Distribution of the tree and shrub vegetation in the central zone of Darfur, Sudan

Abstract

The vegetation of Central Darfur can be divided into four Formations on physiognomic characteristics. These are:- Semi- Desert Scrub, Thorn Savanna, Woodland Savanna, and Mountain Savanna or steppe.

Each formation can be sub-divided into different edaphic units, and ultimately into distinct Associations on specific grounds. Twelve associations are recognised.

Each association is a distinct and separate entity, and can be recognised on the ground. In only one case has mention been made of an association being in a probable state of ecological advance. The position of the remainder is difficult to assess. In the section on the Acacia mellifera - Commiphora - A. orfata - A. tortilis Association it was stated that this was probably the climatic climax association of Thorn Savanna.

This is not strictly correct, as the writer views this, and other associations, as being in a state of dynamic equalibrium at, or near, the deflected climax. That is, the climatic climax, deflected through the effect of man and his animals. What the true climax is, will not be known until the effect of several decades of complete protection on selected areas can be studied. The writer suggests that the present deflected climax is probably not far removed from the climatic climax, because the incidence of man is not severe.

Apart from the Albizzia-Acacia Association, to which mention has already been made, the writer saw no evidence to suggest an advance, either ecologically or geographically, in any of the associations. Conversely, apart from degradation of the vegetation in the vicinity of towns, there is no evidence of a retreat in any association.

In dealing with some of the associations, particularly the northern ones, the remark, 'of little interest to forestry' will be found. What is really meant by that, is, that these associations are of no use for afforestation, or the commercial aspects of forestry. They are, of course, of inestimable value in a protective role; soil protection, and also to a lesser degree, maintenance of the regional climate, and water supplies.

Destruction of thorn savanna and thorn scrub, resulting in soil instability, accelerated erosion, dust storms and reduced water supplies, are to be seen, all too frequently, in the Sudan, and elsewhere in Africa.

The ecological order established for the different species, should be of use to all who deal with land-use.

From an inspection of an area, an estimate of its value can be made from the ecological status of the various species present. Further, if the climatic value be known, then the species, and their propotions, gives a direct measure of the edaphic value of the site. Some such method of assessing site -values is constantly required in forestry, and in other professions dealing with land.

The ecological order established for the different species, should be of use to all who deal with land-use. From an inspection of an area, an estimate of its value can be made from the ecological status of the various species present. Further, if the climatic value be known, then the species, and their propotions, gives a direct measure of the edaphic value of the site. Some such method of assessing site -values is constantly required in forestry, and in other professions dealing with land.