Ecosystem developmental stage modulates belowground energy flux responses to chronic nitrogen enrichment: the buffering role of increased precipitation
Description
Global change is increasingly driven by interactions among multiple environmental drivers, yet predicting responses of belowground ecosystems remains a prominent challenge—particularly during abandoned farmland rewilding, which can fundamentally reshape food-web functioning. How developmental stages of secondary succession regulate energetic responses of soil food webs to concurrent nitrogen (N) enrichment and altered precipitation remains insufficiently understood. Here, we combined a 12-year field manipulation experiment in a naturally recovering old-field grassland with a global meta-analysis to investigate how chronic N addition and water addition influence the energetic organization of soil nematode food webs across contrasting rewilding stages. We quantified nematode community composition, ecological indices, food-web properties, energy fluxes, and flow uniformity, and evaluated whether locally observed temporal patterns were generalizable across published field studies globally. We found that rewilding stage substantially restructured the energetic architecture of soil food webs: long-term rewilding communities supported higher total energy fluxes and more balanced energy redistribution than early-rewilding communities. N enrichment exerted strongly stage-dependent effects, producing relatively limited functional changes during early rewilding but significantly suppressing energy transfer efficiency and flow uniformity after ecosystem maturation. Increased water availability partially alleviated N-induced energetic degradation in long-term rewilding ecosystems by maintaining trophic connectivity and stabilizing energy redistribution. These patterns were consistently supported by the global meta-analysis, indicating that succession-dependent energetic responses represent a widespread ecological phenomenon. Our findings demonstrate that cropland rewilding is a fundamental regulator of belowground energetic organization and determines ecosystem sensitivity to interacting global change drivers. By linking long-term rewilding with food-web energetics, this study identifies successional trajectory as a previously underappreciated source of context dependency in global change ecology and provides a mechanistic framework for improving predictions of terrestrial ecosystem functioning under future N deposition and changing precipitation regimes.