150
CLAUDE J. GRENOT
(3) the lower Saharan vegetation, the inferior desert stage, where the annual precipitation is in excess of 50 mm. Here there is contracted
vegetation.
At the level of the lower desert stage, it is difficult to determine associations because the vegetation is diffuse. Higher levels of classification associations can be determined.
c. Cartography. Cartographic representations of the vegetation of the
vast area have just begun to be formulated. There are already several
sketches, made on a large scale, but with much approximation: Béni-Abbès
(South Oranais) at 1 to 2 X 10
6
, Guinet (1954); Gabes-sidi Chammakh
(South Tunesia) at 1 to 2 X 10
5
, Le Houérou (1955); Ghardaia (South
Algeria-Constantine) at 1 to 5 X 10
5
, Barry and Faurel (1963); Largeau
(Mid Sahara) at 1 to 1 X 10
6
, Quézel and Gillet (1964); Alger-Laghouat
at 1 to 1 X 10
6
, Barry et al (1970); El Golea at 1 to 1 X 10
6
, Barry
et al ( 1970 ) ; In Salah at 1 to 1 X 10
6
, Barry et al (1970).
It is premature to give a presentation of the groups of vegetation of
the Sahara. An attempt to synthesize all that is known about these groups
was made by Quézel (1965). Certain types of vegetation common to parts
or all of the Sahara were studied.
2. Groups of Edaphic Origin
The whole of the Sahara is well represented by groups of hydrophiles
and psammophiles.
a. Hydrophil Groups. Sources of nonsaline water are rare in the Sahara.
These few sources, trickling water or ponds, have a poor flora, consisting
of tempered elements or cosmopolitans, such as the associations of a marsh
in the heart of the Sahara (see Fig. 28) with reeds and rushes of more
temperate lands (Corti, 1942; Leredde, 1954; Bruneau de Miré and
Quézel, 1957). Thus the hydrophilic vegetation is composed of ubiquitous
species, such as Samolus valerandi, June us maritimus, Scirpus holoschoenus, and Tamarix gallica.
b. Psammophile Groups. The works of botanical geography concerning
the vegetation of the Sahara sands are numerous (Zolotarevsky and Murat,
1938; Maire, 1933, 1940; Braun-Blanquet, 1939; Guinochet, 1951;
Quézel, 1956; Leredde, 1957; Le Houérou, 1962; J. Killian, 1960).
The vegetation of living dunes and ergs is characterized by the association of Calligonum comosum and Aristida pungens. It is composed
of few nearly identical species throughout the Sahara. There is, however,
a preponderance of hemicryptophytes. The most characteristic plants for
the Saharan sands are Aristida pungens, Cyperus conglomeratus, Malcolmia aegyptiaca, and Cornulaca monacantha, but some bushy vegetation,
CLAUDE J. GRENOT
(3) the lower Saharan vegetation, the inferior desert stage, where the annual precipitation is in excess of 50 mm. Here there is contracted
vegetation.
At the level of the lower desert stage, it is difficult to determine associations because the vegetation is diffuse. Higher levels of classification associations can be determined.
c. Cartography. Cartographic representations of the vegetation of the
vast area have just begun to be formulated. There are already several
sketches, made on a large scale, but with much approximation: Béni-Abbès
(South Oranais) at 1 to 2 X 10
6
, Guinet (1954); Gabes-sidi Chammakh
(South Tunesia) at 1 to 2 X 10
5
, Le Houérou (1955); Ghardaia (South
Algeria-Constantine) at 1 to 5 X 10
5
, Barry and Faurel (1963); Largeau
(Mid Sahara) at 1 to 1 X 10
6
, Quézel and Gillet (1964); Alger-Laghouat
at 1 to 1 X 10
6
, Barry et al (1970); El Golea at 1 to 1 X 10
6
, Barry
et al ( 1970 ) ; In Salah at 1 to 1 X 10
6
, Barry et al (1970).
It is premature to give a presentation of the groups of vegetation of
the Sahara. An attempt to synthesize all that is known about these groups
was made by Quézel (1965). Certain types of vegetation common to parts
or all of the Sahara were studied.
2. Groups of Edaphic Origin
The whole of the Sahara is well represented by groups of hydrophiles
and psammophiles.
a. Hydrophil Groups. Sources of nonsaline water are rare in the Sahara.
These few sources, trickling water or ponds, have a poor flora, consisting
of tempered elements or cosmopolitans, such as the associations of a marsh
in the heart of the Sahara (see Fig. 28) with reeds and rushes of more
temperate lands (Corti, 1942; Leredde, 1954; Bruneau de Miré and
Quézel, 1957). Thus the hydrophilic vegetation is composed of ubiquitous
species, such as Samolus valerandi, June us maritimus, Scirpus holoschoenus, and Tamarix gallica.
b. Psammophile Groups. The works of botanical geography concerning
the vegetation of the Sahara sands are numerous (Zolotarevsky and Murat,
1938; Maire, 1933, 1940; Braun-Blanquet, 1939; Guinochet, 1951;
Quézel, 1956; Leredde, 1957; Le Houérou, 1962; J. Killian, 1960).
The vegetation of living dunes and ergs is characterized by the association of Calligonum comosum and Aristida pungens. It is composed
of few nearly identical species throughout the Sahara. There is, however,
a preponderance of hemicryptophytes. The most characteristic plants for
the Saharan sands are Aristida pungens, Cyperus conglomeratus, Malcolmia aegyptiaca, and Cornulaca monacantha, but some bushy vegetation,