Number of global change factors alters plant-soil feedbacks via its effect on soil fungal communities

Plants and soil microbes are often challenged by multiple global change factors (GCFs), and their responses to single GCFs may differ from those to multiple GCFs due to synergistic or antagonistic interactions. Therefore, changes in number of GCFs may alter plant-soil feedbacks. We conditioned a soil by growing a plant of Hydrocotyle verticillata in the soil for three months, and then grew a plant of the same species in a sterilized bulk soil inoculated with the live or the sterilized conditioned soil under no, single, two or four GCFs. The strength of plant-soil feedbacks calculated by root biomass was positive in the treatment with four GCFs, but not in any of the other three treatments. The strength of plant-soil feedbacks based on shoot biomass was positive in the treatment with single and four GCFs, but not in the treatments with no or two GCFs. Furthermore, the strength of plant-soil feedbacks was closely related to changes in soil fungal composition mediated by changes in number of GCFs. These results indicate that increasing number of GCFs can alter plant-soil feedbacks via changing fungal legacies that plants leave in the soil. Our results highlight the importance of multiple GCFs in regulating plant-microbial interactions.