Ecologia Mediterranea

N. BOUCHENEB, S.S. BENHOUHOU
Introduction
The most important studies on the flora and
vegetation of the Ahaggar are those of Maire
(1940), Quézel (1954; 1965; 1997) and Barry
et al. (1972; 1981). The Ahaggar has a diversified
flora estimated between 350 to 400
species (Maire 1940; Quézel 1965; Quézel
1997) which features several endemics (Olea
europaea subsp. laperrinei (Batt. & Trab.)
Cif., Myrtus nivellei (Batt. & Trab.), Lavandula
antineae Maire) and relict trees (Pistacia
atlantica Desf.). The vegetation in the
Ahaggar is found in valleys, on wadis and
nearby terraces that cut their way through the
mountain massifs and outwash zones where
underground sub-surface water flows are permanent.
Phytosociological studies in the Ahaggar
started with the work of Maire (1940) followed
by in-depth studies undertaken by
Quézel (1954) in the Ahaggar. Later, Quézel
(1965) proposed a global syntaxonomical
framework for the northern, north-western,
central and southern Sahara. Further phytogeographical
studies, with a particular focus
on the vegetation of the In Salah and Tamanrasset
regions, enabled Barry et al. (1981) to
make a detailed analysis of the plant groupings
belonging to the Acacia-Panicum desertic
savannah.
Figure 1 – Geographical localisation of Tamanrasset in the Ahaggar
(Central Sahara).
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More recent contributions to vegetation studies
in the Ahaggar have explored areas of the
range not previously investigated, such as
Halem (1990) who describes the vegetation of
two major wadis in the Tefedest and
Abdelkrim (1992), who identified a new association
Pistacia atlantica-Myrtus nivellei in
the Taessa region. Further investigations in
remote, relatively inaccessible sites south of
Tamanrasset enabled Boucheneb (1999) to
describe several plant groupings. Phytosociological
studies of the region have therefore
been sparse and, considering the vast territories
covered by the Ahaggar, plant community
description for the area is far from being complete.
The objectives of the present work are
to identify the major ecological gradients
associated with the differentiation of several
wadi plant communities related to different
wadi types and to provide detailed descriptions
of vegetation units sampled for the first
time in the Tamanrasset region. The described
plant communities are then put in a wider
geographical context by comparing them with
similar communities in other mountainous
areas of the Saharo-Arabian belt.
Study area and methodology
Geology and geomorphology
The Ahaggar, a vast territory in the centre of
the Sahara, is located 2000 km south from the
Algerian coast (Figure 1). The region covers
450,000 km 2 of mainly mountainous nature
with two major subareas: a metamorphic and
igneous area in the central part of the Ahaggar
and the Tassilian shield at the periphery
(Fabre 1976). The central area consists of significantly
younger rocks than the shield area
and is characterised by several character
regions, of which the most important are the
Attakor culminating at the Mount Tahat with
an altitude of 2918 m, the north-south aligned
Tefedest (highest summit at 2400 m) and the
Amadror, famous for its salt-flats (Lelubre
1952).
This basement complex has undergone several
sedimentation cycles, the products of
which have been cleared during successive
subsequent erosion cycles. Within such a context,
alluvia strewn on wadi beds hold shallow
sub-surface water flow, which constitutes
the main water resource in this area. The
wadis sampled in the Tamanrasset region
ecologia mediterranea – Vol. 38 (2) – 2012