Early growth and insect herbivory of Neoboutonia Macrocalyx seedlings in different sized gaps in Kabale National Park

Abstract

Gap size is considered as a key factor to tree colonization and succession. Small gaps often show a species composition that is distinctly different from larger gaps. This species niche differentiation is influenced by plant life and herbivory. Early growth, survival and insect herbivory of Neoboutonia macrocalyx seedlings in different sized gaps in Kibale National Park were investigated. The aim of this study was to assess the regeneration potential of Neoboutonia macrocalyx seedlings in gaps of different sizes in Kibale National Park. To achieve this aim, data were collected from Neoboutonia macrocalyx seedlings planted in 22 gaps in Kibale National park. For each gap, the gap size and canopy openness were determined. Gaps were grouped into small (≤ 500 m2), medium (>500≤ 1000 m2) and large (>1000 m2). Four plots of 50x50cm were established in each gap. In each plot, ten N. macrocalyx seeds were sown. After one month, the following growth parameters were observed monthly in each gap for a period of six months: seedling height (cm), leaf area (cm2), total number of leaves and number of new apical leaves developed per month. Herbivory was determined by calculating the percentage of leaf area missing and seedling survival was determined by counting the number of seedlings that were still alive at the end of the experiment (six months). It was found that seedling growth increased with increase in gap size and herbivory was higher in small gaps than in large gaps. Seedling survival was higher in large gaps than small gaps. These results indicate that regeneration of N. macrocalyx is best in gaps that are over 1000m2. It is recommended that N. macrocalyx should be used in large gaps as a colonizing tree species to restore the lost forest trees and enrichment planting should be encouraged where natural regeneration has failed.