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