Original Investigation of the Role of Plant Functional Diversity in Governing Carbon Sequestration and Nutrient Cycling in the Montane Ecosystems of Plateau State

Montane ecosystems provide disproportionately high ecosystem service values per unit area, and understanding how plant functional diversity governs carbon sequestration and nutrient cycling in the Jos Plateau montane ecosystem of Plateau State, North Central Nigeria, represents an original contribution to the ecology of Nigerian highland systems. This study conducted an original investigation of the relationships among plant functional diversity, above-ground carbon stocks, and nutrient cycling rates (nitrogen mineralisation, phosphorus availability, and decomposition rate) across 36 plots distributed across intact montane forest, degraded woodland, and recovering grassland-forest mosaic habitats on the Jos Plateau. Plant functional trait measurements (specific leaf area, leaf nitrogen content, leaf dry matter content, wood density, and root tissue density) were obtained from 148 species representing greater than 90% of plot basal area. Community-weighted mean traits and functional diversity metrics (functional richness, functional dispersion, and Rao's quadratic entropy) were calculated. Carbon stocks were estimated from allometric equations using DBH and height measurements. Nutrient cycling rates were measured using buried ion exchange resins (nitrogen), Hedley sequential phosphorus fractionation, and standardised litter decomposition assays. Structural equation modelling was used to test direct and indirect pathways linking functional diversity to carbon and nutrient cycling outcomes. Results confirmed that community-weighted mean wood density was the strongest direct predictor of above-ground carbon stocks. Functional dispersion (rather than richness) was the strongest predictor of nitrogen mineralisation rate and decomposition speed, consistent with the biomass ratio hypothesis. The study makes an original empirical contribution to functional ecology theory in Nigerian montane systems, demonstrating that trait dispersion rather than species richness drives key ecosystem functions in this highly threatened landscape.

Keywords: plant functional diversity, carbon sequestration, nutrient cycling, Jos Plateau, montane ecosystem