Response characteristics of grassland ecosystem biomass to grazing intensity in China

Grassland ecosystem functions are affected to a large extent by grazing activities. However, owing to the associated spatial heterogeneity, the influence of grazing intensity on grassland ecosystem biomass and the underlying mechanisms remains unclear. In this study, we analyzed data from 335 field data to clarify the response of grassland ecosystem biomass to grazing activities in China. We established that the size of the priming effect of grazing activities on total biomass, aboveground biomass and belowground biomass is -0.25 +/- 0.09 (95% confidence interval [CI]: -0.42 to -0.07), -0.47 +/- 0.05 (-0.57 to -0.37) and -0.18 +/- 0.04 (-0.29 to -0.10), respectively. Grazing was found to significantly reduce both the biomass of grassland ecosystems (p < 0.01) and the average effect value of temperate, meadow and desert steppes with respect to vegetation type (p < 0.05). The descending order of the effects of grazing intensity on biomass was heavy, light and moderate, with light and heavy grazing significantly reducing grassland biomass (p < 0.01), whereas moderate grazing made a comparatively smaller contribution. Furthermore, explained heterogeneity analysis revealed that soil water content was positively associated with the effect size, and path analysis indicated that soil bulk density, precipitation and average annual temperature have a significant direct influence on the effect value (p < 0.05). Given the minimal impact of moderate grazing on biomass, we suggest that stocking at moderate densities could represent an effective approach for restoring degraded grasslands. Moreover, increasing soil water content could contribute to effectively reducing grazing-related damage to the biomass of grassland ecosystems.