Biomass carbon stocks and sequestration potential of remnant forests in the subtropical highlands of Ethiopia

Abstract

Forest fragmentation and anthropogenic disturbances adversely affect carbon sequestration by reducing forest structural integrity, biomass accumulation, and ecosystem functioning in tropical landscapes. In the northwestern Ethiopian highlands, forests persist mainly as highly fragmented remnants; however, the extent to which fragmentation alters their carbon sequestration potential remains insufficiently quantified. This study assessed the effects of forest patch size and disturbance intensity on carbon stocks across aboveground biomass, belowground biomass, litter, and soil organic carbon pools. Data were collected using 20 m × 20 m plots for trees, with nested 5 m × 5 m subplots for shrubs and litter. A total of 71 woody species belonging to 33 families were recorded across small, medium, and large forest patches. Large forest patches stored significantly ( p < 0.05) higher carbon stocks, with 588.3 Mg CO 2 e ha −1 in biomass, 2.72 Mg CO 2 e ha −1 in litter, and 580.8 Mg CO 2 e ha −1 in soil organic carbon, compared with medium and small patches. Carbon stocks were positively associated with forest patch area and negatively with disturbance intensity. Protecting large forest patches, restoring degraded forest fragments, and improving landscape connectivity will be essential policy measures for enhancing carbon sequestration and maintaining ecosystem integrity in fragmented tropical landscapes.