Assessing changes in soil organic carbon stocks and vulnerability to land degradation in Western Ghats, South India: Is it restorative enough?

Soil organic carbon stock is an important universal land degradation indicator. Owing to the depletion in soil nutrients, the pace of land degradation has increased in the Western Ghats of South India. To understand the changes in surface and subsurface soil organic carbon stocks and vulnerability to land degradation upon land use change, a study was carried out along the natural forest and coffee plantation ecosystems of Western Ghats in South India. The study sites were located in Chikmagaluru of Karnataka and Wayanad and Idukki districts of Kerala. Soil organic carbon stocks (SOC) at the surface (0-30 cm) were higher, 9.10 t C ha-1 and 7.49 k t C ha-1 in forest soils of Chikmagaluru and Idukki, respectively, and the subsurface (30-100 cm) SOC stocks were higher in the coffee plantation ecosystems, 9.11, 9.87, and 8.41 t C ha-1, respectively, in Chikmagaluru, Wayanad, and Idukki. Vulnerability analysis revealed that Chikmagaluru forest (0.57) and coffee (0.51), Wayanad forest (0.58) and coffee (0.55) land uses were low, and both the land uses in Idukki were medium in the status of land degradation with scores of 0.65 and 0.60, respectively, in forest and coffee ecosystems. The difference in the status of land degradation was mainly because of changes in soil reaction, surface, and subsurface SOC stock. An increase in soil pH, CEC, and available nutrients upon conversion to coffee plantation along with increased subsurface carbon storage have confirmed the restorative properties of coffee land use even after conversion from natural forests.