Distribution patterns and environmental drivers of soil fauna communities in China

Soil fauna are vital components of belowground ecosystems, playing key roles in maintaining soil structural stability, driving organic matter decomposition, regulating nutrient cycling, and contributing to carbon sequestration. These ecological functions are not driven by individual species alone but instead emerge from the structural attributes and functional complementarities of entire soil faunal communities. Soil fauna density and taxonomic richness are fundamental indicators of community structure: density reflects the intensity of biological activity and energy flux, whereas taxonomic richness is closely linked to functional diversity and niche utilization. Understanding the mechanisms that regulate these structural attributes is therefore essential for elucidating subterranean ecological processes and for assessing soil ecosystem functioning and responses to environmental change. Soil fauna communities exhibit remarkable species diversity and pronounced variation in body size, which not only reflects their life-history strategies but also influences their energetic demands and resource utilization patterns. Consequently, body size serves as a key determinant of their sensitivity to environmental factors and the mechanisms underlying their ecological responses. Despite the recognized ecological importance of soil fauna, the spatial patterns and underlying drivers of soil faunal community structure remain insufficiently understood. In particular, systematic comparisons across body-size groups are lacking, limiting our ability to generalize ecological mechanisms across taxa. Against this backdrop, China provides an exceptional natural laboratory for disentangling the environmental drivers of soil faunal communities. The country spans from cold-temperate to tropical zones and encompasses a broad spectrum of ecosystems—from humid forests to arid grasslands, and from lowland plains to high-elevation plateaus—thereby offering extensive environmental gradients and geographic heterogeneity. Therefore, we compiled and analyzed 4,490 observational records from across China and used multivariate modeling approaches to identify the principal environmental drivers of soil faunal communities. Classification into micro-and mesofauna (and macrofauna (>2 mm)enabled direct comparison of body-size–dependent distributional and ecological patterns. Our results revealed significant differences in both density and taxonomic richness among soil fauna of different body-size groups. The mean density of micro-and mesofauna was 11,159 ind. m–2, markedly higher than that of macrofauna at 137 ind. m–2. The presence of a litter layer significantly enhanced both faunal density and taxonomic richness. Litter presence exerted multifaceted and positive effects on soil faunal communities, with its influence generally exceeding that of increased soil depth alone. Forest habitats were notably more effective than croplands in maintaining taxonomic richness, underscoring the critical role of microenvironmental conditions and habitat type in shaping community structure. The density of macrofauna was closely associated with isothermality and precipitation seasonality, whereas the taxonomic richness of micro-and mesofauna showed a negative correlation with soil pH. Climatic variables emerged as the primary predictors of faunal density. In contrast, soil properties, including pH, silt content, and soil moisture content, exhibited stronger explanatory power for taxonomic richness. Spatial analysis revealed distinct distributional patterns across China: faunal density peaked in southern regions, whereas taxonomic richness was highest in the east. These patterns reflect the zonal influence of climatic and edaphic factors on belowground communities. By establishing an environmental-response framework across body-size classes, this study elucidates the ecological differentiation among soil fauna of varying sizes and clarifies the respective roles of climatic and soil conditions in shaping their biogeographical distributions.