Response of soil micro-food webs to climate change in karst ecosystems: A soil translocation experiment based on tiankeng

Karst tiankengs are established hotspots of biodiversity for macro-organisms. In contrast, the soil micro-food web, structured around microbes, protozoa, and nematodes, represents a critical yet understudied component of subsurface ecosystem diversity and functioning. Its patterns of diversity and underlying maintenance mechanisms remain largely unresolved. To address this, we conducted a three-year bidirectional soil translocation experiment between the interior and exterior of a tiankeng, assessing responses of the soil micro-food web and soil multifunctionality to these distinct habitats. We found that soil translocation significantly altered the diversity, composition, and structure of the micro-food web, with variation in responses across different trophic levels. These shifts were primarily driven by the contrasting environmental regimes, including temperature, humidity, and soil resource availability, between the tiankeng interior and the external environment. Specifically, outward translocation negatively impacted key attributes of the micro-food web. Enhanced competitive interactions between bacteria and fungi exerted bottom-up control, restructuring the entire network. Notably, the tiankeng interior sustained a more complex and stable soil micro-food web, supported higher levels of soil multifunctionality, and demonstrated that micro-food web complexity is pivotal in regulating multifunctionality. Our findings underscore the potential of tiankengs to act as climate refugia and biodiversity reservoirs under future climate change scenarios. Moreover, tiankengs can serve as natural open‑top laboratory models, offering a novel and powerful perspective for simulating the responses of subsurface ecosystems to climate change.