Deepened snow cover mitigates soil carbon loss from intensive land use in a semi-arid temperate grassland

Carbon (C) loss due to soil erosion is a major issue in semi-arid
grasslands. The extent of soil erosion is determined by soil properties
and vegetation structure, especially during the non-growing season. In
many Inner Mongolian grasslands, intensive land use, such as overgrazing
and mowing, has severely reduced plant cover and damaged soil structure,
which has exacerbated soil C loss by erosion. At the same time, increasing
winter snowfall due to climate change is stimulating plant growth and
altering plant composition. However, we do not know how changes in winter
snow cover interact with land-use practices to regulate soil C loss due to
erosion. Here, we conducted a six-year snow manipulation experiment under
different land-use practices (control; moderately mowed, MM; heavily
mowed, HM) to measure net changes in soil depth, soil C, plant biomass,
and vegetation structure. After six years, soil C loss under ambient snow
was three times greater in the MM and four times greater in the HM
treatment compared with controls during non-growing season. However,
deepened winter snow alleviated erosion-induced soil C loss by 14%, 47%,
16% in the controls, MM and HM treatments, respectively. The severity of
soil C loss declined with increasing aboveground biomass (AGB), surface
root biomass and vegetation structure. Vegetation structure and AGB
explained more of the variation in soil C loss than surface root biomass,
possibly because a complex canopy and plant cover increases overall
surface roughness, thereby reducing soil C loss. Intensified land use
reduced AGB, surface root biomass and vegetation structure, but deepened
snow increased overall surface roughness by promoting AGB. Hence, our
study demonstrates that deepened snow can alleviate soil C loss due to
land use practices by promoting AGB.