ABSTRACT
This study was carried out in Bala; a village located in the cotton-based farming system zone of Western Burkina Faso. The objective was to assess the effect of increased cotton cultivation on the spatial dynamics and structural characteristics of the woody vegetation. Using aerial photos; an analysis of the land use for the years 1952; 1981 and 1999 was carried out. An inventory covering 25 smallholders' fields and fallows as well as the vegetation of a protected area (biosphere reserve of hippopotamus ponds) was carried out to evaluate the gradients of tree species richness and density. The results showed drastic changes in land use in Bala between 1952 and 1999. Cultivated areas which covered only 10 of the total land surface of the village in 1952 increased to 48 in 1999. A total of 44 woody species from 34 genera and 26 botanic families were recorded; out of which; 31 species were found in the protected area; 15 species in relatively recent fallows and 12 species in cultivated lands. Tree density in cultivated areas decreased as farmers' level of mechanization shifted from manual cultivation to partial ploughing; complete ploughing and motorized farming. On the other hand; tree species richness and density were higher both in the protected area and fallows than in cultivated lands confirming the key role that protection and fallowing play in the reconstitution of woody vegetation. Management of woody vegetation should take into account the level of mechanisation and the needs of farmers in order to sustain the production of indigenous trees on farms while allowing the intensification of the production of annual crops