The Mean Temperature of the Coldest Season is the Main Factor Influencing the Relationship Between Biodiversity and Biomass in the Desert Shrubland of Western Inner Mongolia.

The biodiversity-ecosystem functioning (BEF) relationship has been a central focus in ecology, yet its nature and strength remain contentious. In natural ecosystems, these relationships are modulated by a suite of abiotic (e.g., climate, soil) and biotic (e.g., community composition) factors, and often result in complex and context-dependent patterns. This study investigated xerophytic shrub ecosystems in western Inner Mongolia. We used Random Forest models to identify the key environmental drivers of biodiversity and community biomass. Based on these findings, Structural Equation Modeling was applied to disentangle the direct and indirect effects of environmental factors on biodiversity, biomass, and their relationship. Results showed that climatic factors are the primary drivers of community biomass, with the mean temperature of the coldest season being the key limiting climatic factor. Shrub species richness was primarily influenced by shrub density, followed by soil total carbon content. Species richness showed no significant direct effect on biomass. Instead, the mean temperature of the coldest season and soil pH directly determined shrub biomass, thereby modulating the observed BEF relationship. These findings extend BEF theory to natural ecosystems and underscore the role of winter temperature as a key driver of community biomass, with implications for predicting ecosystem responses to climate change.