Total and labile pools of organic carbon in relation to soil biological properties under contrasting land-use systems in a dry mountainous region

Abstract

This study evaluated the effect of contrasting land-use systems on changes in pools of total organic carbon (TOC) and its labile fractions, and identified the sensitivity of soil properties as a minimum data set (MDS) for assessing soil quality change in a dry, mountainous Himalayan region in India. The soils under mono (barley/mustard/oats)- and double (barley-buckwheat/barley-turnip)-cropping systems had significantly (p < .05) lower TOC by ∼34 and 20%, while the less labile C (Fract. 3) concentration was lower by ∼46 and 48%, respectively, compared with the agro-forestry (popular/willow). The stable C pool (Fract. 3 + Fract. 4) comprised ∼74, 77, 86, 74 and 73% of TOC in soils under mono-cropping, double-cropping, agro-forestry, orchards and vegetable crops, respectively. Land-use significantly impacts the sensitivity of labile C fractions, viz. water extractable organic C (WEOC), microbial biomass C (MBC) and organic C fractions of variable oxidizability (i.e. Fract. 1, Fract. 2, Fract. 3 and Fract. 4). The sensitivity analysis showed a change of ∼21.5–56.2% in the TOC pool, with the highest change for soils under vegetable crops and the lowest for double-cropping. Soil protein exhibited a significant relationship with TOC and its fractions, enzymatic and biochemical properties, and soils’ fine fraction (silt and clay). The stable C pool exhibited a significant linear relationship with soils’ finer fraction (silt = 0.82**; clay = 0.78**, p < .01), indicating that the mineral matrix had a profound influence on C stabilization in soils. The land-use systems with higher soil total glomalin (TG) content had higher moisture retention capacity and stable C pool. The principal component analysis (PCA) identified TG, Fract. 3 and available-K as most important soil quality indicators for discriminating change in soil health in a cold, dry Himalayan region.