Context‐dependent responses of soil microbes and nematodes to grazing: Evidence from a global meta‐analysis

Abstract Livestock grazing is one of the most important land‐use activities in grassland ecosystems, imposing significant impacts on soil community abundance, composition and biodiversity. Soil microbiota, such as microbes and nematodes, are key components of soil micro‐food webs and contribute substantially to ecosystem functioning. However, it remains unknown how grazing affects soil microbiota on a global scale. In this study, we conducted a meta‐analysis based on 146 published studies encompassing 1560 paired observations across various environments to gain comprehensive insights into the influences of grazing on the abundance and diversity of soil microbes and nematodes. We found that grazing significantly decreased soil microbial biomass, total nematode abundance and the abundance of all nematode trophic groups except for fungal‐feeders, particularly in temperate grasslands. Such effects were stronger under continuous, heavy‐intensity and long‐term grazing than under rotational, light or short‐term grazing regimes. Sheep grazing, as opposed to cattle grazing or mixed grazing by both sheep and cattle, reduced the abundance of soil microbes and nematodes. While the overall effects of grazing on microbial and nematode diversity are limited, significant declines were observed under heavy, continuous or long‐term grazing compared to light, rotational or short‐term grazing. Synthesis and applications . Our study indicates that intense (e.g. heavy or continuous) grazing, long‐term grazing or grazing by sheep substantially suppresses the abundance and diversity of soil microbes and nematodes. These declines in abundance and diversity would undermine the roles of the soil food webs, thereby impairing ecosystem processes such as organic matter decomposition and nutrient cycling. Therefore, maintaining light to moderate grazing intensity, implementing rotational grazing or extended rest periods, and prioritizing cattle or mixed‐livestock grazing are essential to protect soil food webs and maintain grassland ecosystem functions under increasing human pressures. Read the free Plain Language Summary for this article on the journal's blog .