Revue internationale d'écologie méditerranéenne International ...

ANNIK SCHNITZLER, CLAIRE ARNOLD
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more stable architecture. Vines are small and
perennial (hemicryptophytes, nanophanerophytes).
Evergreen oaks are particularly rich in
sclerophyllous vines. Deciduous oak forests are
favourable to vine diversity because of deep
soils and low altitudes, but vines are restricted
to understoreys, except shade tolerant phanerophytes
such as Hedera helix.
Version anglaise abrégée
Vines are unique among forest components.
They begin their life as self-supporting
seedlings, then become mechanically unstable
and need external support for continuing
ascension. Vines have developed morphological
and physiological specialisations for
crossing forest strata and gaining access to
resources between trees and shrubs. The
strategies for ascension are various and range
from minor adaptations, such as simple
sprawling over other plants, scrambling, or
hooks, to more specialized and efficient
mechanisms, such as stem twining, tendrils,
adventitious roots or other adhesive structures,
all associated with active searching of
support. Some vines are also shade tolerant
and can survive as sprawling individuals.
In the Mediterranean area, vines are limited
by shallow soils and summer drought, but
they have developed specific strategies to
adapt to such constraints. Their diversity and
abundance within forest communities vary
however with the ecological conditions. This
paper performs a meta-analysis of studies of
vines in forests of the Mediterranean basin to
investigate (1) their diversity in the main forest
types of the Mediterranean; 2) their ecological
specificities. The study is based on the
meta-analysis of 229 forest communities from
the phytosociological literature. We have classified
these communities into five types:
deciduous oak forests (G); evergreen oak
forests (J), deciduous mountain forests (F),
conifer forests (K), floodplain forests (U).
Four life-traits were associated to the analysis
(foliar type, mode of climbing, longevity
and place in the forest strata).
The total number of vines is 51, dominated by
Fabaceae and Convolvulaceae, which correspond
to the major vines of Europe. The
global mean richness in vines is 6.9 species,
which corresponds to a proportion of 12.4%
related to the mean total richness of the
forests. 12 species dominate the Mediterranean
forests, including for the most abun-
dant ones: Hedera helix (59%), Smilax aspera
(44%) and Clematis vitalba (34%) for the
high strata, Tamus communis (54%) and
Asparagus acutifolius (41%) for underlayers.
The genus Hedera is particularly abundant in
forests and able to rapid mutations (polyploidy)
on islands, but the whole polyploid
series has kept the same strategies. The
colonisation of islands was easy for all vines
dispersed by birds. Among the six islands
investigated, Sicily includes the larger number
of vine species.
A rather low proportion of vines (20%) live
in the canopy. These vines are either phanerophytes
or hemicryptophytes, they are mainly
deciduous, they use a various array of climbing
modes and some of them may reach
impressive sizes. Vines of the understorey are
more species-rich, mainly deciduous, perennial,
and of small size. The climbing modes
are various, but adventitious roots are absent
while hooks are frequent.
The communities of vines differ in function
of the ecological conditions displayed within
forest types. We have distinguished two major
groups: 1) Floodplain forests (U), characterized
by a high forest dynamics and a high
level of resources, are highly favourable for
vines. Vines are of great size, dominated by
deciduous species and phanerophytes, and
often luxuriant and abundant. 2) All other forest
types (J, G, K, F), characterized by a lower
forest dynamics and more stable architecture.
Vines are small, live at low densities, opportunities
of reproduction are limited by the size
of the gaps. Two forest types (J) and (G) however
are rich in vines: evergreen forests (J) are
rich in sclerophyllous vines, deciduous forests
(G) are rich in deciduous vines, thanks to
deep soils. The taxonomic richness is limited
in conifer forests (K) and mountain forests (F)
(particularly in beech) because of either lack
of soils or organic soils.
The taxonomic diversity of Mediterranean
forests was compared to other forests of close
ecology (Canarian islands, Chile, California).
Forests of the current Mediterranean landscape
have deeply changed compared to
ancient forests with high naturalness, and the
vine communities have adapted to these
human changes. Native forests offered more
suitable habitats for vines thanks to a more
buffered microclimate and the conservation of
deep and moist soils. These conditions probably
helped canopy vines to reach larger sizes
and to occupy wider surface areas.
ecologia mediterranea – Vol. 36 (1) – 2010