Vascular plants in eastern Africa rift valley saline wetlands

Abstract

Plants form a major component of aquatic biota by virtue of their trophic position. Most inland saline ecosystems, particularly lakes in the East African Rift System, are known as spectacular avian habitats. The population density of Lesser Flamingos is especially high due to the frequently high algal biomass productivity, which forms the main food. These environments also provide habitats to a unique vegetation of vascular plants adapted to saline environments. Vascular plants in the littoral zone and the associated floodplains of EARS lakes are dominated by two families-Poaceae and Cyperaceae-but about ten other families are commonly observed in shoreline areas with mild salinity. The two halophytes Cyperus laevigatus and Sporobolus spicatus are common along the shores of most East African saline lakes. Although the contribution of these plants to allochthonous input into the open water may not be significant, they play a significant role in providing nutrition to terrestrial herbivores associated with these ecosystems. The open-water and littoral zones of highly saline lakes are devoid of aquatic macrophytes with a few exceptions where freshwater percolates into the system. In most East African saline wetlands, salinity to some extent limits higher plant diversity. This prevents these ecosystems from being choked by noxious vascular aquatic weeds, particularly floating macrophytes that prefer low salinity conditions. Nonetheless, in some saline wetlands in Australia and parts of Europe, higher plant diversity and biomass occur.