Effect of Selective Logging Regimes on Biodiversity and Ecosystem Function in Sapele Division, Delta State

Selective logging remains the dominant timber extraction system in Nigeria's lowland rainforests, yet evidence-based evaluation of how different selection intensities affect biodiversity and ecosystem function is scarce in the national literature, limiting the development of credible reduced-impact logging standards. This study examines the differential effects of low-intensity (less than five stems per hectare), medium-intensity (five to ten stems), and high-intensity (over ten stems) selective logging on plant species richness, bird diversity, soil carbon, and litter decomposition rates in Sapele Division, Delta State. A stratified sampling design matched logged sites by pre-harvest floristic composition, using unlogged forest as controls. Vegetation, bird, and soil assessments were conducted in permanent plots at one, three, and five years post-harvest. Mixed effects models were used to isolate logging intensity effects from natural variation. Medium-intensity logging produced no statistically significant effect on plant species richness relative to controls at five years post-harvest, while high-intensity sites showed persistent species richness deficits and significantly altered canopy structure. Bird assemblage composition shifted substantially in high-intensity logged areas, with forest interior specialists declining and generalist species increasing. Soil carbon declined significantly only in high-intensity plots, attributed to compaction and reduced litter input. The study proposes a maximum threshold of seven stems per hectare as a scientifically grounded sustainability standard for selective logging in the Sapele ecotype, alongside mandatory gap-planting of commercially important species. Keywords: selective logging, biodiversity, ecosystem function, Delta State, reduced-impact logging