Human Use Of Forest Trees And Its Impact On Tree Diversity And Abundance In Chemususu Forest, Baringo County, Kenya

ABSTRACT 

Trees provide both direct and indirect benefits to humans, who depend on them for their livelihoods. Forest ecosystems are vulnerable to over-utilization and exploitation due to the sensitivity of its complex and highly diverse ecosystem. The aim of the study was to determine the human impact on tree species diversity, abundance, plant population structure and uses of forest trees by local communities adjacent to Chemususu forest Reserve in Koibatek Sub-County, Baringo County. Questionnaires and interview schedules were used to collect data on uses of trees; the target group were households within 3km stretch from the forest edge. The data on trees species, diversity, abundance and plant population structure was collected by systematic sampling using six parallel belt transects each starting from the forest edge. Sampling was conducted in quadrats of 20m x 20m (for trees) located along the transects at 500m intervals. In each of the quadrats, all the trees species were identified, counted and diameter at breast height (DBH), measured at 1.36m outside the bark to the nearest cm. Indicators of human disturbance were assessed to determine the extent of human impact. The Statistical Package for Social Sciences (SPSS) was the main tool for quantitative data analysis from both questionnaires and interview schedules. Analysis of Variance (ANOVA) was used to test whether the mean number of cut stems and debarked trees varied with distance from forest edge. ANOVA was also used to test for variation in the mean diversity indices, tree species abundance and DBH with distance from forest edge. In both cases, tukey test was used to separate the means. Shannon-Wiener Diversity index (Magurran, 1988) was computed. Pearson’s correlation was carried out to determine the relationship between abundance of cut stems and debarked trees with distance from human settlement in each study plot and to investigate the relationship between mean species abundance, diversity, and DBH with distance from human settlement. Majority of the local residents had stayed in the region for more than 15 years and perceive the forest as important for various uses, 98.4% for spiritual and cultural purposes, timber (97.52%), tourism and recreation (96.3%) and hunting (97.1%).Three trees species, Olea europaea, Dombeya torrida and Olea capensis were used for firewood as well as charcoal and formed a large proportion of used trees. Trees used for timber Juniperus procera, Podocarpus falcatus and the exotic cupressus lusitanica had been heavily extracted. There was no significant relationship between the number of charcoal kilns and distance from the forest edge (r = - 0.849; P=0.069). This also applied to the number of plots with evidence of pit sawings with distance from the forest edge (r = 0.555; P =0.333) but the number of plots with split stems decreased significantly with distance from the forest edge (r = -0.892; P = 0.043).There was no significant variation in the mean number of cut stems and mean number of debarked trees with distance from human settlement (F(4, 25) =0.082; P= 0.546) and (F (4, 25) =1.795; P=0.162), respectively. Tree diversity did not vary with distance from human settlement (F (4, 25) = 1.67; P=0.189).There was a significant difference in the mean number of trees in different DBH classes (F (4, 25) = 5.181; P =0.002). The number of trees on the lower DBH classes was more than those on the higher classes at various distance intervals, but this difference was not statistically significant. The study showed that the community role in forest degradation was significant and they highly depended on it for their livelihood. Thus, it was important to understand the relationship between the community and the forest. Alternative sources of trees used for timber and charcoal should be encouraged to reduce pressure on forest trees.