Effect of grazing exclusion and rotational grazing on labile soil organic carbon in north China

Abstract

Overgrazing has caused serious grassland soil deterioration and significant soil organic carbon (SOC) losses. Controlled grazing is recommended for restoring grassland and enhancing SOC stocks. Studies have suggested that, in particular, labile organic carbon (C) is a sensitive indicator for soil degradation and SOC recovery, but few studies of the effect of different grassland management practices have been published so far. Here, we investigate the effects of long‐term grazing exclusion and short‐term rotational grazing with different grazing intensities on labile SOC, including hot water extractable organic C (HWEC) and particulate organic C (POC), as well as potential N mineralization (Nmin) rate in soils (0–10 cm) of two grasslands in Xilinhot, Inner Mongolia. Treatments include long‐term (34 years) exclusion, medium‐term (21 years) exclusion and continuous grazing (ambient grazing) at one of the sites, and we investigate no grazing, light grazing, moderate grazing and high‐grazing intensity at the study site for rotational grazing. Our results show that grazing exclusion significantly enhances labile SOC stocks and potential Nmin rate compared to ambient grazing (e.g., POC stock at long‐ and medium‐term exclusion and ambient grazing are 5.71 ± 0.94 Mg C ha−1, 3.25 ± 0.30 Mg C ha−1 and 2.12 ± 0.38 Mg C ha−1, respectively). However, after two decades of exclusion, the potential for further C sequestration is limited. Five years of rotational grazing significantly enhances HWEC, but not POC and potential Nmin rate, when comparing the highest grazing intensity (1.88 sheep ha−1 yr−1) with grazing exclusion during the same period. We conclude that rotational grazing may be a viable alternative to exclusion, offering a more rational use of grassland without causing soil C loss. We also show that HWEC is a particularly sensitive labile SOC indicator and is tightly correlated to POC and potential Nmin rate. Highlights We investigated effects of grazing exclusion and rotational grazing on labile soil organic carbon. Grazing exclusion increased labile SOC and the highest level appeared in medium‐term exclusion. Five years of high‐intensity rotational grazing increased HWEC with no significant effects on POC. Rotational grazing is a viable alternative to grazing exclusion management.

Grazing accelerates labile and recalcitrant soil carbon loss driving by rare microbial taxa in a desert steppe

“…However, we found grazing remarkably decreased labile organic C (DOC, MBC, and POC), which could be attributed to the decrease in plant C input. Aboveground and belowground biomass decreased by 15–43% and 11–29% with the increasing of grazing intensity at our experimental site (Figure S4), which in turn decreased the contribution of litter inputs and root exudates to labile organic C. Our result is consistent with previous reports that grazing could significantly decrease the labile organic C fraction in comparison with grazing exclusion (Dong et al, 2021; Wiesmeier et al, 2012). Labile organic C, relatively young organic C fractions with high turnover rates, have been widely used as an indicator of SOC dynamics (Six, Merckx, Kimpe, Paustian, & Elliott, 2000) since it is more sensitive to disturbance than total SOC (Spohn & Giani, 2011).…”

The global carbon sink potential of terrestrial vegetation can be increased substantially by optimal land management

“…Rotational grazing feeds animals in different fields in rotation depending on the forage condition. Both exclosure and rotational grazing are believed to be good strategies that have proved effective in protecting vegetation 58 . In addition, restgrazing allows grazing fields to be rested and grazed on a rotational base.…”

Effect of Grazing Exclusion and Rotational Grazing on Soil Aggregate Stability in Typical Grasslands in Inner Mongolia, China

“…Recently, several policies (e.g., Prohibiting Grazing Policy and Returning Grazing Lands to Grasslands) were implemented to restore the degraded grassland in northern China. When grazing is excluded, as the input of organic matter increases, it may have a beneficial effect on soil organic carbon (SOC) and physical structure, but excessive litter accumulation on the surface soil immobilizes organic carbon (Reeder and Schuman, 2002) and inhibits plant growth (Xiong and Nilsson, 1999;Dong et al, 2021). So, long-term absence of grazing may inhibit important ecosystem functions.…”