The effect of human disturbance on tree species composition and demographic structure in Kalinzu Forest Reserve, Uganda

摘要

Tree abundance and species composition in the mechanically logged, intensively pitsawn and minimally disturbed areas of Kalinzu Forest Reserve were determined. The spatial and diameter size-class distribution of ten selected tree species representing pioneer, secondary colonizer, understorey, canopy, dominant and endangered species were also assessed. The species were: Musanga leo-errerae, Trema orientalis, Funtumia africana, Strombosia scheffleri, Oxyansus speciosus, Parinari excelsa, Tabernaemontana holstii, Newtonia buchananii, Lovoa swynnertonii and Entandrophragma angolense. The mean stem density of all trees >= 0.5 m in height was 2809.1 per hectare and 150 species were enumerated in the three forest areas. Most individuals (47.73%) and species (75.0%) were recorded in the minimally disturbed and least in the mechanically logged areas. Of the selected species, F. africana was the most abundant (n = 789) and widely distributed in each of the areas. Entandrophragma angolense was the least abundant (n = 63) and most of its individuals (74.6%) were recorded in the minimally disturbed area. Funtumia africana and S. scheffleri (subcanopy), O. speciosus and T. holstii (understorey), N. buchananii (canopy) and P. excelsa (an upper canopy and a climax species of this forest reserve) had an inverse J-shaped diameter size-class structure while pioneer species (M. leo-errerae and T. orientalis) had a bell-shaped size-class structure.