Distribution of soil organic carbon and potential carbon sequestration in an alpine meadow grazed by domesticated yak in Zeku, Qinghai-Tibetan Plateau, China

Abstract

The effects of grazing on the soil carbon of an alpine meadow on the Qinghai-Tibetan Plateau were studied. The aims were to estimate the effects of grazing on the spatial and vertical distribution of soil organic carbon, estimate the potential carbon sink and provide suggestions for sustainable grassland management. Biomass and soil characteristics of the topmost 1 m soil layer in plots under three different grazing intensities were investigated. Soil organic carbon density (SOCD) and stocks (SOCS) were calculated as weighted averages. Soil organic carbon content (SOCC) decreased with increasing grazing intensity and soil depth, with the highest values observed in the top 30 cm of the soil layer at light grazing (LG) sites. Soil water content, total carbon, and biomass had a positive relationship with SOCC. However, bulk density was negatively correlated with SOCC. The lowest SOCD and SOCS were in the 30–100 cm soil layer at heavy grazing (HG) sites, indicating that HG could have significant negative effects on SOC. It could take at least ∼60 years for C stocks at HG sites to reach a steady state. A regime of low grazing is recommended for combining C sequestration with sustainable development.