Mycorrhizal Diversity, Function, and Soil Carbon Dynamics in Degraded and Restored Tropical Forests of Akwa Ibom State

Arbuscular and ectomycorrhizal fungi are central mediators of soil carbon stabilisation, nutrient cycling, and plant community assembly in tropical forest soils, yet their diversity, functional attributes, and role in post-degradation soil recovery in Nigerian coastal forests remain entirely uncharacterised. This study investigates mycorrhizal diversity, functional guild composition, and soil carbon dynamics across a forest degradation and restoration gradient in Akwa Ibom State, representing the first comprehensive mycorrhizal ecology study in Nigerian coastal forest ecosystems. Five stand types were studied: intact forest, lightly degraded forest, heavily degraded forest, early-stage restoration (three years), and advanced restoration (ten years). Metabarcoding of soil environmental DNA using the ITS1 and ITS2 amplicons generated mycorrhizal community profiles from 180 soil samples across the gradient. Functional guild assignments were derived from FUNGuild database classifications. Mycorrhizal biomass was estimated using ergosterol extraction and phospholipid fatty acid analysis. Soil organic carbon fractionation distinguished mineral-associated and particulate organic matter pools as proxies for mycorrhizal-mediated carbon stabilisation. Results reveal a 74% decline in arbuscular mycorrhizal fungal species richness and a 58% decline in ectomycorrhizal richness in heavily degraded stands compared to intact forest. Mineral-associated organic matter fractions were significantly correlated with ectomycorrhizal biomass across the gradient, indicating a functional link between mycorrhizal community structure and stable carbon formation. Advanced restoration plots showed partial mycorrhizal community recovery but remained distinct from intact forest in functional guild composition. The study recommends mycorrhizal inoculation of restoration plantings as a management intervention to accelerate soil carbon recovery. Keywords: mycorrhizal fungi, soil carbon, forest restoration, metabarcoding, Akwa Ibom State