Decoupled stability of above and belowground productivity across global change drivers

Grassland ecosystems are central regulators of global carbon cycling and biodiversity, yet it remains unclear whether belowground productivity consistently maintains greater stability compared to aboveground productivity across diverse environmental perturbations. Previous studies have predominantly focused on aboveground productivity stability, potentially overestimating ecosystem vulnerability by neglecting critical belowground processes. By synthesizing 1,513 experimental observations from 113 studies spanning 85 grasslands worldwide, we quantify the responses of productivity, temporal stability, and carbon allocation to nine global change drivers, including nutrients enrichment, precipitation shifts, elevated CO₂, warming, mowing and grazing. Our results reveal that belowground net primary productivity (BNPP) consistently exhibits high temporal stability across all global change drivers, highlighting an intrinsic resistance of belowground processes to environmental fluctuations. In contrast, aboveground net primary productivity (ANPP) stability is significantly influenced by climatic variability, particularly precipitation and aridity. These distinct patterns suggest fundamental ecological asymmetry: rapid, climate-sensitive aboveground processes contrast markedly with slower, soil-buffered belowground dynamics. Notably, shifts in carbon allocation toward belowground components emerge as a critical ecological mechanism enhancing and sustaining belowground stability. Our findings challenge the notion of unified top-down control of grassland functioning and provide a mechanistic framework for predicting ecosystem vulnerability and designing resilience-based grassland management under global environmental changes.