Soil aggregate- and particle-associated organic carbon under different land uses in Nepal

Soil aggregation is an important process of C sequestration and hence a useful strategy to mitigate the increase in concentration of atmospheric C[O.sub.2]. 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. Macroaggregates (>2 mm) were abundant in forest soils (41-70%) while microaggregates ( Abbreviations: BD, bulk density; CEC, cation exchange capacity; DF, degraded forest and shrub land; DS, dense Shorea forest; PS, pine-Shorea forest; SC, Schima-Castanopsis forest; SNK, Student-Newman-Kuels test; SOC, soil organic carbon; SOM, soil organic matter; SPS, Shorea-pine-Schima forest; WSA, water stability of soil aggregates.