Botanical features of the Algerian Sahara

by William Austin Cannon

The southern spurs of the Saharan Atlas lie to the north of Laghouat, within 3 miles of the oasis. This range (the Nomad Mountains) is not over 266 meters in height. Higher mountains extend both to the west and to the east, but only the Nomads are visited. There are also two high, rocky hills on opposite edges of the oasis, the town lying between, and it is perhaps because of their presence that the water is forced to the surface, or near the surface, and the oasis is formed. The hill to the west of the town is called the Rocher des Chiens. On the south side of the Nomad Mountains is a long outcropping of gypsum; the south face of these mountains is also abrupt, carrying little soil; but on the northern face the slope is gradual and there is much soil, although rocks are abundant.

Two localities only in the Nomad Mountains were seen. One was in a pass through which caravans travel en route to Laghouat, from the High Plateau or the more distant Tell; the second to the east of the pass is much less often visited by flocks. The physical plant conditions appeared to be the same in both locations. As one approaches the mountains from the south the number of plants grows less until on the south face they quite disappear, but on attaining the crest they quickly increase and form a noticeable element in the landscape. In fact, the flora of the northern gentle slope, where the soil conditions are relatively favorable, is much richer than on the plain or the dunes. Had the shrubs been of good size they would have been very conspicuous.[10]

A certain area on the north slope of the Nomad Mountains, not far from the pass through which the Oued Mzi goes, was selected for making a census of the plant population. Here the number of individuals, as well as their size, showed that the moisture relations were good as compared with those of the plain. On an area 16 meters square 422 living perennials were found, mainly of the following species: Acanthyllis tragacanthoides, Asparagus spinosa, Deverra scoparia, and Zollikoferia spinosa. The most numerous, Zollikoferia, was represented by 96 individuals. The general character of the habitat and the plants is sufficiently well shown in fig. [8] and does not need further mention in this place.

EFFECTS OF GRAZING ON VEGETATION NEAR LAGHOUAT.

It is generally recognized that a potent influence is exerted by man, and the lower animals, in shaping the flora of an arid region, not only as regards the kind and number of plants, but also as concerns certain of the leading characteristics of the plants themselves. The action is largely such as brings about a survival of the “useless” forms, so that we do not know, from the plants we meet in the desert to-day, how many or what kinds of plants it might support. It also may be true that no desert shows the modifying effects of the causes suggested more than the northern Sahara.

The gazelle (Gazella dorcas) is the leading wild animal preying upon the desert plants in the northern Sahara. It is frequently seen by the traveler to-day and was present in large numbers no longer ago than 50 years (Tristram). It is said by the Arabs to feed on the fresh shoots and leaves of many species of shrubs and trees, especially the betoum (Pistacia atlantica), as well as on the annual vegetation for the relatively short period when it is to be had. Other species of gazelle, according to Tristram, range farther to the south. Other herbivorous animals of the region are hares, antelope, moufflon, and bubale. The moufflon, at the time of Tristram’s visit, was “far from uncommon throughout the whole of the mountain districts, whether wooded or bare,” but the bubale, “the wildest of the wild game of North Africa,” appears not to go north of the Oued Rirh, while its home is farther south. It is impossible to know the number of wild animals subsisting on native desert vegetation, but the list given, which might be extended, suggests that it is by no means small. Although the population of wild herbivorous animals is at present considerable, it was probably much greater a few years ago, the decrease being due, as Tristram says, not so much to the greatly increased population as to the more efficient weapons used by the Arabs in hunting.[11]

Laghouat has been inhabited by the Arabs continuously for about 1,000 years, during which time the oasis and its environs have been the source of supply of all of the fuel used and for much, if not the most, of the food consumed both by the Arab and his flocks. Naturally, the food for the inhabitants of the oasis is won from the oasis itself, but that for the beasts is derived from the desert. While it is impossible to learn the number of sheep, camels, and goats which from century to century have ranged over the desert pastures, there is no reason for supposing it was not large, as at present is the case. For example, in the department of Algiers, in 1907-08, the number of sheep is reported to have been 2,109,071; of goats 1,156,500, and of camels 23,912.[12] Of these a large percentage is to be found in and to the south of the Saharan Atlas Mountains. In portions of the colony farther south, or in regions even more desertic than at Laghouat, the number of camels, sheep, and goats is surprisingly large. The statistics for 1907-08 give the population of the three classes of animals in the southern territories, that is, the territories of Ain-Sefra, Ghardaia, Touggourt, and the oases of the Sahara, as follows: sheep, 1,932,392; goats, 588,121; camels, 126,088.

The flocks of sheep and goats range at various distances from the source of their water-supply. It is quite usual for the goatherds to gather their flocks in early morning, returning to the oasis in the evening to distribute the goats to their various owners; but probably in most cases the flocks of sheep, with some goats, return to water once in two or three days, thus being able to stray from 20 to 40 kilometers into the desert. Being less dependent on water, the camels range a much greater distance. It thus appears that the area grazed over by the flocks of the Arabs is fairly circular in form, with a radius of 40 or more kilometers from the wells, and that the range of the camels may be much greater than this. It should also be noted that the caravan routes are broad tracts where all vegetation fit for fuel or food has been utilized Between the two sources of destruction referred to, the stationary and continuous and the frequent but not continuous, little territory passes untouched as a source of food-supply.

A visit to the wood markets of the town indicates to what ends the natives resort to obtain fuel. (See figs. [2] and [3.]) Among many kinds of wood, some are from the oasis itself, such as the willow, plane, and palm; some from the mountains, like juniper, pine, and oak; and some from the oued, like the jujube and Tamarix. Much of the fuel is at present brought three days’ journey by camel. Usually the subaerial portions only of the plants are used, but in the case of the jujube both root and branches are gathered. The fuel requirements have apparently brought about the extinction of some species from certain of their earlier habitats; for example, the betoum (Pistacia atlantica) probably formerly either grew in the oasis of Laghouat or near by, since it was formerly in common use as a fuel. Tristram mentions the betoum, and no other species, as a source of fuel, but inquiry failed to show that at present this species is in general use for this purpose; but the betoum is a familiar sight in the region of the dayas south of Laghouat, where it is the only arboreal species of the region.

From what has been said regarding the large numbers of domestic animals that gain their entire living on the desert, it follows that of plants growing within the range of the flocks only such as are poisonous, distasteful, armed, or otherwise protected, escape partial or complete consumption. Only such species as are too small for fuel or can not be eaten by animals attain to the usual development year by year. In the vicinity of Laghouat the most prominent of the immune plants is the quedad (Acanthyllis tragacanthoides), which is well protected by its stout spines; and even this species is not wholly undisturbed. The jujube, also, although not common here, is provided with short spines. It is stated by Massart[13] that the camels used by him, not having eaten for five days, consumed the branches of the jujube in spite of the spines, and that Anvillea radiata, a composite with acrid juice, was passed by. Perhaps the plants most frequently eaten are of the genus Haloxylon, generally distributed from the High Plateau southward into the region of the M’Zab. That this genus is not exterminated is interesting, since it is rarely permitted to come into flower and fruit, and it appears not to reproduce to any extent, if at all, in a vegetative way.