Assessment of Tree Species Diversity and Carbon Storage in Agroforestry Systems in Enugu State, South East Nigeria

Agroforestry systems represent a productive land use option that can simultaneously support food production, biodiversity conservation, and carbon sequestration in rural landscapes. This study assessed tree species diversity and carbon storage capacity in three types of agroforestry systems practised in smallholder farms in Enugu State: homegardens, taungya plantations, and parkland agroforestry. Vegetation inventories were conducted in twenty-five-metre by twenty-five-metre plots across all system types and adjacent natural forest reference sites. Trees were identified, measured for diameter at breast height, and height estimated using a clinometer. Above-ground carbon stocks were estimated using published allometric equations for West African forests. Results showed highest tree species diversity in homegardens, which supported locally adapted fruit trees and timber species arranged in a multi-layered structure. Taungya plantations had the lowest species diversity but highest carbon density per unit area due to high stocking densities of fast-growing species. Parkland systems had intermediate diversity and moderate carbon storage, with species including Irvingia gabonensis and Dacryodes edulis dispersed through food crop fields. Carbon stocks across all systems were substantially lower than reference forest values but significantly higher than monoculture crop fields. The study recommends promotion of homegarden and parkland systems as priority interventions for integrating biodiversity and climate benefits into Enugu State agricultural development policy. Keywords: agroforestry, tree diversity, carbon storage, Enugu State, smallholder farming.