Grazing altered soil aggregates, nutrients and enzyme activities in a Stipa kirschnii steppe of Inner Mongolia
2022
Grasslands are a major biome on Earth, and their soils play a dominant role in the overall ecosystem functions and dynamics. Though the majority of global grasslands are used for grazing, the impact of grazing on soil structure and soil quality remains unclear due to large variations among grasslands. In this study, we assessed soil nutrient content, enzyme activities and soil aggregates at 0–30 cm depth under different grazing intensities, including a treatment of grazing exclusion. Heavy grazing reduced content of soil nitrogen, potassium, and soil urease and sucrase activities. While grazing increased the mechanical stability of soil aggregates, it reduced the water stability of soil aggregates. With increasing grazing intensity, water stability of the aggregates was correspondingly weakened, as was the erosion resistance of the soil. The soil urease activity, available soil nutrients, mean weight diameter by wet sieving (w-MWD), and geometric mean diameter by wet sieving (w-GMD) showed significant high sensitivity to grazing intensity in this Stipa kirschnii dominated grassland in Inner Mongolia. Overall, the soil quality at the heavy grazing site appeared poor compared with that at the light grazing site. For developing grazing management strategies, it is clear that heavy grazing should be avoided in this type of grasslands, albeit continued monitoring of soil structure is needed to explore the potential long-term consequences of the grazing.
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