Tree species diversity and stand structure of a peri-urban tropical forest: a case study of Zika forest, Uganda

Abstract

Tree species diversity, density and stand structure were assessed in 30 square plots of (30*30) m in 25ha of Zika Peri-urban Tropical forest, along Entebbe road 23km from the capital, Kampala, Central Uganda. The flora (tree) distribution of Zika forest of Central Uganda is relatively well documented by Polhill in 1952 in the Flora of Tropical East Africa (FTEA) However it has been long from pre-colonial era and ever since much has changed in tree diversity demography over time due to anthropogenic pressure and other Natural factorsThe objectives of this study include,to determine tree species diversity (computation of tree biodiversity indices) in Zika forest reserve and to assess the forest stand structure in terms of diameter size classes. The research data and findings will help us to understand the patterns of tree species composition and diversity that will allow monitoring and management of forest dynamics (species and habitat diversity) over time and to assess the effects of disturbance and climate change on plant demography. Based on a census of all trees with girth or diameter at breast height (DBH) ≥ 5 cm, tree community characteristics like stem density, diversity and species composition. All living trees were recorded by species using an identification guide by Katende and diameter was recorded using a Vanier caliper and a diameter tape for large trees. All trees were assigned to families.A total of 2245 individuals of 35 families and 79 species were recorded, with most dominant families Moracea 12.9%, Fabacea 12.03%, Euphorbiacea 9.04% and Sapotacea9%. Most dominant tree species were Symphoniaglobulifera 8.8%, Garciniabuchananii5.6% and Newtoniabuchananii 5.2% showed the highest percentage values. It was noticed that the most species was contributed by Moracea and of tree density 291- ha, Shannon- Weiner index ranged from 0.055-3.186, the Simpson index ranged between 0.001-0.0383 in plots 13, 15, 19, 14, 27 and 7 respectively.The linear regression analysis carried out with a significance level,∝= 0.05, with a confidence interval of 95% and a P- value = 0.000. Therefore we are 95% confident rejecting the null hypothesis (H0 :), accepting and verifying the alternative hypothesis (Ha :) that there is a significance relationship between the individual number of trees and the tree diameter size. The forest is under a critical threat due to the anthropogenic and up-coming real estate business. Zika Forest is degraded, its regeneration is at risk therefore re-demarcation of the forest, use of other energy alternatives, enrichment planting and deployment of forest guards, Public awareness campaigns, capacity building and stringent punishments should be set. A systematic and comprehensive management plan is required to better conservation and sustainable utilization.