Effects of water depth and livelihood activities on plant species composition and diversity in Nyando floodplain wetland, Kenya

The influence of water levels and livelihood activities on plant species composition, diversity and structuring of wetland ecosystem is a concern as wetlands undergo human exploitation and the increasing threat from climate change. To evaluate the effect of seasonal changes in water depth and human activities, plant density and species composition were assessed in wet and dry seasons and in natural and converted wetland zones of the Nyando papyrus wetland, Kenya. Three transects with different water regimes and livelihood activities were identified. Overall, 30 plant species were identified. In the less disturbed zone, differences between transects were small and 79 % (dry season) to 99 % (wet season) of the plant density consisted of obligate and facultative wetland plants. These groups were dominated by Cyperus papyrus and Vossia cuspidata. In the converted zone, facultative, facultative upland and upland plants became more important with 36 % of the plant density. The seasonally inundated zone had species diversity and species richness increased under dry conditions with more facultative upland species. In the converted zone, disturbance caused by vegetation removal, cropping and other livelihood activities lead to lower soil moisture and more colonization opportunity for facultative and upland species that are more adapted to dry conditions.