Quantitative Assessment of Carbon Sequestration Potential and Biomass Accumulation in Selected Forest Ecosystems of Southern Nigeria

Abstract

This study quantitatively assessed biomass accumulation and carbon sequestration potential across selected forest ecosystems in Southern Nigeria. The ecosystems evaluated included Tropical Rainforest, Freshwater Swamp Forest, Mangrove Forest, Secondary Forest, and Mixed Forest. Field inventory data on diameter at breast height (DBH), tree height, species composition, and density were collected and used to estimate aboveground and belowground biomass through established allometric equations. Carbon stock was derived using standard conversion factors, while carbon dioxide equivalent (CO₂e) was computed to determine sequestration potential. Results revealed significant variation in forest structure, biomass accumulation, and carbon storage among the ecosystems. The Tropical Rainforest recorded the highest biomass (567.4 ± 38.9 Mg ha⁻¹), carbon stock (283.7 ± 19.5 Mg C ha⁻¹), and carbon sequestration potential (1040.2 ± 71.5 Mg CO₂ ha⁻¹), followed by Freshwater Swamp and Mangrove Forests. The Secondary Forest exhibited the lowest biomass and carbon stock despite having the highest tree density, indicating that tree size and forest maturity are stronger determinants of carbon storage than stem abundance. Correlation and regression analyses showed strong positive relationships between carbon stock and forest structural variables, particularly basal area (r = 0.95) and DBH (r = 0.93). The regression model explained 89.1% of the variation in carbon stock, confirming that forest structure and species diversity are key predictors of carbon sequestration potential. The study concludes that Southern Nigerian forest ecosystems are significant carbon sinks with strong potential for climate change mitigation. It recommends the conservation of mature forest stands, restoration of degraded ecosystems, and integration of biodiversity conservation into climate policy frameworks to enhance long-term carbon storage and ecosystem sustainability.