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

Abstract

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 6‐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 6 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 above‐ground 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. A free Plain Language Summary can be found within the Supporting Information of this article.

The grassland carbon cycle: Mechanisms, responses to global changes, and potential contribution to carbon neutrality

“…Overgrazing occurs widely across the world and around 20% of the world's native grasslands have been converted to cultivated crops [ 3 , 130 ]. Overgrazing and agricultural management practices not only reduce surface roughness by altering vegetation coverage and canopy structure [ 131 , 132 ], but also damage surface soil biological crusts [93] , which enhances the strength of strong wind shearing forces to the soil surface [92] . Consequently, large amounts of fine surface soil particles are lost via erosion, reducing soil C stocks [ 95 , 96 ].…”

“…Screening for species with suitable leaf and root traits, strong resistance to climate fluctuations, and complementary functions within the plant community could therefore accelerate C sequestration during grassland restoration [ 9 , 164 ]. In addition, as wind erosion is one of the biggest threats to the loss of topsoil in degraded grasslands, ensuring a complex canopy structure can improve resistance of the system to wind erosion while increasing the ability of the vegetation to capture dust deposition [ 92 , 132 ]. As grassland restoration and management can alter surface albedo, which will feedback to local climate, it is also important to assess how restoration and management practices might affect the grassland water cycle and energy balance [153] .…”

Canopy structure: An intermediate factor regulating grassland diversity-function relationships under human disturbances

“…Communities with more complex canopy structures intercept light more efficiently and conserve more water by reducing transpiration loss, and therefore generally result in higher ANPP [ 24 , 25 ]. For grasslands, where strong wind occurs frequently, the canopy with a higher surface roughness can also act as a physical barrier to resist wind-induced mechanical stress and therefore influences grassland stability [ 26 , 27 ]. With the change of plant species compositions and human activity intensity, canopy structure can be altered greatly [ 28 , 29 ].…”