High AMF diversity benefits ecosystem multifunctionality
Our results confirmed that high AMF diversity enhanced ecosystem multifunctionality, aligning with our expectations. Previous studies have already demonstrated the benefits of AMF diversity on ecosystem primary net productivity (Wagg et al., 2011) and nutrient reserve (Köhl and van der Heijden, 2016). In our study, the increase of ecosystem multifunctionality through high AMF diversity was primarily mediated by improved plant growth, particularly in net photosynthetic rates and aboveground biomass (Figure 3). Contrary to our expectations, high AMF diversity had no significant effect on most soil functions, compared to low AMF diversity (Figure 4, Table 1). This may stem from our use of sterilized soil, which was only inoculated with AMF without introducing other fungi or bacteria.
Increasing evidence suggests that the nutrient cycling functions of AMF are not performed in isolation but require collaboration with other soil microorganisms (Zhang et al., 2022; Sun et al., 2023; Wang et al., 2024). For instance, previous results have linked soil functions, such as organic nitrogen availability (Rozmoš et al., 2022) and soil N2O emissions (Li et al., 2023b) to the hyphosphere core microbiome. In our experiment, the absence of soil microbial communities likely prevented AMF from recruiting distinct microbes into their hyphosphere, thereby diminishing the contribution of AMF diversity to soil functions. A global meta-analysis of field experiments highlighted a positive correlation between ecosystem multifunctionality and AMF richness (Ma et al., 2021). However, this correlation may not be directly due to the AMF alone but rather influenced by the hyphosphere microbiomes.
Thus, we speculate that the high plant productivity in high plant diversity communities may not be solely due to plant diversity itself. A study by Wilsey et al. (2023) found that biodiversity in native plant-dominated communities was significantly positively correlated with net primary productivity. However, this positive correlation is eliminated in communities dominated by exotic species, which may be due to the presence of more pathogenic microorganisms in exotic plant-dominated communities. This highlights the importance of multiple trophic levels BEF study. Previous results have shown that multi-trophic diversity can better explain and predict ecosystem multifunctionality than single-trophic level diversity (Soliveres et al., 2016; Li et al., 2024). Li et al. (2024) found that different trophic groups exhibit varying correlations with ecosystem functions. For example, in grasslands, AMF diversity showed a significant correlation with provisioning multifunctionality (including plant productivity and community stability), rather than with multifunctionality (Li et al., 2024), which is consistent with our findings.