Floristic survey and ecological factors determining the vegetation structure of Taita Hills Hilton wildlife sanctuary
Odhiambo, Ogol Eric
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Taita Hills are located in southeast Kenya, 25km west of Voi in the Taita Taveta district. The surrounding plains have a general altitude of 600-700m above sea level. At the foot of Taita Hills, the Taita Hills Hilton Wildlife Sanctuary covers an area of about 110km2 and in some places rises to an altitude of about 1200m above sea level. The Taita Hills Hilton Safari Lodge, Salt Lick Hilton Safari Lodge and Safari Hilton Camp are located within this Sanctuary. The sanctuary, which has an efficient road system designed to enable game viewing by guests at the three Hilton International (K) facilities, lies adjacent to Tsavo West National Park, to which it is linked by a game corridor stretching over a distance of about 5km. Local herds of the African elephant (Loxodonta Africana Blummenback) are found between Maktau and Kasigau stretches of the National Park, traversing Taita Hills Hilton Wildlife Sanctuary, Lwalenyi Group Ranch and land owned by neighbouring communities. The Taita Hills Hilton Wildlife Sanctuary management has created additional water supplies by deepening the natural clay pans thereby increasing the volume of water retained. The management has also created an artificial water supply in front of the Salt Lick Lodge. By design, the criteria used for particular pans and the artificial water supply primarily in the social requirement of keeping animals within the sanctuary and in the economic value of animal population as a tourist attraction. During the dry season, animal density within the sanctuary increases considerably as the artificial water provided in front of the Salt Lick Lodge becomes the only watering point for most of the game. The resulting high density of elephants and other animals within the sanctuary invariably results in extensive damage to plants, some of which are evidently not regenerating with a considerable loss in habitat and species diversity. The specific objectives of the study included: a floristic survey; assessment of the role of edahic factors on local plant distribution; static ecological survey of the role of elephants in vegetation structuring; development of an up to date vegetation map of the sanctuary and establishment of permanent sampling plots. A total of 142 plants were identified to species level including two endemic species: Zimmermania ovata and podocarpus usambarensis. The study has produced, for the first time, a detailed description of the vegetation of the Hilton Taita Hills Wildlife Sanctuary. The study has shown that elephants play an important role in vegetation structuring and species composition within the sanctuary. The elephants damage trees, effectively killing mature individuals and much of the regeneration base of most natural tree species. It is probable that the elephants create high light conditions that may retard development of natural tree species. The herbs and shrubs such as Acalypha fruticosa then become better competitors and this results in the recession of the riverine community. Detrended Canonical Correspondence Analysis (DCCA) of the relationship between 7 environmental variables and species composition and abundance for the Sanctuary showed that the most important environmental factors are Phosphorus, pH and Calcium. The permanent sampling plots established, with a comprehensive database, provide a time reference for assessing future changes in vegetation and function as a basis for further ecological studies. Finally, the study has suggested avenues for further ecological and social studies to provide adequate knowledge about the environment of Taita Hills Wildlife Sanctuary.