sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

SDÜ Faculty of Forestry Journal
designers or planners of the green spaces, since some disturbances such as sunburn
lesions or leaning stems by light deficit are generally due to inadequate designs. In
fact, in natural environment most of these problems are very unusual. For all these
reasons, the municipal green spaces management programmes should be look
through in order to adapt conservation strategies to deal better with abiotic
problems.
Besides, abiotic diseases were much less frequent in shrubs, with 20-48% of
total disturbances depending on the considered year. Aphids were responsible of a
great number of the biotic diseases, since it was the second problem, after dead
plants. However, this result would have been pretty different if dead plants had
been considered as an abiotic or biotic agent.
4.9 Abiotic diseases affect a greater rank of tree and shrubs species.
Abiotic diseases affect a greater variety of species (Table 7), which is
reasonable if it is taken into account the fact that they are prompted by human
activities or physical agents. However, biotic diseases seemed to be more specific
in some plant species; for example, lace bugs (Corythuca ciliata), leaf beetle
Galerucella luteola and Pseudomonas syringae subsp. savastanoi affected only one
species (plane tree, Siberian elm and oleander, respectively). Concerning pests, this
result would confirm the idea held by some authors who maintain that most
herbivorous pests are specialized and only eat few taxa of plants (Rocray, 1983;
Galvin, 1999; Raupp et al., 2001).
Table 7. Affected species by biotic and abiotic diseases. Tree and shrub species affected
by biotic and abiotic diseases and the percentage of the total species, in all the years and in
all the inventoried green spaces.
Trees Total
Affected by
biotic
diseases
Affected by
abiotic
diseases
228
Shrubs Total
Affected by
biotic
diseases
Affected by
abiotic
diseases
Species 73 38 57 Species 77 32 40
% of
species
100 52.1 78.1
% of
species
100 41,6 51,9
4.10 Positive association between naturalness of tree species and their
health status.
Pyšek’s criteria are used to define the naturalness of the tree (Pyšek , 1995). It is
considered the national scale, therefore, all those species defined as natural of
Spain according to those criteria, are classified as native in this survey.
Bibliography is used to make easier this controversial task (López González, 2002;
Real Jardín Botánico, 2009).
A ji-squared test on the data shows that the relationship between health status
(damaged or undamaged SYG) and naturalness (native or exotic SYG) is
significant at 95% level (Table 8). The probability for an exotic SYG to be
damaged is greater (0.68) than the probability for a native SYG (0.59). However,