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Gut microbiota are determined by both the food ingested and physiological conditions of the host. In soil food webs, detritivore animals occupy various trophic niches, spanning from primary decomposers to predators. However, the relative contribution of food resources and species attributes of consumers to gut microbial communities in soil detritivores has not yet been explored. In this study, we investigated gut bacteria and fungi of oribatid mites (Oribatida, Acari), ubiquitous and diverse soil microarthropods feeding on a variety of food resources, to uncover the contribution of host phylogenetic relatedness and trophic niches to the assemblages of gut microbiota. Abundance and community composition of bacteria and fungi were characterized by qPCR and Illumina sequencing, respectively. Gut bacterial communities were more closely correlated with host phylogenetic affinity, whereas gut fungal communities were more closely correlated with the trophic niches of the host. Community phylogenetic analysis suggests that deterministic processes predominated in the assembly of both bacterial and fungal communities in most of the studied oribatid mite species. Integrating phylogenetic distance and trophic niche distance of hosts resulted in the highest correlation coefficients between host species and their gut microbial communities suggesting that both evolutionary history and current trophic niches shape gut microbial communities. Bacteria in the gut may comprise commensals or mutualists facilitating digestion which potentially coevolved with the host, while the fungal community in the gut reflects the trophic niches of the consumer likely suggesting that they form part of the diet and serve as food resources of soil detritivore microarthropods. [ABSTRACT FROM AUTHOR]

We conducted a microcosm experiment with soil being sterilized, reinoculated with native microbial community and subsequently manipulated the bacterivorous nematodes, including three treatments: without (CK) or with introducing one species of the two bacterivores characterized with different body size but similar c-p (colonizer-persister) value ( Rhabditis intermedia and Protorhabditis oxyuroides, accounted for 6 and 59% of bacterivores in initially undisturbed soil, respectively). We monitored the NO and CO emissions, soil properties, and especially quantified gross N transformation rates using N tracing technique after the 50 days incubation. No significant differences were observed on soil NH and NO concentrations between the CK and two bacterivores, but this was not the case for gross N transformation rates. In comparison to CK, R. intermedia did not affect soil N transformation rates, while P. oxyuroides significantly increased the rates of mineralization of organic N to NH , oxidation of NH to NO , immobilization of NO to organic N and dissimilatory NO reduction to NH . Furthermore, the mean residence time of NH and NO pool was greatly lowered by P. oxyuroides, suggesting it stimulated soil N turnover. Such stimulatory effect was unrelated to the changes in abundance of bacteria and ammonia-oxidizing bacteria (AOB). In contrast to CK, only P. oxyuroides significantly promoted soil NO and CO emissions. Noticeably, bacterivores increased the mineralization of recalcitrant organic N but decreased soil δC and δN values, in particular for P. oxyuroides. Combining trait-based approach and isotope-based analysis showed high potential in moving forward to a mechanistic understanding of bacterivore-mediated N cycling. [ABSTRACT FROM AUTHOR]

Tomoceridae is common but among the most problematic groups of Collembola. Its position within Collembola and the relationships within the family remain obscure. This also extends to the generic division of the subfamily Tomocerinae that remains controversial. This study examines these issues by integrating both molecular and morphological evidence. Our molecular phylogeny based on rDNA sequences supports the monophyly of Tomoceridae and the sister relationship between Tomocerinae and Lepidophorellinae. Reconstructions and tree topology tests constraining monophyly did not resolve the relationships between Tomoceridae and other collembolan groups. We also examined the morphology of the first instar (primary) larvae, which has significant phylogenetic value among higher Collembola. Mapping primary chaetotaxy onto our molecular phylogeny provided further evidence for the unique position of Tomoceridae within Entomobryomorpha and Collembola. The monophyly and subfamilial classification within Tomoceridae were validated here, whereas its position among Collembola will need further studies in a broader consideration across the major collembolan orders. Within Tomocerinae, the monophyly of Pogonognathellus was demonstrated, but the status of Tomocerus and Tomocerina is still to be resolved. [ABSTRACT FROM AUTHOR]

A soil culture experiment was conducted to determine whether a plant hormone, indole-3-acetic acid (IAA), could influencefluoranthene(Flu) removal from soil. Four treatments were utilized: (i) unplanted soil (CK), (ii) soil planted with ryegrass (P), (iii) soil planted with ryegrass and treated with 0.24 mg kg−1IAA (P+0.24), (iv) soil planted with ryegrass and treated with 2.4 mg kg−1IAA (P+2.4). The Flu initial concentration was 200 mg kg−1. After 3 months, the percentage of Flu removal and plant root biomass were significantly increased under the P+2.4 and the removal rate was 35.68%. The total Flu content in plants was higher than that in the other treatments. The Flu concentration was significantly increased in the shoots, but not significantly altered in the roots. The highest translocation factor was observed in the P+2.4. Increase in number of bacteria, actinomycetes and fungi were observed in the planted treatments, and the amount of fungi was significantly increased in P+2.4. Flu removal was related to the Flu in ryegrass, and was insignificantly correlated with the stimulation of soil microflora, which suggesting that IAA may work mainly on improving plant growth, the Flu uptake, and eventually leading to enhanced remediation of Flu polluted soil. [ABSTRACT FROM PUBLISHER]

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]

Purpose: Prometryne with moderate to low mobility in soil is a ubiquitous environmental pollutant in water and soil. Bioremediation is widely used to remove pollutants from contaminated soil. Bacterial-feeding nematodes have been tested on the decomposition of soil organic matter and the release of nutrients through their interaction with soil microorganisms, but little attention has been paid to their effects on the removal of herbicides in soil. In this study, we investigated the effects of bacterial-feeding nematodes ( Cephalobus Bastian) on the dissipation of prometryne and microbial activity in prometryne contaminated soil. Materials and methods: Cultured with prometryne for a period of 6 months, prometryne-degrading bacteria strains P-1 and P-2 were isolated from sediments obtained from Anhui Huaxing Chemical Industry Co., Ltd. (Anhui Province, China). Bacterial-feeding nematodes were reared on Nematode Growth Medium agar plates (NGM) supplemented with prometryne for 5 months. Gnotobiotic microcosm experiments were conducted by inoculating both nematodes and prometryne-degrading bacteria strains P-1 ( Ochrobactrum sp.) and P-2 ( Bacillus sp.) into the contaminated soil. Soil samples were analyzed for prometryne concentration, the number of bacteria and nematodes, basal soil respiration, and enzyme activities. Results and discussion: The results show that (1) about 50-66% of the prometryne is dissipated in the treatments with nematodes and the dissipation rate is raised by 5-7% compared with the treatments without nematodes. The nematodes have positive effects on the dissipation of prometryne through their interaction with bacteria in soil; (2) the nematode grazing can increase the population size of bacteria; and (3) the introduction of nematodes can enhance basal soil respiration and soil enzyme activities, that is, soil microbial activity. Conclusions: The inoculation of nematodes enhanced microbial activity in contaminated soils and accelerated the dissipation of prometryne, and thus nematodes can be used in restoration of contaminated sites by accelerating pollutants dissipation in the future. [ABSTRACT FROM AUTHOR]

Abstract: A field experiment was carried out to investigate the methane emission pattern in a double-rice cropping system under conventional and no tillage in southeast China. The treatments included conventional tillage cultivation in both early rice and late rice (T–T) and conventional tillage in early rice but no-till in late rice (T–NT). The maximum methane emission rate of T–T and T–NT was 21.71mgm−2 h−1 and 24.70mgm−2 h−1 in early rice, respectively; and 18.52mgm−2 h−1 and 7.32mgm−2 h−1 in late rice, respectively. The seasonal amount of methane emission from the T–T and T–NT was not significantly different in early rice, but significant different (P <0.05) in late rice, with the values 6.57gm−2 and 3.04gm−2, respectively. In comparison with early rice, the seasonal amount methane flux of late rice was reduced by 29% and 68% in the T–T and T–NT, respectively. The decrease of methane emission in the T–NT was attributed to lower dissolved organic carbon (DOC) content and higher soil bulk density. In conclusion, no tillage practice conducted in rice cropping season will markedly decrease methane emission for the rice cropping system. [Copyright &y& Elsevier]

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]

This paper has been retracted. [ABSTRACT FROM AUTHOR]

How biodiversity affects terrestrial productivity is important to the maintenance of ecosystem services under global change. Although the crucial role of plant–soil feedbacks (PSF) in determining diversity–productivity relationship has been increasingly recognized in recent years, its legacy effects on subsequent diversity–productivity relationship are still unclear.We conducted a classic PSF experiment to assess how plant diversity‐conditioned soils influenced subsequent plant diversity–productivity relationships, where three plant diversity levels (1, 4 and 8 species) were planted in soils conditioned at three diversity levels (conditioned by 1, 4 and 8 species for 3 years). In addition, to test the role of soil microbial diversity in mediating the effects of soil conditioning diversity, the three plant diversity levels were planted with low, moderate and high soil biodiversity created by a soil inoculum dilution.The results showed that plant productivities were promoted by mixed‐conditioned soils (4 and 8 species) comparing to mono‐conditioned soils (1 species). Productivity was positively related to planted diversity in mixed‐conditioned soils, while showed no relation with planted diversity in mono‐conditioned soils. Productivity was promoted by soil biodiversity when 4 and 8 species were mixed planted, while did not change when 1 species was planted.Synthesis and applications. Our results highlight that PSF is crucial to strengthen the positive effects of biodiversity on productivity, implying that diversifying cropping systems should be encouraged in agroecosystem management to benefit from positive PSF effects. The importance of soil legacy for optimizing plant productivity is particularly important for conditioning soils with an intermediate number of plant species. [ABSTRACT FROM AUTHOR]

Solid additives can effectively overcome/alleviate the deficiencies of pure liquid lubricants themselves. However, the additive morphology involved in most of the reported solid additive/liquid lubricant systems is mostly irregular. They take more into account species differences and ignore the potential advantages of the sizes of unequal particles for the purpose of superlubricity. Herein, a mixed unequal-diameter sphere additive/ionic liquid analogue (Uneq-SA/ILA) model system is designed from the perspective of asymmetric contact between unequal-diameter spheres. It can easily enter a stable macroscopic superlubricated state (coefficient of friction as low as 0.0046) with negligible wear relative to an equal-diameter sphere additive/ILA system. Such excellent lubrication performance is attributed to the synergy of asymmetric contact between unequal-diameter spheres and low-shear-viscosity ILA; the ILA adsorbed on the sphere additive makes asymmetric slip interface between the spheres mainly concentrated inside the ILA, avoiding direct point-to-surface contact between the spheres. The film thickness of 948 μm implies that unequal-diameter spheres in the ILA have a normal accumulation space during contact, and the lubrication mechanism is dominated by hydrodynamic lubrication. This study deepens the understanding of asymmetric contact function of solid additives and provides new insights for the design of next-generation solid additive/liquid superlubrication systems. [Display omitted] [ABSTRACT FROM AUTHOR]

Intense human activities break the grassland–livestock balance and accelerate grassland degradation. We evaluated the use of native dominant species combined with arbuscular mycorrhizal fungi (AMF) in order to recover grassland and restrain grassland degradation. We conducted a full factorial greenhouse experiment to evaluate the interaction effects of native species of distinct traits grass Lolium perenne (L) and legume Trifolium repens (T) with arbuscular mycorrhizal fungi (AMF) inoculation on grass productivity and soil properties across non-degraded, lightly degraded, and severely degraded soils. The grass–legume mixture was manipulated with five ratios (T:L = 1:0, T:L = 1:1, T:L = 3:1, T:L = 1:3, T:L = 0:1). The results showed that L. perenne significantly increased grassland productivity at different grass–legume ratios, regardless of AMF presence or absence. AMF inoculation increased plant N and P content uptake and improved the productivity of degraded grasslands, especially in severely degraded grasslands. The NO3−-N and available P concentrations increased in soil when the legume component increased from T:L = 0:1 (grass monoculture) to T:L = 1:0 (legume monoculture). This may be because the presence of Lolium perenne (L) can promote nitrogen fixation in legumes. Structural equation modeling indicated that grass–legume mixtures directly affected plant biomass, whereas AMF affected plant biomass via providing plant nutrients. A soil quality index based on minimum datasets indicated a significant positive effect of artificial grassland establishment on soil quality. We conclude that planting T:L = 0:1 and T:L = 1:3 combined with AMF inoculation can be used to recover degraded grassland production, and planting T:L = 1:1 and T:L = 1:3 plus AMF inoculation can be applied for grassland nutrient accumulation and stability maintenance. [ABSTRACT FROM AUTHOR]

A trait-based approach is adopted to understand the responses of the soil nematode food web following cover crops incorporated into the soil, i.e., afterlife effect of plant. We conducted an in situ microcosm experiment with two cover crops including leguminous Astragalus sinicus L. (A. sinicus), characterized by high nutrient content, and gramineous Lolium multiflorum Lam (L. multiflorum), characterized by high C and lignin content, representing the acquisitive and conservative side of the economic spectrum, respectively. Furthermore, two incorporation rates were set to represent low and high biomass production of cover crops that could be incorporated into the soil. Soil main microbial groups, nematode food web, and physicochemical properties were analyzed at weeks 4 and 18 after cover crops incorporated into the soil. Results showed that, regardless of time, cover crops affected the abundance and composition of the soil nematode food web. L. multiflorum supported higher nematode abundance and more complex nematode food web than A. sinicus, charactering with higher fungivore/bacterivore, predator/prey, maturity index, and structure index, particularly under the high incorporation rates. In addition, A. sinicus improved much more resource availability (mineral N and dissolved organic C) than L. multiflorum. Together, the quantity and quality of plant residues jointly drive soil food web structure, and a trait-based framework facilitates the mechanical understanding of afterlife effect of plant on soil ecosystems. [ABSTRACT FROM AUTHOR]

Plants act as ecosystem engineers playing fundamental roles in steering their surroundings, including soil abiotic and biotic conditions, soil organisms, and the complex soil food web they comprise. Trait‐based approaches have been considered a 'Holy Grail' in linking plants to ecosystem functions, but the mechanistic relationship between plant traits and the soil food web as an indicator of soil health remains poorly understood.We examined this relationship for 16 cover crop species differing in leaf and root traits in a field experiment where corn, Zea mays was the main crop. Based on functional traits, the cover crop species were categorized into two ecological strategies at either end of the resource acquisitive‐conservative spectrum. We investigated the effects of cover crop ecological strategies on corn productivity and soil health. We used soil nematodes as an indicator of soil health and analysed soil physico‐chemical properties and microbial community activities.We found that acquisitive cover crops supported higher soil resource availability, bacterial energy channels in the soil food web, and greater corn productivity than conservative cover crops. In contrast, conservative cover crops supported higher abundances of fungivores and omni‐carnivores than acquisitive cover crop, which reflected a more structured and complex soil food web, implying a healthier soil ecosystem. Conservative cover crops also increased corn productivity compared to the no cover crop control treatment.Synthesis and applications. Collectively, this work shows that cover crops with distinct ecological strategies had their own strengths to enhance ecosystem functions: acquisitive and conservative cover crops improved crop productivity and soil health, respectively. These results indicates that farmers and policy makers can make trait‐based choices in selecting cover crop best serving the local needs. This points to a win‐win solution for food production and ecosystem sustainability. [ABSTRACT FROM AUTHOR]

Soil has become a major hotspot of biodiversity studies, yet the pattern and timing of the evolution of soil organisms are poorly known because of the scarcity of paleontological data. To overcome this limitation, we conducted a genome-based macroevolutionary study of an ancient, diversified, and widespread lineage of soil fauna, the elongate-bodied springtails (class Collembola, order Entomobryomorpha). To build the first robust backbone phylogeny of this previously refractory group, we sampled representatives of major higher taxa (6 out of 8 families, 11 out of 16 subfamilies) of the order with an emphasis on the most problematic superfamily Tomoceroidea, applied whole-genome sequencing methods, and compared the performance of different combinations of data sets (universal single-copy orthologs [USCO] vs. ultraconserved elements]) and modeling schemes. The fossil-calibrated timetree was used to reconstruct the evolution of body size, sensory organs, and pigmentation to establish a time frame of the ecomorphological divergences. The resultant trees based on different analyses were congruent in most nodes. Several discordant nodes were carefully evaluated by considering method fitness, morphological information, and topology test. The evaluation favored the well-resolved topology from analyses using USCO amino acid matrices and complex site-heterogeneous models (CAT |$+$| GTR and LG |$+$| PMSF (C60)). The preferred topology supports the monophyletic superfamily Tomoceroidea as an early-diverging lineage and a sister relationship between Entomobryoidea and Isotomoidea. The family Tomoceridae was recovered as monophyletic, whereas Oncopoduridae was recovered as paraphyletic, with Harlomillsia as a sister to Tomoceridae and hence deserving a separate family status as Harlomillsiidae Yu and Zhang fam. n. Ancestral Entomobryomorpha were reconstructed as surface-living, supporting independent origins of soil-living groups across the Paleozoic–Mesozoic, and highlighting the ancient evolutionary interaction between aboveground and belowground fauna. [Collembola; phylogenomics; soil-living adaptation; whole-genome sequencing.] [ABSTRACT FROM AUTHOR]