Nonlinear response of soil microfauna network complexity and stability to multilevel warming in an old-growth subtropical forest.

The influence of climate warming on soil microbes and the mechanisms underlying these effects have become the subject of intense focus in microbial ecology and climate change research. However, it is largely unknown how warming affects soil microfauna network complexity and stability or how warming-induced changes may affect ecosystem functioning in old-growth forests. Here, we conducted a 3-year multilevel warming experiment in an old-growth subtropical forest using infrared heating with five treatments: ambient soil temperature and 0.8°C, 1.5°C, 3.0°C, and 4.2°C above ambient soil temperature. We found that soil microfauna network complexity and stability and multinutrient cycling were significantly higher under warming and showed similar hump-shaped trends across rising temperatures. The nonlinear responses of soil microfauna network complexity and stability were primarily linked to soil temperature, moisture, organic carbon, and microbial biomass. Importantly, we found that soil multinutrient cycling was positively influenced by microfauna network complexity and stability. Consequently, our findings provide insights into the key role of soil microfauna network structure in regulating soil multinutrient cycling, highlighting the need to consider soil organisms' potential interactions and that it is crucial to preserve soil microfauna "interactions" for ecosystem management in forests under global change.IMPORTANCEIt is largely unknown how warming affects soil microfauna network complexity and stability or how warming-induced changes may affect ecosystem functioning in old-growth forests. We conducted a 3-year multilevel warming experiment in an old-growth subtropical forest using infrared heating. We found that soil microfauna network complexity and stability were significantly higher under warming treatments and displayed nonlinear responses to different warming levels. Soil multinutrient cycling was positively and significantly influenced by microfauna network complexity and stability. Given that complex interconnections between soil microfauna are critical for sustaining ecosystem functioning, protecting microfauna "interactions" may be critical to mitigating the adverse impacts of warming-induced biodiversity reduction on ecosystem functioning.