Ecosystem services under different grazing intensities in typical grasslands in Inner Mongolia and their relationships

Grazing, as the main land use of grasslands, is a key factor affecting the supply of ecosystem services1 (ESs) as well as the relationships between ESs. Using four grazing intensities, including control check, light grazing, moderate grazing, and heavy grazing, this paper quantified eight key ESs, including biodiversity, herbage intake, herbage quality (herbage crude protein content), climate regulation (soil organic carbon density), soil mineralization nitrogen, soil conservation (aboveground biomass), wind prevention and sand fixation (belowground biomass), and soil erosion prevention(litter biomass), in typical grassland areas of Inner Mongolia. Structural equation models were used to illustrate the impact of grazing on ESs through biodiversity, and the root mean square error was used to quantify the level of trade-offs for ES pairs. The results of this study indicated that grazing intensity (GI) significantly affected all ESs (p < 0.05), except for soil organic carbon density and soil mineralization nitrogen. As GI increased, provisioning services increased, while most regulating services decreased, and there was a general trade-off relationship between regulating services and other ones. In order to realize the maximum ESs benefit and the minimum trade-offs for ES pairs, the optimal grazing intensity for typical grasslands of Inner Mongolia should be between 170 (standard sheep units) SSU · d · hm−2 · y−1 and 340 SSU · d · hm−2 · y−1. The results of this study provide a decision-making foundation for grassland grazing management policies for the sustainable development of Inner Mongolian grasslands.