – 1 (1) –<br />
Chalcides chalcides – 1 (1) –<br />
Lacerta bilineata 3 (3) 17 (15) 13 (11)<br />
Podarcis muralis 33 (26) 21 (16) 17 (13)<br />
Podarcis sicula<br />
Aves<br />
2 (2) 4 (3) 3 (3)<br />
Passeriformes (ad) – 8 (7) 9 (6)<br />
Passeriformes (nestlings)<br />
Mammalia<br />
– 6 (2) 7 (4)<br />
Clethrionomys glareolus – 14 (11) 19 (15)<br />
Apodemus flavicollis 2 (2) 4 (4) 6 (4)<br />
Rodentia indet. – 3 (3) 4 (4)<br />
Crocidura sp. – 1 (1) 2 (2)<br />
Insectivora indet. – 1 (1) –<br />
Table 3. Prey eaten by Coluber viridiflavus at a mature Oak Forest<br />
in central Italy (“Macchia di Manziana”), years 1986-1996.<br />
Both the absolute numbers of food items and the numbers of individuals<br />
from which a given prey type have been found are indicated (in parentheses).<br />
PREY TYPE JUVENILES ADULT ADULT<br />
MALES FEMALES<br />
Reptilia<br />
Lacerta bilineata 2 (2) 5 (5) 4 (4)<br />
Podarcis muralis 9 (7) 8 (5) 5 (4)<br />
Podarcis sicula<br />
Aves<br />
3 (3) – –<br />
Parus caeruleus – 2 (2) 1 (1)<br />
Sylvia atricapilla – 1 (1) –<br />
Serinus serinus – – 2 (2)<br />
Carduelis chloris – 3 (1) 1 (1)<br />
Passeriformes indet. (ad) – 2 (2) 2 (2)<br />
Passeriformes (nestlings)<br />
Mammalia<br />
– 4 (2) 5 (2)<br />
Clethrionomys glareolus 2 (2) 8 (8) 12 (10)<br />
Apodemus flavicollis 3 (3) 17 (12) 19 (15)<br />
Rattus rattus – 1 (1) 4 (4)<br />
Crocidura sp. – 1 (1) –<br />
Insectivora indet. – 1 (1) –<br />
Table 4. Prey eaten by Elaphe longissima at a mature oak forest<br />
in central Italy (“Macchia di Manziana”), years 1986-1996.<br />
Both the absolute numbers of items and the numbers of individuals<br />
from which a given prey type has been found are indicated (in parentheses).<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 75-91<br />
preyed upon in similar rates by the two sexes (fig. 2B,<br />
p. 82). In all classes of individuals, and in both species,<br />
the preponderance of Podarcis muralis versus P. sicula<br />
in the diets depended merely on the much higher abundance<br />
in the field of the former species versus the latter<br />
(Rugiero, Capizzi & Luiselli, unpublished data).<br />
In terms of taxonomic dietary composition, there were<br />
significant inter-specific differences amongst adults<br />
(c 2 test, P < 0.00005):<br />
(i) the dietary spectrum of C. viridiflavus was wider<br />
than that of E. longissima at all ages, and included frogs<br />
and invertebrates which were not taken at all by the latter<br />
species;<br />
(ii) C. viridiflavus preyed much more frequently than<br />
E. longissima on lacertids and other reptiles, and also<br />
occasionally consumed snakes and snake-shaped lizards<br />
(Chalcides chalcides and Anguis fragilis);<br />
(iii) C.viridiflavus preyed less frequently than E.longissima<br />
on rodents and other small mammals;<br />
(iv) C. viridiflavus preyed more frequently on Clethrionomys<br />
glareolus than on Apodemus flavicollis, however,<br />
the opposite was true for E. longissima;<br />
(v) The two snake species consumed a similar amount<br />
of small sized birds (Passeriformes).<br />
The numbers of food items recorded for each species<br />
were not enough to allow for any search of consistent<br />
patterns across years.<br />
▲ Prey size. — Unfortunately, our data on prey size are<br />
less comprehensive than that of prey type because in<br />
several instances the weight of the ingested bolus was<br />
not recorded.This prevented us from calculating intersexual<br />
or inter-annual differences in terms of ‘predator-size-prey-size’<br />
relationships.<br />
We recorded prey size and predator size for 31 C. viridiflavus<br />
(snake mass = 151.5 ± 71.5 g; prey mass =<br />
11.4 ± 7.7 g, N = 31), and 21 E.longissima (snake mass<br />
= 186.4 ± 101.4 g; prey mass = 27.3 ± 20.0 g, N = 21).<br />
Mean snake mass was not significantly different between<br />
the species (t = 1.55, df = 50, P = 0.154) but<br />
E. longissima preyed upon significantly heavier prey than<br />
C. viridiflavus (t = 4.01, df = 50, P = 0.0002). Prey<br />
mass/predator mass ratio averaged 0.075 ± 0.11 g in<br />
C. viridiflavus,and 0.147 ± 0.19 g in E.longissima.These<br />
averages were not significantly different (t = 1.70, df =<br />
50, P = 0.0958). In both species there was a positive<br />
relationship between prey mass and predator mass<br />
(C. viridiflavus:Spearman’s r = 0.739, N = 31, ANOVA<br />
F 1,29 = 32.63, P < 0.0001; regression equation — Prey<br />
Mass = -0.673 + 0.08 x Body Mass; figure 3A, p. 83;<br />
81
82<br />
◆ LORENZO RUGIERO, DARIO CAPIZZI, LUCA LUISELLI<br />
Figure 2. Proportion of the main types<br />
of vertebrates (rodents, lacertids, and birds)<br />
as prey of juveniles, adult males<br />
and adult females of Coluber viridiflavus<br />
(A) and Elaphe longissima (B)<br />
at a mature Oak Forest in central Italy<br />
(“Macchia di Manziana”).<br />
Figure 1.Total number<br />
of specimens of<br />
Coluber viridiflavus<br />
and Elaphe longissima,<br />
observed year-by-year<br />
(1986-1996) at a mature<br />
Oak Forest in central Italy<br />
(“Macchia di Manziana”).<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
INTERACTIONS BETWEEN SYMPATRIC SNAKES, COLUBER VIRIDIFLAVUS AND ELAPHE LONGISSIMA… ◆<br />
Figure 3. Relationships between prey mass<br />
and predator mass in (A) Coluber viridiflavus<br />
and (B) Elaphe longissima at a mature<br />
Oak Forest in central Italy<br />
(“Macchia di Manziana”).<br />
For statistical details, see the text.<br />
E. longissima: r = 0.701, N = 21, ANOVA F 1,19 = 18.4,<br />
P = 0.004; regression equation – Prey Mass = 1.554 +<br />
0.138 x Body Mass; fig. 3B). The regression line for<br />
C. viridiflavus did not differ from that for E. longissima<br />
in terms of slope (ANCOVA: F 1,48 = 2.747, P = 0.104,<br />
pooled slope = 0.114) but did for elevation (ANCOVA<br />
F 1,49 = 15.233, P = 0.0003).<br />
It is well known that, in snakes, prey size is dependent<br />
on predator size not only in terms of absolute size<br />
(length and mass), but also in terms of relative head size<br />
(see Arnold, 1993). Concerning our species, there were<br />
not only significant inter-sexual differences in mean<br />
head sizes (e.g. Springolo & Scali, 1999), but also a<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 75-91<br />
reversed condition in comparison to absolute sizes:<br />
although E. longissima attained on average a bigger size<br />
(longer SVL and heavier mass) than C. viridiflavus, it<br />
nevertheless had a smaller head size (relatively to body<br />
length) than the latter species (Rugiero et al., unpublished<br />
data from several localities of <strong>Mediterranea</strong>n central<br />
Italy). However, we did not measure head length in<br />
most of the snake specimens captured at the study area,<br />
and so we could not directly analyse the relationships<br />
between head size and prey size. To handle this problem,<br />
we retained for the analyses those cases in which<br />
the head size of the fed snakes was measured (N = 8 in<br />
C. viridiflavus, N = 10 in E. longissima), and predicted<br />
83
84<br />
◆ LORENZO RUGIERO, DARIO CAPIZZI, LUCA LUISELLI<br />
(by the use of partial correlation analysis) the head<br />
length of all the other fed specimens.To do this, we calculated<br />
the slope of the regression SVL against head<br />
length for 117 C. viridiflavus and 64 E. longissima examined<br />
by us in the area of Rome (years 1992-1997)<br />
(the relative statistics are not presented here for brevity,<br />
but are available from authors), and calculated from the<br />
slopes of these regressions the predicted head length of<br />
our specimens for their known sex and SVL.Then, we<br />
run (i) the predicted measures of head length against<br />
the measures of prey mass, and (ii) the SVL of the<br />
various snakes against the prey mass, and finally we<br />
compared slopes of these two regressions by an heterogeneity<br />
of slopes test. In C. viridiflavus, we obtained<br />
significant positive relationships between both head<br />
length and SVL versus prey mass (in all cases, Spearman’s<br />
r > 0.55, N = 31, P < 0.001), and the slopes of<br />
these two regression lines were similar (F = 4.325, P ><br />
0.21).The same was not true for E. longissima, in which<br />
the slope of the regression line between SVL and prey<br />
mass differed significantly from that of the regression<br />
line between head length and prey mass (Spearman’s r<br />
= 0.216, N = 21, P > 0.1; heterogeneity of slopes test:<br />
F = 21.443, P < 0.0001). Practically speaking, whereas<br />
Figure 4. Relationships between<br />
body and air temperatures in<br />
(A) Coluber viridiflavus and<br />
(B) Elaphe longissima at a mature<br />
Oak Forest in central Italy<br />
(“Macchia di Manziana”).<br />
For statistical details, see the text.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
INTERACTIONS BETWEEN SYMPATRIC SNAKES, COLUBER VIRIDIFLAVUS AND ELAPHE LONGISSIMA… ◆<br />
in C. viridiflavus the specimens with a bigger head tended<br />
strongly to prey upon bigger organisms, the same<br />
relationships was not evident in E. longissima. It is certainly<br />
a surprising result in view of other snake studies<br />
published to date, where there is a strong parallel between<br />
snake body size, head size and prey size (e.g.<br />
Forsman, 1991a, b, 1992, 1993; Werner, 1994).<br />
● Do Coluber viridiflavus and Elaphe longissima differ<br />
from each another in terms of thermal ecology attributes?<br />
▲ A total of 33 Tb readings were taken from adult<br />
C. viridiflavus, and 21 from adult E. longissima. Tb averaged<br />
25.4 ± 3.1°C in C. viridiflavus, and 23.4 ± 1.8 °C<br />
in E. longissima. These averages were significantly different<br />
(t = 2.68, df = 52, P = 0.0099).Ta averages were<br />
23.6 ± 4.1 °C relating to captured C. viridiflavus, and<br />
22.2 ± 3.6 °C for E.longissima. These averages were not<br />
significantly different (t = 1.28, df = 52, P = 0.206).<br />
Tb was positively correlated to Ta in both species (figure<br />
4; for C. viridiflavus: Spearman’s r = 0.855, ANOVA<br />
F1,31 = 84.38, P < 0.0001; regression equation – Tb =<br />
10.303 + 0.640 x Ta; for E. longissima: r = 0.857,<br />
ANOVA F1,19 = 52.65, P < 0.0001; regression equation<br />
– Tb = 13.723 + 0.438 x Ta). The regression line for<br />
C. viridiflavus did not differ from that for E. longissima<br />
in terms of slope (ANCOVA: F1,50 = -0.099, P = 0.993,<br />
pooled slope = 1.240) or elevation (ANCOVA F1,51 =<br />
2.713, P = 0.106). In both species, the regression Ta- Tb differed significantly from the line of ideal perfect<br />
poikilothermy (i.e. the line of absolute correlation between<br />
Ta and Tb) (for C. viridiflavus: ANCOVA on<br />
slopes, F1,62 = 26.618, P < 0.0001; for E. longissima:<br />
ANCOVA on slopes, F1,38 = 86.536, P < 0.0001).<br />
Considering that in some snake species (both from<br />
<strong>Mediterranea</strong>n and tropical regions) Tb is influenced by<br />
body size (SVL) (Luiselli & Zimmermann, 1997;<br />
Luiselli & Akani, 2002), we tested whether the same<br />
relationship occurred in our study species. Tb was not<br />
significantly correlated to SVL in either species (fig. 5;<br />
for C. viridiflavus: r = 0.201, ANOVA F1,31 = 1.305,<br />
P > 0.35; regression equation – Tb = 19.726 + 0.067 x<br />
SVL; for E.longissima:r = -0.051, ANOVA F1,19 = 0.049,<br />
P > 0.82; regression equation – Tb = 24.235 - 0.08 x<br />
SVL).The regression line for C.viridiflavus did not differ<br />
from that for E. longissima in terms of slope<br />
(ANCOVA: F1,50 = 1.066, P = 0.308, pooled slope =<br />
1.240) but did for elevation (ANCOVA F1,51 = 7.159,<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 75-91<br />
P = 0.01). In C. viridiflavus, a few gravid females with<br />
a SVL of 85-95 cm had higher body temperatures<br />
(> 30 °C) than other individuals (fig. 5, p. 86).<br />
DISCUSSION<br />
● Do the populations of Coluber viridiflavus and Elaphe<br />
longissima exhibit annual fluctuations in <strong>Mediterranea</strong>n<br />
habitats?<br />
▲ We demonstrated that, apart from minor variations<br />
(likely due to random effects in the samples) both the<br />
absolute apparent abundance and the relative abundance<br />
of the two species (i.e. the ratio between the abundances<br />
of one species versus the other) did not vary<br />
significantly between years.This suggests a relative stability<br />
of our study system over the years, which in turn<br />
is likely to be due to the mature and stable conditions<br />
of the general environment, which is currently experiencing<br />
only moderate disturbance from forestry activities.<br />
In addition, habitat fragmentation is relatively<br />
scarce, and there is good quality habitat along the buffer<br />
zones; both these factors probably contribute to the<br />
observed stability in the abundance patterns of the two<br />
species.<br />
The average density of C. viridiflavus was slightly lower<br />
at our study area than at a thermo-<strong>Mediterranea</strong>n coastal<br />
locality of central Italy (Castel Fusano), where it was<br />
approximately 3.5 specimens x ha-1 (Filippi & Luiselli,<br />
2001). On the other hand, the density of E. longissima<br />
is nearly identical in these two sites (being approximately<br />
1.5 specimens x ha-1 at Castel Fusano (Filippi &<br />
Luiselli, 2001).This is likely to be dependent upon the<br />
more continental bio-climate of Manziana compared to<br />
Castel Fusano.There are very few data on the densities<br />
of these snakes from other European regions. In southern<br />
Switzerland, Bretscher (1999) found a density of<br />
E. longissima nearly identical to that observed at our<br />
Italian sites (i.e. 1.3 specimens x ha-1 ), and a density of<br />
C. viridiflavus that was slightly lower (1.4 specimens x<br />
ha-1 ). His study area was, however, more heterogeneous<br />
than our own. Other studies from southern Switzerland<br />
present density estimations of 46-83 specimens x ha-1 for E. longissima (Pillet, 1997) and 40 specimens x ha-1 for C. viridiflavus (Hofer, 2001a). These estimations<br />
cannot be compared directly with our own because they<br />
are based on counts along a line transect over a longterm<br />
period, and do not take into account mortality,<br />
immigration and emigration rates.<br />
85
86<br />
◆ LORENZO RUGIERO, DARIO CAPIZZI, LUCA LUISELLI<br />
In addition, our study demonstrated a sexual size dimorphism<br />
in both species studied here, where males were<br />
longer than females.This is in full agreement with previous<br />
studies on Italian conspecific populations of both<br />
C. viridiflavus (Springolo & Scali, 1999; Capula et al.,<br />
2000; Scali & Montonato, 2000) and E.longissima (Scali<br />
& Montonato, 2000) and these unsurprising results do<br />
not merit further discussion.<br />
● Do Coluber viridiflavus and Elaphe longissima exhibit<br />
any resource partitioning in terms of habitat utilization,<br />
and any patterns occur consistently among years over a<br />
long-term period?<br />
Figure 5. Relationships between body temperatures<br />
and body length in (A) Coluber viridiflavus and<br />
(B) Elaphe longissima at a mature Oak Forest<br />
in central Italy (“Macchia di Manziana”).<br />
In the plot, relative to C. viridiflavus, note that<br />
the six individuals with SVL of approximately<br />
85-95 cm and high body temperatures<br />
(around 30-33 °C) were gravid females.<br />
For statistical details, see the text.<br />
▲ At our study area, the two species appeared different<br />
from each another in terms of macro-habitat selection.<br />
In contrast, the populations of the two species from southern<br />
Switzerland showed a habitat overlap of approximately<br />
81 % (Hofer, 2001b), although E.longissima was<br />
again more linked than C. viridiflavus to sites with closed<br />
canopy (Bretscher, 1999; Hofer, 2001b). A strong<br />
preference for cool, forested spots was also observed in<br />
E.longissima from Neckar-Odenwald region (Germany)<br />
(Gomille, 2002).<br />
The inter-specific differences in the use of macro-habitat<br />
types, although predictable on the basis of previous<br />
accounts from both Italy (Luiselli & Capizzi, 1997) and<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
INTERACTIONS BETWEEN SYMPATRIC SNAKES, COLUBER VIRIDIFLAVUS AND ELAPHE LONGISSIMA… ◆<br />
elsewhere (Vuagniaux, 1977; Naulleau, 1984; Bretscher,<br />
1999; Hofer, 2001a, 2001b), may be related to either<br />
synecological issues (i.e. habitat partitioning between<br />
sympatric competitors to reduce inter-specific competition<br />
- see Saint Girons, 1975 for another case of sympatric<br />
European snakes) or eco-physiological factors (i.e.<br />
external proximate constraints on the life-history of the<br />
two species – cf. Barbault, 1991; Barbault & Stearns,<br />
1991). Our data cannot exclude either hypothesis, and<br />
it is likely that both may contribute to explain the observed<br />
patterns (see also Filippi & Luiselli, 2001).To resolve<br />
which of the two issues contributes more to the observed<br />
pattern, specific ad-hoc experiments (e.g. controlled<br />
removal) are needed. To properly consider synecology<br />
we must include the effects of interference from other<br />
competitors (e.g. other snakes, mustelids, raptors, etc.)<br />
that have proven to interact with C. viridiflavus and<br />
E. longissima elsewhere (e.g., Capizzi & Luiselli, 1996).<br />
The general preference of C. viridiflavus for open<br />
(drier and sunnier) macro-habitats is most likely related<br />
to its specific thermal and physiological tolerances,<br />
and this correlates well with the overall distribution of<br />
this species in Europe, especially considering that it<br />
can be found in the very hot regions in the extreme<br />
south of Italy (Bruno & Maugeri, 1977). At the same<br />
time, the preference of E. longissima for forested spots<br />
is likely to be related to the fact that this is a northernmore<br />
species and central Italy (southern Latium) is its<br />
southernmost limit. Indeed, immediately south of<br />
Latium, E. longissima is replaced by Elaphe lineata,<br />
which was until recently considered a subspecies of<br />
longissima but considerable genetic and morphological<br />
divergence has now promoted it to the rank of full<br />
species (Lenk & Joger, 1994; Lenk & Wüster, 1999).<br />
Similar habitat utilisation patterns to the ones found<br />
in this study occur in a coastal locality of <strong>Mediterranea</strong>n<br />
central Italy, where C. viridiflavus was found<br />
in dry and sunny places and E. longissima in cooler and<br />
shadier places (Filippi & Luiselli, 2001). Thus, external<br />
eco-physiological cons-traints (e.g. climate) may<br />
well explain the local macro-habitat selection of the<br />
two species, as well the temporal constancy of this<br />
apparent resource partitioning pattern which was<br />
observed at our study area.<br />
● Do Coluber viridiflavus and Elaphe longissima differ<br />
from each another in terms of thermal ecology attributes?<br />
▲ Our data on the thermal ecology of the two species<br />
also support this suggestion because C.viridiflavus maintains<br />
higher body temperatures than sympatric E. lon-<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 75-91<br />
gissima. Considering that (i) the slopes of the regressions<br />
T b against T a are similar between species, and that (ii)<br />
in both cases they are significantly different from the<br />
ideal line of perfect poikilothermy, it is likely that the T bs<br />
of C. viridiflavus were higher because they were captured<br />
in sunnier spots than specimens of E. longissima. It<br />
is also evident that E.longissima maintained its T b at lower<br />
values by both avoiding direct exposure to the sun (the<br />
same as in several tropical snakes, e.g. Akani et al.,2002)<br />
and also becoming active earlier in the morning (Rugiero<br />
et al., unpublished data). In practice, the thermoregulatory<br />
ability of the two species should be physiologically<br />
similar but, given their different thermal requirements,<br />
the two species adopt diverging behavioural and microhabitat<br />
selection strategies to maintain their T bs around<br />
their species-specific optimal values. In contrast to semiaquatic<br />
snakes from both Europe (cf. Luiselli &<br />
Zimmermann, 1997) and tropical Africa (Luiselli &<br />
Akani, 2002), there was no influence of body size (SVL)<br />
on T bs of either species, and this can be interpreted either<br />
as inefficient thermoregulation or the lack of a physiological<br />
trade-off between body size and T b. In this regard<br />
it is, however, important to remark that a few gravid C.<br />
viridiflavus had higher T bs than other individuals (males<br />
and non-gravid females).This may reflect a shift towards<br />
selecting higher T bs in gravid individuals (Beuchat,<br />
1986), as has been observed in another European oviparous<br />
snake (Luiselli & Zimmermann, 1997). If this is<br />
the case, it is evident that gravid females should select<br />
higher T bs by being active at high T as (> 30 °C, see figure<br />
4). However, our data are too few to draw any firm<br />
conclusions, especially considering that there is no general<br />
rule for squamate reptiles (cf. Gibson & Falls, 1979;<br />
Shine & Lambeck, 1990; Schwarzkopf & Shine, 1991;<br />
Akani et al., 2002; Luiselli & Akani, 2002). Ad-hoc experiments<br />
are to be planned to resolve this issue.<br />
● Do Coluber viridiflavus and Elaphe longissima exhibit<br />
any resource partitioning in terms of food preferences?<br />
▲ As previously observed in another agro-forest environment<br />
of <strong>Mediterranea</strong>n central Italy (Capizzi &<br />
Luiselli, 1996), the feeding niche of C. viridiflavus was<br />
remarkably different from that of E.longissima.This can<br />
be better seen by separately examining (a) adults and<br />
juveniles, and (b) prey types and prey sizes.<br />
The major inter-specific differences were observed when<br />
comparing the taxonomic dietary composition of juveniles<br />
of the two species. Indeed, C. viridiflavus juveniles<br />
87
88<br />
◆ LORENZO RUGIERO, DARIO CAPIZZI, LUCA LUISELLI<br />
were much more eclectic predators than juvenile E.longissima,<br />
preying upon many lizards and newborn mice<br />
as well as several invertebrates (earthworms and arthropods),<br />
which were totally avoided by E. longissima.<br />
Considering that snakes respond to both chemical and<br />
visual stimuli (Arnold, 1993) and most are relatively<br />
specialized in their prey preferences (Mushinsky, 1987),<br />
this indicates that C.viridiflavus may respond to an unusually<br />
wide range of stimuli and, hence, have an unusually<br />
wide dietary spectrum.<br />
The same trend, although less pronounced, was also<br />
observed in the adults; both C. viridiflavus and E. longissima<br />
foraged on lizards, rodents and birds, but<br />
C. viridiflavus occasionally also fed on frogs and<br />
arthropods, which were not consumed at all by E. longissima<br />
(Luiselli & Rugiero, 1993; Rugiero & Luiselli,<br />
1995). Other spectacular examples of high dietary<br />
generalism are found among tropical elapids, e.g.<br />
cobras and tree cobras (Pawvels et al., 1999; Luiselli<br />
& Angelici, 2000; Luiselli et al., 2002). It is also noteworthy<br />
that both species had several birds in their stomachs,<br />
which reflects the good climbing ability, viz.<br />
semi-arboreal habits, of these snakes (Naulleau, 1984,<br />
1987, 1989). A case of direct predation of the one species<br />
(C. viridiflavus) versus the other (E. longissima)<br />
was also recorded, but it is very unlikely that this kind<br />
of interference competition may be of any relevance<br />
for the dynamics of the studied system. It must be noticed<br />
that C. viridiflavus has been sometimes claimed to<br />
exercise a strong pressure on the populations of sympatric<br />
snakes (e.g., Cattaneo & Carpaneto, 2000, for<br />
the case of Elaphe quatuorlineata), but there is no<br />
reliable field dataset to confirm this assertion.<br />
If we consider that offspring and subadult snakes<br />
are often prey-limited and relatively emaciated when<br />
captured in the wild (Filippi, 1995; Luiselli &<br />
Angelici, 1996), it may be assumed that the interspecific<br />
differences observed may greatly help<br />
coexistence of these species via reducing inter-specific<br />
competition, which is likely more intense<br />
among juvenile snakes than among adult snakes, at<br />
least in the <strong>Mediterranea</strong>n environments (Luiselli &<br />
Angelici, 1996). On the other hand, we do not<br />
believe that the taxonomic diet difference between<br />
the adults of these species reflects competitive pressure<br />
to reduce dietary niche overlap.This is because<br />
adult C. viridiflavus has a diet composition completely<br />
different from that of E. longissima even in<br />
areas where the latter species is not present, e.g. in<br />
Montecristo island (Thyrrenian sea, Tuscan archi-<br />
pelago – where its main prey are anuran amphibians<br />
(Zuffi, 2001). The fact that C. viridiflavus preyed<br />
more upon Clethrionomys glareolus than Apodemus<br />
flavicollis, whereas the reverse was true for E. longissima,<br />
does not again imply any resource partitioning,<br />
but merely reflects the different habitat selection<br />
of these two rodents. Clethrionomys glareolus are<br />
found in clearings, which is better habitat for C. viridiflavus<br />
than E. longissima; and Apodemus flavicollis<br />
occur in mature forests, which are better habitat for<br />
E. longissima than C. viridiflavus (Amori et al., 1986;<br />
Capizzi & Luiselli, 1996b). So, we definitely think<br />
that the differences in taxonomic dietary composition<br />
reflect diverging species-specific preferences in<br />
habitat utilization (and hence in prey communities<br />
available) rather than community-based mechanisms<br />
of resource partitioning.<br />
Regarding the relationship of prey-size relative to predator-size,<br />
we observed that C. viridiflavus occasionally<br />
foraged on very small organisms (arthropods)<br />
and E. longissima occasionally ate relatively large animals<br />
(rats), but in most cases the two species showed<br />
a similar pattern.<br />
● Can the interspecific differences observed be interpreted<br />
as a result of competitive relationships or via species-specific<br />
eco-physiological constraints?<br />
▲ In conclusion, our study demonstrated that: (1)<br />
these snake species do exhibit a clear-cut pattern of<br />
resource partitioning in terms of habitat utilization,<br />
and, in consequence of it, also in terms of dietary<br />
habits, and these patterns occur consistently among<br />
years over a long-term period; (2) the populations of<br />
these snakes do not exhibit remarkable annual fluctuations<br />
in <strong>Mediterranea</strong>n habitats; (3) these snakes<br />
differed clearly each from the other in terms of thermal<br />
ecology attributes, and it is most probably linked<br />
to interspecific differences in micro-habitats (Filippi<br />
& Luiselli, 2001) and macro-habitats (Luiselli &<br />
Capizzi, 1997; this study). In general, we suggest that<br />
species-specific eco-physiological requirements appear<br />
to explain the coexistence patterns of the two species<br />
better than any community-based synecological factors.<br />
Indeed, only the niche differences in prey types<br />
of subadults may be explained with competition pressure<br />
to reduce dietary niche overlap. However, it is<br />
obvious that field experiments designated ad-hoc<br />
should be used to test specifically for the various questions<br />
posed by this study, and we are currently working<br />
on these experimental procedures.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
ACKNOWLEDGEMENTS<br />
We are indebted to the “Università Agraria di Manziana”<br />
for several kinds of assistance when in the field.<br />
Many researchers, and especially U. Agrimi, M. Capula,<br />
and E. Filippi, were of invaluable help in collecting data<br />
and discussing with us about the subject of this study.<br />
Two anonymous referees, G.C. Akani, M. Capula, F.M.<br />
Angelici, E. Filippi, E. Vidal, and especially J. Lea commented<br />
upon a preliminary draft of this manuscript, and<br />
gave also linguistic assistance.<br />
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90<br />
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1351.<br />
LUISELLI L. & RUGIERO L., 1993. Food habits of the Aesculapian<br />
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NAJBAR B., 1999a. Breeding biology of the Aesculapian snake<br />
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Ojczysta, 55 (2): 5-20.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
INTERACTIONS BETWEEN SYMPATRIC SNAKES, COLUBER VIRIDIFLAVUS AND ELAPHE LONGISSIMA… ◆<br />
NAJBAR B., 1999b.The diet of the Aesculapian snake Elaphe longissima<br />
longissima (Laurenti) in the Bieszczady Zachodnie<br />
Mountains (SE Poland). Chronmy Przyrode Ojczysta, 55 (2):<br />
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NAJBAR B., 2000a. The Aesculapian snake Elaphe l. longissima<br />
(Laurenti, 1768) population in Bieszczady (Poland) between<br />
1990-1998. Bulletin of the Polish Academy of Biology,48: 41-51.<br />
NAJBAR B., 2000b. The state of the Aesculapian snake Elaphe l.<br />
longissima (Laurenti, 1768) population in Poland. Bulletin of<br />
the Polish Academy of Biology, 48: 53-62.<br />
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snakes: example of Elaphe longissima.In:Van Gelder,<br />
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de la Société Herpétologique de France, 52: 45-53.<br />
NAULLEAU G., 1992a. Reproduction de la couleuvre d’Esculape<br />
Elaphe longissima Laurenti (Reptilia, Colubridae) dans le<br />
Centre Ouest de la France. Bulletin de la Société Herpétologique<br />
de France, 62: 9-17.<br />
NAULLEAU G., 1992b. Activité et température corporelle automnales<br />
et hivernales chez la Couleuvre d’Esculape Elaphe longissima<br />
(Squamata, Colubridae) dans le Centre Ouest de la France.<br />
Bulletin de la Société Herpétologique de France, 64: 21-35.<br />
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berus en Loire-Atlantique : un problème de compétition interspécifique.<br />
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ecologia mediterranea, tome 28, fascicule 2, 2002, p. 75-91<br />
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91
Conséquences phytoécologiques<br />
de la restauration d’un écosystème dunaire fixé<br />
avec le tamaris (Tamarix gallica L.), en Algérie<br />
Phytoecological consequences of a sand dune restauration<br />
with tamaris (Tamarix gallica L.), in Algeria<br />
Khéloufi Benabdeli 1, Halima Mohammedi 1, Noreddine Letereuch-Belarouci 2<br />
1. Faculté des sciences, département des sciences de l’environnement, Université Djilali-Liabes, BP89 Sidi Bel-Abbes, 22000 Algérie<br />
2. Faculté des sciences, département de foresterie, Université de Tlemcen, Algérie<br />
Résumé<br />
La lutte biologique contre l’ensablement grâce à l’utilisation du<br />
Tamarix gallica Wahl. donne des résultats intéressants, tant du<br />
point de vue écologique qu’économique. L’évolution phytoécologique<br />
de la dune fixée et mise en défens est nettement perceptible à travers<br />
l’analyse des résultats dendrométriques et phytoécologiques obtenus.<br />
Les résultats attestent d’une remontée biologique où le Tamarix<br />
gallica joue un rôle déterminant dans la lutte contre l’ensablement<br />
en favorisant (par une protection et un ombrage) l’installation d’une<br />
strate herbacée.<br />
Les paramètres dendrométriques permettant d’évaluer l’évolution<br />
de la production ligneuse sont le nombre de brins par cépée, la hauteur<br />
moyenne, le diamètre et la surface terrière. Leur quantification<br />
aux différents âges laisse apparaître une augmentation du<br />
nombre de brins par hectare (densité), un accroissement annuel<br />
moyen de la hauteur de 56 cm. Le diamètre à 1,30 m connaît lui<br />
aussi un accroissement moyen annuel de 0,57 cm, soit une augmentation<br />
annuelle moyenne de la surface terrière de 0,00709 m 2.<br />
Une plantation à une densité moyenne de 1 600 plants par hectare,<br />
Tamarix gallica permet une production de matière ligneuse,<br />
très sollicitée dans la région, de l’ordre de 0,28 m 3/ha et par an,<br />
soit un accroissement moyen annuel moyen de 0,31 m 3/ha. Cette<br />
production peut répondre aux besoins de deux familles et contribuera<br />
à assurer une protection de cet écosystème, utile pour ses utilisateurs.<br />
Mots-clés<br />
Tamarix gallica, paramètres dendrométriques, restauration écologique,<br />
fixation des dunes, Algérie.<br />
Short version<br />
The use of Tamarix gallica as biological sand binder provides interesting<br />
results from anecological and economical point of view. These<br />
species induces also a valuable biomass. Increased contribution of<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 93-99<br />
Saharo-sindian species balance the decrease role of ubiquitous species,<br />
but Mediterraneen species stay relatively constant. An appreciable<br />
increase of species number can be seen as composed to the<br />
control plot; increase from 6 to 12, for genera, and from 9 to 15<br />
for species. A dynamic process and fluctuation for species in each<br />
biogeographic element are then documented. The number of genera<br />
greatly depends on species fluctuations witch are under the effect of<br />
many parameters not always under control. In such a situation, it<br />
is obvious that the fencing system play a determinant role in the<br />
restoration process. Dendrometric parameters witch permit the evaluation<br />
of woody biomass production and itsevolutionare number<br />
of shoot by plant, the height mean, the diameter and ground cover.<br />
Quantification of these parameters at differents stages shows an<br />
increase of shoot number per hectare (density), and an increase of<br />
the annual mean height by 56 centimeter. The diameter at 1.30<br />
meter show also an increase of 0.57 cm witch correspond to an<br />
annual mean increase of its cover of 0.00709 m 2.<br />
With a mean plantation density of 1600 plants per hectare, Tamarix<br />
gallica induces a annual production of ligneous matter of 0.28 m 3<br />
per hectare, i.e. an annual increase of 0.31 m 3 per hectare. This<br />
production would contribute to solve some needs of fuel wood, and<br />
should benefit the ecosystem mainly because of its use by local population.<br />
The combinaison of fencing system and plantation of woody<br />
species, as Tamarix, permit to yield appreciable results. This ligneous<br />
plant with its rapid growth allow the establishment of a favorable<br />
microclimate, and the establishment of a herbaceous stratum could<br />
play an important role in the dune stability and the evolution of<br />
this ecosystem. Local population takes care of fencing audits maintenance,<br />
because of wood and animal feed produced in return of<br />
their participation of the protection process.<br />
Keywords<br />
Tamarix gallica, dendrometric parameters, ecological restoration,<br />
dune fixation, Algeria.<br />
93
94<br />
◆ KHÉLOUFI BENABDEL, HALIMA MOHAM<strong>MED</strong>I, NOREDDINE LETEURECH-BELAROUCI<br />
INTRODUCTION<br />
Par leur instabilité et leurs mouvements continuels sous<br />
l’influence des vents dominants, les ensembles dunaires sont<br />
source de préjudices économiques et écologiques pour l’espace<br />
qu’ils envahissent. La résultante de ces mouvements<br />
est un ensablement qui constitue un processus important<br />
de la désertification si l’on retient la définition qui en a été<br />
donnée par Le Houérou (1969) : « La désertification est considérée<br />
comme étant un ensemble d’actions qui se traduisent par<br />
une réduction du couvert végétal, aboutissant à l’extension de<br />
paysage désertique caractérisés par des regs, des hamadas et des<br />
ensembles dunaires. »<br />
Un grand nombre d’espèces végétales sont utilisées à<br />
travers le monde pour lutter contre l’ensablement et elles<br />
montrent toutes, à un certain moment, leur limite. Ainsi,<br />
pratiquement 6 millions d’hectares sont transformés en<br />
désert chaque année et plus de 20 millions d’hectares<br />
montrent une productivité nulle, suite à ce phénomène<br />
(Oldache, 1988). En Algérie, cet ensablement est bien<br />
présent, et le rempart naturel que constitue la steppe n’arrive<br />
pas à lutter efficacement contre l’avancé des dunes<br />
car la steppe dégradée ne permet plus le piégeage du sable.<br />
Dans cette zone de transition toutes les biocénoses suivent<br />
une dynamique régressive (Pouget, 1979).<br />
La lutte contre l’ensablement dans une commune de<br />
l’ouest de l’Algérie a été menée en utilisant du Tamarix<br />
mis en défens pendant plusieurs années. Cette espèce permet<br />
la stabilisation des dunes et l’installation d’une strate<br />
herbacée à l’origine d’une remontée biologique perceptible.<br />
L’étude porte sur le suivi du comportement de cette<br />
espèce dans son utilisation comme moyen de lutte biologique<br />
contre l’ensablement qui menace cette localité et<br />
les terres agricoles environnantes. Des plantations d’âges<br />
différents ont été étudiées afin de comparer la dynamique<br />
de la végétation dans le temps et dans l’espace.<br />
Caractéristiques stationnelles<br />
de la zone étudiée<br />
Les paramètres climatiques retenus sont ceux du poste<br />
météorologique de Mécheria (Algérie occidentale), situé<br />
à une quinzaine de kilomètres de la zone d’étude, dans la<br />
même zone géographique et dans l’étage aride, d’où sa<br />
représentativité à défaut de poste météorologique in situ.<br />
La carte pluviométrique dressée par l’Office national de<br />
la Météorologie, sur la base des données de la période<br />
1950-1980, situe la localité de Ain Benkhélil et ses environs<br />
dans la tranche pluviométrique des 200 mm de pluviométrie<br />
moyenne annuelle. Le régime pluviométrique<br />
est du type APHE, favorable à une activité végétative malgré<br />
la longueur de la période de sécheresse qui s’étale<br />
d’avril à octobre.<br />
Les températures moyennes minimales du mois le plus<br />
froid m sont de 1,7 °C et celles du mois le plus chaud M<br />
de 35,1 °C ; le quotient pluviothermique d’Emberger est<br />
de 20, ce qui permet de classer la zone d’étude dans l’étage<br />
bioclimatique aride inférieur frais selon la classification<br />
d’Alcaraz (1962). D’après les fluctuations des paramètres<br />
climatiques interannuels, le climat varie de l’aride au semiaride<br />
inférieur (Mederbal, 1992 ; Djelouli, 1981).<br />
Les sols de la zone sont peu évolués, d’apport d’origine<br />
éolienne, et caractérisés généralement par trois horizons<br />
difficilement discernables. Le taux de sable est toujours<br />
supérieur à 78 % (78 à 95 %), celui de l’argile est<br />
inférieur à 12 % (4 à 12 %) et les limons ne dépassent<br />
jamais 10 % (1 à 10 %). Le taux de matière organique<br />
varie essentiellement dans les horizons superficiels et diminue<br />
selon la profondeur de 1,5 à 0,5 %. Le pH est compris<br />
entre 7,2 et 8,5 (Bachir, 1993).<br />
Contexte floristique et phytoécologique<br />
La carte de végétation réalisée par le Centre de<br />
recherche en biologie terrestre de l’Université d’Alger, en<br />
1977, signale la présence des espèces dominantes suivantes<br />
: Lygeum spartum L., Retama retamWebb., Aristida<br />
pungens L., Stipa tortilis Desf., Artemisia herba-alba Asso.,<br />
Arthrophytum scoparium Schrank., Thymelaea microphylla<br />
Coss. En fait, les trois dernières espèces ne sont que rarement<br />
présentes, alors que d’autres espèces caractéristiques<br />
de biotopes salés et d’espèces psammophiles de terrains<br />
humides telles que Tamarix gallica L., Phragmites communis<br />
Trin., Stipa lagascae R. et S., Helianthemum lippii<br />
Ball sont constamment présentes (Djelouli, 1981).<br />
La strate herbacée, dominante, est représentée par des<br />
espèces appartenant à une dizaine de familles (tableau 1) où<br />
dominent les Graminées avec 10 genres et 11 espèces, les<br />
Composées avec 7 genres et 7 espèces et les Chénopodiacées<br />
avec 6 genres et 6 espèces, les Légumineuses avec 5 genres<br />
et 6 espèces et les Crucifères avec 3 genres et 5 espèces.<br />
D’autres familles sont également présentes, mais ne sont pas<br />
signalées, car très faiblement représentées, avec un nombre<br />
de genres et d’espèces généralement inférieur à 2, comme<br />
les Convolvulacées, les Liliacées, les Géraniacées, les<br />
Malvacées, les Plombaginacées, les Polygonacées, les<br />
Saxifragacées, les Aizoacées, les Capparidées, les<br />
Frankéniacées, les Inulées et les Onogracées.<br />
Les Graminées, les Composées, les Chénopodiacées<br />
et les Légumineuses jouent donc un rôle déterminant dans<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
CONSÉQUENCES PHYTOÉCOLOGIQUES DE LA RESTAURATION D’UN ÉCOSYSTÈME DUNAIRE FIXE AVEC LE TAMARIS…<br />
Éléments géographiques 1990 1994 1996 Témoin<br />
la végétation de la zone. Les espèces végétales les plus<br />
constantes se répartissent comme suit (tableau 1) : 1 à 2<br />
plurirégionales ; 8 à 9 méditerranéennes ; 5 à 7 saharosindiennes<br />
; et 3 à 8 endémiques. En comparant à la placette<br />
témoin, une évolution est nettement perceptible, car<br />
cette dernière ne regroupe que 3 plurirégionales, 4 méditerranéennes,<br />
2 saharo-sindiennes et 3 endémiques.<br />
Les travaux de Djebaili (1978, 1990) mettent en évidence<br />
les groupements à Stipa tenacissima L., Artemisia<br />
herba-alba Asso. et Lygeum spartum L. qui sont rattachés<br />
au Lygeo-Stipetalia (Braun-Blanquet et De Bolos, 1957)<br />
enrichi de nombreuses thérophytes et psammophytes<br />
endémiques du Maghreb. Les autres groupements à<br />
Lygeum spartum et Stipa tenacissima et ceux à Lygeum spartum<br />
et Thymelaea microphylla Coss. peuvent également<br />
être rattachés au Lygeo-Stipetalia, tout comme les groupements<br />
vivaces steppiques maghrébins de l’aride (Rivas-<br />
Martinez, 1977).<br />
MÉTHODOLOGIE<br />
Espèces % Espèces % Espèces % Espèces %<br />
Plurirégionales 1 5 2 9 2 9 3 25<br />
Méditerranéennes 9 43 9 39 8 36 4 33<br />
Saharo-sindiennes 7 33 5 28 6 27 2 17<br />
Endémiques 3 14 7 31 9 38 3 25<br />
Tableau 1. Évolution du spectre des éléments biogéographiques dans la zone de mise en défens entre 1990 et 1996.<br />
Des placettes d’observation et de mesures, avec des<br />
unités d’observations de 20 pieds en moyenne (Dagnélie,<br />
1957), soit une surface de 10 m 2,ont été retenues. Douze<br />
placettes ont été installées dans le périmètre protégé à raison<br />
de 4 par catégorie d’âge (2 ans, 5 ans et 10 ans). Une<br />
placette n’ayant bénéficié ni de plantation ni de mise en<br />
défens a été choisie à l’intérieur de la zone pour servir<br />
d’espace témoin.<br />
Dans un but de cerner la dynamique phytoécologique,<br />
deux relevés phytoécologiques ont été effectués par placette<br />
et par catégorie d’âge, soit 24 relevés ; seule la notion<br />
d’absence et de présence a été retenue pour évaluer l’évolution<br />
quantitative des espèces en comparaison avec la<br />
parcelle témoin.<br />
Les travaux de fixation de dunes entrepris dans la zone<br />
d’Ain Benkhélil (Naama) durant la campagne de planta-<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 93-99<br />
tion 1988/89 se sont faits selon les données techniques<br />
suivantes : la densité de plantation est de 1 600 plants par<br />
hectare ; les plants de Tamarix gallica L. sont issus de boutures<br />
élevées en pépinière pendant 9 mois en moyenne et<br />
ont une hauteur oscillant entre 0,60 et 1 m et un diamètre<br />
de l’ordre de 1,5 à 3 cm au collet. La plantation se fait en<br />
ouvrant un trou de 30 cm de profondeur suivie d’un tassement<br />
du sol et d’un arrosage de 20 litres d’eau. La superficie<br />
plantée est mise en défens pendant neuf années<br />
(1988/89 à 1996/97).<br />
Une évaluation permanente et annuelle de la diversité<br />
végétale a été faite au mois de mai des années 1990, 1994,<br />
1996 et les résultats obtenus comparés à ceux de la placette<br />
témoin qui représente une certaine stabilité phytoécologique<br />
de la zone étudiée soumise à une utilisation.<br />
RÉSULTATS ET DISCUSSIONS<br />
Dynamique de la flore spontanée<br />
L’exploitation des résultats du comportement des<br />
espèces dans les parcelles protégées et plantées de Tamarix<br />
permet d’apprécier le rôle de chaque espèce dans la dynamique<br />
évolutive de l’écosystème dunaire fixé. La fréquence,<br />
la phytomasse et la productivité en unités fourragères<br />
sont des paramètres déterminants pour classer les<br />
espèces et comprendre l’importance écologique de chacune<br />
d’elles dans les conditions précitées.<br />
La phytomasse totale obtenue dans l’écosystème<br />
dunaire fixé par le Tamarix, estimée par Bergheul en 1990<br />
avec une pluviométrie moyenne de l’ordre de 269 mm<br />
étalés sur 61 jours, est très proche de nos résultats. Elle<br />
est évaluée à 533 kilogrammes de matière sèche par hectare<br />
(kg MS/ha) pour la zone témoin. Deux ans après une<br />
mise en défens, la phytomasse atteint 1 032 kg MS/ha, et<br />
après une autre période de deux ans de protection, elle<br />
diminue à 384 kg MS/ha. La pluviométrie moyenne de<br />
95
96<br />
◆ KHÉLOUFI BENABDEL, HALIMA MOHAM<strong>MED</strong>I, NOREDDINE LETEURECH-BELAROUCI<br />
1990 1994 1996<br />
Types biologiques Espèces % Espèces % Espèces %<br />
Thérophytes 4 19,04 7 30,43 9 35<br />
Chaméphytes 7 33,03 7 30,43 6 23<br />
Hémicryptophytes 6 28,57 5 21,47 5 19<br />
Phanérophytes 1 4,76 1 4,33 1 3<br />
Géophytes – – 1 4,33 2 6<br />
Tableau 2. Évolution du spectre biologique dans la zone de mise en défens entre 1990 et 1996.<br />
1990 1994 1996<br />
Types biologiques Espèces % Espèces % Espèces %<br />
Thérophytes 4 40 3 22 6 0<br />
Chaméphytes 2 20 4 28 3 25<br />
Hémicryptophytes 2 20 3 22 1 8<br />
Cryptophytes 1 10 2 14 1 8<br />
Phanérophytes 1 10 1 7 1 8<br />
Géophytes – – 1 7 – –<br />
Tableau 3. Évolution du spectre biologique de la placette témoin entre 1990 et 1996.<br />
Espèces Zone témoin Mise en défens Mise en défens Mise en défens<br />
(1990) (1994) (1996)<br />
Freq. C. Freq. C. Freq. C. Freq. C.<br />
Cynodon dactylon Pers. 67 4 – – 19 2 20 2<br />
Aristida pungens L. 13 2 – – 19 2 18 2<br />
Peganum harmala L. 10 2 13 2 – – 8 1<br />
Malva parviflora L. 6 2 – – – – – –<br />
Echinops spinosus 5 2 21 2 10 2 8 2<br />
Helianthemum lippii Ball. 19 2 20 2 20 2 22 3<br />
Zygophyllum album 23 2 5 2 7 2 9 1<br />
Scirpus holoschoenus L. 6 2 8 2 17 2 21 3<br />
Phragmites communis Adams. 48 3 28 3 9 2 6 1<br />
Tamarix gallica L. 5 2 24 2 46 4 52 4<br />
Onopordon acaulis 4 2 10 2 4 2 5 1<br />
Schismus barbatus P.B. 4 2 3 2 6 2 8 2<br />
Stipa lagascae L. – – 37 3 23 2 19 2<br />
Iris sisyrinchium L. – – 5 2 – – 4 1<br />
Coronilla juncea L. – – 2 2 – – 2 1<br />
Thymelaea microphylla Tourn. – – 6 2 3 2 – –<br />
Lygeum spartum L. – – 5 2 31 3 43 4<br />
Muricaria prostata Desv. – – 2 2 – – 2 1<br />
Malcolmia africana R. Br. – – 9 2 – – – –<br />
Astragalus gombo L. – – 4 2 10 2 18 3<br />
Launaea resedifolia L. – – 8 2 6 2 4 1<br />
Phytomasse kg MS/ha 336,51 – 474,27 – 976,30 – 1 124,60 –<br />
Equivalent UF/ha 35 – 45 – 105 – 115 –<br />
Recouvrement global 20 % – 10 % – 40 % – 50 % –<br />
Freq. : fréquence ; C. : coefficient d’abondance dominance ; UF : unité fourragère ; kg MS/ha : kilogramme de matière sèche par hectare<br />
Tableau 4. Dynamique phytoécologique exprimée par la fréquence et l’abondance des principales espèces végétales de la zone d’étude.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
CONSÉQUENCES PHYTOÉCOLOGIQUES DE LA RESTAURATION D’UN ÉCOSYSTÈME DUNAIRE FIXE AVEC LE TAMARIS…<br />
cette période est légèrement plus faible que celle de l’année<br />
1990, seulement 256 mm sur 57 jours.<br />
Cette chute nette de phytomasse peut avoir trois justifications<br />
possibles : l’impact de la différence de précipitations<br />
; l’écosystème a atteint son maximum de production<br />
et régresse ; les parcelles ont été utilisées illicitement<br />
la nuit par les troupeaux.<br />
Les résultats obtenus après une mise en défens et une<br />
plantation en Tamarix gallica L. sont assez remarquables<br />
par rapport à l’état de dégradation des autres espaces de<br />
la région. Les formations végétales issues de cette mise en<br />
valeur sont un taillis de Tamarix sur une strate buissonnante<br />
permanente dont le taux de recouvrement moyen<br />
est de 10 à 20 % et une pelouse à espèces annuelles à l’origine<br />
de la phytomasse relativement importante quantifiée.<br />
Par espèces, la phytomasse est très fluctuante (tableau 4),<br />
avec une prédominance d’Aristida pungens, Lygeum spartum,<br />
Helianthemum lippii, Peganum harmala, Stipa lagascae,<br />
Astragalus gombo, Launaea residifolia, Helianthemum hirtum,<br />
Thymelaea microphylla et Ononis natrix. Respectivement entre<br />
1990 et 1994, puis 1994 et 1996, la phytomasse a connu des<br />
augmentations de 474, 976 et 1124 kilogrammes de matière<br />
sèche par hectare comparée à la placette témoin qui n’offre<br />
qu’une biomasse fluctuant entre 456 et 588 kg MS/ha, soit<br />
une moyenne de référence plus ou moins stable de 522 kg<br />
MS/ha.<br />
La placette témoin montre une abondance des espèces<br />
éphémères (tableau 3), où les espèces indicatrices de<br />
dégradation par les pressions anthropozoogènes dominent.<br />
Dès la première mise en défens apparaissent des<br />
espèces vivaces recherchées par les troupeaux pour leur<br />
apétabilité telles que : Aristida pungens, Lygeum spartum et<br />
Stipa lagascae. Dans la steppe à alfa, Le Houérou (1968)<br />
signale que ces trois espèces peuvent se réinstaller facilement<br />
sous l’effet d’une amélioration des conditions climatiques,<br />
édaphiques (notamment par une diminution<br />
du piétinement) et de la conduite des troupeaux.<br />
Ce sont surtout les espèces saharo-sindiennes qui<br />
ont connu un accroissement de leur rôle alors que celui<br />
des pluri-régionales a diminué. Les méditerranéennes,<br />
quant à elles, sont restées relativement constantes. Le<br />
nombre de genres présents connaît, par rapport à la<br />
placette témoin, une progression appréciable en 1990,<br />
1994 et 1996, avec respectivement des gains de 6, 11<br />
et 12, alors que pour les espèces les gains sont de 9, 11<br />
et 15. Le tableau 2 donne un aperçu sur la dynamique<br />
et la fluctuation du nombre de genres et d’espèces par<br />
élément biogéographique. La mise en défens joue un<br />
rôle déterminant dans cette évolution de la composition<br />
spécifique.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002, p. 93-99<br />
Les résultats obtenus en nombre d’espèces et en pourcentage<br />
par type biologique récapitulé dans le tableau 3<br />
laisse apparaître une certaine instabilité des végétaux temporaires<br />
(thérophytes et géophytes) alors que les végétaux<br />
ligneux (phanérophytes et chaméphytes) et les hémicryptophytes<br />
présentent une certaine stabilité.<br />
Comparaison entre relevés phytoécologiques<br />
L’évolution phytoécologique a pu être appréciée après<br />
une mise en défens et introduction de Tamarix gallica.<br />
Les espèces qui ont le plus progressé sont Echinops spinosus,<br />
Tamarix gallica, Schismus barbatus, Stipa lagascae,<br />
Lygeum spartum et Astragalus gombo. Par contre, il faut<br />
noter une diminution ou disparition d’espèces telles que<br />
Malva parviflora, Zygophyllum album, Peganum harmala<br />
et Phragmites communis. La composition floristique<br />
moyenne est proche de celle des steppes de la région,<br />
telle que définie par Djebaili (1982), avec une dominance<br />
de Chaméphytes et d’Hémicryptophytes. La mise<br />
en défens, ou l’utilisation équilibrée de cet écosystème,<br />
conduit donc généralement à une remontée biologique<br />
appréciable.<br />
Le recouvrement global a connu une diminution lors<br />
des deux premières années de mise en défens, essentiellement<br />
à cause des perturbations causées par les travaux<br />
de préparation du sol et de plantation, le taux de couvert<br />
est alors passé de 20 à 10 %. Après six ans de protection,<br />
le recouvrement est passé de 10 à 40 %, atteignant même<br />
50 % après huit ans de mise en défens.<br />
La phytomasse aérienne a également connu une augmentation<br />
récapitulée comme suit :<br />
Année Pluviométrie Phytomasse en Unités<br />
en mm kg MS/ha fourragères<br />
1988 247 336.51 35<br />
1990 269 474.27 45<br />
1994 256 976.30 105<br />
1996 273 1124.68 115<br />
Les résultats obtenus sont assez proches de ceux de<br />
Bergheul (1990) et Bachir (1993) qui ont travaillé dans<br />
la même zone, mais avec des objectifs et approches différents.<br />
Les légères différences enregistrées se localisent<br />
essentiellement dans le nombre d’espèces recensées, le<br />
coefficient d’abondance-dominance et la biomasse avec<br />
une marge d’erreur oscillant entre 15 et 20 %.<br />
La phytomasse, après une diminution pendant les<br />
premières années, augmente considérablement entre 2 et<br />
4 ans de mise en défens, puis se stabilise au-delà de 5 ans<br />
97
98<br />
◆ KHÉLOUFI BENABDEL, HALIMA MOHAM<strong>MED</strong>I, NOREDDINE LETEURECH-BELAROUCI<br />
Paramètres quantifiés Phytomasse sèche en kg MS/ha<br />
Espèces principales Pt 1990 1994 1996<br />
Aristida pungens L. 205 286 248 373<br />
Peganum harmala L. 57 38 45 71<br />
Helianthemum lippii Ball. 157 75 121 137<br />
Tamarix gallica L. 103 131 221 295<br />
Stipa lagascae L. – 83 28 19<br />
Lygeum spartum L. – 14 304 366<br />
Thymelaea microphylla Tourn. – 25 12 11<br />
Ononis natrix L. – 5 5 7<br />
Astragalus gombo L. – 11 8 18<br />
Launaea resedifolia L. – 6 13 14<br />
Helianthemum hirtum Ball. – – 16 13<br />
Total 522 474 976 1 124<br />
Pt : parcelle témoin (check plot).<br />
qui semble être le stade d’équilibre (tableau 5). La phytomasse<br />
des steppes à Lygeum spartum est estimée à<br />
350 kg MS/ha et par an, selon le Centre de recherche<br />
en biologie terrestre (CRBT, 1978) ; à 500 kg MS/ha,<br />
selon Aidoud (1983). En matière de productivité, Le<br />
Houérou (1971) l’évalue, pour les steppes arides où la<br />
pluviométrie oscille entre 200 et 300 mm/an, entre 80<br />
et 150 kg MS/ha.<br />
Comportement du Tamarix gallica<br />
Tableau 5. Évolution de la biomasse végétale chez les principales espèces de la zone d’étude.<br />
En plus de la restauration de l’écosystème, constatée<br />
par la bonne “remontée biologique”, l’espèce introduite<br />
procure une biomasse ligneuse intéressante. Dans ces<br />
zones, les besoins en bois comme source d’énergie domestique<br />
sont très élevés et ont été estimés, dans des conditions<br />
écologiques similaires, dans le sud du massif forestier<br />
de Télagh (Oranie-Algérie), à plus de 0,6 stères par<br />
famille et par jour, soit 60 kilogrammes (Benabdeli, 1983).<br />
Les paramètres dendrométriques permettant d’évaluer<br />
l’évolution de la production ligneuse sont le nombre de<br />
brins par cépée, la hauteur moyenne, le diamètre et la surface<br />
terrière. La quantification de ces paramètres aux différents<br />
âges laisse apparaître une augmentation du nombre<br />
de brins par hectare (densité), un accroissement annuel<br />
moyen de la hauteur de 56 cm. Le diamètre à 1,30 m<br />
connaît lui aussi un accroissement moyen annuel de<br />
0,57 cm, soit une augmentation annuelle moyenne de la<br />
surface terrière de 0,00709 m2 (voir les résultats détaillés<br />
dans le tableau 6).<br />
Avec une plantation à une densité moyenne de 1600<br />
plants par hectare, le Tamarix gallica permet une production<br />
de matière ligneuse de l’ordre de 0,28 m3/ha et<br />
par an, soit un accroissement moyen annuel moyen de<br />
0,31 m3/ha. Selon les besoins moyens par famille en bois<br />
domestique, la productivité d’un hectare de Tamarix gallica<br />
permet de faire face aux besoins de deux familles.<br />
Paramètres 1990 1994 1996 Moyenne<br />
Nombre de cépées par hectare 1350 1325 1295 1323<br />
Nombre de brins par hectare 2525 6375 7025 5308<br />
Hauteur moyenne en cm 3,61 4,62 5,21 4,48<br />
Diamètre moyen en cm 3,99 4,63 5,17 4,59<br />
Surface terrière par brin en cm 2 0,0017 0,0027 0,0034 0,0026<br />
Surface terrière par hectare en m 2 0,0425 0,0675 0,0814 0,0638<br />
Tableau 6. Evolution des paramètres dendrométriques du Tamarix gallica dans la zone mise en défens.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
CONSÉQUENCES PHYTOÉCOLOGIQUES DE LA RESTAURATION D’UN ÉCOSYSTÈME DUNAIRE FIXE AVEC LE TAMARIS…<br />
CONCLUSION<br />
De toutes les espèces végétales utilisées pour la lutte<br />
contre l’ensablement, le Tamarix gallica, dans les conditions<br />
écologiques particulières de Mécheria (Ain Ben-khélil)<br />
semble donner des résultats de stabilisation des dunes<br />
appréciables. La colonisation de l’écosystème dunaire par<br />
une strate herbacée et arbustive est réelle ; ainsi il y a une<br />
bonne “remontée biologique”, garante d’une stabilisation<br />
du sol particulaire et de l’installation d’une dynamique<br />
phytoécologique progressive. Les résultats obtenus ne sont<br />
pas tous dus à l’introduction du Tamarix gallica, puisque<br />
la mise en défens joue aussi un rôle important.<br />
La combinaison entre la mise en défens et la plantation<br />
d’espèces ligneuses comme le Tamarix gallica permet<br />
d’aboutir à une restauration appréciable. Ce ligneux à<br />
croissance rapide permet de créer un microclimat favorable<br />
à l’installation d’une strate herbacée, jouant un rôle<br />
important dans la stabilisation des dunes et l’évolution de<br />
l’écosystème. Les riverains respectent la mise en défens,<br />
car elle leur procure des unités fourragères et du bois de<br />
feu en contrepartie de leur participation à la sauvegarde<br />
de cet espace.<br />
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LE HOUÉROU H.-N., 1969. La végétation de la Tunisie steppique<br />
(avec références aux végétations analogues d’Algérie, de Libye<br />
et du Maroc). Ann. Inst. Nation. Agro., 42:624 p.<br />
LE HOUÉROU H.-N., 1971. Les bases écologiques de la production<br />
pastorale et fourragères en Algérie. FAO, Rome : 60 p.<br />
LE HOUÉROU H.-N., 1979. La désertification des régions arides.<br />
La Recherche, 99:21-27.<br />
<strong>MED</strong>ERBAL K., 1992. Compréhension des mécanismes de transformation<br />
du tapis végétal : approches phytoécologique par<br />
télédétection aérospatiale et dendroécologie de Pinus halepensis<br />
Mill. dans l’ouest algérien.Thèse doctorat d’État, Univ.<br />
Aix-Marseille III : 229 p.<br />
OLDACHE E., 1988. Contribution à l’étude de la fixation des<br />
dunes dans la région d’El Mesrane (Djelfa) et Bousaada<br />
(M’sila). Thèse de magister, INA, Alger : 98 p.<br />
POUGET M., 1979. Les relations sol-végétation dans les steppes<br />
sud-algéroises (Algérie). Thèse doctorat d’État, Univ. Aix-<br />
Marseille III, 555 p.<br />
RIVAS-MARTINEZ S., 1977. Sur la syntaxonomie des pelouses<br />
thérophytiques de l’Europe occidentale. In : La végétation<br />
des pelouses sèches à thérophytes. Coll.Phytosociol.,6:55-71.<br />
99
A new colony of critically endangered Northern<br />
Bald Ibises has been discovered in an Al Badia<br />
(desertic steppe) area of central Syria<br />
A new colony of critically endangered Northern Bald Ibises<br />
(Geronticus eremita) has been discovered in an Al Badia (desertic<br />
steppe) area of central Syria.The small colony contained three pairs<br />
which were discovered incubating eggs, and a seventh adult.This is<br />
the first evidence of the continued breeding of Northern Bald Ibises<br />
in the Middle East since a colony at Birecek in Turkey became extinct<br />
in 1989.The new birds were found in spring 2002 by a team carrying<br />
out wildlife surveys on behalf of the Syrian Government’s<br />
Ministry of Agriculture and Agrarian Reform (MAAR).<br />
Survey Team leader, Associate Professional Officer, Wildlife<br />
Expert, Gianluca Serra said, « Discovering this bird was like finding<br />
the Arabian Phoenix regenerated from the ashes.The survey work<br />
through remote and rough terrain was some of the most exciting and<br />
challenging fieldwork we had ever experienced.Throughout it all, my<br />
Syrian colleagues from MAAR, Ghazy Al-Qaim and Mahmoud<br />
Abdallah, were optimistic that Northern Bald Ibises still existed in<br />
the Al Badia or desertic steppe of central Syria because we had received<br />
reports of their presence from Bedouin nomads and local hunters.<br />
» Dr Michael Rands, Director of BirdLife International, said<br />
« This fascinating species, once common throughout much of the<br />
Middle East and southern Europe, is now on the brink of global<br />
extinction, despite much conservation effort in Morocco and Turkey.<br />
This fantastic discovery gives new hope that the Northern Bald Ibis<br />
can be saved, and the BirdLife Partnership will do all it can to assist<br />
the Syrian authorities to conserve this amazing threatened species for<br />
future generations to enjoy. »<br />
The Northern Bald Ibis was formerly widespread across the<br />
<strong>Mediterranea</strong>n region, but has suffered a long-term decline and<br />
now has an extremely small population. The reasons behind<br />
decline include human persecution, loss of steppe or unintensive<br />
agricultural areas, pesticide poisoning, human disturbance<br />
and dam construction. Until this recent discovery, the total world<br />
population was put at 220 individual birds, confined to two colonies<br />
in north-west Morocco.The Northern Bald Ibis is classified<br />
as Critically Endangered according to the World Conservation<br />
Union (IUCN) Red List criteria. This means it faces an extremely<br />
high risk of extinction in the wild in the immediate future.<br />
The discovery was made at the end of an extensive two-year<br />
programme of wildlife surveys aimed at producing a biodiversity<br />
inventory for Al Talila Reserve, the first Syrian protected area.<br />
Contact: Birdlife International, Wellbrook Court,<br />
Girton Road, Cambridge, CB3 0NA, United Kingdom.<br />
(http://www.birdlife.net/news).<br />
ecologia mediterranea, tome 28, fascicule 2, p. 101-105<br />
Faits de conservation en Méditerranée<br />
<strong>Mediterranea</strong>n Conservation News<br />
The Iberian lynx needs networks of large reserves<br />
The Iberian lynx, an endemic species of southern Iberia, is<br />
considered by the IUCN as the most endangered felid in the<br />
world. Recent research made at Estación Biológica de Doñana<br />
(Sevilla, Spain) has focused on the factors responsible of lynx<br />
decline (Rodríguez & Delibes, 2002-2003). In 1953 myxomatosis,<br />
a viral disease, quickly spread across the Iberian peninsula<br />
resulting in a strong drop of rabbit numbers (virtually the only<br />
lynx prey species) which lasted for decades. An analysis of the<br />
subsequent range contraction during a 35-year period shows that<br />
only lynx populations inhabiting areas larger than 500 km 2 were<br />
able to persist. The extinction of these small lynx populations<br />
has been attributed to demographic stochasticity related with<br />
metapopulation disequilibrium.The refill of gaps, i.e. vacant territories,<br />
may have accounted for reduced fragmentation of larger<br />
populations.There was also strong indication that migration<br />
from neighbouring sources was essential for the survival of vulnerable<br />
small populations.<br />
Simple regression models could be used to choose where<br />
conservation efforts should be located in order to optimise the<br />
persistence of lynx populations. The quality of lynx habitat in<br />
terms of scrubland structure and rabbit availability was probably<br />
higher around 1950 than it is nowadays. Keeping human<br />
pressure low, and assuming that habitat quality was restored to<br />
the former levels, several nature reserves larger than 50,000 ha<br />
should be established and saturated with populations of about<br />
100 adults to guarantee lynx survival in the short to medium<br />
term (30 to 50 years). Reserves of this size can be labelled “large”<br />
for European standards. Moreover, reserves should be arranged<br />
in networks where inter-population distance should be minimised<br />
within a maximum of 30 km, a figure close to the upper threshold<br />
for lynx dispersal distance. Intervening habitats between<br />
reserves may be not as good as within reserves but their structure<br />
should facilitate migration between lynx populations, and<br />
sources of disperser mortality must be removed.<br />
For more information read:<br />
— RODRÍGUEZ A. & DELIBES M., 2002.<br />
Internal structure and patterns of contraction in the geographic<br />
range of the Iberian lynx. Ecography, 25: 314-328.<br />
— RODRÍGUEZ A. & DELIBES M., 2003.<br />
Population fragmentation and extinction in the Iberian lynx.<br />
Biological Conservation, 109: 321-331.<br />
ALEJANDRO RODRÍGUEZ<br />
Dept. of Applied Biology, Estación Biológica de Doñana, CSIC,<br />
Avda. María Luisa s/n, 41013 Sevilla, Spain.<br />
email address: alrodri@ebd.csic.es<br />
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◆ FAITS DE CONSERVATION EN MÉDITERRANÉE / <strong>MED</strong>ITERRANEAN CONSERVATION NEWS<br />
Quelles sont les chances de maintien d’un ligneux<br />
endémique relictuel ? Le cas de la bourdaine bétique<br />
(Frangula alnus subsp. baetica) en Andalousie<br />
La bourdaine bétique, Frangula alnus subsp. baetica (Rhamnaceae),<br />
est un ligneux endémique, éminemment résiduel et vulnérable,<br />
présent dans quelques populations du sud de l’Espagne<br />
et du nord-ouest du Maroc (région biogéographique béticorifaine).<br />
Au Maroc, il se localise dans quelques ravins du revers<br />
septentrional du Tidighin (Rif), entre 1 400 et 1 750 m d’altitude,<br />
en bordure de sources et suintements permanents parmi<br />
la cédraie, en compagnie de Betula pubescens subsp.celtiberica.En<br />
Andalousie, une vingtaine de populations de bourdaine existent<br />
au fond de certains vallons humides de basse altitude (entre 125<br />
et 700 m) des provinces de Huelva, Cadiz et Malaga, en particulier<br />
dans les barrancos de la Sierra del Aljibe.<br />
Une récente étude conduite par Hampe et Arroyo (2002) ont<br />
étudié en détail les processus de recrutement et de régénération de<br />
diverses populations andalouses de cette relique tertiaire. Les individus<br />
de ces petits peuplements de bourdaine semblent souffrir de<br />
dépression de consanguinité et d’une baisse de fitness ; la reproduction<br />
femelle s’avère anormalement basse puisque seulement<br />
1,4 % d’ovules sont produits. Les arbres ne sont reproducteurs<br />
qu’au bout d’un vingtaine d’années (DBH = 6 cm). Au sein d’un<br />
secteur de ripisylve long de 600 m, Hampe et Arroyo (2002) ont<br />
calculé que 82 % des adultes produisaient des drupes, soit un total<br />
d’environ 748 000 graines viables. Ces fruits charnus sont dispersées<br />
par endozoochorie par divers oiseaux sédentaires (Erithacus<br />
rubecula, Sylvia atricapilla et Turdus merula) ;cependant ce processus<br />
est relativement limité et inefficace comparé à d’autres ligneux<br />
méditerranéens, puisque seulement 36 % des fruits matures sont<br />
consommés par les oiseaux. En fait, la dispersion secondaire lors<br />
des épisodes de crues hivernales joue un rôle majeur en entraînant<br />
les graines à plus ou moins longue distance des peuplements, le<br />
plus souvent dans des banquettes d’alluvions récentes. La prédation<br />
post-dispersion des fruits s’effectue presque exclusivement par<br />
le mulot qui engendre une perte très importante de graines, de<br />
l’ordre de 73 +/- 14 %. L’augmentation depuis les années 1970 du<br />
gibier introduit pour la chasse (Capreolus capreolus,Cervus elaphus)<br />
accroît aussi notablement les pressions d’herbivorie. De plus, les<br />
débroussaillements réalisés en périphérie de ripisylve favorisent les<br />
phénomènes érosifs et les événements de rapide montée des eaux,<br />
d’où un recrutement plus réduit de la bourdaine. Mais les conditions<br />
de sécheresse des banquettes alluvionnaires représentent le<br />
facteur de mortalité des plantules le plus important.Au total, aucune<br />
des 1 124 plantules recensées en juin 1997 n’a survécu en septembre<br />
1999. Dans ce contexte, le nombre de juvéniles et de jeunes<br />
arbres est réduit, et le pic de distribution culmine pour les classes<br />
d’âge comprises entre 25 et 30 ans (DBH = 8-10 cm), c’est-à-dire<br />
celles correspondant aux années favorables sur le plan pluviométrique.<br />
Sous l’influence des changements globaux, l’exacerbation<br />
prévue des périodes de sécheresse et des épisodes extrêmes et soudains<br />
d’inondation pourrait encore plus menacer la régénération<br />
des peuplements et même entraîner l’extinction de cette relique tertiaire<br />
en situation déjà fort précaire.<br />
Pour en savoir plus lire :<br />
— HAMPE A. & ARROYO J., 2002. Recruitment and regeneration<br />
in populations of an endangered South Iberian Tertiary relict tree.<br />
Biological Conservation, 107 : 263-271.<br />
FRÉDÉRIC MÉDAIL<br />
Institut méditerranéen d’écologie et de paléoécologie (IMEP, CNRS-<br />
UMR 6116), Université d’Aix-Marseille III,<br />
Faculté des sciences et techniques de Saint-Jérôme.<br />
Case 461. F-13397 Marseille Cedex 20.<br />
A <strong>Mediterranea</strong>n pest attacks a relict pine forest<br />
under climatic warming (Sierra Nevada, Southern Spain)<br />
The National Park of Sierra Nevada (southeastern Spain) is<br />
inhabited by a highly diversified flora, including species that are<br />
common in northern latitudes and remained relict in the southern<br />
high mountains due to the glaciations.Thus, Sierra Nevada harbours<br />
the southernmost populations of the Scots pine (Pinus sylvestris<br />
L.), a pine species widely distributed in Europe. These<br />
populations belong to the endangered, endemic subspecies nevadensis,<br />
which forms the treeline at about 2 100 m a.s.l. in these<br />
mountains. This altitude protect these trees from the attack of a<br />
severe defoliating <strong>Mediterranea</strong>n pest, the pine processionary<br />
moth Thaumetopoea pityocampa, strongly limited by low winter<br />
temperatures. However, as a consequence of climatic change, the<br />
pine processionary caterpillar has increasingly attacked these<br />
populations of Scots pine in recent years.The decade 1991-2000<br />
was the warmest one of the 20th century. Coinciding with several<br />
consecutive winters of mild temperatures and strong rainfall,<br />
a severe outbreak of the pine processionary caterpillar spread to<br />
higher altitudes than usual. Scots pine populations in Sierra<br />
Nevada, both natural and afforested, repeatedly underwent severe<br />
defoliations during the winters of 1997 and 1998.The detrimental<br />
effects of the caterpillar defoliation on the pine varied.The growth<br />
rate was severely reduced, seed production was unusually low and<br />
seeds were of smaller size in defoliated pines. Complete and repeated<br />
defoliation for more than two consecutive winters exhausted<br />
energy reserves, inflicting some pine deaths. In a healthy population<br />
of pines with a good regeneration capacity, the negative<br />
impact of these outbreaks would be negligible. However, the Scots<br />
pine in Sierra Nevada has limited regeneration capacity, owing<br />
to high pre- and postdispersal seed predation, scant success in<br />
seedling establishment due mostly to summer drought, and<br />
delayed growth in saplings and juveniles because of the high herbivore<br />
pressure. If winter temperatures continue to rise as a consequence<br />
of the climatic warming, uphill invasion of the processionary<br />
will be faster than pine displacement. Outbreaks will be<br />
more frequent and more severe, crippling the regeneration of<br />
these forests.The wide altitudinal gradient of Sierra Nevada offers<br />
the possibility of studying the detrimental effects of climate change<br />
in these and other plant species, and of experimenting with possible<br />
measures to mitigate or avoid such negative impact.<br />
For more informations read:<br />
— HÓDAR, J.A., CASTRO, J.& ZAMORA, R.2003.<br />
Pine processionary caterpillar Thaumetopoea pityocampa<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
as a new threat for relict <strong>Mediterranea</strong>n Scots pine forests under<br />
climatic warming. Biological Conservation, in press.<br />
JOSÉ A. HÓDAR<br />
Grupo de Ecología Terrestre, Departamento de Biología Animal y Ecología,<br />
Facultad de Ciencias, Universidad de Granada, E-18071 Granada, Spain<br />
email address: jhodar@ugr.es – Website : www.ugr.es/~rnm220<br />
État de conservation du cyprès de Duprez<br />
(Cupressus dupreziana) au Sahara central ;<br />
une espèce en voie d’extinction ?<br />
Le cyprès de Duprez (Cupressus dupreziana A. Camus) est<br />
un conifère rarissime et remarquable par sa présence au centre<br />
du Sahara, à 60 km du Tropique du Cancer. Vivant sous climat<br />
hyper-aride où la moyenne annuelle des précipitations est estimée<br />
à 30 mm, il peut dépasser 20 m de hauteur et atteindre 12 m<br />
de circonférence. Dès sa découverte en 1924 sur les hauteurs du<br />
plateau du Tassili n’Ajjer (sud-est algérien), il a été déclaré espèce<br />
en voie de disparition. Les vieux arbres aperçus dans les lits<br />
d’oueds laissaient croire qu’il s’agissait d’individus reliques d’une<br />
forêt constituées sous un climat humide et survivant actuellement<br />
grâce à la présence de nappes phréatiques. En 1978, l’Union<br />
internationale pour la conservation de la nature (UICN) l’a inscrit<br />
sur la liste rouge des espèces les plus menacées d’extinction<br />
au monde.<br />
Durant 47 ans, le recensement des arbres vivants s’est fait au<br />
gré de missions diverses : géologiques, militaires, archéologiques,<br />
zoologiques et botaniques. La plus fructueuse fut celle d’un forestier<br />
algérien Saïd Grim (inédit), qui entre 1971 et 1972 a décrit<br />
230 cyprès vivants et 153 morts sur pied répartis sur une bande<br />
de 120 km de long et 6 km en moyenne de large, longeant la bordure<br />
sud-ouest du plateau du Tassili. L’exhaustivité de ce dénombrement,<br />
la précision des descriptions et des localisations des<br />
arbres, a permis d’estimer l’évolution démographique de ce peuplement<br />
grâce à un recensement précis effectué entre 1997 et<br />
2001.<br />
Vingt arbres parmi les 230 recensés par Grim ont été retrouvés<br />
morts, alors que 23 autres sujets ont été découverts, ce qui<br />
le fixe l’ensemble de la population mondiale connue à 233 cyprès<br />
vivants. Parmi les arbres nouvellement inventoriés, deux très<br />
jeunes individus sont remarquables car ils se situent sur l’itinéraire<br />
de la mission Grim. Le premier, de 3,4 m de hauteur et<br />
32 cm de circonférence est situé à quelques mètres d’un vieux<br />
sujet décrit par Grim à l’oued In Gharohane (24° 27’ N,<br />
9° 47’ E). Le second, dans l’oued In Ellidj (24° 57’ N, 9° 21’ E),<br />
atteint 37 cm de circonférence et 3 m de hauteur. Il se situe à<br />
proximité de 6 arbres décrits en 1971. Ces deux sujets correspondent<br />
vraisemblablement de régénérations naturelles par<br />
graines. Des observations de plantules et semis près des vieux<br />
arbres furent signalées dans les années 1940 et 1960. Cependant,<br />
l’idée d’une inéluctable disparition de ces plantules n’ayant pas<br />
assez développé leur système racinaire qui leur permettrait de<br />
surmonter les sécheresses successives demeurait incontestable.<br />
Or, l’existence de ces jeunes arbres indique pourtant la persistance<br />
d’une régénération, certes rare, mais qui peut échapper en<br />
ecologia mediterranea, tome 28, fascicule 2, p. 101-105<br />
FAITS DE CONSERVATION EN MÉDITERRANÉE / <strong>MED</strong>ITERRANEAN CONSERVATION NEWS ◆<br />
partie à la fois à la sécheresse et aux perturbations humaines et<br />
pastorales. Cependant, la perte de près de 8 % en 29 ans du<br />
nombre total des cyprès vivants est considérable et d’autant plus<br />
inquiétante qu’elle est dûe à l’exploitation humaine. L’émondage<br />
pastoral, les prélèvements de bois pour le chauffage et la cuisson<br />
par les nomades et les touristes n’épargnent pas les cyprès<br />
vivants. Dans une zone où le bois est rare et où il n’existe aucune<br />
mesure effective de protection pour cette espèce, le cyprès de<br />
Duprez demeure, malgré sa capacité naturelle de régénération<br />
in situ, en danger d’extinction au Tassili n’Ajjer.<br />
Pour en savoir plus, lire :<br />
— ABDOUN F. & BEDDIAF M., 2002. Cupressus dupreziana<br />
A. Camus : répartition, dépérissement et régénération au Tassili<br />
n’Ajjer, Sahara central. Comptes Rendus Biologies, 325 : 617-627<br />
FATIHA ABDOUN<br />
Institut méditerranéen d’écologie et de paléoécologie<br />
(IMEP, CNRS-UMR 6116), Université d’Aix-Marseille III,<br />
Faculté des sciences et techniques de Saint-Jérôme.<br />
Case 461. F-13397 Marseille Cedex 20.<br />
email : f.abdoun@caramail.com<br />
From pets to pest: the endemic <strong>Mediterranea</strong>n<br />
shearwater threatened by feral cats<br />
The <strong>Mediterranea</strong>n shearwater Puffinus yelkouan is, along<br />
with the Balearic shearwater Puffinus mauretanicus, one of the<br />
only two pelagic seabirds strictly restricted to the confined<br />
<strong>Mediterranea</strong>n basin. Until recently, these two species were considered<br />
as distinct subspecies of Yelkouan shearwater P. yelkouan<br />
but the two taxa are now distinguished by their specific morphological,<br />
ecological, behavioural and genetic features. The<br />
<strong>Mediterranea</strong>n shearwater is a medium-size species that breeds<br />
exclusively on islands or islets within rocky habitats. The distribution<br />
and the size of the colonies within the <strong>Mediterranea</strong>n<br />
basin remain largely unknown. The total world breeding population<br />
is considered to amount to only 15,000 to 20,000 pairs<br />
but this number is suspected of being largely overestimated.<br />
However, virtually nothing is known about what threatens the<br />
<strong>Mediterranea</strong>n shearwater either at sea or ashore. A recent study<br />
evidenced the possible impact of feral cat Felis catus on this species,<br />
a phenomenon that until now, has generally been considered<br />
limited. The analysis of 650 feral cat scats from Port-Cros<br />
island (south-east France), showed that this introduced predator<br />
preys regularly on <strong>Mediterranea</strong>n shearwaters (remains were<br />
found in 2,8 % of scats analysed). Even though it was impossible<br />
to quantify the total amount of shearwaters killed yearly by<br />
feral cats on the small island of Port-Cros, this study, the first on<br />
this topic, undoubtedly evidenced that the feral cat predation on<br />
the <strong>Mediterranea</strong>n shearwater may be more important than previously<br />
expected. All the recorded predation cases corresponded<br />
to adult shearwaters, killed during the first half of their breeding<br />
cycle, probably when their vocal activity was intense (display<br />
activities). There was no predation case corresponding to chick<br />
or fledging young. It is quite surprising that <strong>Mediterranea</strong>n shearwater<br />
remains were only found in scats collected far from the<br />
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colonies and not in those collected close to the colonies. This<br />
showed that feral cats from the inland of Port-Cros can travel<br />
long-distances to specifically prospect <strong>Mediterranea</strong>n shearwaters<br />
colonies.This preliminary study stressed the urgent need for<br />
further investigation on the conservation status of the <strong>Mediterranea</strong>n<br />
shearwater and on what threatens this species, in order<br />
to set up accurate conservation action plans.<br />
Contact : Eric Vidal, Institut méditerranéen d’écologie<br />
et de paléoécologie (IMEP, CNRS-UMR 6116),<br />
Faculté des sciences et techniques de Saint-Jérôme,<br />
case 461, 13397 Marseille cedex 20, France.<br />
email : eric.vidal@univ.u-3mrs.fr<br />
The effect of nature conservation on flowering<br />
of Paeonia mascula in Israel<br />
Mount Meiron Nature Reserve is the largest <strong>Mediterranea</strong>n<br />
reserve in Israel, dominated by Quercus calliprinos an evergreen<br />
sclerophylous tree. Paeonia mascula (L.) Mill. reaches here its southern<br />
border of distribution and is a main visitor’s attraction. In<br />
1965 it was declared a nature reserve and drastic decrease in<br />
woodcutting and goat grazing affected the landscape. The area<br />
turned from a mosaic of dens and open maquis into homogeneous<br />
thick evergreen oak woodland. Under such shaded conditions,<br />
Paeonia plants survive but do not flower which is a threat<br />
to the local population.The aim was to explore the optimal light<br />
regime and to examine the effect of wood thinning on Paeonia<br />
growth and flowering. In autumn 1997, 15 experimental plots<br />
(5 x 5 m) were established. All trees were removed from 5 plots.<br />
Relative PAR radiation and Paeonia plant-height were measured<br />
and the plants and flowers were counted in May for four years.<br />
Flowering plants were 47 cm high while non-flowering plants<br />
were only 27 cm high. Relative radiation of 30-40 % in plots seems<br />
to be optimal for Paeonia growth and flowering.We conclude that<br />
the Paeonia population is endangered by shading, and active management<br />
actions to open the dense maquis are recommended.<br />
For more informations read:<br />
— NE’EMAN G. 2003. To be or not to be – the effect of nature<br />
conservation management on flowering of Paeonia mascula (L.)<br />
Miller in Israel. Biological Conservation, 109: 103-109.<br />
GIDI NE’EMAN<br />
Department of Biology, Faculty of Science and Science Education,<br />
University of Haifa at Oranim, Tivon 36006, Israel.<br />
email address: gneeman@research.haifa.ac.il<br />
Dehesa’s lizards are worth to be conserved too<br />
In the iberian peninsula, the structure and configuration of<br />
holm oak (Quercus ilex) dehesa woodland is the result of human<br />
intervention, through clearance, thinning and pruning of the once<br />
natural vegetation.Traditional management techniques have created<br />
a patchwork of sectors that differ in their structure and composition<br />
of understorey vegetation.To understand how the fauna<br />
responds to these gradients, we can use models that relate the<br />
abundance of a species to variables describing the habitat structure.<br />
Previous studies have shown that dehesas maintain more<br />
diverse bird communities than adjacent treeless pasture, areas of<br />
cultivation and even <strong>Mediterranea</strong>n forest. Thus, dehesa management<br />
seemed to favour biodiversity. However, there has been<br />
very little research on other representative animal groups.There<br />
is a danger that focusing conservation activities on a few charismatic<br />
species may overlook important features for other species.Thus,<br />
one should take account of the ecology of a wide spectrum<br />
of species to develop maximum conservation of the biological<br />
diversity.<br />
Lizards are one of the more prominent groups of animals in<br />
<strong>Mediterranea</strong>n climates, whith many endemic species that reach<br />
high densities, and that are important keys in the trophic chains.<br />
Researchers from the Department of Evolutionary Ecology of<br />
the Madrid Natural History Museum (CSIC) have analysed<br />
whether different management techniques of a dehesa area in<br />
Central Spain affect the populations of several species of lizards.<br />
The results showed that lizards did not use microhabitats at random.<br />
They preferentially used forested areas with scrub and<br />
island rocky outcrops, while they avoided open herbaceous areas.<br />
Furthermore, characteristics of a dehesa patch influenced both<br />
population densities and species richness of lizards. Lizards were<br />
more abundant when the understorey bushy vegetation increased.<br />
In contrast, grasslands or cereal fields were scarcely occupied<br />
even if holm oak trees were present, because low shrubs<br />
were scarce here. Shrub cover is primarily important in providing<br />
cover against predators, but it is insufficient for lizards in<br />
most dehesa plots because of regular clearance management.<br />
Therefore, some of the traditional management practices of dehesas<br />
may negatively affect lizard populations. These conclusions<br />
could have wider implications for the design of wildlife reserves,<br />
which has been previously based on the umbrella species concept<br />
(e.g., “conserving imperial eagles habitat will provide conservation<br />
for all other species”). An integrated design and management<br />
of protected areas would require a detailed analysis of habitat<br />
requirements of other representative animal groups.<br />
For more informations read:<br />
— Martín, J. & López, P. 2002. The effect of <strong>Mediterranea</strong>n<br />
dehesa management on lizard distribution and conservation.<br />
Biological Conservation, 108: 213-219.<br />
JOSÉ MARTÍN<br />
Departamento de Ecología Evolutiva<br />
Museo Nacional de Ciencias Naturales<br />
José Gutiérrez Abascal, 2. E-28006 Madrid. Spain.<br />
email address: Jose.Martin@mncn.csic.es<br />
When gulls drive beetle communities on islands<br />
Island communities are very sensitive to disturbances, and<br />
pressure exerted by colonial seabird in particular. Seabirds are<br />
known to be a major ecological factor driving both species assemblage<br />
patterns and community dynamics of plants on islands.<br />
However, very little was known about the response of insect<br />
assemblages to seabirds, although the important ecological and<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
functional role of insects within all ecosystems. A recent study<br />
aimed to assess the response of beetle communities to the<br />
influence of a Yellow-legged gull Larus cachinnans colony on a<br />
small <strong>Mediterranea</strong>n island.This study was conducted on Bagaud<br />
island, which is a fully protected reserve within Port-Cros<br />
National Park (south-east France), where the Yellow-legged gulls<br />
are the most densely clumped. Beetle communities were sampled<br />
three times during spring and autumn 2001 to increase the<br />
probability of sampling uncommon and seasonal species and to<br />
meet the successive stages of gull behaviour and abundance<br />
during their breeding cycle. A total of 255 beetle specimens from<br />
28 species and 15 families was collected. Surprisingly, species<br />
richness and abundance of beetles were not significantly affected<br />
by gulls. However, ordination of beetle assemblages showed<br />
that there was a marked change in species composition along the<br />
gradient of gull influence. Gull colony also affected distribution<br />
of feeding-types of beetles, as the Tenebrionidae family in general,<br />
and Bioplanes meridionalis in particular, seemed to draw strong<br />
benefit from such a disturbance. Tenebrionidae species, as they<br />
are polyphagous, markedly increased at the expense of phytophagous<br />
species that decreased. Collected species were likely to<br />
be found in other gull-free environments and were not strictly<br />
endemic to <strong>Mediterranea</strong>n islands. Some of them presented<br />
however some particular conservation interests: Asida dejeani,<br />
Otiorhynchus vitellus, Thorictus grandicollis, Dichillus minutus,<br />
Trachyphloeus laticollis and Ocypus fortunatarum that were stated<br />
either uncommon or restricted to <strong>Mediterranea</strong>n regions.<br />
For more informations read:<br />
— ORGEAS J., VIDAL E. & PONEL P. 2003. Colonial seabirds change<br />
beetle assemblages on a <strong>Mediterranea</strong>n Island. Ecoscience, in press.<br />
JÉRÔME ORGEAS<br />
Institut méditerranéen d’écologie et de paléoécologie<br />
(IMEP, CNRS-UMR 6116), Faculté des sciences et techniques<br />
de Saint-Jérôme, case 461, 13397 Marseille cedex 20, France.<br />
email address: jerome.orgeas@univ.u-3mrs.fr<br />
Immature eagles recruited as breeder alert us about future<br />
changes in population trends: the case of Bonelli’s Eagle in<br />
Andalusia.<br />
The most common techniques used to evaluate the status<br />
and trend of bird populations generally detect changes in population<br />
tendency once they have already occurred, therefore lac-<br />
ecologia mediterranea, tome 28, fascicule 2, p. 101-105<br />
FAITS DE CONSERVATION EN MÉDITERRANÉE / <strong>MED</strong>ITERRANEAN CONSERVATION NEWS ◆<br />
king of predictive capability. The Bonelli’s Eagle Hieraaetus fasciatus<br />
is an endangered bird of prey that has suffered a rapid<br />
decline in its whole distribution range.The checking of the breeding<br />
population is easy by the fact that breeding individuals<br />
occupy year-round territories, and because by adult and immature<br />
eagles have different plumage which allow to age them accurately.<br />
The Department of Applied Biology of the Estación Biológica<br />
de Doñana disposed of a more than 20 years data set on the evolution<br />
of the breeding territories of this eagle in Andalusia, as<br />
well as the breeding performance of pairs.We analysed the trend<br />
of the Andalusia population during a long-term period and discover<br />
that, in spite of the number of occupied territories have<br />
remained stable, both productivity (measured as number of<br />
young fledged per occupied territory) and age at fist breeding<br />
(measured as number of immature eagles on breeding pairs)<br />
decreased in the last decade.<br />
In our case, it was possible to attribute the detected decrease<br />
in the age at first breeding to a decrease in adult survival rate. A<br />
lack of adults within the population allows the immature eagles<br />
to occupy empty breeding places, resulting in a decrease on the<br />
breeding performance at the population level, probably due to<br />
the lower breeding experience of young. An increase in immature<br />
within the breeding population therefore represents an earlywarning<br />
signal of a change in two extremely important demographic<br />
parameters, as productivity and adult survival rate. For<br />
this reason, monitoring the age at first breeding can be considered<br />
as a new tool in conservation biology, useful to detect changes<br />
in population trends of long-lived species with deferred maturation<br />
age. Therefore, it will allow researcher to plan conservation<br />
strategies well before an endangered population could reach<br />
a low threshold of productivity and/or number of adult breeding<br />
individuals, ensuring more effectiveness in population management<br />
and lower costs of intervention.<br />
For more informations read:<br />
BALBONTÍN J., PENTERIANI,V. & FERRER,M.2003.Variations in the age<br />
of mates as an early-warning signal of changes in population trends?:<br />
the case of Bonelli’s eagle in Andalusia. Biological Conservation, 109:<br />
417-423.<br />
J. BALBONTÍN,V.PENTERIANI ET M. FERRER<br />
Estación Biológica de Doñana (CSIC), Department of Applied Biology.<br />
Avda. Maria Luisa s/n. Sevilla 41013. Spain<br />
e-mail: balbonja@ebd.csic.es<br />
105
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◆ FAITS DE CONSERVATION EN MÉDITERRANÉE / <strong>MED</strong>ITERRANEAN CONSERVATION NEWS<br />
ASINARA DECLARATION on OIL POLLUTION AND CONSERVATION OF BIODIVERSITY<br />
INTRODUCTION<br />
An international conference was held at Porto Torres (Sardinia) from 17th to 20th October 2002 on Oil Pollution and Conservation of Biodiversity.<br />
80 participants coming from 17 different countries, among whom the world experts on oil polluted wildlife, were attending this conference.They<br />
decided to formulate the Asinara Declaration pleading for various priority actions to be taken to safeguard marine fauna and flora and their habitats<br />
from oil pollution.<br />
Isola dell’Asinara (Sardinia), 20th October 2002<br />
the Delegates of the Conference on Oil Pollution and Conservation of Biodiversity, organized at Porto Torres, Sardinia (17-20 October<br />
2002) by the Asinara National Park, IFAW (International Fund for Animal Welfare) and <strong>MED</strong>MARAVIS (<strong>Mediterranea</strong>n Marine Bird<br />
Association):<br />
Item 1. Control of Tanker Traffic in Biological Sensitive Areas<br />
While considering the marine ecosystem as vital for the survival of mankind and harbouring unique biota evolved in diverse<br />
geo-morphological, climatic and oceanographical conditions,<br />
Realizing that numerous species of marine biota, particularly seabirds with a high oil vulnerability index, have population levels<br />
that are critically low and are directly threatened by oil pollution,<br />
Considering that marine wildlife is a natural resource not only to be exploited for economic interests but is also of great scientific,<br />
ecological, educational, aesthetic and recreational importance for the general public,<br />
Being aware that many marine, island and coastal habitats are directly threatened by oil pollution,<br />
Noting that these habitats are essential for the survival of such biota,<br />
Urge<br />
— the regional and national governments, with the co-operation of the competent international institutions to establish marine<br />
Nature Reserves and Zones of Tanker Traffic Control,<br />
— the International Maritime Organization (I.M.O.) to encourage third parties to respect the designated Zones of Tanker<br />
Traffic Control.<br />
Item 2. Separation Lanes for Shipping<br />
Considering that coastal wildlife and its habitats are extremely vulnerable in narrow straits,<br />
Taking note that traffic of oil tankers and of vessels carrying hazardous cargo is often very dense in the narrow straits of the<br />
<strong>Mediterranea</strong>n and Black Seas,<br />
Invite all national governments concerned,<br />
— to install radar controlled separation lanes for shipping in narrow straits of high biological interest,<br />
— to have in place in these straits an oil contingency plan that deals explicitly with oiled wildlife and provides for effective<br />
wildlife response.<br />
Item 3. Stricter Implementation of Maritime Regulations<br />
Realising that the current maritime regulations as promulgated by the International Maritime Organization (IMO) are not fully<br />
implemented and do not guarantee an environmentally correct management of vessels,<br />
Being aware that certain countries, members of the Paris Memorandum of Understanding on Port State Control, do not meet<br />
the target of inspecting 25 % of vessels visiting their ports,<br />
Observing that many vessels do not use port reception facilities for processing oil residues despite the fact that some ports<br />
have installed adequate disposal facilities in order to prevent oil pollution from bilge, cargo and ballast,<br />
Considering that the European Directive 2000/59 regarding port reception facilities for ship-generated waste will enter into<br />
force on 28th December 2002,<br />
Recommend to all national governments and concerned international institutions to:<br />
— adopt and fully implement the existing agreements under MARPOL 73/78 and its Annexes, the Regional Memoranda of<br />
Understanding, the Barcelona and Bucharest Conventions and relevant Protocols,<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
ecologia mediterranea, tome 28, fascicule 2<br />
FAITS DE CONSERVATION EN MÉDITERRANÉE / <strong>MED</strong>ITERRANEAN CONSERVATION NEWS ◆<br />
— to provide adequate shore reception facilities for vessels’ generated wastes,<br />
— to refuse all uncertified vessels in ports unless they are sailing to a repair yard for careening or dismantling,<br />
— to improve the inspection of vessels’ structure,<br />
— to develop a data base of vessels to be consulted by charterers.<br />
Item 4. Prosecution<br />
Being fully aware of the severe impact on seabirds and their habitats by the successive groundings and break-ups of vessels at<br />
sea as well as by illegal discharges and dumping at sea of fuel oils and their residues,<br />
Considering that the owner(s) of the transported cargo are directly responsible for vessel control during port operations and<br />
on the high seas, and that IMO is responsible for the safety of maritime traffic,<br />
Realizing the importance of cumulative costs by oil pollution for marine wildlife, fisheries, tourism and health,<br />
Urge governmental and juridical authorities:<br />
— to vigorously enforce MARPOL regulations on oil discharges from vessels,<br />
— to review the safety regulations of maritime traffic in straits of ecological importance,<br />
— to enforce the practice of the “polluter pays” principle over and above the ceiling<br />
level of the oil company’s insurance cover,<br />
— to earmark mitigation payments for oiled wildlife to the benefit of its rehabilitation and the protection of its habitats.<br />
Item 5. Research<br />
Observing that not enough data exist on the distribution at sea of marine wildlife during its life cycle,<br />
Realizing that marine wildlife can be extremely vulnerable to mineral oil pollution at sea,<br />
Considering the high risk of contamination for marine wildlife from oil pollution, toxic chemicals and all vessels’ generated<br />
waste,<br />
Invite the national governments, the competent international institutions as well as the private oil industry and shipping companies:<br />
— to finance annual surveys and monitoring programmes of marine wildlife and its distribution at sea,<br />
— to sponsor the publication of regional guides and atlasses related to the distribution of coastal and marine biota,<br />
— to launch research programmes on population dynamics and age structure of mortality of oil-prone species especially seabirds,<br />
— to define the best methods for the effective treatment and cleaning of ballast waters.<br />
Item 6. Effective Oiled Wildlife Response<br />
Being aware that the immediate rehabilitation and release of rare oiled seabird species are important for maintaining their populations<br />
at a level which guarantees their long term survival,<br />
Knowing that biological “hot-spots” of coastal and marine biota are generally found in isolated areas as well as in wildlife reserves<br />
that do not have the necessary facilities and equipment to protect marine wildlife,<br />
Urge local, regional and national authorities, as well as the specialized nongovernmental<br />
organizations:<br />
— to establish wildlife contingency plans for areas of major importance for vulnerable<br />
marine wildlife in the <strong>Mediterranea</strong>n and Black Sea regions,<br />
— to identify and acquire the necessary equipment for their implementation,<br />
— to organize training courses in the treatment of oiled wildlife and rehabilitation of their habitats,<br />
— to disseminate technical information on the biology, conservation and rehabilitation of marine and coastal biota threatened<br />
by oil pollution.<br />
Cala Reale, Isola dell’Asinara, 20th October 2002<br />
Agreement validated unanimously by the conference participants and signed by the three conference organizers:<br />
Barbara CALLAHAN Eugenio COSSU Xaver MONBAILLIU<br />
International Fund President Asinara Secretary-General<br />
for Animal Welfare National Park <strong>MED</strong>MARAVIS<br />
Anchorage, USA Porto Torres, Italy Saint-Maximin, France<br />
107
Écologie : de l’écosystème à la biosphère<br />
Christian Lévêque<br />
Dunod, Masson Sciences, Paris : 502 p. (2001)<br />
Le livre de Christian Lévêque est une contribution originale<br />
et moderne dans la série des ouvrages consacrés à l’écologie générale.<br />
Originale surtout dans son écriture ; en effet, plutôt que de<br />
fournir une somme de connaissances dans les divers domaines<br />
de l’écologie avec de nombreux exemples à l’appui, il propose<br />
une vision bien plus synthétique où sont privilégiées les grandes<br />
théories, leurs controverses et leurs domaines d’applications. Y<br />
sont présentés les paradoxes et paradigmes les plus modernes en<br />
écologie, le tout dans une écriture accessible aux non-spécialistes,<br />
avec de multiples encarts pour les lecteurs désirant approfondir<br />
tel ou tel domaine. Enfin, l’auteur a délibérément choisi<br />
comme objet d’étude “l’écosystème” et il montre combien cette<br />
unité de travail en écologie est pertinente. Enfin, en rapport avec<br />
la spécialité de recherches de l’auteur, les exemples seront surtout<br />
pris dans le domaine de l’écologie des eaux courantes, ce<br />
qui est relativement rare en comparaison des autres ouvrages qui<br />
s’intéressent surtout aux écosystèmes continentaux terrestres.<br />
Ce sont surtout les premiers chapitres (1-4) qui font l’originalité<br />
du travail de Christian Lévêque ; ils sont consacrés aux<br />
natures de l’écologie et à la construction de la pensée scientifique<br />
en écologie des écosystèmes. La lecture de ces chapitres<br />
est à conseiller à tout écologue, qu’il soit étudiant ou chercheur<br />
confirmé, car ils permettent de bien identifier l’écologie en tant<br />
que science à travers l’originalité de ses approches, méthodes,<br />
finalités fondamentales et appliquées. C’est donc une “saine”<br />
lecture qui permet au lecteur de se resituer par rapport aux<br />
contextes fondamentaux, courants de pensée et applications en<br />
écologie.<br />
Les autres chapitres de la deuxième partie, consacrée à la<br />
structure et l’organisation des écosystèmes, traitent plus classiquement<br />
de l’application des principes de physique en écologie<br />
(5) et de l’écologie factorielle (6), pour se terminer par trois chapitres<br />
consacrés aux problèmes d’échelles, de hiérarchies et de<br />
l’hétérogénéité spatiale (7-9). Inutile de signaler l’importance de<br />
ces notions vis-à-vis des recherches menées en écologie. Elles<br />
sont particulièrement bien présentées ici et intègrent les apports<br />
les plus récents des recherches en cours.<br />
La troisième partie est consacrée au fonctionnement des écosystèmes,<br />
avec, notamment, deux chapitres présentant deux problématiques<br />
très actuelles, d’une part la dynamique des peuplements<br />
et l’équilibre de la nature (10), d’autre part les relations<br />
ecologia mediterranea, tome 28, fascicule 2, p. 109-111<br />
entre diversité biologique et fonctionnement des écosystèmes<br />
(12). Les problèmes de disparition d’espèces, d’espèces envahissantes<br />
et d’espèces clés sont particulièrement bien présentés.<br />
Ces chapitres sont toujours illustrés par des exemples pris dans<br />
les domaines de l’écologie aquatique.<br />
Enfin, la quatrième partie concerne l’écologie globale, avec,<br />
notamment, un apport important sur les interactions entre dynamique<br />
des écosystèmes et changements globaux. Ici aussi,<br />
Christian Lévêque apporte une contribution très importante à<br />
un débat d’actualité.<br />
Nous recommandons donc la lecture de l’ouvrage de<br />
Christian Lévêque aux étudiants et aux plus confirmés d’entre<br />
nous, car il se lit presque comme un roman et permet de resituer<br />
le lecteur et ses problématiques de recherches dans les débats<br />
les plus modernes en écologie fondamentale.<br />
THIERRY DUTOIT<br />
Institut méditerranéen d'’écologie et de paléoécologie<br />
(IMEP, CNRS-UMR 6116), Université d’Aix-Marseille I,<br />
Faculté des sciences et techniques de Saint-Jérôme.<br />
Case 461. F-13397 Marseille Cedex 20.<br />
Endemic plants of Greece<br />
The Peloponnese<br />
Analyses d’ouvrages<br />
Kit Tan avec la collaboration de G. Iatrou,<br />
dessins de B. Johnsen<br />
Gad Forlag, Copenhagen, 480 p., 111 pl. couleur (2001)<br />
email: sekr@gads-forlag.dk<br />
Après des décennies de travaux floristiques et phytoécologiques<br />
qui ont fait nettement progresser la connaissance du patrimoine<br />
floristique grec, il était temps de synthétiser tout ce corpus<br />
de connaissances dans des flores modernes. Une équipe internationale,<br />
essentiellement composée de Scandi-naves et de Grecs<br />
s’est attelée à l’ouvrage, et, après la Mountain Flora of Greece<br />
(1986-1991), est sorti en 1997 le premier volume de l’excellente<br />
Flora Hellenica. Dans cette lignée, une série de trois volumes est<br />
plus spécialement destinée à détailler la flore endémique de<br />
Grèce, et le présent ouvrage Endemic plant of Greece. The<br />
Peloponnese est le premier publié. D’après les estimations fournies,<br />
le Péloponnèse comporte ca. 2 960 espèces et sous-espèces<br />
dont 355 sont des endémiques greques et 4,6 % des endémiques<br />
strictes de la dition. Cette haute richesse en endémiques s’avère<br />
109
110<br />
◆ ANALYSES D’OUVRAGES<br />
particulièrement bien mise en exergue par cet ouvrage qui allie<br />
une qualité iconographique exceptionnelle à une rigueur et une<br />
documentation scientifique de tout premier plan.<br />
L’introduction botanique, riche de 65 pages, constitue une<br />
précieuse entrée en matière sur le plan géographique, géologique<br />
et phytoécologique. Des données numériques et biogéographiques<br />
sur l’ensemble de la flore endémique grecque, notamment<br />
celle des montagnes, permettent de bien resituer l’originalité<br />
de cette flore au sein du monde méditerranéen. Puis, sont<br />
détaillées les diverses régions d’intérêt botanique, avec mention<br />
des principales caractéristiques abiotiques, et bien entendu, des<br />
particularités floristiques de chacune d’entre elles. Ceci constitue<br />
un précieux guide pour le botaniste qui voudra parcourir les<br />
monts du Chelmos, Killini, Parnon, Taygète…<br />
L’ensemble des endémiques du Péloponnèse est ensuite passé<br />
en revue, avec, curieusement, l’inclusion d’une dizaine de plantes<br />
non-endémiques, ce qui peut induire une certaine confusion,<br />
même si elles sont signalées dans le texte. Chaque taxon fait l’objet<br />
d’une description botanique précise suivie de données sur<br />
l’habitat et l’écologie, la distribution, le nombre chromosomique,<br />
et d’un court texte précisant les aspects taxonomiques et systématiques<br />
; la carte de répartition de l’espèce est précise et issue<br />
de la base de données mise au point pour le projet Flora Hellenica.<br />
Il faut encore insister sur la qualité des planches iconographiques<br />
couleur qui font ressortir les moindres détails morphologiques<br />
diagnostiques et qui accompagnent la quasi-totalité des espèces<br />
décrites. Trois taxons nouveaux pour la science, dont une nouvelle<br />
espèce (Carum depressum Hartvig & Kit Tan), sont décrits,<br />
et sept combinaisons nouvelles sont proposées ; parmi ces dernières,<br />
ériger Cyclamen peloponnesiacum en tant qu’espèce semble<br />
très discutable, et le récent article de Debussche et Thompson<br />
(in Bot. J. Linn. Soc., 2002) montre qu’il vaut mieux continuer à<br />
considérer ce taxon comme une sous-espèce de C. repandum car<br />
les différences morphologiques et génétiques ne sont pas suffisamment<br />
tranchées. Mais, par ailleurs, cet ouvrage permet de<br />
mettre au jour des données chorologiques sur des taxons présumés<br />
disparus comme Adonis cyllenea Boiss. qui se rencontre en<br />
fait dans plusieurs localités du nord de la péninsule !<br />
En attendant la parution des volumes consacrés à la Grèce<br />
continentale et aux îles égéennes, il faut souhaiter qu’un travail<br />
de cette qualité fasse des émules et que d’autres territoires du<br />
bassin méditerranéen puissent bénéficier de cette approche qui<br />
contribue à faire mieux connaître et donc – espérons-le – protéger<br />
ce patrimoine naturel méditerranéen si riche mais si menacé.<br />
FRÉDÉRIC MÉDAIL<br />
Institut méditerranéen d'’écologie et de paléoécologie<br />
(IMEP, CNRS-UMR 6116), Université d’Aix-Marseille III,<br />
Faculté des sciences et techniques de Saint-Jérôme.<br />
Case 461. F-13397 Marseille Cedex 20.<br />
Écologie des forêts naturelles d’Europe.<br />
Biodiversité, sylvigenèse,<br />
valeur patrimoniale des forêts primaires<br />
Annick Schnitzler-Lenoble<br />
Editions TEC & DOC, Paris : 271 p. (2002)<br />
Pour tous les écologues qui auraient pu penser qu’il n’existe<br />
plus de forêts primaires en Europe, l’ouvrage d’Annick<br />
Schnitzler-Lenoble sera une révélation. En effet, il existe encore<br />
en Europe, et surtout en Europe de l’Est, des massifs forestiers<br />
dont le fonctionnement écologique peut être considéré comme<br />
proche de celui d’écosystèmes forestiers naturels ou primaires.<br />
C’est dans les domaines de la sylvigenèse, du fonctionnement<br />
(rôle des perturbations, des stress) et de l’analyse hiérarchique<br />
de l’écosystème forestier (ch. 3 et 4) que l’ouvrage d’Annick<br />
Schnitzler-Lenoble apporte le plus d’informations originales en<br />
liaison avec les problématiques de recherches de l’auteur. Les<br />
autres chapitres sont beaucoup plus conventionnels et présentent<br />
la place des forêts au niveau de la biogéographie européenne<br />
(ch. 1) et les composants de l’écosystème forestier (ch. 2) illustrés<br />
avec des planches photos présentant un joli bestiaire de la<br />
faune des forêts européennes. Ces deux derniers chapitres sont<br />
purement descriptifs et rapidement traités. Il est regrettable qu’ils<br />
ne soient pas précédés d’un chapitre ou d’une introduction définissant<br />
le plus clairement possible les écosystèmes forestiers avant<br />
de présenter leur place en Europe. Cette définition n’arrivant<br />
qu’au début du sixième chapitre.<br />
Les chapitres consacrés à la biodiversité des forêts d’Europe<br />
depuis la fin du Tertiaire (ch. 5 et 6) sont également en déséquilibre<br />
avec les chapitres consacrés au fonctionnement de l’écosystème<br />
forestier. En effet, ici, plus qu’à la présentation de résultats<br />
scientifiques originaux, nous assistons à la présentation d’une<br />
liste de sites relevant davantage d’un guide naturaliste. Cependant,<br />
grâce au militantisme de l’auteur et à sa passion pour la conservation<br />
des forêts primaires, le chapitre 7 constitue un très bon<br />
argumentaire sur la nécessité de protéger les dernières reliques<br />
de forêts primaires en Europe.<br />
En conclusion, le livre d’Annick Schnitzler-Lenoble est une<br />
contribution originale et importante à l’écologie et à la gestion<br />
des forêts primaires d’Europe. La rédaction de cet ouvrage est<br />
cependant inégale et oscille entre la présentation de résultats<br />
scientifiques originaux relativement pointus et une approche plus<br />
naturaliste. Ce compromis devrait cependant permettre à chaque<br />
lecteur de trouver des éléments pour ses propres recherches ou<br />
augmenter ses connaissances en matière d’écologie forestière.<br />
THIERRY DUTOIT<br />
Institut méditerranéen d'’écologie et de paléoécologie<br />
(IMEP, CNRS-UMR 6116), Université d’Aix-Marseille I,<br />
Faculté des sciences et techniques de Saint-Jérôme.<br />
Case 461. F-13397 Marseille Cedex 20.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
Important bird areas in Africa<br />
and associated islands: priority sites<br />
for conservation<br />
Fishpool L.D.C. & Evans M.I. (eds)<br />
Newbury and Cambridge, UK: Pisces.<br />
Publications and Birdlife International<br />
(Birdlife Conservation Series N° 11), 1 144 p. (2001)<br />
Cet ouvrage monumental représente la dernière-née des<br />
publications de Birdlife International, consortium mondial d’organisations<br />
consacrées à la conservation durable des oiseaux et<br />
de leurs habitats. Ce volume correspond à la traduction écrite<br />
de l’exécution de l’ambitieux programme IBA (Important Bird<br />
Areas) conduit sur le continent africain et les îles adjacentes (y<br />
compris certaines terres australes de l’Océan indien ou de<br />
l’Atlantique sud). Ce document résulte des contributions d’un<br />
très grand nombre d’ornithologues amateurs ou professionnels,<br />
d’experts dans le domaine de la conservation et d’une centaine<br />
de rédacteurs. Sur la base du croisement de critères complexes<br />
de vulnérabilité et de rareté d’espèces et d’inventaires et cartographies<br />
de terrain, cette compilation identifie un total de 1 228<br />
IBA couvrant une superficie de plus de deux millions de km 2 ,<br />
soit environ 7 % de la région considérée (58 pays). L’essentiel<br />
de l’ouvrage est constitué par 58 sous-chapitres (un par pays ou<br />
territoire) comprenant une description générale de la situation<br />
écologique et ornithologique de la zone concernée, une cartographie<br />
des IBA identifiées, un tableau synthétique des critères<br />
de classification retenus, ainsi qu’autant de fiches descriptives<br />
ecologia mediterranea, tome 28, fascicule 2, p. 109-111<br />
ANALYSES D’OUVRAGES ◆<br />
complètes que de zones identifiées. Enfin, une bibliographie souvent<br />
abondante est également présentée.<br />
Les territoires sous bioclimat méditerranéen, bien que spatialement<br />
minoritaires à l’échelle du continent africain comptent<br />
une densité particulièrement élevée d’IBA identifiées. Ainsi, le<br />
Maroc, l’Algérie, l’Egypte, la Tunisie et la Province du Cap en<br />
Afrique du Sud, figurent parmi les territoires africains présentant<br />
la plus grande valeur en termes d’abondance de zones à fort<br />
intérêt pour la conservation du patrimoine avifaunistique. Les<br />
critères les plus fréquemment retenus correspondent à la présence<br />
d’espèces d’oiseaux fortement menacées à l’échelle mondiale<br />
(species of global conservation concern) ou à la concentration<br />
d’une part notable des effectifs mondiaux de certains taxons.<br />
Incontestablement, un tel ouvrage de synthèse faisait défaut<br />
à la recherche ornithologique africaine et nul doute que sa publication<br />
et sa large diffusion (le prix demeure modeste au regard<br />
de la masse de données présentées) constitueront une aide précieuse<br />
à la planification et la dynamisation de la politique de<br />
conservation des oiseaux sur ce continent incroyablement varié<br />
et contrasté. En outre, ce livre devrait grandement participer à<br />
éclairer un plus vaste public y compris celui des décideurs, sur<br />
la formidable diversité de l’avifaune africaine et sur sa situation<br />
de conservation souvent critique, tant dans la partie méditerranéenne<br />
que dans le reste du territoire.<br />
ERIC VIDAL<br />
Institut méditerranéen d'’écologie et de paléoécologie<br />
(IMEP, CNRS-UMR 6116), Université d’Aix-Marseille I,<br />
Faculté des sciences et techniques de Saint-Jérôme.<br />
Case 461. F-13397 Marseille Cedex 20.<br />
111
Trivelly Elyse<br />
Boisement spontané des pelouses sèches :<br />
trajectoires historiques, représentations sociales<br />
et perspectives de gestion<br />
Thèse de doctorat en sciences soutenue le 03 juillet 2002 à l’Université<br />
d’Aix-Marseille III, Faculté des sciences de Saint-Jérôme, IMEP<br />
(CNRS-UMR 6116), case 461, 13397 Marseille Cedex 20, France.<br />
Jury<br />
Raphaël Larrere (directeur de recherche, INRA-Ivry), Bernard Brun (MCF<br />
HDR, Univ. Provence), rapporteurs ; Thierry Tatoni (professeur, Univ.<br />
Aix-Marseille III), Jacques Daligaux (MCF, Univ. Provence), Pierre Frapa<br />
(directeur d’étude, Agence Paysages, Avignon), examinateurs ; Thierry<br />
Dutoit (MCF-HDR, Univ. Provence) et Marcel Barbero (professeur, Univ.<br />
Aix-Marseille III), co-directeurs.<br />
Les pelouses sèches connaissent aujourd’hui un regain d’intérêt<br />
au sein de la communauté scientifique, en raison de leur biodiversité.<br />
Or, face à la baisse d’une pression agropastorale pluriséculaire,<br />
elles sont soumises à un phénomène de boisement spontané provoquant<br />
leur régression généralisée. Ce travail vise à apporter une contribution<br />
au débat sur l’écologie de la restauration par une analyse pluridisciplinaire.<br />
Nous avons ainsi recours à l’histoire, la géographie et<br />
l’écologie d’une part, pour comprendre ce phénomène sur nos deux<br />
sites d’étude situés dans le sud-est de la France, les crêtes du Grand<br />
Luberon (Vaucluse) et le plateau de Caussols (Alpes-Maritimes), et<br />
d’autre part à la sociologie afin d’appréhender les représentations<br />
sociales de ces espaces, à l’heure de leur mise en gestion conservatoire.<br />
Il s’agit ainsi d’obtenir un double éclairage, territorial et social,<br />
sur un phénomène qui met en jeu les relations d’une société à son<br />
espace et d’en tirer des enseignements en terme d’aide à la décision<br />
de gestion.<br />
Mots-clés : pelouses, pression agropastorale, restauration, écologie,<br />
Luberon, sociologie, gestion.<br />
ecologia mediterranea, tome 28, fascicule 2, p. 113-115<br />
Résumés de thèses de doctorat en sciences<br />
Rathgeber Cyrille<br />
Impact des changements climatiques et de l’augmentation<br />
du taux de CO2 atmosphérique sur la productivité<br />
des écosystèmes forestiers : exemple du pin d’Alep<br />
(Pinus halepensis Mill.) en Provence calcaire (France)<br />
Thèse de doctorat en sciences soutenue le 08 juillet 2002 à l’Université<br />
d’Aix-Marseille III, Faculté des sciences de Saint-Jérôme, IMEP<br />
(CNRS-UMR 6116), case 461, 13397 Marseille Cedex 20, France.<br />
Jury<br />
Joël Guiot, directeur de recherche (CEREGE, Aix-en-Provence), co-directeur<br />
; Philip Roche, maître de conférence (IMEP, Marseille), co-directeur<br />
; Jean-Luc Dupouey, directeur de recherche (INRA, Champenoux),<br />
rapporteur ; Félix Kienast, directeur de recherche (WSL, Birmensdorf),<br />
rapporteur ; Serge Rambal, ingénieur de recherche (CEFE, Montpellier),<br />
examinateur ; Carlo Urbinati, professeur (Université de Padoue), examinateur.<br />
La dendroécologie, qui a pour support la mesure de la croissance<br />
des arbres, dispose de données bien adaptées à l’étude de l’impact<br />
des changements climatiques et atmosphériques sur la productivité<br />
des peuplements forestiers. Les méthodes statistiques classiques de<br />
quantification de la relation cerne/climat ne sont pas capables de<br />
prendre en compte l’effet d’une dérive probable des facteurs environnementaux,<br />
pas plus que l’effet de l’augmentation du taux de CO2 atmosphérique. C’est pourquoi un modèle bioclimatique et un modèle<br />
biogéochimique ont été développés.<br />
Les données provenant de 21 peuplements de pin d’Alep ont permis<br />
de calculer un indice synthétique de croissance qui exprime les<br />
variations inter-annuelles de productivité. Ainsi, pour chaque peuplement,<br />
les trois types de modèle utilisés ont pu être confrontés aux<br />
indices de croissance et validés. Les variations de productivité des<br />
peuplements étudiés sont principalement contrôlées par les fluctuations<br />
du bilan hydrique.<br />
Le modèle biogéochimique n’est pas sensible aux changements<br />
climatiques, mais simule une très forte augmentation de la productivité<br />
liée à l’augmentation du taux de CO2. Le modèle climatique de<br />
croissance simule, en réponse aux changements climatiques, une forte<br />
augmentation de productivité liée à l’augmentation des températures<br />
printanières. Le modèle bioclimatique, en revanche, simule une diminution<br />
significative de la productivité liée à une augmentation de la<br />
sécheresse estivale. La réaction d’un peuplement dépend des conditions<br />
stationnelles. L’exposition, en effet, détermine le bilan thermique<br />
alors que la pente, la capacité hydrique du sol et la perméabilité du<br />
sous-sol contraignent le bilan hydrique.<br />
Mots-clés : dendroécologie, changements climatiques, augmentation<br />
du taux de CO2 atmosphérique, productivité forestière, conditions<br />
stationnelles, modèles de croissance, région méditerranéenne,<br />
pin d’Alep.<br />
113
114<br />
◆ RÉSUMÉS DE THÈSES<br />
Gachet Sophie<br />
Organisation de la biodiversité forestière :<br />
vers une modélisation de la dynamique du sous-bois<br />
en fonction des pratiques sylvicoles<br />
Thèse de doctorat en sciences soutenue le 13 novembre 2002<br />
à l’Université d’Aix-Marseille III, Faculté des sciences<br />
de Saint-Jérôme, IMEP (CNRS-UMR 6116), case 461,<br />
13397 Marseille Cedex 20, France.<br />
Jury<br />
Thierry Tatoni (professeur, Univ. Aix-Marseille III), directeur de thèse ;<br />
Richard Michalet (professeur, Univ. Bordeaux I), François Romane (IR,<br />
CEFE-CNRS, Montpellier), rapporteurs ; Philippe Dreyfus (CR, INRA-<br />
Avignon), Marcel Barbero (professeur, Univ. Aix-Marseille III), Renzo<br />
Motta (professeur, Univ. Turin, Italie), examinateurs.<br />
Pour des raisons historiques et dans un contexte écologique à<br />
fortes contraintes, certains types de formation forestière sont en évolution<br />
notable en région méditerranéenne française. Connaître l’impact<br />
des interventions sylvicoles sur la biodiversité forestière constitue<br />
donc une préoccupation majeure pour les gestionnaires. Dans le<br />
mont Ventoux (Vaucluse), une remontée biologique des feuillus est<br />
observée dans des forêts de pins noirs d’Autriche plantées vers 1900<br />
(restauration des terrains de montagne). L’inventaire floristique<br />
montre que le cortège spécifique du sous-bois est sensible aux changements<br />
générés par cette maturation, aux niveaux taxonomique et<br />
fonctionnel (via les attributs vitaux des espèces). Quatre modèles<br />
liant les caractéristiques dendrométriques du peuplement aux proportions<br />
des différents attributs (spectres biologiques) sont réalisés<br />
et comparés, et des simulations de l’évolution conjointe du peuplement<br />
et du sous-bois sont effectuées sur un siècle.<br />
Mot-clés : écologie forestière, sylviculture, diversité floristique, remontée<br />
biologique, pin noir, hêtre<br />
Véla Errol<br />
Biodiversité des milieux ouverts<br />
en région méditerranéenne : le cas de la végétation<br />
des pelouses sèches du Luberon (Provence calcaire)<br />
Thèse de doctorat en sciences soutenue le 06 décembre 2002<br />
à l’Université d’Aix-Marseille III, Faculté des sciences<br />
de Saint-Jérôme, IMEP (CNRS-UMR 6116), case 461,<br />
13397 Marseille Cedex 20, France.<br />
Jury<br />
Thierry Tatoni, professeur (Univ. Aix-Marseille 3), directeur de thèse ;<br />
Thierry Dutoit, maître de conférence (Univ. Aix-Marseille 1), rapporteur<br />
; Pierre Pech, professeur (Univ. Paris 1), rapporteur ; Marcel Barbero,<br />
Professeur (Univ. Aix-Marseille 3), examinateur ; Gérard De Belair, maître<br />
de conférence (Univ. Annaba, Algérie), examinateur ; Edouard Le Floc’h,<br />
ingénieur de recherche (CNRS, Montpellier), examinateur.<br />
L’érosion de la biodiversité mondiale rend urgente l’étude des<br />
points chauds d’endémisme et de richesse spécifique, afin d’élaborer<br />
une stratégie globale de conservation. Parmi ces régions sensibles,<br />
le bassin méditerranéen abrite notamment une flore vasculaire remarquable<br />
(30 000 taxons dont 50 % sont endémiques). Suite à une<br />
régression généralisée en Europe, les pelouses sèches et autres milieux<br />
ouverts sont devenus des habitats d’intérêt communautaire jugés prioritaires,<br />
tant la responsabilité patrimoniale qui incombe aux gestionnaires<br />
des espaces naturels paraît grande. Bien étudiés en contexte<br />
médio-européen, ces milieux, bien que plus riches et plus répandus,<br />
restent méconnus en contexte méditerranéen.<br />
En Provence calcaire (SE France), le site du Luberon a été inventorié<br />
et un réseau de placettes permanentes a été mis en place et suivi<br />
pendant cinq ans (1995-1999). Plusieurs approches complémentaires<br />
ont été utilisées, la méthodologie principale se basant notamment<br />
sur différentes échelles de perception (du mètre carré à l’écocomplexe).<br />
À partir de relevés floristiques, nous avons pu décrire<br />
l’organisation de la végétation face aux conditions stationnelles et aux<br />
régimes de gestion (stress et perturbations), et en dégager les principaux<br />
bio-indicateurs. À travers les éléments endémiques autochtones<br />
qu’ils hébergent, ces écosystèmes semi-naturels possèdent une<br />
richesse patrimoniale qui leur est propre. Mais cette richesse originelle<br />
est renforcée par l’histoire de la pression anthropique (coupes<br />
de bois, feux, pâturage ovin et caprin) grâce à laquelle ils ont hérité<br />
d’un patrimoine associé plus récent. Cette histoire et ses variations<br />
impliquent aujourd’hui une dynamique spatio-temporelle de la végétation<br />
et une réponse spécifique des groupes fonctionnels de plantes.<br />
Dans le cadre des mesures agri-environnementales (aide financière<br />
aux éleveurs et accompagnement scientifique et technique aux gestionnaires),<br />
il est possible d’améliorer le protocole de suivi, de proposer<br />
des protocoles expérimentaux, et de réorienter le choix des<br />
actions à mettre en œuvre pour une gestion conservatoire.<br />
Si le contexte socio-économique de l’Europe de l’Ouest au lendemain<br />
du XXe siècle est le même quel que soit le cadre biogéographique<br />
étudié (médio-européen ou méditerranéen), il est cependant<br />
très différent en Afrique du Nord bien que le cadre biogéographique<br />
soit similaire. Un travail de recherche serait à envisager dans les pays<br />
du sud de la Méditerranée afin d’y étudier la problématique des<br />
milieux ouverts, d’identifier les enjeux patrimoniaux et de hiérarchiser<br />
les priorités de conservation.<br />
Mots-clés : bases de données floristiques, biogéographie, biologie<br />
de la conservation, espèces menacées, gestion des milieux naturels,<br />
pastoralisme, phyto-écologie, secteurs d’endémisme.<br />
ecologia mediterranea, tome 28, fascicule 2, 2002
Vila Bruno<br />
Influence d’un grand mammifère phytophage<br />
sur la dynamique forestière – Étude dendrochronologique<br />
des conséquences actuelles et passées de l’introduction<br />
du cerf à queue noire sur la végétation ligneuse<br />
de l’archipel de Haida Gwaii (Canada)<br />
Thèse de Doctorat en sciences soutenue le 16 décembre 2002<br />
à l’Université d’Aix-Marseille III, Faculté des Sciences<br />
de Saint-Jérôme, IMEP (CNRS-UMR 6116), case 451,<br />
13397 Marseille Cedex 20, France.<br />
Jury<br />
Pekka Niemelä, professeur, Université de Joensuu, Finlande, rapporteur ;<br />
Regino Zamora, professeur, Université de Grenade, Espagne, rapporteur ;<br />
Michel Denis, directeur d’Unité, CEMAGREF, examinateur, Jean-Louis<br />
Martin, directeur de recherche, CNRS, examinateur ; Jean-Louis Edouard,<br />
chargé de recherche, CNRS, directeur de thèse ; Frédéric Guibal, chargé<br />
de recherche, CNRS, directeur de thèse.<br />
Le but de ce travail est d’identifier et d’évaluer les conséquences<br />
de la phytophagie exercée par un grand mammifère sur la végétation<br />
ligneuse du sous-bois pour comprendre comment le phytophage<br />
modifie la dynamique forestière. Nous avons utilisé la situation quasiexpérimentale<br />
de l’introduction du cerf à queue noire (Odocoileus<br />
hemionus sitkensis Merriam) sur l’archipel de Haida Gwaii (Colombie<br />
Britannique, Canada), recouvert d’une forêt tempérée pluviale jusqu’alors<br />
dépourvue de grand phytophage. Par l’étude des âges, l’approche<br />
dendrochronologique a mis en évidence le blocage du processus<br />
de régénération des deux principales espèces arbustives, le<br />
salal (Gaultheria shallon Pursh) et l’airelle (Vaccinium parvifolium<br />
Smith in Rees) conduisant à la disparition progressive mais totale du<br />
sous-bois. Associée à des analyses chimiques, l’approche dendrochronologique<br />
a mis en évidence le ralentissement de la régénération<br />
modulé par les défenses physiques chez l’épicéa (Picea sitchensis<br />
(Bong.) Carrière) et le tsuga (Tsuga heterophylla (Raf.) Sarg.) et une<br />
sélection des individus basée sur l’expression de défenses chimiques<br />
chez le thuya (Thuja plicata D. Donn ex Lamb.). Les changements<br />
disproportionnés induits par le phytophage entre les différentes<br />
espèces entraînent une modification de la dynamique forestière qui<br />
se traduira à long terme par un changement en composition de la<br />
forêt. L’approche historique rendue possible par l’étude des structures<br />
d’âge des espèces arbustives et des cicatrices laissées par le cerf<br />
sur les espèces arborescentes montre que si le cerf a rapidement colonisé<br />
tout l’archipel, des hétérogénéités spatiales et temporelles apparaissent,<br />
en liaison avec des facteurs géographiques (l’isolement, la<br />
présence/absence de montagne), des facteurs humains (présence/<br />
absence d’exploitation forestière et de chasse), l’habitat et le climat.<br />
Mots-clés : phytophage, pression d’abroutissement, dynamique forestière,<br />
insularité, cervidé, dendrochronologie, Picea sitchensis, Tsuga<br />
heterophylla, Thuja plicata, Vaccinium parvifolium, Gaultheria shallon.<br />
ecologia mediterranea, tome 28, fascicule 2, p. 113-115<br />
Kiss Laurence<br />
RÉSUMÉS DE THÈSES ◆<br />
Impact des incendies sur les communautés<br />
de gastéropodes terrestres en basse Provence calcaire<br />
Thèse de doctorat en sciences soutenue le 18 décembre 2002<br />
à l’Université d’Aix-Marseille III, Faculté des sciences<br />
de Saint-Jérôme, IMEP (CNRS-UMR 6116), case 451,<br />
13397 Marseille Cedex 20, France.<br />
Jury<br />
Roger Prodon (directeur d’études, EPHE, Montpellier II) rapporteur ;<br />
Markus Pfenninger (maître de conférence, Université de Francfort) rapporteur<br />
; Christopher Carcaillet (directeur d’études, EPHE) Montpellier II)<br />
rapporteur ; Robert Cameron (professeur, Université de Sheffield) examinateur<br />
; Marcel Barbero, (professeur, Université d’Aix-Marseille III)<br />
co-directeur ; Frédéric Magnin (chargé de recherche, CNRS, Aix-<br />
Marseille III) directeur.<br />
Le feu est une perturbation majeure des écosystèmes méditerranéens.<br />
Malgré un nombre important d’études traitant de l’impact du<br />
fe