Ale Olanrewaju Olabode^1,, Oke David²

This study was conducted to investigate the impact of forest degradation on the status of total, particulate and mineral-associated soil organic carbon content. This study was carried out in three selected sites based on the level of degradation (undisturbed, partly degraded and degraded forest parts) in Akure Forest Reserve which is geographically located in a humid rainforest zone of Akure South local government area of Ondo State, Nigeria. Four sampling plots of 25m x 25m in dimension were laid in alternate positions along the transect cut through each of the selected forest sites. Soil core samples were collected at 5 different points along the diagonal of each plot at the depths of 0-10cm, 10-20cm and 20-30cm using a soil auger. At the end of this study, it was found that total organic carbon (TOC) was highest in soil under partially degraded forest and the lowest in soil from undisturbed forest. Particulate organic carbon (POC) was highest in partially degraded forest (9.71) and lowest in undisturbed forest (7.89). In contrast, soil under undisturbed forest had the highest mineral-associated organic carbon (14.32), while soil under degraded forest had the lowest (13.21). The results of the analysis show a significant difference at P>0.05 among the different forest degradation type and across soil depths (0-10 cm > 10-20 cm > 20-30 cm). Soil under partially degraded forest stored significant organic carbon due to litter deposition from illegally felled trees, enhancing carbon levels. This soil also shows improved physicochemical properties. The stable fraction of organic carbon (MOC) was highest in soil under undisturbed forest, while particulate organic carbon (POC) peaks in soil under partially degraded forest. The study also assessed soil physical and chemical properties, finding that degradation led to increased bulk density and reduced porosity, potentially affecting water retention and root penetration. pH levels were slightly lower in degraded areas, while available phosphorus and total nitrogen showed marked decreases. These findings highlight the significant impact of forest degradation on soil carbon stocks and overall soil health, emphasizing the importance of forest conservation for maintaining ecosystem services and mitigating climate change.

Forest degradation, soil organic carbon, carbon sequestration, tropical forest ecosystems, soil properties