Strengthened trophic interactions in soil micro‐food webs stimulate soil carbon storage under vegetation restoration

Land degradation and climate change threaten soil food‐web structure and soil functioning. However, it remains unclear how vegetation restoration and variations in temperature and precipitation influence trophic interactions in soil micro‐food webs and trigger cascading effects on soil multifunctionality. Here, we conducted a field experiment to investigate the effects of converting degraded croplands into planted forests and naturally regenerated shrublands on trophic interaction strength, as indicated by energy fluxes through multitrophic groups, and on soil multifunctionality (e.g. carbon storage, nutrient supply and water retention). We found that both restoration regimes optimized soil microbial and nematode communities by increasing the relative abundance of Proteobacteria and Basidiomycota, fungal diversity and the abundance and biomass of omnivorous‐predatory nematodes. Trophic interaction strength and soil carbon storage were significantly enhanced by vegetation restoration, particularly under the natural restoration regime. In croplands, nematode metabolic rates and energy fluxes through microbivores and the entire micro‐food web significantly decreased with rising mean annual temperature. However, these negative correlations were mitigated by vegetation restoration. The linear mixed models showed that soil food‐web energetic structure explained the most variation in soil multifunctionality, carbon storage, phosphorus supply, nitrogen supply and water retention. The structural equation models further indicated that vegetation restoration‐induced optimization of soil food‐web energetic structure significantly increased soil carbon storage and marginally increased soil water retention. Synthesis and applications . Vegetation restoration amplifies the positive cascading effects of multiple trophic groups on soil carbon storage. Our findings also underscore the importance of considering soil multitrophic interactions as a critical factor for enhancing soil functioning in the context of global change.