地球科学と気候変動ジャーナル

抽象的な

Effects of Enrichment Planting On Population Structure, Diversity and Canopy Cover of Indigenous Tree Species in Mount Kenya Forest, Kenya

Peter G. Njoka, Charles M. Warui, Purity G. Limbua

This study aimed at assessing the role of enrichment planting on population structure, diversity and canopy cover in open gaps in an indigenous tropical forest. Five selected indigenous tree species namely Croton megalocarpus, Fagara microphylla, Markhamia lutea, Newtonia buchananii and Vitex keniensis were investigated. Systematic random sampling was conducted on two sites namely, the enriched and control sites where five study plots of 100m by 20m each were established. There was no significant difference in overall mean tree density and the mean density of seedlings between the enriched and control site, F (9, 4) =1.19, p=0.33 and F (9, 4) =0.64, p=0.75. However there was a significant difference in mean sapling density, F (9, 4) =2.16, p=0.04. There was no significant difference in mean density of adults trees, F (9, 4) =1.5, p=0.18 nor mean DBH, F (9, 4) =0.8, p=0.62. There was significant difference in mean tree height, F (9, 3) =2.39, p=0.04 and in mean diversity of indigenous trees, F (1, 4) =124.6, p=0.0004. There was no significant difference in mean canopy cover, F (9, 4) =0.26, p=0.98. The study established that areas left out of enrichment planting exhibited a remarkably lower density of trees in the forest. Seedlings and saplings formed the majority of trees compared to the low number of adults on both the enriched and control sites. Overall study established anthropogenic disturbances to markedly disrupt the forest. Species richness was notably higher on the control site where enrichment planting was not carried out. Canopy cover was found to be slightly higher on the control site where no trees were replanted after logging. A combination of silvicultural techniques are recommended to restore such forests. In addition a mixture of both indigenous and exotic tree species is necessary to improve the overall forest structure.