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Biodiversity can enhance soil multifunctionality through strengthening biotic interactions in soil food webs, but largely unknown in agroecosystems. We therefore predicted that vermicompost, serving as an organic amendment and soil health conditioner, could enhance trophic interactions among bacteria, fungi and nematodes and mediate synergies and trade-offs among soil functions, especially when substituting synthetic fertilizer was applied to soils. Soil multifunctionality was assessed from plant growth and product quality, carbon and nutrient cycling, water and climate regulation in an intensive cropping system. Pepper, tomato and spinach were cultivated in rotation annually, with substituting vermicompost as a nutrient replacement for synthetic fertilizer for 5 years. Results showed that substituting a moderate dose of vermicompost for synthetic fertilizer offered the highest soil multifunctionality by enhancing synergies among multiple functions. The vermicompost-stimulated multifunctionality was primarily attributed to the cascading effects of the complex food web structure induced by omnivorous nematode. These effects were regulated by the physicochemical environment of the vermicompost-amended soil. Notably, the multifunctional benefits degraded when higher rates of vermicompost were applied, suggesting that over-use of vermicompost combined with an inadequate amount of synthetic fertilizer could simplify soil food web structure and decrease soil functions, mainly due to the nutrient limitation and increasing harmful substances as indicated by C:N stoichiometry, heavy metals and antibiotic resistance genes. In intensive agricultural systems, finding an optimal balance of organic amendments and synthetic fertilizer that supports complex soil food web interactions is therefore crucial for promoting multiple soil functions and particularly sustaining the production of high-quality food crops. • The highest soil multifunctionality was observed in moderate vermicompost substitution. • Moderate vermicompost addition enhanced synergies among multiple functions. • Soil food web structure coordinated by omnivores was associated with multifunctionality. • Vermicompost supported multifunctionality of ecologically intensive agriculture. [ABSTRACT FROM AUTHOR]

Abstract Transgenic Bacillus thuringensis (Bt) crops are widely deployed to control lepidopterous pests with minimal impact on non-target soil invertebrates. However, most of the results were obtained from field works, the great environmental variation may conceal the small spatial-temporal scaled changes in microhabitats, such as those created near the roots (rhizosphere) or around decomposing residues (detritusphere), which are expected to impact free-living soil organisms more than the bulk soils. The objective of this study was to assess the impact of root and straw residues of transgenic crops on soil, by comparing nematode communities in the rhizosphere (soil microsites only affected by living root), the detritusphere (soil microsites affected by crop aboveground residues) and the rhizosphere-detritusphere interface (soil microsites intensively co-affected by root and residues) of Bt rice and its non-Bt near isoline. Bt rice did not affect nematode abundance and community composition, however, it enhanced the network connections within nematode communities, in both the rhizosphere and detritusphere, indicating the frequency of co-occurring species increased due to the moderate stress of crystal (Cry) as a labile resource of protein or as a moderate pressure of toxic compounds. Furthermore, 60–80% of the correlation between Cry protein (Cry1Ab/Cry1Ac) and nematode genera were positive in the rhizosphere and detritusphere of Bt rice, suggesting that higher Cry protein concentration was associated with the intensive co-occurrence among nematode populations. This finding offers new insights into how the biotic interactions of non-target soil community response to both live and dead parts of transgenic crop, highlighting the moderate stress of Cry protein might affect the community structure and consequent functioning of soil ecosystem based on the elaborately developed knowledge of biotic interactions via ecological network analysis. Graphical abstract Unlabelled Image Highlights • The risk of Bt crop on soil fauna was assessed in the hotspots of root and residues • Bt crop did not affect nematode abundance and community composition • Bt crop enhanced trophic connections within nematode communities • Cry protein may serve as a moderate pressure favoring species co-occurrence [ABSTRACT FROM AUTHOR]

Energy dynamics within ecological communities are important in delivering ecosystem services. However, it remains elusive how the energy fluxes within soil food webs respond to agricultural fertilization regimes. Here, we studied the effects of long-term organic amendments and mineral fertilizers on the energetic structure of soil nematodes from a food-web perspective. We replicated our experiment in a rice paddy and in an upland maize cropping system. Results showed that the abundance of most trophic groups was higher in organically amended soils compared with mineral fertilizer treatments in both systems. Organic amendments, but not mineral fertilizers, increased the energy flux of total nematodes and most trophic groups compared with the no-fertilizer treatment. Furthermore, organic amendments increased the relative allocation of energy flux to microbivores but decreased the relative allocation to herbivores, supporting a higher flow uniformity than mineral fertilizers. We further found that organic amendments favored a higher total energy flux by supporting a greater nematode diversity, while sustained a higher flow uniformity by altering nematode community composition. Taken together, the result provides the evidence that a complex and species-rich community could transfer more energy to support ecosystem services. A broader perspective on linkages of biodiversity and energy dynamics spanning multitrophic groups is crucial for sustainable management, particularly in the light of non-random species loss under future environmental change. [Display omitted] • Organic amendments increased total energy flux and flow uniformity. • High flow uniformity resulted from increasing relative energy flux of microbivores. • Energy fluxes and flow uniformity were positively linked with nematode diversity. • Effect of diversity decline on energy loss was stronger in paddy than upland fields. [ABSTRACT FROM AUTHOR]

Anthropogenic activities are supposed to reduce global biodiversity and negatively influence the development of diverse groups in the tree of life. Yet how agricultural management shapes the diversity of microscopic organisms and their evolution in the soil, especially at large spatial scale, remains unknown. Here, we investigated how agricultural land-use affected the biodiversity and the underlying evolutionary events of soil nematodes by comparing their communities in natural and agricultural soils covering a latitudinal transect spanning 2500 km across China. In natural habitats, nematode phylogenetic and taxonomic diversity and species richness showed a hump-shaped relationship with latitudes and peaked at 30° N, while in agricultural habitats those community matrices did not change across the studied latitudinal spectrum. Meanwhile, agricultural management reduced both diversity and richness of nematodes with the effect being more pronounced in subtropical zones. However, evolutionary diversification rates were greater in agricultural than in natural habitats across the entire latitudinal range. This was associated with reductions of soil organic carbon and nitrogen as well as shifts of nematode community compositions towards rapidly evolving taxa (r–strategists) in agricultural habitats. Together, our results suggest that the relatively unfavorable environmental status induced by agricultural management could accelerate the community-level speciation rates of nematodes through enriching rapidly evolving taxon. These insights increase our understanding of the systematic impacts of agricultural activities on soil biodiversity that might facilitate conservation and restoration policies for the purpose of sustainable agriculture. • Phylogenetic comparative methods were applied for soil nematode diversity analysis. • Speciation rates was greater in r-strategists. • Community weighted speciation are greater in agricultural habitats. • Speciation rates were related to soil organic carbon and pH. [ABSTRACT FROM AUTHOR]

One of the greatest challenges in soil ecology is to disentangle the plant-mediated bottom-up factors regulating soil biodiversity and community composition. The soil food web, fundamentally driving nearly all ecosystem functions, is controlled by the quantity and quality of root-mediated resources. Here, a trait-based approach was adopted to explore the divergence of soil nematode functional guilds and their connections to root traits belonging to distinct plant resource-use strategies. Root traits and rhizosphere nematode functional guilds were measured on four plant species in an ex-arable field. Results showed that plant species exhibiting acquisitive strategies promoted nematode abundance in contrast to species with conservative strategies. Further, the results also supported that plant resource-use strategies could regulate nematode life strategies in a bottom-up manner. However, lower proportions of opportunist nematodes in rhizosphere were found in acquisitive plants rather than conservative plants, mainly attributed to the stronger top-down regulation as a dominant control within the former than the later ones. Structure equation modeling revealed that root length density could primarily modulate nematode abundance and functional guilds mainly through changes in nitrogen availability of rhizosphere, as indicated by mineral N and enzymatic stoichiometry. Overall, our findings extend the conceptual framework based on a trait-centred view spanning plants to the soil food web, and this knowledge is critical to understand the mechanisms of ecosystem process. • Acquisitive plants promoted nematode abundance and K-strategist nematodes. • Conservative plants supported mainly r-strategist nematodes. • Root length density was the key root trait for regulating soil nematodes. [ABSTRACT FROM AUTHOR]