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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.]

Rapid urbanization profoundly affects global biodiversity. How urbanization modifies soil biodiversity and perturbs nematodes remains limited. Here, we investigated soil nematodes in four land-use types: Parks, residential areas, natural forests, and maize fields across 12 cities in China. Urban parks and surrounding forests had similar nematode richness exceeding that in urban residential areas and surrounding farmlands. Nematode communities in parks and residential areas were, however, more homogenous than in forests and farmlands. Variations in nematode assemblages in both core urban and urban surroundings were mainly due to taxa replacement, indicating that nematodes were spatially isolated in cities. Urban residential areas were colonized by the lowest number of specialists (i.e., with narrow niche width) and smaller body sizes. Urban parks, conversely, served as hotspots for soil nematodes in cities. Together, our results indicate that urbanization processes reduce nematode diversity, with e.g., 30% loss in residential areas compared to forests, and homogenize soil nematode communities.

Anthropogenic land use is threatening global biodiversity. As one of the most abundant animals on Earth, nematodes occupy several key positions in belowground food webs and contribute to many ecosystem functions and services. However, the effects of land use on nematode abundance and its determinants remain poorly understood at a global scale. To characterize nematodes' responses to land use across trophic groups, we used a dataset of 6,825 soil samples globally to assess how nematode abundance varies among regional land-use types (i.e. primary vegetation, secondary vegetation, pasture, cropland and urban) and local land-use intensities (i.e. human-managed or not). We also quantified the interactive effects of land use and environmental predictors (i.e. mean annual temperature, annual precipitation, soil organic carbon, soil pH, global vegetation biomass and global vegetation productivity) on nematode abundance. We found that total nematode abundance and the abundance of bacterivores, fungivores, herbivores, omnivores and predators generally increased or were not affected under management across land-use types. Specifically, the most numerically abundant bacterivores were higher in managed than in unmanaged secondary vegetation habitats and urban areas, and herbivores were more abundant in managed than in unmanaged primary and secondary vegetation habitats. Furthermore, the numbers of significant environmental predictors of nematode abundance were reduced and the magnitude and the direction of the predictors were changed under management. We also found that nematode abundance was more variable and less determined by environmental factors in urban than in other land-use types. These findings challenge the view that human land use decreases animal abundance across trophic groups, but highlight that land use is altering the trophic composition of soil nematodes and its relationships with the environment at the global scale.

Global biodiversity is being threatened by climate change and human activities. Prior studies have demonstrated the negative concequences of land-use such as conversion of forest into monoculture, while its effects on belowground organisms especially soil invertebrates remain unclear. Earthworms are well-known ecosystem engineers that deliver multiple ecosystem functions including decomposition, carbon sequestration and plant growth. Yet, all of those functions are negatively affected by land-use conversion. Previous studies concerning land-use effects on soil biodiversity were generally conducted at a single site and small spatial scale, how soil biodiversity changes across spatial scales remains poorly understood.In current study, earthworms were quantitatively sampled from 41 sites in three land-use types (i.e., farmland, orchard and forest at each site, five replicates) in subtropical region of China. Earthworm species were identified using both morphological and molecular methods. Earthworm density, biomass and body size were recorded. Notably, the species were also classified into different functional guilds. Totally, 84 species (or subspecies) were identified. Generally, local diversity (α diversity) was higher in agricultural lands than in forest lands, however, the opposite was true for regional diversity (γ diversity). In addition, the density of earthworm was the lowest in forest, while the biomass and body size were higher in agricultural lands. A higher proportion of endogeic and anecic earthworms were found in farmland and orchard than in forest. The land-use caused changes in soil properties contributed to the difference in earthworm diversity, abundance, biomass and body size.In conclusion, we suggest that the impacts of human land-use on soil earthworm assemblage are scale-dependent, and the diversity, abundance, biomass and body size respond differently to land-use. Researches on different scales about land-use effects to soil biodiversity are urgently needed.

Soil biota, across multitrophic levels, regulates nutrient cycling and plant performance, and thereby play an important role in delivering multiple ecosystem functions. Soil nematodes occupy diverse positions in the soil food web, such as herbivores, bacterivores, fungivores, omnivores, and predators. Therefore, soil nematodes are usually considered as potential bio-indicators of soil quality or soil health under agricultural managements. However, there is a knowledge gap on how nematode multitrophic biodiversity (here the numbers of nematode trophic groups) affects soil multifunctionality.This study combined field and laboratory experimental approaches to quantify and disentangle the aforementioned issue. First, we explored the impacts of compost application on nematode assemblages as well as multifunctionality based on a long-term field experiment. Results showed that compost application stimulated multitrophic biodiversity by the increase of microbivore and omnivore-predator abundance, while decreasing the herbivores. Besides, the increase of nematode multitrophic biodiversity was accompanied with the soil multifuctionality. Then a complete factorial design microcosm experiment was conducted with manipulating nematode trophic levels (microbivores, herbivores and omnivore-carnivores) to test the hypothesis that increasing multitrophic biodiversity will lead to higher soil multifuctionality as indicated by plant growth and defense to the pests. Consistent with the hypothesis, we found that integrating different trophic levels, i.e. maximum multitrophic biodiversity, could promote plant growth and notably the resistance to pest infestation through changing plant chemical composition. Particularly, we found microbivores reduced root biomass while omnivore-carnivores increased plant shoot biomass. The presence of omnivore-carnivores could suppress the abundance of insect (brown planthoppers) by regulating soil microbiome. In summary, the increment of soil multitrophic biodiversity have multifunctional consequence.Overall, we provide direct experimental evidence for the multifunctional roles of soil multitrophic biodiversity. Further, soil organic management practices, regardless of organic amendments, non-tillage or growing cover crops, that improving soil habitat like resource and structure, and consequently promoting soil biodiversity especially higher-level biotic associations or trophic interactions may ultimately contribute to sustaining multiple ecosystem services including both crop productivity and pathogen controls. Such knowledge helps advance the mechanical understanding of biotic drivers of soil ecosystem functioning. It also highlights that organic management could strengthen the carbon-based ecosystem services if considering the extra benefits provided by soil biodiversity. Overall, our study corroborated organic management will be crucial to implement an ecologically multifunctional agriculture.

Soil fauna are now recognized as key components of soil and plant health, but how soil fauna modulates or even dictates plant stress responses remains unknown.Prior studies found the impacts of soil fauna on the plantprioritize either growth or defence depends on the feeding types of herbivores, suggesting that aboveground responses to herbivores and soil fauna are interconnected.However, the molecular and metabolism mechanism underlying this relationship is unclear.Theoretically, soil biotic interactions modified by soil fauna can drive above-ground responses, but there is still shortage of experimental evidence. Here, we aimed to test whether and how the plant survival strategies subjective to different feeding types of herbivores, were affected by rhizosphere microbial interactions exerted by soil fauna. We hypothesized that aboveground stress responses in plants can be orchestrated through coordinating belowground biotic interaction by soil fauna-root commensals.First, we set out a complete factor design experiment under field condition by manipulating earthworms (Metaphire guillelmi) and the types of above-ground insects (cell-feeding, thrips: Frankliniella occidentalis; phloem-sucking, aphid: Myzus persicae). Soil physicochemical analysis and leaf RNA-seq were used to expound how earthworms dictates the trade-off between plant growth and defence. Second, to further explore the soil biotic-mediate pathway in the presence of earthworms. A microcosm experiment was performed by using a re-inoculated different soil community (obtained from 1000 and 20 μm sieves, respectively) collected from the field, with and without earthworms in the absence of herbivores. We used amplicon sequencing and plant metabolite analysis to elucidate how earthworm function by shaping rhizosphere biotic interactions.We report here that belowground commensals can orchestrate aboveground stress responses in plants through biotic interaction. Earthworms suppressed thrips number, consistent with a resource-cost model. Contrary, earthworms promoted aphids’ number through the hormone antagonism model. Notably, soil biotic properties affected plant performance rather than soil abiotic properties mediated by earthworm. The microcosm experiment verified that rhizosphere microbial diversity and community structure shaped by earthworms reformed plant performance. In inoculated soil conditioned by earthworms, soil microbiome tended to be bacterial community towards primary metabolic processes, strengthening the interaction between fungi and bacteria in the rhizosphere. Further, the strengthened rhizosphere microbial interactions were increased plant shoot biomass and soluble sugar accumulation but decreased JA content. Taken together, effects of soil fauna on plant growth-defence relationships depend on the feeding types of herbivores, mainly attributing to the shifts in rhizosphere microbial interactions. Phenotypic plasticity and aboveground stress responses in plants can therefore be governed by soil fauna-root commensals.

Anthropogenic activities have profoundly increased the nutrient inputs into soil through inorganic nitrogen (N) and phosphorus (P) fertilization and atmospheric deposition over recent decades. In grasslands, nutrient enrichment is one of the most important global change factors affecting a range of ecosystem functions and services. Nutrient enrichment promotes some functions such as plant production, but at the cost of other ecosystem functions, which may obscure the net effects on multiple ecosystem functions (i.e., ecosystem multifunctionality). In particular, nutrient enrichment can strongly reduce above- and below-ground biodiversity, which might threaten ecosystem services that delivered by biodiversity. However, our understanding of the importance of soil biota as a component of nutrient-enrichment effects on ecosystem multifunctionality is still limited.Taking advantages of a long-term field study and a controlled microcosm experiment, we explored whether and how nutrient enrichment affects ecosystem multifunctionality in a Tibetan alpine meadow. The diversity of soil biota across multiple trophic, including bacteria, fungi, protists and nematodes for two consecutive years were investigated from a 13-year field experiment under a gradient of N and P enrichment. A total of 14 ecosystem functions that are influenced by soil biota were measured and were grouped into five categories: (1) nutrient cycling, (2) SOM decomposition, (3) carbon and nutrient cycling drivers, (4) soil structure, and (5) pest control. To generate a comprehensive understanding of the biodiversity-ecosystem-function relationship under nutrient enrichment, a microcosm inoculation experiment using the dilution-to-extinction approach was conducted with soil samples with or without nutrient enrichment.Our results showed that nutrient enrichment weakened multifunctionality by reducing the multidiversity across soil food webs. Specially, soil biodiversity at higher trophic levels (e.g., microbivorous nematode) supported a greater number of ecosystem functions at high levels of functioning than those of lower trophic levels, such as bacteria and fungi. Microcosm experiment further demonstrated that nutrient enrichment weakened the relationships between soil biodiversity and ecosystem multifunctionality. Together, our results provide insight into the importance of soil biodiversity for maintaining soil multifunctionality under nutrient enrichment, as well as providing strong support for inclusion of multiple aspects of soil biodiversity in conservation and management policies under global change scenarios.

The functional performance of soil ecosystems following disturbance determines ecosystem stability, and although contributions of bacterivorous nematodes to soil ecosystems are recognized, their roles in functional stability have received little attention. The objective of this study was to evaluate the roles of bacterivorous nematodes in functional stability following stress. In a factorial laboratory experiment, soil microcosms were prepared with two levels of nematode abundance, either an enriched abundance of bacterivores (Nema soil) or background abundance of nematodes (CK soil), and three levels of stress, copper, heat, or an unstressed control. The resistance and resilience of nematode abundance, as well as soil microbial function by determining decomposition of plant residues and microbial substrate utilization pattern using a BIOLOG microplate, were followed post stress. The relative changes of two dominant bacterivores, Acrobeloides and Protorhabditis, responded differently to stresses. The resistance and resilience of Protorhabditis were greater than that of Acrobeloides to copper stress during the whole incubation period, while both bacterivores only showed higher resilience under heat stress at the end of incubation. The enrichment of bacterivores had no significant effects on the soil microbial resistance but significantly increased its resilience to copper stress. Under heat stress, the positive effect of bacterivores on soil resilience was only evident from 28 days to the end of incubation. The differences in the responses of soil function to stress with or without bacterivores suggested that soil nematodes could be conducive to ecosystem stability, highlighting the soil fauna should be taken into account in soil sustainable management.

Two greenhouse experiments using soils from long-term field plots were carried out to test whether and how soil factors modulated by organic amendments feed back to rice plant growth and defense against an aboveground herbivore, the planthopper Nilaparvata lugens. Using factorial combinations of sterilized soil and soil inocula obtained from chemically amended plots (i.e., control treatment) or chemically plus organically amended plots (i.e., organic treatment), we disentangled the effects of biotic and abiotic soil properties on plant and planthopper performance. We found that, compared with abiotic soil properties, soil biological factors were the main drivers in regulating plant growth performance. Specifically, soil biota that are shaped by the organic treatment had high microbial abundance and diversity and enhanced rice plant tolerance (i.e., increasing plant total biomass) and resistance (i.e., decreasing amino acid and sugar concentrations) to planthoppers. Moreover, the organic treatment simultaneously increased plant growth and defense against planthoppers, which could be explained by high soil nutrient availability driven by soil biota. Our results demonstrate the importance of synergistic effects of soil biota and soil abiotic factors on plant growth and resistance to herbivory. These findings are important for better understanding the mechanisms and impacts of ecological intensification as well as the potential of steering soil communities to reduce the use of chemical fertilizers and pesticides and further optimize crop production.

Insecticidal crystal (Cry) proteins produced by genetically modified rice that enter the soil via pollen dispersal, plant residues, and root exudation may disturb soil health. In the present study, we assessed the influences of transgenic Bt rice (i.e., HH1 with Cry1Ab/Cry1Ac) cultivation on the dynamics of soil carbon and nutrients under field conditions during 2013-2016. Transgenic treatments (transgenic Bt rice vs. its parental line (i.e., MH63) of non-Bt rice) have no consistently significant effects on soil property, including available nitrogen, available phosphorus, available potassium, total nitrogen, and total phosphorus, while apparent seasonal changes were observed. Besides, the variations of soil nutrients in the paddy field of transgenic Bt rice did not exceed their resistance capacities, except total organic carbon (TOC; RS (resistance) = 1.51) and total potassium (TK; RS = 2.62) in 2013 and TK (RS = 1.94) in 2014. However, the TOC and soil nutrient of TK in the paddy field of transgenic Bt rice have recovered to the pre-perturbation status after harvest (RL (resilience) = 1.01, F = 0.01, P = 0.91; RL = 0.98, F = 0.34, P = 0.58; RL = 0.99, F = 1.26, P = 0.29). Moreover, the paddy yield of transgenic Bt rice was consistently higher than that of its parental line of non-Bt rice. These results suggested that the cultivation of transgenic Bt rice has no adverse impact on soil stability in terms of soil carbon and nutrients and paddy yield.

Anthropogenic conversion of natural to agricultural land reduces aboveground biodiversity. Yet, the overall consequences of land-use changes on belowground biodiversity at large scales remain insufficiently explored. Furthermore, the effects of conversion on different organism groups are usually determined at the taxonomic level, while an integrated investigation that includes functional and phylogenetic levels is rare and absent for belowground organisms. Here, we studied the Earth's most abundant metazoa?nematodes?to examine the effects of conversion from natural to agricultural habitats on soil biodiversity across a large spatial scale. To this aim, we investigated the diversity and composition of nematode communities at the taxonomic, functional, and phylogenetic level in 16 assemblage pairs (32 sites in total with 16 in each habitat type) in mainland China. While the overall alpha and beta diversity did not differ between natural and agricultural systems, all three alpha diversity facets decreased with latitude in natural habitats. Both alpha and beta diversity levels were driven by climatic differences in natural habitats, while none of the diversity levels changed in agricultural systems. This indicates that land conversion affects soil biodiversity in a geographically dependent manner and that agriculture could erase climatic constraints on soil biodiversity at such a scale. Additionally, the functional composition of nematode communities was more dissimilar in agricultural than in natural habitats, while the phylogenetic composition was more similar, indicating that changes among different biodiversity facets are asynchronous. Our study deepens the understanding of land-use effects on soil nematode diversity across large spatial scales. Moreover, the detected asynchrony of taxonomic, functional, and phylogenetic diversity highlights the necessity to monitor multiple facets of soil biodiversity in ecological studies such as those investigating environmental changes.

Although the enrichment of antibiotic resistance genes (ARGs) in diverse organic soils have been explored, understanding of the ecological processes governing the composition of ARGs in long-term organically fertilized soils still remains limited across typical agricultural regions. Thus, the distribution and assembly of ARG profile in three typical agricultural soils (black soil, fluvo-aquic soil, and red soil) under long-term contrasting fertilization regimes (chemical-only vs organic-only) were investigated using high-throughput qPCR (HT-qPCR). The application of organic manure significantly increased the abundance and number of ARGs across soils, as compared to those with chemical fertilizer. Organic manure application enriched the abundance of mobile genetic elements (MGEs), which were positively associated with ARGs. In addition, it is long-term organic fertilizer that enriched the number and abundance of opportunist and specialist ARGs in the fluvo-aquic and red soils, but not black soils. The number and abundance of most generalist ARGs did not change significantly among different fertilization or soil types. The assembly process of the ARG profiles tends to be more deterministic in organically fertilized soils than in chemically fertilized soils. These results suggest that long-term organic fertilizer application may contribute to the persistence and health risk of the soil antibiotic resistomes (especially specialist ARGs).

Soil organic carbon (SOC) sequestration under elevated CO2 concentration (eCO2 ) is a function of carbon (C) input and C retention. Nitrogen (N) limitation in natural ecosystems can constrain plant responses to eCO2 and their subsequent effects on SOC, but the effect of eCO2 on SOC in N-enriched agroecosystems with cultivars highly responsive to eCO2 is largely unknown. We reported results of SOC dynamics from a field free-air CO2 enrichment experiment with two rice cultivars having distinct photosynthetic capacities under eCO2 . A reciprocal incubation experiment was further conducted to disentangle the effect of changes in litter quality and soil microbial community on litter-derived C dynamics. eCO2 significantly increased total SOC content, dissolved organic C and particulate organic C under the strongly responsive cultivar, likely due to enhanced organic C inputs originated from CO2 stimulation of shoot and root biomass. Increases in the residue C : N ratio and fungal abundance induced by eCO2 under the strongly responsive cultivar reduced C losses from decomposition, possibly through increasing microbial C use efficiency. Our findings suggest that applications of high-yielding cultivars may substantially enhance soil C sequestration in rice paddies under future CO2 scenarios.

Aims Roots bridge above and belowground systems, and play a pivotal role in structuring root-associated organisms via influencing food resources and habitat conditions. Most studies focused on the relationships between plant identity and root-associated organisms, however, little is known about how root traits affect nematode communities within the rhizosphere. Methods We investigated the relationships between root traits of four plant species and nematode diversity, community structure and trophic complexity in an ex-arable field. Results While the relative abundance of herbivorous nematodes was negatively associated with specific root length (SRL), specific root area (SRA), root length density (RLD) and root C: N ratio, free-living nematodes were positively affected by these traits, implying a multifaceted effect of root traits on root-associated organisms. Importantly, we found that finer root systems promoted the complexity of the nematode community, by increasing the relative abundance of high trophic-level nematodes (i.e., omnivores and predators) and enhancing nematode diversity. Conclusion Our findings suggest that root traits could be reliable indicators of soil community structure and interactions, and provide new insights into soil biodiversity and functional maintenance.

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.

Learning time of student is precious, over-practice of target knowledge component wastes student’s time, however, under-practice may mean the student may not grasp target knowledge component properly. To any student, it is helpful if intelligent tutoring system can determine how many practice opportunities needed for mastery of knowledge component. In this paper, to improve student’s learning efficiency, a method of predicted learning curve based on grey models is proposed to determine the counts of practice op-portunity for mastery of knowledge component. The experimental results show that the predicted value on error rate of practice opportunity over knowledge component with the proposed method is much closer to the value of real learning curve than the predicted learning curve produced by learning factors analysis. It implies the proposed prediction method is potential to present reasonable practices for personalized tutoring.

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.

The double-cropping of winter wheat and summer maize is a major grain production system in China which occupies more than half the double-cropping systems of the country’s dryland area. This cropping system has experienced a decreased crop yield and soil quality and the limiting factors are poorly known. The goal of this study was to conduct a systematic evaluation of wheat yield and soil quality from 132 fields along a regional scale in China. The specific objectives were (i) to establish a minimum data set (MDS) in wheat phase under the wheat-maize cropping system (ii) to evaluate soil quality of the wheat field and determine the factors limiting wheat productivity. The wheat-maize cropping system was partitioned into three productivity levels (high, medium and low) according to the wheat yield. Twenty-six soil indicators, including soil microbiological, chemical and physical factors were measured and analyzed. Using Pearson correlation analysis we identified eight key soil indicators that determine wheat yield. We then used principal component analysis to determine an MDS, which included soil organic matter, alkali-hydrolyzable nitrogen, the ratio of microbial biomass nitrogen to total nitrogen, and available zinc. One-way analysis of variance based on the individual contribution of each MDS indicators under three productivity, revealed available nitrogen, soil organic matter and the ratio of microbial biomass nitrogen to total nitrogen was the most important indicators on limiting wheat yield. A soil quality index (SQI) based on scoring and weighting of MDS indicators was integrated as a tool for assessing farmland soil quality. Based on the MDS, high (HP), medium (MP) and low (LP) productivity received mean SQI of 0.55, 0.48 and 0.39, respectively. The significant positive correlation between SQI and wheat yield suggests that this is a good representative of the MDS for the wheat-maize cropping system in China. We conclude that our SQI may be an effective and practical tool to guide a strategic, regional goal with respect to sustainable high yields.

Earthworm gut played an important role in the transformation of various contaminants in the soil environments. With the increasing application of organic fertilizer recently, the ingestion of antibiotics, antibiotic resistance bacteria (ARB), and antibiotic resistance genes (ARGs) made the earthworm gut a potential favorable micro-environment for the transmission of ARGs in the soil. In this work, the conventional plate incubation and high-throughput sequencing methods were both employed to investigate the composition of the cultivable and overall ARB/ARGs in the Metaphire guillelmi earthworm gut. A total of 87 cultivable isolates that resisted tetracycline (TC) and/or sulfadiazine (SD) were obtained, most of which belonged to phylum Firmicutes, genus Bacillus. Meanwhile, the counts of isolates with TC-SD dual resistance were higher than those with sole SD or TC resistance. Moreover, higher ARB counts and diversity were detected in the earthworm gut by high-throughput sequencing technique than those by the classical plate cultivation. Overall, the combination of conventional cultivable bacteria isolation and high-throughput sequencing methods provided a comprehensive understanding of the ARB composition in the earthworm gut. The results demonstrate that the earthworm gut is a hospitable micro-environment for ARB colonization. The potential role of earthworm intestinal ARB and ARGs proliferation in soil environments warrants further research.

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.

Organic amendments such as vermicompost and biochar have been reported to enhance soil fertility and crop productivity. However, whether the co-application of both amendments has synergistic effects or whether such benefits are accompanied by the risk of gaseous nitrogen (N) loss in an agroecosystem remains unknown. A soil column experiment with a fully factorial design was conducted using three levels of vermicompost (no dose, low dose (1%, weight:weight), and high dose (3%, weight:weight)) without or with biochar (1%, weight:weight) to investigate their effects on rice growth and gaseous N loss across the crop growing season. Our results demonstrated that synergistic interactions existed between vermicompost and biochar in promoting crop yield. Compared with biochar amendment alone, biochar combined with vermicompost significantly (P

Nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) could be used to reduce nitrogen (N) loss and improve N use efficiency in agroecosystems. However, the DMPP effect on N dynamics at the microscale remains largely unknown. A microcosm experiment was conducted to evaluate the effects of DMPP and fertilizer application method on N fate, including 15NH4+-N, (15NO3−+15NO2−)-N, MB15N and N losses at the centimeter-scale. The isotope labelled 15N-urea was applied to soil with or without DMPP. Two fertilizer application methods were compared, including mixed with soil (mix-application) or concentrated on the soil surface (spot-application). After 28 days of incubation at 28 °C, DMPP amended with urea significantly increased soil pH and 15NH4+-N concentrations but decreased (15NO3−+15NO2−)-N concentrations in both horizontal and vertical directions compared with urea application alone. Such effect was more obvious within 0–2 cm and weakened with increasing distance from the fertilizer zone. DMPP addition significantly increased N losses compared with urea application alone, which is mainly due to the increased ammonia volatilization caused by high pH and NH4+ concentrations. The application method of urea and DMPP also had different effects on N performance, depending on the distance and spatial directions of microsites. And the N losses in the mix-application treatment (32%) were significantly lower than in the spot-application treatment (37%) when urea was applied alone. We concluded that DMPP addition significantly slowed down nitrification processes, and urea mixed with soil is better than concentrated on the soil surface in reducing N losses when urea was applied alone.

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.