Plant Diversity Maintains Soil Detritivore Activity Under Drought

Biodiversity loss and increasing drought events due to climate change threaten ecosystem stability by disrupting soil organic matter decomposition. Soil detritivores play a crucial role in mitigating this impact through the fragmentation of organic residues, enhancement of microbial activity, and modification of soil structure, ultimately regulating soil organic carbon cycling and nutrient availability. However, the interactive effects of plant diversity and extreme drought on their activity remain unknown. To investigate this, we measured soil detritivore feeding activity and its differences between soil layers in a long-term grassland experiment (2018-2023) that manipulated both plant diversity and projected precipitation patterns. The results presented here focus on two distinct periods: (1) the establishment of the experiment (2018-2022), during which all plots experienced ambient rainfall, and (2) the first year of precipitation manipulation (2023), when plots were split into drought and control treatments. During the establishment phase, we found that plant diversity increased soil detritivore feeding activity, an effect that strengthened and stabilized over time. During the first year of precipitation manipulation, we found that plant diversity increased feeding activity under both control and drought conditions, with higher activity during drought. Under control, both feeding activity and its positive relationship with plant diversity declined with soil depth. In contrast, during drought, feeding activity remained stable, and the positive effects of plant diversity increased with depth. These results suggest vertical shifts in feeding activity maintain the benefits of plant diversity for decomposition under drought. Preserving plant diversity could mitigate drought impacts on detritivore activity and soil organic matter decomposition, enhancing ecosystem resilience to climate extremes.