Conservation tillage regulates the influence of drought on multitrophic network complexity and improves soil multifunctionality

Global climate change is leading to increasingly severe droughts, which affect not only microbial communities but also the maintenance and stability of terrestrial ecosystem functions and services. In agricultural ecosystems, conservation tillage can improve the traits of soil microbial communities and increase soil nutrients. However, our understanding of whether conservation tillage helps plants cope with drought stress to improve soil function through regulation by microbial communities remains limited. In this study, we investigated the effects of constant moisture and drought and rewetting on the diversity, structure, and co-occurrence networks of microbial communities and their functional potential, as well as their relationships with soil multifunctionality, via the use of soil samples from long-term conservation tillage and traditional tillage. These results indicated that drought and rewetting did not significantly affect the alpha-diversity of the soil microbial communities. Compared with traditional tillage, conservation tillage significantly increased ecosystem multifunctionality and network complexity. However, drought and rewetting significantly reduced the abundance of most functional genes associated with soil multinutrient cycling. Moreover, drought and rewetting diminished the influence of biodiversity on multifunctionality, whereas network complexity consistently emerged as the critical factor regulating multifunctionality under varying soil moisture conditions. Overall, this study provides new evidence that conservation tillage plays a beneficial role in mitigating the impacts of water stress on the belowground micro-food web and agroecosystem functions. Our findings highlight the importance of incorporating soil multitrophic microbial coexistence patterns into the assessment of ecosystem functions and services in the context of global climate change.