The Incidence of the Biotic Factor in Northern Sudan

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Abstract
Observations were made on a 75-acre enclosure near Omdurman, with a view to demonstrating the influence of the biotic factor on desert vegetation. Salient climatological and edaphic features are briefly discussed and man''s activities outlined. Vegetation, a mixture of shrubs, perennial and annual grasses was sampled quantitatively inside and outside the enclosure. On the whole, a marked response to fencing was clearly visible. Protection resulted in an increase in density and vigor of the vegetation, so that greater coverage and consequently better soil stabilization were attined. The time factor appears to be important, more prolonged protection producing greater plant coverage. Grazing, in addition to reducing vegetative material, may induce in some plants the production of a certain growth form. Importance of willful removal of vegetation and soil by man and animals in creating desert conditions is discussed.