Earthworm ecotype diversity mitigates resource limitations of microbial community in arable soils

Resource limitation hinders soil biota to sustain multiple ecosystem functions. Earthworms are known for their ecotype diversity and the ability to accelerate nutrient cycling. However, the roles of earthworm ecotype diversity in alleviating soil resource limitations have yet to be discovered. Here, we conducted a microcosm study to investigate whether the increase of earthworm ecotypes, including epigeic Eisenia foetida, endogeic Metaphire guillelmi, and epi-endogeic Amynthas corticis, could promote soil nutrient provision by stimulating soil microbial communities. Earthworm ecotype diversity resulted in greater phosphorus contents than the earthworm inoculated alone, which were associated with increased fungal richness and network complexity. The result suggests that the increase of earthworm ecotype diversity drives the fungi-based micro-food web. Further, the alternations of extracellular enzymes related to nitrogen and phosphorus hydrolysis are also coupled with the richness, community composition, and network topology of fungi rather than those of bacteria, suggesting the more predominant effects of fungi in mediating extracellular enzymes. Thus, the increase of earthworm ecotype diversity could alleviate the resource limitation by steering fungal communities to excrete more hydrolysis enzymes. Our findings shed new light on the essential roles of earthworm ecotype diversity in strengthening microbiome-mediated functions in resource limited environments.