Abstract/Overview
Forest fragmentation occurs when large continuous forests are perforated by small holes or broken up into edges and smaller patches to form a non-perforated matrix of open spaces. Global researches have shown that primary attributes of the remnant forest fragment that may influence patterns of species richness include: fragment area, fragment isolation, fragment edge to interior ratio, and the fragment shape complexity. In Sub Saharan Africa, for example, high human population densities resulting from rapid increase of population has led to numerous anthropogenic activities with negative impacts on forest fragments, consequently, affecting the tree species richness. Various studies on Kakamega forest have generally revealed effects of fragmentation and habitat loss emanating from anthropogenic activities. Few studies have analyzed the influence of forest fragmentation attributes such as total edge length, edge density on tree species richness and tree species relative abundance. The theoretical approach guiding this study was based on the Island Biogeography Theory. The purpose of this study was to assess the influence of forest fragmentation on tree species richness in the fragments of Kakamega forest, Kakamega County. The specific objectives of this study were to: determine the influence of total edge length of forest fragments on tree species richness in the detached fragments of the Kakamega forest; establish the influence of the edge density of the forest fragments on tree species richness; and assess the influence of edge density and total edge length on tree species relative abundance. The study adopted a cross-sectional correlational research design. Proportionate random sampling was used. A sample of 30 plots each measuring 2m by 2m was established randomly in the fragments (0-200m from the edge towards the interior);Malava: Kisere: Ikuywa in that order for field sampling and measurements. Data was collected using tools such as measuring tapes,metre rule,GPS 64s Garmain and suunto inclinometer. A total of 39 species of trees were recorded from the three fragments with Funtumia africana being recorded as the most abundant species. The results show that 96%, 95%, and 96% variation of tree species richness in. Malava (r2 = 0.96), Kisere (r2 = 0.95) and Ikuywa (r2 = 0.96) in that order can be explained by the total edge length of the fragments. Moreover, 83%, 85%, and 92% variation of tree species richness in. Malava (r2 = 0.83), Kisere (r2 = 0.85) and Ikuywa (r2 = 0.92) in that order can be explained by the edge density of the fragments. The 92%, 83% and 92% variation of tree species relative abundance in Malava (r2 = 0.92), Kisere (r2 = 0.83) and Ikuywa (r2 = 0.92) in that order can be explained by the total edge length of the fragments. The edge density also explained 87%, 94% and 94% variation of tree species relative abundance in Malava (r2 = 0.87), Kisere (r2 = 0.94) and Ikuywa (r2 = 0.94) in that order. It was concluded that tree species richness and tree species abundance in the detached portions of Kakamega forest were dominantly influenced by forest fragment total edge length and fragment edge density. For us to conserve more tree species we recommend maintenance of the total edge length of the fragments above 15km with edge density (3.413.79mm2) in order to maintain high tree species richness and tree species relative abundance