Grazing exclusion significantly improves grassland ecosystem C and N pools in a desert steppe of Northwest China

Abstract

Grazing exclusion is often implemented as an effective management practice to increase the sustainability of grassland ecosystems. However, it remains unclear if grazing exclusion can improve ecosystem services related to carbon (C) and nitrogen (N) sequestration in grassland ecosystems. We investigated the effects of 11years of grazing exclusion on plant biomass and diversity, soil properties (pH, soil water content (SWC), bulk density (BD), soil organic carbon (SOC), total nitrogen (TN), and C/N ratio), and the C and N stocks of plants and soils in a desert grassland of Northwest China. Grazing exclusion improved plant aboveground biomass and diversity, as well as SWC, SOC, and TN contents, but lowered the belowground biomass, root/shoot ratio, pH, and BD. Moreover, grazing exclusion strongly influenced the C and N stocks of the ecosystem, and the annual mean ecosystem C and N sequestration rates were 0.47 and 0.09Mgha−1yr−1, respectively, over 11years of grazing exclusion. Soil C stocks were most dynamic in the top 30cm of the soil, and N stocks mainly changed in the top 20cm after grazing exclusion. Our results indicated that grazing exclusion is an effective measurement on improving the ecosystem C and N pools in desert steppe of Northwest China.