Generalist versus specialist: a contrasted sociology of woody and herbaceous species in a fallow-land rotation system in the West African savanna (Bondoukuy, Western Burkina Faso)
In order to study the co-existence and niche breadth of savanna species, an analysis of the distribution of the species in the various levels of a phyto-sociological hierarchy was assessed using the INDVAL method. It so performs a through-scale analysis of the species distribution and provides a hierarchical assessment of the landscape pattern. A hierarchy of four levels was obtained on the one hand for the herbaceous species and on the other hand for the woody species. The sociological significance of the groups is established with the aid of the diagnostic species specific to each one of them. Except in one case, there is no correspondence between the groups of herbaceous species and the groups of trees. In addition, the majority of the woody species is eurytopic, particularly in the case of the small shrubby species. The large woody species characteristic of woodland or dry deciduous forest, seem however, to be more specialized, with a more restricted ecological amplitude. Thus, the anthropization of the savanna corresponds to a loss of the specialist woody species that constitute the initial vegetation. With regards to the herbaceous species, although many of them are very widespread, the existence of a sociological organization at a low hierarchical level expresses their capacity to exploit specific conditions, which vary on a small scale.