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Both contemporary and historical factors are documented to be crucial in regulating species diversity and distribution. Soil fauna contribute substantially to global biodiversity and ecosystem functioning, while it is unclear whether and to what extent historical factors shape their diversity patterns. Here, we used soil nematodes as a model organism to test historical effects on soil fauna and to investigate the relative importance of climatic, soil, and historical factors. Based on nematode distribution data in 16 natural sites at a large scale (ranging from 22 to 40°N) in mainland China, we conducted elastic net regression model to test the effects of climatic (e.g., mean and seasonality of temperature/precipitation), soil (e.g., soil carbon, nitrogen, and pH), and historical (e.g., temperature/precipitation anomaly and the velocity of the change since the Last Glacial Maximum) variables on nematode genus richness and Shannon's diversity. Additionally, variation partitioning was used to determine the contribution of the three predictor sets to the explanation of both Jaccard and Bray–Curtis community dissimilarity. We found that climate generally explained more variations in both diversity and composition than soil and historical predictors in our samples. We also showed that although historical factors (e.g., temperature change velocity) were correlated with nematode diversity and composition, the pure effects of these historical factors were negligible. In other words, the historical effects were commonly represented by their interactions with current climatic and soil factors within our selected sites. Our results indicated that contemporary factors, especially climate, may outperform historical factors in regulating soil nematode diversity patterns at large scales. [ABSTRACT FROM AUTHOR]

Emerging knowledge of plant–soil biotic interactions and the role of soil organisms in shaping the world aboveground is advancing our understanding of ecosystem function. Nematodes are the most abundant animals on Earth. They are morphologically and functionally diverse, and play key roles in ecosystem function, making them ideal for developing a trait-based understanding of adaptation to the environment and for assessing their contributions to ecosystem function. Trait-based approaches allow us to capture the functional attributes of organisms beyond their taxonomic identity, provide insights on evolutionary fitness, and make global comparisons possible. We propose the nematode economics spectrum (NES), analogous to the plant economic spectrum, which describes the tradeoffs among growth, reproduction, and survival, potentially enabling us to predict the impacts of global change on nematode ecological strategies and the associated changes in ecosystem function. Trait-based approaches are being increasingly adopted to understand species' ecological strategies and how organisms influence ecosystem function. Trait-based research on soil organisms, however, remains poorly developed compared with that for plants. The abundant and diverse soil nematodes are prime candidates to advance trait-based approaches belowground, but a unified trait framework to describe nematode ecological strategies and assess their linkages with ecosystem function is lacking. We categorized nematode traits as morphological, physiological, life history, and community clusters, and proposed the nematode economics spectrum (NES) to better understand nematode ecological strategies and their association with ecosystem function. We argue that bridging the NES and the plant economics spectrum will facilitate a more holistic understanding of ecosystem carbon and nutrient cycling under global change. [ABSTRACT FROM AUTHOR]

Abstract The development of soil sustainability is linked to the improved management of soil biota, such as earthworms, and crop residues to improve soil physical structure, enhance microbial activities, and increase nutrient cycling. This study examined the impacts of maize residue (65.8C/N ratio, dry biomass 0.75 kg m−2) incorporation and earthworms (70 g Metaphire guillelmi m−2) on the resistance and resilience of soil C and N cycling to experimentally applied stresses. Field treatments were maize residue incorporation, maize residue incorporation with earthworm addition, and an unamended control. Resistance and resilience of C mineralization, ammonia oxidation, and potential denitrification were investigated over 28 days following a persistent stress of Cu (1 mg Cu soil g−1) or a transient heat stress (50 °C for 16 h). The results indicated that C mineralization was more resistant and resilient than ammonia oxidation and denitrification to either a persistent Cu or a transient heat stress. The application of maize residues significantly increased soil microbial biomass, C mineralization, ammonia oxidation and potential denitrification compared with the unamended control. Maize residues significantly improved the resistance and resilience of N processes to Cu and heat stress. The presence of earthworms significantly increased potential denitrification but had limited positive effect on functional resistance and resilience. This study suggested crop residue incorporation would strongly increase soil functional resistance and resilience to persistent and transient stresses, and thus could be a useful agricultural practice to improve soil ecosystem sustainability. Highlights • C cycling is more resistant and resilient to Cu and heat than N cycling • Resistance and resilience are primarily improved by the addition of crop residues • C and N processes can recover from heat rather than Cu [ABSTRACT FROM AUTHOR]

Global change in organismal stoichiometry and biodiversity is often correlated with energy dynamics in ecological networks that underpin the functioning of terrestrial ecosystems and services. However, we know little about which facets of biodiversity, such as taxonomic, functional, and phylogenetic diversity, account for most of the variation in the energy dynamics of ecological networks along litter stoichiometry gradients. Here, we quantified how multiple facets of biodiversity impact energy fluxes of soil food webs through time in agricultural fields incorporating litter from six plant species of varying C:N stoichiometry. We found that community biomass and energy flux in soil food webs decreased while community maintenance cost (i.e. energy flux to biomass ratio) increased with increasing litter C:N ratio. Taxonomic, functional, and phylogenetic diversity of soil nematodes declined along increasing litter C:N stoichiometry, and together explained 73 % and 51.3 % of variation in community biomass, 71.6 % and 49.2 % of variation in energy flux, and 59.8 % and 37.4 % of variation in community maintenance cost in early and later decomposition stages, respectively. Functional and taxonomic diversity were highly associated with energy dynamics in early decomposition stages, while phylogenetic diversity emerged as the central predictor in later decomposition stages. By identifying the crucial role of multi-faceted biodiversity conservation facilitated by low C:N litter in driving the energy dynamics of food webs, these findings shed new light on the applicability of energy dynamics for linking biodiversity and ecosystem functioning under global change scenarios. • Energy storage, flux and use efficiency decrease with increasing litter C:N ratio. • Multi-faceted biodiversity correlates with energy storage, flux and use efficiency. • The importance of biodiversity facets to energy dynamics differs over time. • Energy dynamics underpins biodiversity-ecosystem functional relationships. [ABSTRACT FROM AUTHOR]

As ubiquitous ecosystem engineers, earthworms play an important role in shaping the architecture and functioning of soil systems. However, there is limited knowledge on how earthworms modify the soil microbiome in relation to soil biogenic aggregates, hot-spots formed by earthworms, especially in agricultural systems. We investigated microbial communities in physical fractions and bulk soil from an arable field with consecutive rice - wheat cropping after manipulating earthworms and organic amendments for 13 years. Earthworms significantly enhanced soil aggregation by 33.4% across two consecutive cropping seasons. The assemblage of bacterial communities varied strongly between soil aggregate fractions and with earthworm presence, while the assemblage of fungal communities varied most with organic amendments and less between aggregate fractions. Structural equation modelling (SEM) suggests that besides direct effects on bacteria and fungi, earthworms affected bacteria indirectly via increasing soil aggregation (MWD), but mediated fungi via lowering pH, indicating that the role of soil aggregates in structuring soil bacterial communities override that of resource availability. In conclusion, results of our over-decade field experiment suggest that earthworms modify soil microbial communities primarily through mediating soil habitat architecture and affecting resource supply. • A long-term study explored earthworm impacts on aggregate-associated microbiome. • Earthworms increase soil macro-aggregates (>2 mm) formation. • Earthworms modify soil bacterial community mainly via stimulating soil aggregation. • Earthworms modify soil fungal community mainly via changing chemical properties. [ABSTRACT FROM AUTHOR]

Abstract How plants cope with herbivore attack is partially modulated by the biotic and abiotic environment where the plant lives. For instance, theory predicts that soil fertility should drive patterns of plant resource allocation and defensive strategies. Earthworms, by their burrowing and casting activities, modify soil physicochemical properties and soil fertility. Therefore, earthworm-mediated changes in soil properties could alter plant physiology, plant nutritional quality, and ultimately, plant resistance against insect herbivores. We tested this hypothesis by measuring the combinatorial effects of two earthworm species, an epi-endogeic earthworm (Amynthas corticis) and an endo-anecic earthworm (Metaphire guillelmi), on soil properties, tomato plants' physiological traits and plant resistance against the western flower thrips (Frankliniella occidentalis). We found that A. corticis alone increased plant resistance more than M. guillelmi alone or the combination of two species. The increased plant resistance was associated with a significant increase in the defence-related phytohormone jasmonic acid and the production of phenolic compounds. Furthermore, we observed a strong link between earthworm-mediated changes in soil properties and plant eco-physiological traits. Our results thus build toward a better predictive model of how earthworms can simultaneously influence soil parameters, plant productivity and resistance against herbivore pests. Highlights • Earthworms positively affected soil properties and then induced changes in plant chemistry. • Earthworm single-species inoculations increased plant resistance more than dual-species inoculations. • Earthworm dual-species inoculations increased more plant nutrients instead of chemical defences. • Earthworm Amynthas corticis suppressed thrips abundance on tomato plants. [ABSTRACT FROM AUTHOR]

Resource limitation hinders soil biota to sustain multiple ecosystem functions. Earthworms are known for their ecotype diversity and the ability to accelerate nutrient cycling. However, the roles of earthworm ecotype diversity in alleviating soil resource limitations have yet to be discovered. Here, we conducted a microcosm study to investigate whether the increase of earthworm ecotypes, including epigeic Eisenia foetida , endogeic Metaphire guillelmi , and epi-endogeic Amynthas corticis , could promote soil nutrient provision by stimulating soil microbial communities. Earthworm ecotype diversity resulted in greater phosphorus contents than the earthworm inoculated alone, which were associated with increased fungal richness and network complexity. The result suggests that the increase of earthworm ecotype diversity drives the fungi-based micro-food web. Further, the alternations of extracellular enzymes related to nitrogen and phosphorus hydrolysis are also coupled with the richness, community composition, and network topology of fungi rather than those of bacteria, suggesting the more predominant effects of fungi in mediating extracellular enzymes. Thus, the increase of earthworm ecotype diversity could alleviate the resource limitation by steering fungal communities to excrete more hydrolysis enzymes. Our findings shed new light on the essential roles of earthworm ecotype diversity in strengthening microbiome-mediated functions in resource limited environments. [Display omitted] • Earthworm functional diversity mitigates resource limitations in soil. • Earthworm diversity increased fungal rather than bacterial diversity. • Fungi contributed to the soil enzyme composition. • Earthworm functional diversity is needed in conserving microbiome and soil functions. [ABSTRACT FROM AUTHOR]

Earthworms could affect soil C and N cycling process to balance their energy and nutrients requirements, and they could also regulate soil microbial community structure and microbial acquisition for C and N. However, the connection between faunal and microbial stoichiometry in the coupling soil C and N cycling remains poorly understood. In a controlled laboratory experiment, we amended soil with five litters differing in litter chemistry (clover, maize stover, wheat straw, Rumex and bagasse fiber) including a no litter control and treated them without or with earthworms ( Metaphire guillelmi ). After 90 d incubation, we examined changes in earthworm tissue and microbial stoichiometry and different soil C and N fractions. Earthworm tissue C content was rather stable compared with the fluctuation in tissue N, implying that C is under stronger control and associated with higher demand than N. The presence of earthworm significantly enhanced CO 2 emissions and decreased particulate organic carbon (POC) and soil organic carbon (SOC) contents in the low lignin litter species clover, maize stover and wheat straw. Meanwhile, earthworm presence increased N 2 O cumulative emissions but exerted negligible effects on particulate organic nitrogen (PON) and soil total nitrogen (TN) contents irrespective of litter species. Correspondingly, earthworm regulated microbial C and N acquisition as C to N-degrading enzyme activity ratio were nearly doubled in the low lignin litter species clover, maize stover and wheat straw, while it was decreased in the high lignin litter species Rumex and bagasse fiber. However, the structural equation modeling indicated C loss induced by earthworms was mainly attributed to their effects on soil fungi and bacteria abundance, while much less related to C-degrading enzyme activities. In conclusion, litter species controlled earthworm effects on soil C and N loss and associated microbial acquisition for C and N, highlighting the pivotal role of resource chemistry in the regulation of soil fauna impact on soil functioning and ecosystem services. [ABSTRACT FROM AUTHOR]

Elevated atmospheric CO 2 concentrations (eCO 2 ) often increase plant growth but simultaneously lead to the nitrogen (N) limitation in soil. The corresponding mitigation strategy such as supplementing N fertilizer and growing high-yielding cultivars at eCO 2 would further modify soil ecosystem structure and function. Little attention has, however, been directed toward assessing the responses of soil food web. We report results from a long-term free air CO 2 enrichment (FACE) experiment in a rice paddy agroecosystem that examined the responses of soil micro-food webs to eCO 2 and exogenous nitrogen fertilization (eN) in the rhizosphere of two rice cultivars with distinctly weak and strong responses to eCO 2 . Soil micro-food web parameters, including microfauna (protists and nematodes) and soil microbes (bacteria and fungi from phospholipid fatty acid (PLFA) analysis), as well as soil C and N variables, were determined at the heading and ripening stages of rice. Results showed that eCO 2 effects on soil micro-food webs depended strongly on N fertilization, rice cultivar and growth stage. eCO 2 stimulated the fungal energy channel at the ripening stage, as evidenced by increases in fungal biomass (32%), fungi:bacteria ratio (18%) and the abundance of fungivorous nematodes (64%), mainly due to an enhanced carbon input. The eN fueled the bacterial energy channel by increasing the abundance of flagellates and bacterivorous nematodes, likely through alleviating the N-limitation of plants and rhizosphere under eCO 2 . While eCO 2 decreased the abundance of herbivorous nematodes under the weak-responsive cultivar by 59% and 47% with eN at the heading and ripening stage, respectively, the numbers of herbivorous nematodes almost tripled (×2.9; heading) and doubled (×1.6; ripening) under the strong-responsive cultivar with eCO 2 at eN due to higher root quantity and quality. Structural equation model (SEM) showed that lower trophic-level organisms were affected by bottom-up forces of altered soil resources induced by eCO 2 and eN, and effects on higher trophic level organisms were driven by bottom-up cascades with 69% of the variation being explained. Taken together, strategies to adapt climate change by growing high-yielding crop cultivars under eCO 2 may face a trade-off by negative soil feedbacks through the accumulation of root-feeding crop pest species. [ABSTRACT FROM AUTHOR]

• Effect of conservation managements on Collembola under intense rainfall was studied. • Collembolan density declined drastically under anomalously intense rainfall. • Straw buffered the decline of collembolan density under intense rainfall. • Straw, manure and no-tillage changed the functional composition of Collembola. Soil biodiversity is of key importance to many essential ecosystem functions, but currently it is severely threatened by both intensive agriculture and climate changes. Ecological intensification, including organic amendments and less disturbance, is expected to buffer the degradation of biodiversity and ecosystem functioning induced by intensive agriculture, but its effects in the context of climate changes are poorly understood. In the present work, we studied the responses of agricultural soil biodiversity to ecological intensification under different natural rainfall intensities in a subtropical field. We focused on a numerically dominant group of soil microarthropods, the Collembola, and three conservation managements, i.e., straw, manure, and no-tillage. The experimental site was established with a full-factorial design of different managements. Soil physiochemical parameters and the density, taxonomic diversity, and morpho-functional traits of the collembolan community were measured over three consecutive years. Results showed that rainfall intensification markedly reduced collembolan density and had severe impact on large euedaphic species. Straw amendment buffered the detrimental effect of dense rainfall on collembolan density, but aggravated the body size reduction caused by the rainfall. Manure input and no-tillage mainly affected the community functional composition, in which manure favours more active and mobile species characterised by a well-developed furca, whereas no-tillage favoured surface-dwelling species. These results support the hypothesis that external resource enrichment and reduced disturbance would shape the functional traits of soil fauna, and further modified their response to climate change events. Our findings call for more attention on the functional consequences of ecological intensification and the interactions among soil biodiversity, agricultural managements and climate changes. [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]

• Plant species plays a dominant role in shaping nutrient status and microbial community around roots. • Earthworm effects on plant nutrient uptake are dependent on plant species. • Microbial community structure from different plant species rhizosphere increase in similarity by earthworms. • Earthworms overall enhance enzyme activities in acquiring C over nutrients across six plant species. The quantity and quality of plant-derived resources are the primary factors regulating soil microbial communities, however, the top-down control of soil fauna on the soil food web is still underexplored. To integrate bottom-up and top-down forces in mediating soil microbial communities, we evaluated six plant species rhizosphere microbial community structure (indicated by multiple PLFA biomarkers) and functioning (indicated by four different enzyme activities) in the presence and absence of seven adult Metaphire guillelmi earthworms. Six plant species with two legume species (Trifolium repens and Medicago sativa), two grass species (Arundo donax and Lolium perenne) and two grain crops (Triticum aestivum and Zea mays) were used varying with resource demand and nutrient acquisition strategies. We found earthworms led to increasing in similarity of rhizosphere microbial community structure across all studied plant species. For example, the variability of the fungi: bacteria and gram-positive: gram-negative ratios across six plant species was reduced in the presence of earthworms. Furthermore, earthworms generally supported enzyme production in acquiring carbon over nitrogen and phosphorus, and enhanced immobilization sink for N in microbial biomass, suggesting earthworms are more beneficial for microbes in acquiring energy as plant roots-produced enzyme mostly targeted on nutrients. In conclusion, our results revealed a context-dependent earthworm effects on microbial community structure and a general pattern of earthworms in shifting enzyme production across different plant species. [ABSTRACT FROM AUTHOR]

Earthworms have been perceived as benevolent soil engineers since the time of Charles Darwin, but several recent syntheses link earthworm activities to higher greenhouse gas emissions, less soil biodiversity, and inferior plant defense against pests. Our study provides new field-based evidence of the multiple direct and indirect impacts of earthworms on ecosystem functions within an ecological multifunctionality framework (i.e., aggregated measures of the ability of ecosystems to simultaneously provide multiple ecosystem functions). Data from a 13-year field experiment describing 21 ecosystem functions showed that earthworm presence generally enhanced multifunctionality by indirect rather than direct effects. Specifically, earthworms enhanced multifunctionality by shifting the functional composition toward a soil community favoring the bacterial energy channel and strengthening the biotic associations of soil microbial and microfaunal communities. However, earthworm-mediated changes in soil physical structure, pH, and taxonomic diversity were not related to multifunctionality. We conclude that the coordinated actions of earthworms and their associated soil biota were responsible for the maintenance of multifunctionality at high levels in this rice-wheat cropping system. Management of crop residue inputs and reduction of soil physicochemical disturbances should encourage beneficial earthworm effects and support multiple ecosystem services that are vital to sustainable agriculture. • Earthworms enhanced multifunctionality by indirect rather than direct effects • Earthworms shifted functional composition toward bacterial-dominated community • Multifunctionality was unrelated to changes in soil biodiversity, structure, and pH Liu et al. study a 13-year-old field experiment to show that earthworms are beneficial to agroecosystems from a multifunctional perspective. This work incorporates the concerns of negative effects of earthworms in recently published syntheses and highlights the potential pathways in which earthworms contribute to sustainable agriculture. [ABSTRACT FROM AUTHOR]