SECONDARY SUCCESSION IN ABANDONED FIELDS OF DRY TROPICAL NORTHERN CAMEROON

This study evaluates the processes of recolonization of abandoned fiel ds by native vegetation under conditions of intensive human activity ( fire, intensive grazing, firewood cutting) in a semi-arid tropical reg ion savanna of northern Cameroon. Secondary plant succession was studi ed in two series of formerly cultivated fields 1-35 yr after the begin ning of the follow period. Floristic changes and the dynamics of woody plant populations were compared between areas with vertisols (clay te xture) and sandy soils, as a function of length of fallows. Vegetation changed continuously during the 35 years following field abandonment. However, a very abrupt break occurred between 6 and 10 yr, due to inc reasingly intense human pressure during this period. Up to that point, ecological models and mechanisms of succession presented in the liter ature are more or less confirmed by our results. Usually, secondary su ccession is blocked at a stage of wooded grassland as a result of huma n activities.