Context-dependent contributions of arbuscular mycorrhizal fungi to host performance under global change factors

Arbuscular Mycorrhizal Fungi (AMF) contribute to host performance under stress conditions; however, the type and intensity of stress can shape this contribution. Importantly, the benefits of mycorrhizal symbiosis may also vary with the functional group of host plants. It also remains unclear whether multi-species inocula confer greater stress alleviation to hosts or if single-species inocula are sufficient for host resilience. To address these knowledge gaps, we conducted a global meta-analysis of 252 studies from 36 countries on six continents. Our analysis revealed that mycorrhizal associations enhance the phosphorus and nitrogen content of host biomass under these global change factors. However, contrary to previous meta-analyses that found consistently strong impacts of AMF, we found variable contributions of AMF under heat, cold, drought, salinity, pesticide, and heavy metal pollution. Each stress type has a unique impact on the contribution of AMF to host performance, but this impact also varies with the intensity of stress. Single-species AMF inocula contribute more significantly to host performance under stress compared to multi-species inocula. We also show that the contribution of AMF to plant growth response significantly varies across different plant functional groups, with grasses and legumes significantly benefiting from mycorrhizal associations under global change factors. Overall, this study highlights that the contribution of AMF to host performance under stress is highly context-dependent and influenced by various factors, including the type and intensity of stress, the type of inocula, and the functional groups of host plants. Thus, our meta-analysis can help develop hypotheses that can be tested with mechanistic experiments to gain a better understanding of the synergistic relationship between AMF and host plants in overcoming stress.