Strengthened cross-trophic coupling in soil communities enhances soil multifunctionality in fenced grasslands

Grazing can have dramatic influence on vegetation and soil-mediated patterns of diversity, interactions and ecosystem functioning, and their effect is often alleviated through the exclusion of grazers. However, the role of species interactions within below-ground food webs can occur either through single-trophic (microbial only) biodiversity or multi-trophic level biodiversity (including microbes and protists that act as mutualists and predators). Here, we examined soil properties and microbes across pairs of grassland plots spread across China’s major grasslands. Fencing increased soil multifunctionality, driven predominantly by the direct positive effect of multi‑trophic diversity which includes higher‑trophic‑level protists (relative importance: 68.19%), far outweighing the contribution of single‑trophic decomposer diversity alone (31.81%). Multitrophic co-occurrence networks further revealed that fencing increased the proportion of positive cross-trophic associations (i.e., edges linking protists to bacteria or fungi) by 26.6%, and negative cross-trophic associations by 16.4%. This suggests that shifts toward strengthened potential mutualistic and predatory associations were correlated to higher soil multifunctionality. Therefore, restoring the predator tier, not just the decomposer guild, is central to functional recovery in grazed grasslands. Grazing exclusion through fencing increased soil multifunctionality, driven by the direct positive effect of multi trophic diversity outweighing the contribution of single trophic diversity, according to an analysis of soil properties and microbes across pairs of grassland plots across China. Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give... [797 chars]