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Although straw-decomposing microbial inoculants (SDMI) are capable to generally promote the fertility of straw-amended soils, their impact on the release of individual soil major nutrients remains controversial. Additionally, the combined effects of SDMI and environment/management on various forms of nutrients remain poorly documented. To fill these research gaps, we conducted a meta-analysis study using 1214 paired observations from 132 field trials in China. Our results showed that SDMI significantly increases the total and available concentrations of nitrogen, phosphorus, and potassium in soil (p < 0.05), although increases in nutrients varied with different conditions. Moreover, mean annual precipitation (MAP) had significant correlations with the effects of SDMI-amended straw on soil total nitrogen (p = 0.008) and available nitrogen (p = 0.0006). The effect of SDMI-amended straw on soil total phosphorus and soil available potassium was mainly correlated with soil organic matter (p = 0.032) and MAP (p = 0.049), respectively. Our findings indicate that SDMI-amended straw can have a measurable impact on the status of soil major nutrients. In particular, the application of SDMI-amended rice straw with an initial C/N ratio of ≤15 to neutral soils in temperate and subtropical monsoon climates is a promising strategy. [ABSTRACT FROM AUTHOR]

Inoculum size contributes to the invasion potential of pathogens in the soil. However, the role of inoculum size in determining the fate of pathogens in disturbed soils remains unclear. Herein, we investigated the survival rates of a bacterial pathogen, Ralstonia solanacearum, in soils subjected to heat as a simulated disturbance. Our results revealed that heating increased soil resource availability but reduced resource differentiation between R. solanacearum and indigenous bacterial communities. In both non-heated and heated soils, invader abundances increased with inoculum size, with a greater magnitude in heated soils. Inoculum size and heat-induced increases in soil-available carbon and nitrogen best predicted invasion success. Altogether, our findings suggested that the invasion by soil pathogens could be predicted by synergies between heat perturbation and inoculum size. [ABSTRACT FROM AUTHOR]

Risk assessment and ecological effects are a concern of transgenic rice. In this study, the effects of three lines of Bt rice expressing single Cry1Ab protein (Kemingdao: cv. KMD) and fused Cry1Ab/Cry1Ac proteins (Huahui 1: cv. HH1; Bt Shanyou 63: cv. Bt-SY63) on soil mite community were investigated under field conditions. Transgenic treatment (cv. Bt-rice vs. non-Bt rice) significantly decreased the community index of Margalef's richness (SR) of soil mite in KMD, and significantly increased the abundance and the community indexes of Shannon diversity (H'), Pielou's evenness (J) and SR of soil mite in Bt-SY63 (p < 0.05). Transgene type (cv. KMD vs. HH1) did not significantly affect the composition, abundance and the community index (p > 0.05). Breeding type (cv. HH1 vs. Bt-SY63) significantly changed the composition and markedly improved the abundance and the J value in Bt-SY63 (p < 0.05). However, seasonal and inter-annual changes were apparent, and the Bt effects were not consistent at all for the different plant backgrounds over a 2-year period. These results suggested that the cultivation of Bt rice has a significant but transient effect on soil mite community. [ABSTRACT FROM AUTHOR]

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. [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]

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]

The soil microbial food web plays a vital role in soil health, nutrient cycling and agricultural productivity. Notably, there is a distinct paucity of information regarding the effects of heavy metal contamination on trophic-level interactions within the microbial food web of agricultural soils, which experience appreciably metal contamination worldwide. Herein, we investigated trophic interactions among predators (protists), their preys (bacteria and fungi) and competitors (nematodes) under four metal contamination levels using high-throughput sequencing and a laboratory verification experiment. Metal contamination decreased growth of protist-preferential prey (e.g., small-sized and gram-negative bacteria), increased the growth of protist-nonpreferential prey (e.g., pathogenic fungi and Actinobacteria), and had a limited effect on the soil protist-competitor (i.e., nematodes). This resulted in a considerable decrease in the diversity and abundance of protistan consumers and a re-arrangement of their interactions with other organisms. From a systemic view, the direct link was weaker between heavy metal contamination and the protist community than the indirect linkage, i.e., metal-induced changes in the prey community. We further validated these results with laboratory incubation trials that documented growth inhibition of protist (Colpoda) and protist-preferential prey (Spingomonas) versus growth stimulation of protist-nonpreferential prey (Arthrobacter) under metal contamination. These findings indicate that metal contamination collapses trophic-level interactions within the soil microbial food web via bottom-up regulation, providing important implications for managing trophic interactions to maintain agricultural ecosystem services under the challenge of worldwide metal contamination. [Display omitted] • Heavy metals increased bacteria/fungi diversity but decreased protist diversity. • Heavy metals impacted trophic interactions by bottom-up control. • Feeding preference of protist is the mechanism that triggered the cascade effects. [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]

Soil aggregates are the key functional units of soil ecosystems which are essential to biogeochemical cycling and plant growth. However, it remains unclear how fertilization regimes influence soil aggregation, associated resources, and microbial distribution among aggregates, as well as the potential subsequent impacts for other abiotic and biotic processes. For this, a long-term maize cropping field experiment was conducted in the subtropical region of China under four fertilization treatments: no fertilizer, chemical fertilization, organic fertilization, and chemical plus organic fertilization. Additionally, we classified soil aggregates into large macro-aggregates (>2 mm), small macro-aggregates (0.25–2 mm), and micro-aggregates (<0.25 mm) and compared soil nutrients, enzyme activities, and microbial communities of each aggregate fraction and bulk soil as well as crop productivity and plant carbon (C), nitrogen (N), and phosphorus (P). Results showed that long-term organic fertilization (1) increased soil C, N, and P contents within macro-aggregates, while increased bacterial and fungal biomass within all three aggregate size fractions, (2) increased N-acquiring enzyme activity, C:P, and N:P enzyme ratios but decreased phosphatase activity and C:N enzyme ratio regardless of aggregate fractions, and (3) promoted crop productivity but decreased plant C:N, C:P, and N:P ratios compared with chemical fertilization. Additionally, the fungi:bacteria ratio and phosphatase activity decreased, but the gram-positive to gram-negative bacterial ratio, C-acquiring enzyme activity, C:N and C:P enzyme ratios increased with decreasing aggregate size. The partial least squares models confirmed that macro-aggregates had strong effects on crop performance while micro-aggregates was the main determinant of microbial community. Taken together, long-term organic fertilization promotes soil functioning and crop productivity via increasing the proportion of soil macro-aggregates. • Aggregates with different sizes played distinct roles in soil functioning. • Organic fertilization increased crop productivity by promoting macro-aggregation. • Macro-aggregates is an important resource of nutrients promoted plant growth. • Resources in micro-aggregate were conducive to microbial utilization. • Microorganisms in micro-aggregates were C-limited. [ABSTRACT FROM AUTHOR]

Litter decomposability determines litter mass loss rate, but how it affects soil carbon (C) and nitrogen (N) storage remains elusive. We compiled data from 25 litter decomposition studies tracing the fate of C and N during decomposition using stable C and N isotopes. An average of 24% of C lost from decomposing litter was recovered in the soil independent of the decomposition stage and the experimental conditions. In contrast, a higher amount of N lost from decomposing litter was recovered in the soil in laboratory (80%) than in field (58%) experiments. The proportion of the total C and N lost that was transferred to the soil was higher for slowly than for rapidly decomposing litter types. Our results demonstrate substantial soil C and especially N input from decomposing litters and suggest that slowly decomposing litters favor soil C and N storage compared to more rapidly decomposing litters. • On average a quarter of litter C loss is recovered in the soil at much lower rates than litter N. • Litter C recovery rate remained stable along the decomposition process. • Slow-decomposing litters are more efficient in incorporating litter C and N into the soil. [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]