Does Plant Diversity Safeguard Soil Carbon During Drought in a Large-Scale Biodiversity and Climate Experiment?

Climate change threatens biodiversity and ecosystem functioning globally. One key consequence of these interacting global threats is decreased soil organic carbon (SOC). Yet increasing or maintaining SOC is integral to many nature-based climate change mitigation strategies. Understanding how biodiversity loss and changes to the climate, such as an increased incidence of severe drought, alter SOC simultaneously is therefore crucial to understanding the potential for such nature-based climate change mitigation strategies. One way that biodiversity may be key for SOC under severe drought is by maintaining stable soil moisture and temperature at small scales.  

We manipulated planted species richness (1 and 12 mixture) and imposed drought conditions in a large-scale biodiversity and climate variability experiment (BioCliVE) at Utrecht University (Netherlands). We hypothesized that increased plant diversity would sustain aboveground biomass and moderate soil temperature and moisture, thereby preventing SOC decline under drought 

Although planted species richness consistently boosted aboveground biomass, altering soil temperature and moisture, SOC did not change across diversity levels or under short-term drought treatments. These findings suggest that short-term experiments may not capture the slow, often multi-year processes by which soil carbon pools respond to biodiversity-driven ecosystem changes. Our research demonstrates the complexity of soil carbon cycling and highlights the need for longer-term monitoring to detect meaningful changes in SOC. It also raises questions about how quickly and effectively nature-based solutions can deliver the carbon sequestration benefits assumed in many climate mitigation strategies. By examining the interplay among biodiversity, drought, and SOC, our study informs ongoing debates about how global change drivers influence soil carbon stability.