Soil organic carbon pools and stocks in different land uses of a temperate Himalayan region

Land use is a main driver of carbon storage in terrestrial ecosystems, particularly under the resource constrained and temperate mountains of the Himalayas. Impact of different land uses on soil organic carbon (SOC) and its functional pools were recorded from two depths (0–15 and 15–30 cm). The study included seven different land use types, namely wetlands, forests, grasslands, apple orchards, vegetable fields, maize (Zea mays L.) and rice (Oryza sativa L.) fields. The average total SOC in surface and sub-surface soil layers of wetland, forest and grassland soils taken together was 2.6 times higher than average SOC recorded in cropped soils. Average labile carbon in the surface soil layers of wetlands was 11.20 g kg−1. Forests, grasslands, apple orchards, maize, vegetable and rice fields had 39, 25, 21, 20, 18 and 18 per cent more labile carbon, respectively compared with wetland soils. The wetlands store the highest quantity (28 Mg ha−1) of particulate organic carbon in the 0–30 cm soil layer, whereas vegetable soils of the zone retain the least (7 Mg ha−1). The microbial biomass carbon concentration in the rice soils (0.22 mg kg−1) was lowest, however, the highest concentration (0.87 mg kg−1) was observed in wetland soils. The greatest carbon management index among the soils was recorded in forest land use followed by grassland. The total SOC stocks were 18.84 to 61.09 Mg ha−1 in rice and wetland soils, respectively. Therefore, the carbon losses due to land use conversion from wetlands into rice or vegetable fields, and conversion of forest into maize fields are about 40 and 10 Mg ha−1, respectively, in the 0–30 cm soil layer.