Comparative evaluation of tree species populations under different land use types within the university of port harcourt environs

Abstract

Impact of land use changes and varying levels of habitat disturbance on tree populations was evaluated using the spatial analogue technique of studying ecosystem dynamics. Three sites with low, moderate, and high levels of disturbance were purposively chosen from the Biodiversity Conservation Area (BCA), an Unprotected Secondary Regrowth (USR), and an Arable Farmland (AF) respectively, for the study. Tree density and alpha diversity were evaluated in each site. The level of tree species compositional similarity/variation was also ascertained for each pair of the sites, and the extent of change in populations of individual tree species measured for the unprotected sites – USR and AF. Total tree density was highest in BCA (466 trees/hectare) followed by USR (317 trees/hectare) and AF (73 trees/hectare). Tree diversity was highest and lowest in BCA and AF respectively. Tree species compositional variation was higher between BCA and each of USR & AF (66.7%), than between USR and AF (57.1). Harungana madagascariensis, Berlinia grandiflora, and Eleais guineensis were the most abundant tree species in BCA, USR, and AF, respectively. Although, populations of many tree species were found to be drastically reduced or completely lost in the unprotected sites, improvement was observed in populations of few species with Spondias mombin having the highest improvement index (314.29%) in USR while E. guineensis had the highest improvement index (72.7%) in AF. S. mombin is highly valued in the study area because of its edible fruits and diverse medicinal attributes while palm oil and palm kernel oil from E. guineensis contribute immensely to rural livelihoods. Hence, the rural dwellers tend to favour and encourage their growth.