Spatio-Temporal Variation in Species Diversity between Plantation and Secondary Forest of Kakamega Tropical Rain Forest in Kenya

The Kenyan tropical rain forest is under imminent threat of degradation due to the changes in climatic condition and rapid growing human population. This study determined the changes in woody species diversity between natural forest (secondary forest) and plantation forest during different stages of plant succession. The secondary data from three forest blocks was obtained from Kenya Forest Research Institute and used to derive species diversity. Variation in species diversity and abundance was analyzed by SPSS software. Species richness was significantly different between plantation and secondary forest types (P<0.001). Shannon diversity index (H') values ranged between 0.3 and 3 where highest H' was in a middle aged secondary forest. Vegetation types with low species diversity had higher species evenness. Stem density was highest in the secondary forest (1900±18.57 stems ha-1) compared to the plantation forest (516±20.27 stems ha -1). The age of forest influenced the species richness in the plantation forest but species composition strongly influenced species richness in the secondary forest. Therefore, maintenance of higher species diversity in the secondary forest requires protection of remnant species which facilitates recruitment of new species while conservation of rare mature species could facilitate higher diversity in recovering plantation forest. There is need to change the current management practices, which is hardly suitable for maintaining the required plant biodiversity in the Kakamega forest.