Classification of riparian woody plant communities along the Thamalakane River in northwestern Botswana.

Abstract

There is still paucity of information on the species composition of woody species along the Thamalakane River, northern Botswana, which may limit efforts aimed at conserving riparian woodland species. The current study was aimed at classifying the vegetation, and determining the species composition and diversity of the riparian woodland plant communities along the Thamalakane River. It was hypothesized that there will be no different woodland communities along the Thamalakane River. The 71 sampling plots measured 1000m2 (20m × 50m). In each plot,the percentage cover for each species was estimated following the Braun-Blanquet scale. Different woodland communities were determined through Hierarchical Cluster Analysis followed by Indicator Species Analysis. Multi-Response Permutation Procedures (MRPPs) were used to determine whether or not there was a significant separation between the groups. The Kruskal-Wallis test was used to statistically compare the diversity between woodland communities. Five major woodland communities were identified along the Thamalakane River, namely Vachellia tortilis-Gardenia volkensii, Combretum imberbe-Gymnosporia senegalensis, Philenoptera violacea-Garcinia livingstonei, Dichrostachys cinerea-Flueggea virosa and Croton megalobotrys-Colophospermum mopane. There was significant (p <0.05) separation between the plant groups. Species diversity was highest in Dichrostachys cinerea-Flueggea virosa community and lowest in Vachellia tortilis-Gardenia volkensii community. The distribution of woodland species in along Thamalakane river could be influenced by human disturbance, which may override abiotic environmental conditions such as flooding in influencing the composition and distribution of plant species. This calls for proper management initiatives of the riparian vegetation in the study area. Such initiatives may include establishment of exclosures to promote the germination and propagation of the woodland species. Other strategies may include education and awareness creation of the local communities to promote their co-existence with the riparian vegetation.