Simulating effects of grazing on soil organic carbon stocks in Mongolian grasslands

Grassland degradation is a major issue in many parts of the world. Rehabilitation of areas that have been degraded by overgrazing can potentially accumulate soil carbon, but there have been few studies in the vast grasslands of Mongolia. Here, we calibrated and validated Century model with 618 measurements from a soil inventory covering four grassland types in a forest steppe region of Mongolia. Soil organic carbon (SOC) simulated by Century largely agreed with the observational dataset and the sign of SOC response to intensive grazing. We employed the calibrated model to assess SOC accumulation under reduced grazing intensity scenarios, and the projected accumulation rates were 22.0-36.9 g C m−2 yr−1 in the near term (2012-2035). These results imply that reducing the intensity of grazing may be an effective strategy for restoration of degraded grasslands, which can be implemented by reducing livestock numbers and/or by changing the timing and duration of grazing events. Moreover, the simulated SOC accumulation was mainly determined by a conceptual slow pool, which was not supported by experimental observations in similar soils. Therefore, evaluating the long-term climate mitigation through soil carbon accumulation in degraded grasslands still warrants further attention.