Concurrent anthropogenic stressors affect plant-soil systems with different plant diversity levels.

Plant diversity strongly influences ecosystem functioning. Due to human activities, ecosystems are increasingly threatened by the co-occurrence of numerous anthropogenic pressures, but how they respond to this multifaceted phenomenon is poorly documented, and what role plant diversity plays in this process has not been investigated so far. Here, plant-soil systems with different plant diversity levels (3 vs 9 species) were subjected to an increasing number of anthropogenic stressors (0, 1, 2, 5, and 8). Results show that soil properties and functions were directionally driven by stressor number, irrespective of plant diversity level, and plant functional group evenness declined continuously along the stressor number gradient. The impact of stressors on plant-soil systems varied depending on plant diversity, and when plant diversity was higher, concurrent stressors may have interacted more to affect plant-soil systems. Notably, increasing the stressor number tended to diminish the effects of plant diversity. This study represents a first attempt to address the effect of plant diversity under multi-stressor combinations and highlights the importance of emphasizing plant-soil systems in the research field of multifactorial global change. We also suggest that efforts should be made to reduce the number of coacting stressors when managing plant-soil ecosystems.