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Land disturbances (such as cultivation and overgrazing) and global warming have been decreasing soil organic C stocks in alpine regions of China. This study characterized changes in soil aggregation, bulk density, particle density, porosity and water holding capacity in relation to changes in total organic C and carbohydrate-C fractions under a long-term (28 years) annually-cultivated pasture (oats), and a short-term (8 years) introduced perennial pasture (cultivated once at establishment), compared with those in an adjacent native pasture. In annually-cultivated pasture, total soil organic C decreased by 29–41% and various fractions of carbohydrate-C decreased by 33–49% (concentrated acid extract), 14–45% (diluted acid extract) and 15–40% (hot water extract) in 0–30 cm depths. To a similar extent, introduced perennial pasture significantly decreased total soil organic C and various carbohydrate-C fractions only at 0–10 cm depth. Upon cultivation of native pasture for hay, soil aggregate stability (expressed as mean weight diameter, MWD) significantly decreased by 27–54% at 0–30 cm depth, with macro-aggregates (> 0.5–5 mm) tending to form micro-aggregates ( |
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