Phytosociological Study of Nyungwe Montane Savannahs

Abstract

It is uncommon to find savannahs encompassed into tropical montane rainforests. The case of Nyungwe savannahs is one of these particularities and until now no explanation on their origin, structure and dynamics was given. This unprecedented research documented special floristic diversity of montane savannahs of Nyungwe, described the structure of their plant communities to provide data for their sustainable conservation. In this paper origin of these savannahs was discussed. The study was conducted in three sites harbouring five savannahs:Karamba, Nyabitimbo and Muzimu. Eight plant communities (4 in savannah-forest contact zone and other 4 in savannah) were identified with 198 species. Vascular species were distributed in 71 families. Phytogeographic distribution analysis of species showed the predominance of afromontane species (Mo) in sampled savannahs (31%), followed by East African montane species (Mo, EA) with 22% of all species. Montane endemism proved the predominance of ‘relatively restricted endemic species’ identified in 2or3 montane systems (among Kivu-Ruwenzori, ImatongsUsambara, UluguruMlanje, and Ethiopia with 41.1%) followed by ‘afromontane endemic wades’ identified in 4to7 systems representing 39.9%). ‘Local endemic montane species’ represented 31% of all species. Thus, these savannahs are favourable to species coming from almost seven African montane systems.

Keywords: Nyungwe, Plant communities, montane savannahs.