Estimation of Biomass Carbon Storage and Ecological Values of Urban Forest at Chulalongkorn University and its Implications for Carbon Management

Abstract

Rapid urbanization and increasing greenhouse gas (GHG) emissions over recent decades have intensified climate change and air pollution. However, limited studies have quantified carbon storage and ecosystem services of tropical university campus forests using large-scale inventories and site-specific environmental data, particularly in Southeast Asian megacities such as Bangkok. This study aims to quantify biomass carbon storage and assess key ecosystem services of the urban forest at Chulalongkorn University (CU) and to evaluate their implications for campus-level carbon management. In this assessment, a total of 2,394 trees from a complete tree inventory collected in 2021 and 2022 were analyzed. Biomass carbon storage was estimated using both allometric equations and i-Tree Eco model as complementary approaches under different assumptions and to reflect potential variation between two methods for open-grown urban trees. In addition, the model was employed to evaluate major regulating ecosystem services, including carbon sequestration,
air pollution removal, avoided stormwater runoff and oxygen production. To improve local representativeness of model inputs, site-specific hourly meteorological and air pollution data were incorporated. The results revealed that total biomass carbon storage was 1,914.47 tons (7,019.01 tCO₂e) based on manual calculations, whereas the i-Tree Eco model estimated a higher value of 2,796 tons. Furthermore, campus trees were found to sequester 97.81 tons of carbon annually and remove approximately 2.15 tons of air pollutants per year. They also contributed to stormwater management by reducing runoff by 6,460 m³ annually and produced about 260.8 tons of oxygen. Among all species, large and dominant trees in the study area, particularly Albizia saman, contributed the most to overall ecosystem services. The findings highlighted the role of urban forest in supporting carbon neutrality goals, tree conservation prioritization, green infrastructure planning and environmental management of the university, while demonstrating their broader value as nature-based solutions for climate mitigation and urban resilience.