Ecologia Mediterranea

N. BOUCHENEB, S.S. BENHOUHOU
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E1 Rhus tripartita-Olea europaea subsp. laperrinei community
E2 Cassia aschrek-Panicum turgidum community
E3 Tamarix gallica-Desmostachya bipinnata typical community
E4 Tamarix aphylla-Farsetia ramosissima community
E5 Acacia raddiana-Salvadora persica community
E6 Leptadenia pyrotechnica-Chrozophora brocchiana community
Figure 4 – Relevés spread of the whole data set along the first two axis.
ies on desert vegetation (Abd El-Ghani &
Amer 2003; Ali et al. 2000; Anthelme 2007;
Benhouhou et al. 2003b; Dargie & El-Demerdash
1991; Shaltout & Mady 1996; Springuel
and Sheded 1991). The numerical analysis
chosen is a correspondence analysis using
ANAPHYTO (Brian 1991). The second stage
of data analysis was the phytosociological
study of the identified plant units via the association
tables. These are considered as the
basis for any syntaxonomical analysis. The
only framework valid for the Algerian desert
vegetation is the one proposed by Quézel
(1965) and which has thus been considered in
the present analysis. Among the four existing
classes covering all the habitats encountered
in this vast territory two classes were found:
the Pergulario-Pulicarietea Quézel 1965 and
the Asterisceto-Forsskaoletea Quézel 1965.
We considered perennials to be the most
important component in describing the vegetation
units and treated annuals as companions
usually characterised by erratic occurrence.
The latter are of less importance as they
reflect short-lived habitat conditions (Fossati
et al. 1998).
Results
Axis 2
Axis 1
The correspondence analysis applied to the
data matrix (190 relevés and 108 species)
enabled the identification of six floristic
groups (Figure 4). The high eigenvalues for
the first two axes (axis 1: 0.58 and axis 2:
0.45) suggest that two main gradients are at
work. Analysis of the relevés spread along the
first axis clearly indicates that an altitudinal
gradient is responsible for the floristic distribution.
Relevés close to the negative part of
the first axis were taken at an altitude that
varies between 1400 and 1600 m while those
at the other end of the first axis were recorded
between 800 to 900 m. Relevés plotted in the
middle of the axis were taken at the intermediate
altitude of 1200 m. The second axis
shows a textural trend where relevés plotted
towards the negative part of the axis were on
coarse sand mixed with stones and those plotted
at the other end had finer sand in their
edaphic profile.
From the 190 quadrats presented in the ordination,
91 relevé “types” were chosen according
to their floristic content to illustrate and
discuss the six identified communities.
ecologia mediterranea – Vol. 38 (2) – 2012