Effect of Disturbance On the Population Structure and Regeneration of Trees: A Case Study of Acacia xanthophloea (Benth) Woodland in Ol-Pejeta Conservancy in Kenya

Abstract

Tree damage was assessed in 1540 Acacia species (A. xanthophloea) in Olpejeta Conservancy. Using belt transects measuring (20 x 50 m), trees in the sample sites (closed and open) were counted. Measurements were made of Acacia tree count, recruits count, diameter at breast height, and mortality for both adult trees and seedlings. Densities were significantly higher in enclosed areas (398.3 ± 16.60 trees/ha) than open areas (243.3 ± 10.13) trees/ha. Elephants recorded the highest damage to the sampled trees with 54.55% damage while human beings caused 12.85% of the damage. Browsing was the main form of damage in open areas. Mean height for enclosed and open sites was 3.77 ± 4.61 and 5.35 ± 8.81, respectively. These findings suggest that herbivory damage did not have a significant effect on seedling regeneration but rather had an effect on population structure. Debarking caused by elephants occurred in the open areas with the highest being 96% of the sampled trees in the 11-25% damage class. The diameter class quotients fluctuated, an indication of the unstable population thus suggesting the impact of herbivory on population structure. Key recommendations include the creation of more enclosure zones, winning back more space by controlling the densities of browsers, long-term monitoring and the promotion of recruitment and regeneration rather than reducing mature tree loss.