Soil aggregation is an important process of C sequestration and hence a useful strategy to mitigate the increase in concentration of atmospheric CO₂. We studied water stability of soil aggregates (WSA) and soil organic carbon (SOC) associated with aggregates and primary particles in surface (0-10 cm) and subsurface (10-20 cm) layers of cultivated (khet, irrigated lowland, and bari, rainfed upland) and forest lands (dense Shorea forest, degraded forest and shrub land, pine-Shorea forest, Shorea-pine-Schima forest, and Schima Castanopsis forest) in a mountain watershed of Nepal.

Effects of land use, moisture, temperature and substrate on production of CO₂ and consumption of CH₄ were measured in a series of laboratory incubation experiments on bulk soil samples from 0–10, 10–20, 20–40, 40–60, 60–80 and 80–100 cm soil depths under four dominant land uses [forest, grazing land, irrigated rice on level terraces (Khet), and upland maize–millet on sloping terraces (Bari)] of Mardi watershed (area=144 km²), Nepal. In addition, baseline physical and chemical properties of these soils were measured.