Functional diversity and grassland soil carbon stocks under climate change: Insights from global modelling

Grassland stores approximately 20% of global soil organic carbon (SOC). While environmental conditions and management directly affect this storage, the role of functional diversity remains poorly quantified at large scales.We conducted an assessment of functional diversity effects on SOC storage and productivity of managed grassland under climate change using the LPJmL-CSR model. We simulated low (FD-: single dominant strategy) and high (FD+: multiple strategies present) functional diversity under two climate scenarios (SSP1-2.6 and SSP3-7.0) from 1901 to 2100.Results show substantial differences between scenarios. Under SSP1-2.6, SOC declined in FD- but remained stable in FD+. In contrast, under SSP3-7.0, SOC increased in both scenarios due to CO2 fertilization and increasing temperatures. For both climate scenarios FD- remained approximately 30% lower than FD+ by 2100. Productivity showed similar spatial and temporal patterns. Regional analysis revealed distinct mechanisms. In tropical climates, removing subordinate functional types reduced total productivity despite increased growth of remaining species, while in temperate regions, prevented adaptation to warming led to productivity breakdown.Examining the underlying mechanism showed that functional diversity underpins the grassland communities’ potential to adapt to climate change allowing them to compensate for negative effects and acting as an insurance against climate change. To our knowledge, these results confirm findings from local-scale empirical experiments at the global scale for the first time. These findings have implications for carbon farming practices, where maintaining functional diversity could enhance long-term carbon sequestration potential.