Allometric Estimation of Above-Ground Biomass for Selected Tree Species of the University of Vavuniya

Abstract

Forest ecosystems play a vital role in carbon sequestration, helping mitigate the effects of climate change. However, urban and institutional green spaces, which also serve as potential carbon sinks, are often overlooked in carbon stock assessments. This study aims to estimate the above-ground biomass (AGB) and carbon stock of dominant tree species within the University of Vavuniya to assess their contribution to local climate mitigation. This study assessed the biomass of selected dominant tree species within the academic area (24 ha) of the University of Vavuniya, Pampaimadu premises. Biomass was determined by non-destructive methods. Four species were selected for the study, comprising two native and two exotic species, based on their dominance in the area. Azadirachta indica, Bauhinia racemosa, Tectona grandis, and Mangifera indica were the selected tree species. Measurements included Diameter at Breast Height (DBH), height, and GPS locations. Biomass was estimated using allometric equations. A total of 644 trees from the selected species were recorded, with 539 native and 105 exotic trees. Among the selected species, Azadirachta indica was the most dominant across the area. The total biomass of the study area was estimated at 433.17 Mg, comprising 329.97 Mg of above-ground biomass and 103.20 Mg of below-ground biomass. The average biomass per tree was highest for Bauhinia racemosa (1.18 Mg/tree), followed by Tectona grandis (0.67 Mg/tree), Azadirachta indica (0.48 Mg/tree), and Mangifera indica (0.33 Mg/tree). The corresponding average carbon stock values were Bauhinia racemosa (0.55 Mg C/tree), Tectona grandis (0.31 Mg C/tree), Azadirachta indica (0.22 Mg C/tree), and Mangifera indica (0.15 Mg C/tree). Comparison among species showed that native trees, particularly Bauhinia racemosa and Azadirachta indica, contributed substantially more to total biomass and carbon stock than the exotic species. In terms of total biomass, Bauhinia racemosa (208.31 Mg) contributed the most, followed by Azadirachta indica (172.93 Mg), Tectona grandis (33.59 Mg), and Mangifera indica (18.32 Mg). The results provide baseline information for future carbon monitoring and contribute to the University of Vavuniya’s efforts to promote a carbon-neutral campus. These findings can also inform urban greening and climate adaptation strategies in institutional landscapes.