Soil and phytosociological study of two bonds in the Niokolo Koba National Park in a context of biological invasion by Mimosa pigra.
The biological invasion of ponds by Mimosa pigra has been an increasing threat in Niokolo Koba National Park for the past years. This study aims at comparing the Nianaka and Dalafourounté ponds in order to identify the factors behind the invasion of these species. In this respect, we have conducted pedological and phytosociological studies inside, at the edge and around these ponds. The results of the study have shown that Mimosa pigra, in both ponds, grows on a heavy clayey soil with proper mineral nutrition. Moreover, the flora analysis reveals that 35 species belonging to 26 genera divided into 16 families have been inventoried at Dalafourounté while 24 species within 20 genera divided into 13 families have been identified at Nianaka. The proportion of dicotyledons is lower at Nianaka (83.3%) than at Dalafourounté (91.4%) and the opposite is noticed with monocotyledons, 16.7% against 8.6%. Besides, there is a dominance of Combretaceae and Mimosaceae in the flora of both ponds. In addition, Mimosa pigra is only invasive at Nianaka where it is permanently present at the edge and inside the pond while its presence around it is not constant. As a final result of this study, the Mimosa pigra invasion could be originating from the relief and the pond filling up.