Changes in soil properties and carbon fluxes following afforestation and agriculture in tropical forest

Anthropogenic land use change (LUC) affects soil quality and the global carbon (C) pool. Such LUC is a potential threat for forest ecosystems because it can alter soil biome and increases the emission of greenhouse gasses (GHGs). Here, we investigated the changes in soil quality and CO₂ emission following afforestation of reclaimed coal mine land and agriculture land created in a tropical dry deciduous forest of Jharkhand, India. Soil samples were collected from afforested mined soil (AMS), agriculture soils (AGS), and the natural forest soils (NFS) and analyzed for physicochemical and biological properties. Soil infiltration rate and CO₂ efflux were recorded in situ, and C balance and emission coefficient (Ci) were calculated to determine soil C dynamics.Our results demonstrated significant alteration in soil quality parameters (decreases/increases based on the individual parameter) in converted land use. Compared to NFS, soil organic carbon (SOC) stocks decreased by 84% in AMS and 50% in AGS, soil CO₂ efflux increased by 35% in AGS and decreased by 43% in AMS, attributed to differences in vegetation and microbial activities among sites. Principal component analysis showed soil infiltration rate, total nitrogen, and clay content were highly influenced by the LUC and explicitly indicate soil quality. The 4-year old AMS was C negative and had a greater Ci value than AGS and NFS, probably due to the lesser vegetation cover and adverse soil properties. We concluded that the conversion of tropical forests to different lands altered soil quality that can be assessed using indicator parameters like soil infiltration rate, total nitrogen, and clay content. Such LUC tends to switch the forest from a sink to a source of CO₂ whether the end use is afforestation or agriculture. However, land degradation due to surface mining activities had a greater impact on soil quality and C sequestration potential than agriculture.