Secondary succession and factors determining change in soil condition from fallow to savannah in the Sudanian Zone of Benin

Demand for land for agriculture remains one of the greatest threats to the natural vegetation in the Sudanian Zone in Africa. This work aimed to assess the patterns of the secondary succession around the Biosphere Reserve of Pendjari in northern Benin and to establish its relationships with soil properties. Fallow vegetation was stratified by age and four succession states were recognized. Phyto-ecological inventories were carried out within plots of 30 m × 30 m. Soil physico-chemical properties were determined in fallows that best represent the succession states. Numerical analyses of vegetation data resulted in four fallow types, which corresponded to the four vegetation succession states empirically recognized earlier. The first state was characterised by the proliferation of widespread species that disappeared by the third state. The therophytes and chamaephytes, abundant during the first state, were replaced by hemicryptophytes and phanerophytes in the last state. About 22 % of the 233 species recorded were recorded throughout fallow cycle. The first succession state exhibited the highest species richness with 18.6 % of all species exclusive to this state. The transition from the fi rst to the second state was characterised by the disappearance of 77 % of the total species richness. Organic Matter and the Species Richness were the best discriminating variables of the succession states. Soil exchangeable cations (K+, Mg2+ and Ca2+) did not show significant differences between the first and second succession states, but OM and P increased significantly along the succession gradient. The secondary succession exhibited a clear floristic pattern with a progressive establishment of the woody vegetation. This was followed by a gradual recovery of soil fertility through the process of organic matter cycling. The colonization of herb layer by Andropogon gayanus var. bisquamulatus (typical Sudanian species) during the third state can be seen as an indication of a substantial return to soil fertility.

Source de publication: Phytocoenologia, 42 (3 – 4), 181 – 189.

Contacts du ou des auteurs: Emeline P. S. Assédé (assedeemeline@gmail.com), Aristide C. Adomou and Brice Sinsin