Identification of Plant Species along the Riparian Corridor of the Iguameti Stream in Laikipia County Kenya

Abstract

Abstract This study presents the first characterization of riparian vegetation on Iguameti Stream as well as a description of anthropogenic activities within the riparian corridor. Study points fell within the upper reaches of the stream within Laikipia University and lower reaches with a high density of human settlements and farming activities. Sample plots (30m×10m) in the upper and lower reaches of the stream were selected in the phytocoenoses of the study area in such a way that each sample plot was visually homogenous and that all floristic variation in the area was sampled. Based on physiognomical classification, three types of vegetation formations were identified: afromontane forest, woodland and swamp vegetation. Human activities include: introduction of exotic species; timber harvesting; damming; stream channelization; livestock grazing; and land tillage. The upper reaches exhibited minimal disturbance, a detailed vertical stratification with ample canopy, understory, shrub, herb layer, and ground cover dominated by indigenous vegetation. Trichocladus ellipticus, Allophylus sp., Teclea sp, Dombeya goetzinii, Ficus natalensis, Rhus natalensis, Pavonia urens and Cyathula cylindrical were dominant, while in the lower reaches, Pittosporum viridiflorum, Cupressus sp., Eucalyptus sp., Crotalaria agatiflora, Rhus natalensis, Hibiscus fuscus, Hypoestis verticillaris and Rubus sp. were dominant. Species loss was reported in the lower reaches where the buffer strips ˂5m on the left and right banks compared to ˃20m in the upper reaches. Steam damming has caused replacement of riparian vegetation with wetland plants like Crassula schimperi, Hydrocotyl sp., Oenanthe palustris, Sphaeranthus steetzi, Rorippa sp., Polygonum pulchrum, Typha sp. and sedges mainly Cyperus spp. and Fimbristylis sp. Canopy cover decreased from >90% in the upper reaches to < 60% in the lower reaches. Riparian vegetation loss in the upper reaches may cause habitat loss for Colobus guereza kikuyuensis and Aonyx capensis. Urgent strategic multi-disciplinary management of the riparian zone is needed to limit biodiversity loss. Keywords: Biodiversity conservation, climate change, Laikipia County, riparian vegetation, species loss