Multiple global change factors diminish the benefits of AMF diversity to ecosystem multifunctionality

1. Multiple global change factors (GCFs) co-occurring may weaken the positive effects of high biodiversity on ecosystem multifunctionality. Arbuscular mycorrhizal fungi (AMF) play a crucial role in determining ecosystem functionality, yet it remains unclear whether high AMF diversity alleviates the negative impact of multiple GCFs on ecosystem multifunctionality.2. In this study, we conducted a microcosm experiment using Triticum aestivum (wheat) to examine the effects of AMF diversity on ecosystem multifunctionality and individual functions under 0, 1, and 6 GCFs.3. We found that under 0 GCF and 1 GCF treatments, ecosystem multifunctionality in the high AMF diversity treatment was significantly higher than that in the low diversity and non-AMF treatments. However, when 6 GCFs occurred simultaneously, AMF diversity had no impact on ecosystem multifunctionality. Notably, AMF diversity simultaneously promoted plant growth and net photosynthetic rate. High AMF diversity had limited effects on soil functions and did not consistently outperform treatments with lower AMF diversity under multiple GCFs. Despite 6 GCFs strongly reduced the development of AMF, the high-diversity AMF still exhibited the highest root colonization and soil hyphal length density.4. Synthesis. Our results suggested that the simultaneous occurrence of multiple GCFs diminished the benefits of high AMF diversity on ecosystem multifunctionality. However, high AMF diversity consistently improved plant growth under all conditions, possibly due to plants’ selective association with mycorrhizal partners. These findings indicate that reducing global change stressors is essential for maintaining ecosystem functioning. Meanwhile, sustaining AMF diversity remains important for supporting plant productivity in the rapidly changing world.