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Large-scale land degradation occurs in the foothill Himalayas mainly because of soil erosion, accelerated by tillage and poor management practices in agricultural lands and encroachment of land under forest cover. Land use exerts both direct (through C additions) and indirect (through its impact on soil erosion) influence on soil carbon. Partitioning of Total Carbon (TC) in organic and inorganic forms in degraded soils was studied, and compared these with soils under agriculture, horticulture and forest systems. Highest Total Organic Carbon (TOC) was recorded in forest soils followed by horticultural systems, whereas the least was observed in degraded and agricultural systems while Inorganic Carbon (IC) decreased in the sequence of: degraded lands > forest > agriculture ≥ horticulture. TOC stocks in the upper half-a-meter layer were 163.9 Mg ha−1 in forest soils followed by horticulture (144.7 Mg ha−1) while in case of TC, the degraded lands closely followed forest soils. The contribution of IC to TC was about 39% in degraded lands, which was about twice that of its contribution in forest soils. TOC decreased with soil depth whereas IC increased with depth. The increase in IC with depth was minor for agricultural and horticultural soils, whereas it was about 84% for degraded and about 61% for forest soils. Our study highlights the impact of erosion on dynamics of soil carbon and its partitioning and suggests the need to promote better carbon sequestering land use systems towards conservation of top carbon rich soil and promoting sustainability in hill ecosystems particularly in Himalayas. • Total carbon was partitioned into organic and inorganic forms. • Highest TOC was recorded in forest soils, whereas maximum IC was in degraded. • IC was 39% of the TC in degraded lands, which was twice that of in forest soils. • Degraded soils were at par with agricultural soils with respect to TOC. • Increase in IC carbon with depth was 84% for degraded lands. [ABSTRACT FROM AUTHOR]

A study was conducted to assess the impact of different land use systems on labile C pools and soil organic carbon stocks in the foothill Himalayas. Soil samples were collected from four different land use systems viz. agriculture, forest, horticulture and degraded lands from each of the seven locations up to a depth of 0.5m. Potassium permanganate oxidizable (KOC) and microbial biomass carbon (MBC) followed the trend: forest>horticulture>agriculture>degraded lands in each of the depths. In case of soil organic carbon (SOC), agriculture and degraded lands had similar levels. Soil organic carbon stocks in the top half a meter soil were highest in forest soils [47.5 Mg ha-1 (±2.49)] followed by horticultural systems [42.4 Mg ha-1 (±2.92)], degraded [36.3 Mg ha-1 (±4.40)] and agricultural lands [35.1 Mg ha-1 (±3.51)]. Agricultural and degraded lands had up to 25% lower SOC stocks than forest soils, indicating that deforestation or conversion of forest land to agricultural uses is contributing to losses of up to 12.4Mgha-1 SOC over time from the top half a meter layer of soil. The typical decrease of carbon content with depth was the sharpest for agricultural soils, where the values in the lowest depth (30-50cm) were nearly 50% (MBC and SOC) or over 50% (KOC) of that in surface. Among the different carbon pools KOC seemed to be strongly related with soil textural properties including CEC, but overall it seems that land use played a major role in determining C levels in soils. [ABSTRACT FROM AUTHOR]