Ecosystem carbon fluxes represent a key mechanism underlying the precipitation-dependent pattern of ecosystem multifunctionality

Precipitation plays a fundamental role in shaping ecosystem functions, yet ongoing global warming is substantially altering regional precipitation patterns with profound implications for ecosystem multifunctionality ( EMF ). Despite its importance, precipitation-dependent patterns of EMF and their underlying mechanisms remain poorly understood at regional scales. We systematically examined ecosystems (grasslands, shrublands, and forests) spanning precipitation gradients to characterize how EMF varies with precipitation, quantify its sensitivity to precipitation changes, and elucidate the mechanistic role of ecosystem carbon fluxes in mediating these relationships. We identified a pronounced threshold effect in the precipitation- EMF relationship, with EMF peaking at 600–800 mm of annual precipitation. Both water limitation (<200 mm) and excess (>1000 mm) suppressed EMF , demonstrating that moderate precipitation optimizes the simultaneous expression of multiple ecosystem functions. Across semi-humid and semi-arid regions, each 100 mm increase in precipitation elevated EMF by 0.273, 0.483, and 0.187 units in grasslands, shrublands, and forests, respectively, revealing substantial potential for EMF enhancement through moderate precipitation increases in these transitional zones. Importantly, climatic and edaphic factors modulated EMF across vegetation types via distinct carbon flux pathways: elevated ecosystem respiration ( RE ) emerged as the primary driver of grassland EMF , while net ecosystem productivity ( NEP ) played a more critical role in shrublands. Forest EMF responded predominantly to plant species richness and gross primary productivity ( GPP ), though excessive moisture imposed significant constraints. Notably, soil texture and pH consistently predicted EMF across all three ecosystem types. Our results demonstrate that ecosystem carbon fluxes constitute a key mechanistic pathway through which climatic and edaphic factors shape EMF , advancing our understanding of how climate-productivity interactions govern multifunctionality in terrestrial ecosystems.