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Abstract: Subterranean detritivores such as earthworms can increase soil nutrient availability through their burrowing and casting activities. A number of recent studies have explored whether these changes caused by earthworms may in turn affect plant performance and resistance to herbivores, but no formal synthesis of this literature has been conducted to date. We tested for the effects of earthworms on plant growth, resistance and chemical defences against insect herbivores by performing a meta‐analysis of the existing literature up to 2016. We also explored ecological factors that might explain among‐studies variation in the magnitude of the earthworm effects on plant growth and resistance. We found that earthworm presence increases plant growth (by 20%) and nitrogen content (by 11%). Overall, earthworms did not affect plant resistance against chewing herbivores (caterpillars, slugs and rootworms), and even led to a 22% decrease in plant resistance against phloem‐feeding herbivores (aphids). However, earthworm presence increased production of chemical defences by 31% when plants where attacked by cell‐feeders (thrips), and resulted in an 81% increase in resistance against thrips. The magnitude of earthworm effects was stronger when earthworm inoculations consisted of a mix of species and ecological types, and when densities of earthworms were high. These results suggest that earthworm presence is an important factor underlying natural variation in plant defences against herbivores, and call for a better integration of the soil fauna in the studies of plant‐herbivore interaction, both for applied and fundamental research. A plain language summary is available for this article. [ABSTRACT FROM AUTHOR]

The aims of the present study were to compare the toxic effects of benzo[ a]pyrene (B aP) and to screen for rapid and sensitive biomarkers that can be used to assess the environmental risks of B aP in earthworms in different natural soil types. The authors exposed Eisenia fetida to 2 types of soil (red soil and fluvo-aquic soil) spiked with different concentrations (0 mg kg−1, 1 mg kg−1, 10 mg kg−1, 100 mg kg−1, and 500 mg kg−1) of B aP for 7 d or 14 d. Benzo[ a]pyrene-induced weight variation altered the activities of antioxidant enzymes (superoxide dismutase [SOD]; catalase [CAT]; and guaiacol peroxidase [POD]) and changed the content of malondialdehyde (MDA). In addition, using the comet assay, the authors determined the DNA damage in earthworms. The results revealed that the comet assay was suitable for evaluating the genotoxicity of B aP in the soil, even at the lowest examined concentration. The MDA content was the least sensitive indicator of B aP toxicity. A 3-way analysis of variance (ANOVA) was used to determine whether the soil type, exposure concentration, and duration affected the B aP toxicity. The antioxidant enzyme activities and the MDA content were shown to be significantly correlated with the exposure concentration. The percentage of weight variation ( p < 0.001), CAT activity ( p < 0.05), and SOD activity ( p < 0.01) were significantly affected by the soil type, and the POD activity ( p < 0.01), CAT activity ( p < 0.001), and SOD activity ( p < 0.001) were significantly affected by the exposure duration. Therefore, measuring DNA damage in earthworms is a simple and efficient means of assessing B aP genotoxicity in a terrestrial environment, and the effects of the soil type and exposure time on the other parameters that were investigated in E. fetida, which were used as responsive biomarkers, should be considered. Environ Toxicol Chem 2014;9999:1-8. © 2014 SETAC [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]

Abstract: The influence of earthworms on nematodes and protozoan communities was determined during the wheat phase of a six year rice–wheat rotation agro-ecosystem. Experimental plots in the rotation had five treatments, i.e. incorporation or mulching of maize residues with or without added earthworms and a control. The addition of maize residues to soil strongly affected the abundance and community structure of nematodes and protozoa in the absence of earthworms. The presence of earthworms gave significantly lower total nematode numbers at all soil depths following maize residue incorporation than the same treatment without earthworms, and also gave lower (although not significantly) total nematode numbers in the upper soil layer following maize residue mulching than the same treatment without earthworms. This was mainly due to a significant decrease in bacterial-feeding nematode numbers. Earthworms also strongly affected the distribution of the number of total nematodes and two trophic groups (bacterial and plant feeders) with soil depth. In the presence of earthworms, total protozoan and flagellate numbers significantly increased at all soil depths following both incorporation and mulching of maize residues, while numbers of amoebae increased only when maize residues were mulched. Additionally, in earthworm casts total nematode numbers (mainly bacterial and fungal feeders) were significantly higher, whereas total protozoa numbers (mainly flagellates and amoebae) were significantly lower than that in soil from 0 to 5cm layer. These results indicated that earthworm activity could affect the abundance and community structure of microfauna, and change their distribution between soil layers and cast material, depending on the mode of application of organic residues. [Copyright &y& Elsevier]

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]

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]

Our knowledge of the phylogeny of the earthworm genus Amynthas under the family Megascolecidae, which is comprised of a huge number of species, is very limited compared to the better-known and much smaller family Lumbricidae. In order to investigate the phylogenetic relationships among the species within the genus Amynthas , which is the largest genus of the Megascolecidae family, nuclear and mitochondrial DNA sequences of 77 species, including 76 in-group Amynthas species collected from South China and 1 out-group species, were analyzed. A 5402 bp segments composed of whole nuclear 18 S rDNA and the mitochondrial genes COI, COII, ND1, 12 S, and 16 S was assembled from 77 species. Maximum Likelihood and Bayesian analyses of the concatenated sequences were performed. The results revealed evolution of two geographically independent lineages, both showing the ancestral state of two pairs of spermatheca (Sp.p 7/8/9). We found the species groups described by Sims and Easton (1972) to be non-monophyletic, and the origin of the parthenogenetic species group to likely be a quadthecal ancestor. These results provide modest evidence in support of an Indochinese peninsula origin of the Chinese Amynthas species and divergence of the genus once it had spread to mainland China. The findings of this study are consistent with a divergence scenario that resulted in at least one branch spreading to the Southeast of China and another branch spreading to the Southwest of China, but further research is required to confirm this interpretation of the Amynthas phylogeny. [ABSTRACT FROM AUTHOR]

The earthworm functions in agriculture are determined by soil managements, including straw management practices (e.g., straw mulched on soil surface and incorporated into soil), which affect the spatial distribution of resources for earthworms as well as other organisms. However, it remains unclear that how earthworms and straw management practices jointly affect soil C and N forms and their spatial distributions. Based on a decade-long field experiment, we explored the effects of endogeic earthworms (Metaphire guillelmi) on contents of different soil C and N forms across soil depths (0–7.5 cm, 7.5–15 cm and 15–30 cm) under straw surface mulching and incorporation. Under straw mulching, earthworms did not affect the soil organic carbon (SOC) content but reduced the ammonium nitrogen and nitrate nitrogen (NH 4 +-N and NO 3 --N) content regardless of soil depths. And earthworms decreased the contents of total nitrogen (TN), microbial biomass carbon and nitrogen (MBC and MBN) at 0–7.5 cm layer, while increased those of MBC and MBN at 7.5–15 cm layer. In contrast, with straw incorporation, SOC, TN, MBC and MBN contents increased in the presence of earthworms. The most apparent positive effects of endogeic earthworms on the above total and microbial measurements occurred at 7.5–15 cm, with increases ranging from 25.5% to 65.7% under straw incorporation. Earthworms also tended to increase soil NH 4 +-N and NO 3 --N at 7.5–15 and 15–30 cm layers. Overall, the effects of endogeic earthworms depended on the straw management practices and soil depths. The interaction between earthworms and organic straw incorporation causes nutrients accumulated towards subsurface layer. • Soil C and N forms were affected by earthworms and straw management practices. • Endogeic earthworms promoted soil C and N contents under straw incorporation. • Earthworms facilitated subsurface soil nutrient accumulation when straw incorporated. [ABSTRACT FROM AUTHOR]

Abstract: The effect of earthworms on soil hydrolases (protease, urease, invertase, and alkaline phosphatase) and dehydrogenase activities was investigated in maize residue amended rice–wheat rotation agro-ecosystem. Experimental plots in the rotation had five treatments, i.e. incorporation or mulching of maize residues with or without added earthworms and an untreated control. The application of maize residues to soil without earthworms significantly enhanced the five soil enzyme activities compared with the control treatment during rice and wheat cultivation. The presence of earthworms further significantly enhanced protease activity in the soils with both incorporated and mulched maize residues during two cultivation seasons, but only significantly increased alkaline phosphatase activity in the soil with incorporated maize residue during the rice cultivation season. Invertase activity was significantly enhanced by the presence of earthworms in the soil with maize residue incorporation during two cultivation seasons. There were no changes in dehydrogenase activity when earthworms were present. Additionally, the five enzyme activities in earthworm casts were significant higher than those in the surrounding soil, especially dehydrogenase and invertase activities. Whatever the treatment, the values obtained for the enzyme activities in both soil and casts, except for dehydrogenase activity in earthworm casts, were significantly higher under wheat than those in rice-cultivated soil. These results indicate that the presence of earthworms strongly affected soil enzyme activities, depending on the method of organic residue application, and the enhanced enzyme activities of earthworm casts probably contributed to the surrounding soil enzyme activities. [Copyright &y& Elsevier]

• 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]

Biotic interactions in the soil food web have been increasingly recognized as crucial for ecosystem functioning, however there are still knowledge gaps in terms of the associations between macrofauna and microorganisms, particularly in soil hotspot microsites. A manipulative study was performed to investigate the protist community in the drilosphere and casts of three earthworm species (epigeic Amynthas cortices , anecic Amynthas hupeiensis and endogeic Drawida gisti) and a control soil without earthworms. Results showed that earthworm presence significantly increased the relative abundance of parasitic protists (p < 0.05). The diversity of protists within drilosphere and casts depended on earthworm species, with D. gisti and A. hupeiensis increasing diversity and A. cortices decreasing protist diversity (p < 0.05). Structural equation modelling indicated that protist abundance and diversity in the drilosphere were regulated indirectly via neutralized soil pH and accelerated C and N mineralization, while in casts were affected directly through earthworm gut processing and indirectly through elevated water content. In conclusion, the marked effects on soil protist community mediated by earthworms varied from distinct earthworm species and microsites. The present study suggests the necessity to consider interactions between protist and earthworms in evaluating the effects of soil fauna on soil biota and the related ecosystem processes. • Parasitic protist in drilosphere and cast was higher than in earthworm free soil. • Protist community composition depended on earthworm species and microsite type. • Protist communities were affected by pH and nutrient availability in drilosphere. • Earthworm feeding and elevated water content determined protist community in cast. [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]