Tian_et al_2025

2.1. Data collectionWe searched peer-reviewed publications before April 2025 that reported the responses of soil microbes and nematodes to livestock grazing using ISI Web of Science (isiknowledge.com) and China National Knowledge Infrastructure (CNKI, http://www.cnki.net). Search terms were ‘(soil food web* OR soil microorganism* OR soil microbe* OR soil biota OR soil fung* OR soil bacteria* OR soil microbial OR soil nematode* OR soil invertebrate* OR soil fauna OR soil dwelling) AND (graz* OR herbivore* OR livestock OR fenc* OR enclos*)’. The following seven criteria were used to select publications: (i) field-manipulated experiments included a control (no grazing treatment), which had similar conditions to those in grazing plots such as microclimatic factors, vegetation, and soil types; (ii) grazing intensity, grazing regime, grazing duration and livestock type were clearly defined in quantitative or qualitative terms; (iii) grazers were large herbivores to exclude small herbivores such as rodents and grasshoppers; (iv) when more than one publication included the same data from the same study, only data from the most recent paper were selected; (v) when a study included multiple measurements under different abiotic conditions such as different sites and other different manipulation factors (e.g., N addition or ambient), the different measurements and manipulations were considered distinct observations; (ⅵ) when multiple soil depths were examined, only the uppermost layer was evaluated because most studies on soil micro‐food webs focus on topsoil (e.g., 0–20 cm); and (ⅶ) mean value, standard error (SE) or standard deviation (SD), and sample size (n) were explicitly provided. As a result, a meta-data set of 1,560 pairs of observational data from 146 studies was obtained (Figure 1).Data for the abundance and diversity of microbes and nematodes were directly collected from text and tables in the original studies or were extracted from figures using the digitizing software GetData Graph Digitizer (v2.25, http://getdata-graph-digitizer.com). Microbial abundance indices included microbial biomass, bacterial biomass, fungal biomass, fungi:bacteria ratio, Gram-positive (G+) to Gram-negative (G−) bacteria ratio (G+:G–); nematode abundance indices included total nematode abundance and abundances of different trophic groups, i.e., plant-feeders (PF), bacterial-feeders (BF), fungal-feeders (FF), and omnivore-predators (OP). Microbial diversity was evaluated using the Shannon index and OTU richness; nematode diversity was evaluated using the Shannon index and nematode generic richness.We examined the effects of grassland types and grazing management strategies (i.e., grazing intensity, grazing regime, grazing duration, and livestock type) on soil micro‐food webs. Grassland types were classified as temperate grassland (including steppe, prairie, and pampas), alpine grassland, and others (including marsh, mountain, tropical, and Mediterranean) according to climatic factors and grassland biome (Whittaker, 1975). Grazing intensities were grouped into ungrazed or fenced treatments (CK) and light grazing (LG), moderate grazing (MG), and heavy grazing (HG) treatments, according to the original study. Grazing duration was partitioned into short-term grazing (1–5 years), medium-term grazing (5–10 years), and long-term grazing (>10 years). The grazing regime includes continuous grazing and rotational grazing. Livestock types included sheep or goat, cattle or yak, and mixed grazers (including sheep, cattle, and horse).Soil physicochemical properties included soil bulk density (BD), soil moisture (SM), pH, soil organic C (SOC), soil total N (STN), and C:N ratio. Biological variables included plant aboveground biomass (AGB), belowground biomass (BGB), species richness (PSR), and Shannon diversity (PSI). Latitude, mean annual temperature (MAT), and mean annual precipitation (MAP) were collected from papers or its cited papers. The MAT and MAP data were obtained from the online climatic database (https://www.worldclim.org/) when they were not provided in the papers.