Harmonizing soil restoration and microbial diversity: Insights from a Two-Year field experiment with Sedum-Rice rotation systems.

Phytoremediation coupled with agroproduction (PCA) model contributes to sustainable agriculture and environmental management. This study investigated the impact of continuous cropping early/late season rice (RR) and Sedum alfredii-rice rotation (SR) on soil physical and chemical properties, as well as their relationships with soil microbial community. In 2022, SR treatment significantly increased pH value and organic matter content by 7 % and 17 %, respectively, compared to the levels in 2020, while RR treatment showed no change. RR treatment resulted in a significant decrease in soil concentrations of Ca, Mg, and K by 18.42 %, 29.01 %, and 7.77 %, respectively. Furthermore, SR treatment saw reductions of 29.62 % in total Cd and 38.30 % in DTPA extractable Cd in the soil. Over the two years, both treatments notably influenced the diversity, structure, and network of the rhizosphere bacterial and fungal communities, which are crucial for nutrient cycling and plant health. Notably, SR treatment exhibited a more complex network compared to RR, suggesting a greater impact on the interconnected systems. Therefore, these findings highlight the potential of Sedum rotation system to rehabilitate contaminated soils while supporting agricultural practices, which is essential for food security and environmental sustainability. This research direction holds promise for future exploration and application in the fields of phytoremediation and agroecology.

Changes in soil properties and microbial activity unveil the distinct impact of polyethylene and biodegradable microplastics on chromium uptake by peanuts.

Microplastics (MPs) are emerging persistent pollutants, and heavy metals are typical environmental pollutants, with their coexistence potentially compounding pollution and ecological risks. However, the interactive impacts and the relevant mechanisms of heavy metal and different types of MPs in plant-soil systems are still unclear. This study investigated the differential impacts of polyethylene MPs (PE MPs) and biodegradable polybutylene adipate MPs (PBAT MPs) on chromium (Cr) uptake in peanuts, focusing on plant performance and rhizosphere soil microenvironment. Compared with nondegradable PE-MPs, biodegradable PBAT MPs produced less significant influences on plant phytotoxicity, soil Cr bioavailability, and soil properties such as pH, CEC, DOC, and MBC, with the exception of MBN in Cr-contaminated soils. Compared to the control, soil pH and cation exchange capacity (CEC) decreased by MPs, while soil-soluble carbon (DOC), microbial biomass carbon, and nitrogen (MBC and MBN) increased by MPs. Compared to the control, soil-bioavailable Cr increased by 11.8-177.8% under PE MPs treatments, while increased by 5.1-156.9% under PBAT MPs treatments. The highest Cr content in shoots and roots was observed at 500.0 mg·kg-1 Cr level, which increased by 53.1% and 79.2% under 5% PE MPs treatments, respectively, as well as increased by 38.3% and 60.4% under 5% PBAT MPs treatments, respectively, compared with the control. The regression path analysis indicated that pH, MBC, MBN, and soil-bioavailable Cr played a vital role in the changes of soil properties and Cr uptake by peanuts induced by MPs. Soil bacterial community analysis revealed that Nocardioides, Proteobacteria, and Sphingomonas were reduced by the inhibition of MPs, which affected Cr uptake by peanuts. These results indicated that the peanut soil microenvironment was affected by PBAT and PE MPs, altering the Cr bioavailability and plant Cr uptake in Cr-contaminated soil.

The effect of low-temperature straw-degrading microbes on winter wheat growth and soil improvement under straw return.

The application of straw-degrading microbes (SDMs) with straw returned to the field is an effective measure to improve soil quality, increase yield, and maintain soil microorganisms. However, the utilization of SDMs in winter in north China is limited by the poor effects at low temperatures. This study investigated the effects of a new compound SDM, including a novel low-temperature fungus Pseudogymnoascus sp. SDF-LT, on winter wheat yield, soil improvement, and soil microbial diversity. A 2-year field experiment was conducted in two different soil textures of wheat-maize rotation fields with full corn straw return and application of SDMs at an amount of 67.5 kg hm-2. After 2 years of continuous application of SDMs, the winter wheat yield increased significantly, reaching 9419.40 kg hm-2 in Ningjin (NJSDM) and 9107.25 kg hm-2 in Mancheng (MCSDM). The soil properties have been significantly improved compared with the single straw return group, especially the sandy loam soil, whose quality is relatively low. The analysis of soil microbial diversity showed that SDMs significantly reduced the Chao1, Shannon, Simpson, and observed species of the sandy loam soil in the MCSDM group. The Simpson and Shannon indexes of fungi diversity in the two experimental sites were significantly increased by SDMs. The negative correlation of fungi increased from 47.1 to 48.85% in the SDM groups. The soil-dominant microbes changed in the SDM groups, in which the interactions between microbes were enhanced. These results suggested that the SDMs changed the the soil microbial community structure and its diversity and complexity, which is beneficial for crop growth. Our study provided sufficient evidence for the utilization of low-temperature SDMs with straw return in cold winter, which plays a role in soil improvement, especially for low-quality soils, to increase crop yield.

Nonbiodegradable microplastic types determine the diversity and structure of soil microbial communities: A meta-analysis.

As an emerging contaminant, microplastics (MPs) have received considerable attention for their potential threat to the soil environment. However, the response of soil bacterial and fungal communities to MPs exposure remains unclear. In this study, we conducted a global meta-analysis of 95 publications and 2317 observations to assess the effects of nonbiodegradable MP properties and exposure conditions on soil microbial biomass, alpha and beta diversity, and community structure. Our results indicate that MPs increased (p < 0.05) soil active microbial biomass by 42%, with the effect varying with MPs type, exposure concentration, exposure time and soil pH. MPs concentration was identified as the most important factor controlling the response of soil microbial biomass to MPs. MPs addition decreased (p < 0.05) the soil bacterial Shannon and Chao1 indices by 2% and 3%, respectively, but had limited effects (p > 0.05) on soil fungal Shannon and Chao1 indices. The type of MPs and exposure time determined the effects of MPs on bacterial Shannon and Chao1 indices, while the type of MPs and soil pH controlled the response ratios of fungal Shannon and Chao1 indices to MPs. Specifically, soil organic carbon (SOC) was the major factor regulating the response ratio of bacterial alpha diversity index to MPs. The presence of MPs did not affect soil bacterial community structure and beta diversity. Our results highlight that MPs reduced bacterial diversity and richness but increased the soil active microbial biomass, suggesting that MPs could disrupt biogeochemical cycles by promoting the growth of specific microorganisms.

Mineralization and microbial utilization of poly(lactic acid) microplastic in soil.

The current carbon dioxide (CO2) evolution-based standard method for determining biodegradable microplastics (MPs) degradation neglects its priming effect on soil organic matter decomposition, which misestimates their biodegradability. Here, a 13C natural abundance method was used to estimate the mineralization of poly(lactic acid) (PLA) MP in various agricultural soils, and to trace its utilization in different microbial groups. In alkaline soils, the PLA-derived CO2 emissions increased with increasing soil carbon/nitrogen (C/N) ratios, and the mineralization of PLA MP concentrations ranged from 3-33 %, whereas the CO2 evolution method probably over- or under-estimated the mineralization of PLA in alkaline soils with different soil C/N ratios. Low PLA mineralization (1-5 %) were found in the acidic soil, and the standard method largely overestimated the mineralization of PLA MP by 1.3- to 3.3-fold. Moreover, the hydrolysate of PLA MP was preferentially assimilated by Gram-negative bacteria, but Gram-positive bacterial decomposition mainly contributed to the release of PLA-derived CO2 at low MP concentrations (≤ 1 %). Overall, the 13C natural abundance method appears to be suitable for tracking the mineralization and microbial utilization of biodegradable PLA in soils, and the PLA-derived C is mainly assimilated and decomposed by bacterial groups.

A review of factors affecting the soil microbial community structure in wetlands.

Microbial community in wetland soils is crucial for maintaining the stability of the wetland ecosystem. Nevertheless, the soil microbial community is sensitive to the environmental stress in wetlands. This leads to the possibility that the microbial community structure may be influenced by environmental factors. To gain an in-depth understanding in the response of microbial community structure in wetland soils under different environmental factors, this review comprehensively explores the factors of natural conditions (e.g., different types of wetland, soil physical and chemical properties, climate conditions), biological factors (e.g., plants, soil animals), and human activities (e.g., land use, soil pollution, grazing). Those factors can affect microbial community structure and activities in wetland soils through different ways such as (i) affecting the wetland soil environment in which soil microorganisms survived in, (ii) influencing the available nutrients (e.g., carbon, nitrogen) required for microbial activity, and (iii) the direct effects on soil microorganisms (toxicity or promotion of resistant species). This review can provide references for the conservation of microbial diversity in wetland soils, the maintenance of wetland ecosystem balance, and the wetland ecological restoration.

Long-term herbicide residues affect soil multifunctionality and the soil microbial community.

Residues of herbicides with the extensive applications may impact the soil ecosystem and ultimately threaten agricultural sustainability. However, the effects of long-term herbicide residues on soil multifunctionality and the soil microbial community remain poorly understood. Here, we evaluated relationships between soil multifunctionality and soil microbial communities with residual herbicide concentrations by surveying and analyzing 62 black soil samples collected from an agricultural area in northeastern China. Total residual herbicide concentrations varied from 35 to 568 µg/kg in the soil samples. The response of soil multifunctionality to increasing residual herbicide concentrations exhibited an inverted U-shaped relationship with a peak at approximately 310 µg/kg, with net mineralized organic nitrogen (Nm) and total nitrogen (TN) exhibiting the same trend. Microbial community richness was significantly lower in soil samples with high residual herbicide concentrations (> 310 µg/kg, HG) compared to low residual herbicide concentrations (< 310 µg/kg, LG). In addition, the relative abundances of specific keystone microbial genera differed significantly between LG and HG: norank_f_Acetobacteraceae, norank_f_Caldilineaceae, Candidatus_Alysiosphaera, and Gonytrichum. The relative abundances of these genera were also significantly correlated with soil multifunctionality. Structural equation models (SEMs) further showed that herbicide residues influenced soil multifunctionality by affecting these specific keystone genera. Our study demonstrates that long-term herbicide residues significantly impact the multifunctionality of agricultural black soil, where low concentrations stimulate while high concentrations inhibit, underscoring the need for reasonable application of herbicides to maintain soil ecosystem health.

Canopy and understory nitrogen additions differently affect soil microbial residual carbon in a temperate forest.

Atmospheric nitrogen (N) deposition in forests can affect soil microbial growth and turnover directly through increasing N availability and indirectly through altering plant-derived carbon (C) availability for microbes. This impacts microbial residues (i.e., amino sugars), a major component of soil organic carbon (SOC). Previous studies in forests have so far focused on the impact of understory N addition on microbes and microbial residues, but the effect of N deposition through plant canopy, the major pathway of N deposition in nature, has not been explicitly explored. In this study, we investigated whether and how the quantities (25 and 50 kg N ha-1 year-1) and modes (canopy and understory) of N addition affect soil microbial residues in a temperate broadleaf forest under 10-year N additions. Our results showed that N addition enhanced the concentrations of soil amino sugars and microbial residual C (MRC) but not their relative contributions to SOC, and this effect on amino sugars and MRC was closely related to the quantities and modes of N addition. In the topsoil, high-N addition significantly increased the concentrations of amino sugars and MRC, regardless of the N addition mode. In the subsoil, only canopy N addition positively affected amino sugars and MRC, implying that the indirect pathway via plants plays a more important role. Neither canopy nor understory N addition significantly affected soil microbial biomass (as represented by phospholipid fatty acids), community composition and activity, suggesting that enhanced microbial residues under N deposition likely stem from increased microbial turnover. These findings indicate that understory N addition may underestimate the impact of N deposition on microbial residues and SOC, highlighting that the processes of canopy N uptake and plant-derived C availability to microbes should be taken into consideration when predicting the impact of N deposition on the C sequestration in temperate forests.

Effects of returning peach branch waste to fields on soil carbon cycle mediated by soil microbial communities.

In recent years, the rise in greenhouse gas emissions from agriculture has worsened climate change. Efficiently utilizing agricultural waste can significantly mitigate these effects. This study investigated the ecological benefits of returning peach branch waste to fields (RPBF) through three innovative strategies: (1) application of peach branch organic fertilizer (OF), (2) mushroom cultivation using peach branches as a substrate (MC), and (3) surface mulching with peach branches (SM). Conducted within a peach orchard ecosystem, our research aimed to assess these resource utilization strategies' effects on soil properties, microbial community, and carbon cycle, thereby contributing to sustainable agricultural practices. Our findings indicated that all RPBF treatments enhance soil nutrient content, enriching beneficial microorganisms, such as Humicola, Rhizobiales, and Bacillus. Moreover, soil AP and AK were observed to regulate the soil carbon cycle by altering the compositions and functions of microbial communities. Notably, OF and MC treatments were found to boost autotrophic microorganism abundance, thereby augmenting the potential for soil carbon sequestration and emission reduction. Interestingly, in peach orchard soil, fungal communities were found to contribute more greatly to SOC content than bacterial communities. However, SM treatment resulted in an increase in the presence of bacterial communities, thereby enhancing carbon emissions. Overall, this study illustrated the fundamental pathways by which RPBF treatment affects the soil carbon cycle, providing novel insights into the rational resource utilization of peach branch waste and the advancement of ecological agriculture.

Strengthened plant-microorganism interaction after topsoil removal cause more deterministic microbial assembly processes and increased soil nitrogen mineralization.

Topsoil removal, among other restoration measures, has been recognized as one of the most successful methods to restore biodiversity and ecosystem functioning in European grasslands. However, knowledge about how removal as well as other restoration methods influence interactions between plant and microbial communities is very limited. The aims of the current study were to understand the impact of topsoil removal on plant-microorganism interactions and on soil nitrogen (N) mineralization, as one example of ecosystem functioning. We examined how three different grassland restoration methods, namely 'Harvest only', 'Topsoil removal' and 'Topsoil removal + Propagules (plant seed addition)', affected i) the interactions between plants and soil microorganisms, ii) soil microbial community assembly processes, and iii) soil N mineralization. We compared the outcome of these three restoration methods to initial degraded and target semi-natural grasslands in the Canton of Zurich, Switzerland. We were able to show that 'Topsoil removal' and 'Topsoil removal + Propagules', but not 'Harvest only', reduced the soil total N pool and available N concentration, but increased soil N mineralization and strengthened the plant-microorganism interactions. Microbial community assembly processes shifted towards more deterministic after both topsoil removal treatments. These shifts could be attributed to an increase in dispersal limitation and selection due to stronger interactions between plants and soil microorganisms. The negative relationship between soil N mineralization and microbial community stochasticity indicated that microbial assembly processes, to some extent, can be incorporated into model predictions of soil functions. Overall, the results suggest that topsoil removal may change the microbial assembly processes and thus the functioning of grassland ecosystems by enhancing the interaction between plants and soil microorganisms.

Response of soil microbial community structure and function to the sewage leakage: A case study of a 25-year-old cesspool.

Providing many millions of rural households with decentralized sanitation facilities remains challenging. In undeveloped areas, cesspools have still been widely used due to technologically simple and low-cost. However, the influence of cesspools on the surrounding soil remains unclear. In this study, we investigated the influence of a 25-year-old household cesspool on soil physicochemical factors, microbial community composition and function, pathogens and antibiotic resistance genes (ARGs). Soil at the depth around the sewage liquid level (D70) was mostly disturbed where TOC, NO3-N and TP was increased to 16.8 g/kg, 18.2 mg/kg and 1.02 mg/kg respectively. Correspondingly, the element cycling genes of carbon fixation, methanotrophy, nitrogen fixation, ammonia oxidation, and nitrate reduction etc., were increased at D70. Notably, human derived pathogens such as Enterobacter, Salmonella, Pseudomonas aeruginosa, Klebsiella pneumoniae, Prevotella, and Vibrio were highly enriched by 5-10 folders in D70, indicating the potential health risk to human. Mantel tests suggested that EC, TP, pH, NH3-N and particularly NO3-N are important factors that influence the microbial community and element cycling genes in cesspool-affected soil. Overall, this study revealed the impact of household cesspool leakage on the surrounding soil and provided information for the selection and construction of basic sanitation facilities in poor regions.

Difference in microbial community structure along a gradient of crater altitude: insights from the Nushan volcano.

The variation in the soil microbial community along the altitude gradient has been widely documented. However, the structure and function of the microbial communities distributed along the altitude gradient in the crater still need to be determined. We gathered soil specimens from different elevations within the Nushan volcano crater to bridge this knowledge gap. We investigated the microbial communities of bacteria and fungi in the soil. It is noteworthy that the microbial alpha diversity peaks in the middle of the crater. However, network analysis shows that bacterial (nodes 760 vs 613 vs 601) and fungal (nodes 328 vs 224 vs 400) communities are most stable at the bottom and top of the crater, respectively. Furthermore, the soil microbial network exhibited a decline, followed by an increase across varying altitudes. The core microorganisms displayed the highest correlation with pH and alkaline phosphatase (AP, as determined through redundancy analysis (RDA) and Mantel tests for correlation analysis. The fungal community has a higher number of core microorganisms, while the bacterial core microorganisms demonstrate greater susceptibility to environmental factors. In conclusion, we utilized Illumina sequencing techniques to assess the disparities in the structure and function of bacteria and fungi in the soil.IMPORTANCEThese findings serve as a foundation for future investigations on microbial communities present in volcanic soil.

Enhanced degradation of polylactic acid microplastics in acidic soils: Does the application of biochar matter?

Biodegradable plastics, as an alternative to petroleum plastics, are fiercely increasing, but their incomplete degradation under natural conditions may lead to the breakdown into microplastics (MPs). Here, we explored the impacts of chicken manure-derived (MBC) and wood waste-derived biochar (WBC) on the degradation of polylactic acid microplastics (PLA-MPs) during soil incubation for one year. Both biochars induced more pronounced degradation characteristics in PLA-MPs, including enhanced surface roughness, the proportion of MPs < 100 µm by 12.89 %-25.67 %, oxygen loading and O/C ratio to 71.74 %-75.87 % and 1.70-1.76, as well as accelerated carbon loss and the cleavage of ester group and C-C bond. Also, biochar increased soil pH, depleted inorganic nitrogen and available phosphorus, and changed enzymic activity in PLA-MP-polluted soils. We proposed that both biochars accelerated the PLA-MP degradation by inducing alkaline, aminolysis/ammonolysis, oxidative, and microbial degradation. Among these, MBC induced aminolysis/ammonolysis by NH4+ via Fe2+-driven NO3-/NO2- reduction and microbial nitrogen fixation, and oxidative degradation by radicals generated through Fenton/Fenton-like reaction. WBC caused aminolysis/ammonolysis and oxidative degradation mainly through dissimilatory nitrate reduction to ammonium and surface free radicals on biochar. These findings indicate that biochar has the potential to accelerate PLA-MP degradation, and its regulatory mechanism depends on the type of biochar.

Seasonal response of soil microbial community structure and life history strategies to winter snow cover change in a temperate forest.

Snow cover provides a thermally stable and humid soil environment and thereby regulates soil microbial communities and biogeochemical cycling. A warmer world with large reductions in snow cover and earlier spring snowmelt may disrupt this stability and associated ecosystem functioning. Yet, little is known about the response of soil microbial communities to decreased snowpack and potential carry-over effects beyond the snow cover period. Herein, we tested this response by conducting a snowpack manipulation experiment (control, addition, and removal) in a temperate forest. Our results showed that fungi were more sensitive to changes in snowpack. Thicker snowpack increased the diversity of fungi, but had weak effects on the diversity of bacteria in winter. Thickening snow cover promoted the ratio of fungi to bacteria abundance across the year, and such relative increase in fungi abundance was largely driven by Basidiomycota phyla (Agaricomycetes class). Increased snowpack decreased soil nitrate concentration, and produced carry-over biogeochemical effects evidenced by increased summer ß-1,4-glucosidase and N-acetyl-ß-glucosaminidase activities. On a seasonal scale, microbial biomass peaked at both winter and summer; winter microbial community was fungi dominated, while bacteria dominated in summer. The abundances of bacterial phyla had greater seasonal variation than fungal phyla. Specifically, Actinobacteria had greater dominance in winter than in summer, while Acidobacteria, Proteobacteria, and Verrucomicrobia had greater abundance in summer than in winter. Microbial high yield-resource acquisition-stress tolerance life history strategies showed significant seasonal tradeoffs, i.e., resource acquisition and stress tolerance strategies dominated in summer, while high yield strategy dominated in winter. Overall, our findings underline that climate-induced reductions in snow cover can disrupt soil biogeochemical cycling also beyond the snow cover period due to shifts in soil microbial community structure and life history strategies.

Changes in Soil Microbial Communities Induced by Biodegradable and Polyethylene Mulch Residues Under Three Different Temperatures.

Mulching is a common method increasing crop yield and achieving out-of-season production; nevertheless, their removal poses a significant environmental danger. In this scenario, the use of biodegradable plastic mulches comes up as a solution to increase the sustainability of this practice, as they can be tilled in soil without risk for the environment. In this context, it is important to study the microbial response to this practice, considering their direct involvement in plastic biodegradation. This study evaluated the biodegradation of three commercial mulch residues: one conventional non-biodegradable mulch versus two biodegradable ones (white and black compostable Mater-Bi mulches). The experiment was conducted under three incubation temperatures (room temperature 20-25 °C, 30 °C, and 45 °C) for a 6-month trial using fallow agricultural soil. Soil without plastic mulch residues was used as a control. White mater-bi biodegradable mulch residues showed higher degradation rates up to 88.90% at 30 °C, and up to 69.15% at room temperature. Furthermore, incubation at 45 °C determines the absence of degradation for all types of mulch considered. Moreover, bacterial alpha diversity was primarily influenced by plastic type and temperature, while fungal populations were mainly affected by temperature. Beta diversity was impacted by all experimental variables. Predicted functional genes crucial for degrading complex substrates, including those encoding hydrolases, cutinases, cellobiosidases, and lipases, were derived from 16S rRNA gene sequencing data. Cluster analysis based on predicted enzyme-encoding gene abundance revealed two clusters, mainly linked to sampling time. Finally, core microbiome analysis identified dominant bacterial and fungal taxa in various soil-plastic ecosystems during degradation, pinpointing species potentially involved in plastic breakdown. The present study allows an assessment of how different temperatures affect the degradation of mulch residues in soil, providing important insights for different climatic growing zones. It also fills a gap in the literature by directly comparing the effects of biodegradable and polyethylene mulches on soil microbial communities.

Effects of forest age and season on soil microbial communities in Chinese fir plantations.

Understanding changes in the distribution patterns and diversity of soil microbial communities from the perspectives of age-related changes, seasonal variations, and the interaction between the two factors can facilitate the management of plantations. In Chinese fir plantations, we collected soils from different depths in over-mature forests, mature forests, near-mature forests, middle-aged forests, and young forests in summer, autumn, and winter in China's subtropical regions. As the forests developed, bacterial and fungal communities' diversity changed, reached a minimum value at near-mature forests, and then increased in mature forests or over-mature forests. Near-mature forests had the lowest topological properties. The Shannon index of microbial communities varied with seasonal changes (P < 0.05). Bacterial and fungal community composition at genus level was more closely related to temperature indicators (including daily average temperature, daily maximum temperature, and daily minimum temperature) (P < 0.01, 0.5554 < R2 <0.8185) than daily average precipitation (P > 0.05, 0.0321 < R2 <0.6773). Bacteria were clustered by season and fungi were clustered by forest age. We suggested that extending the tree cultivation time of plantations could promote microbial community recovery. In addition, we found some species worthy of attention, including Bacteroidetes in autumn in over-mature forests, and Firmicutes in summer in young forests.IMPORTANCEChinese fir [Cunninghamia lanceolata (Lamb.) Hook] is an important fast-growing species with the largest artificial forest area in China, with the outstanding problems of low quality in soil. Soil microorganisms play a crucial role in soil fertility by decomposing organic matter, optimizing soil structure, and releasing essential nutrients for plant growth. In order to maintain healthy soil quality and prevent nutrient depletion and land degradation, it is crucial to understand the changes of soil microbial composition and diversity. Our study determined to reveal the change of soil microbial community from stand age, season, and the interaction between the two aspects, which is helpful to understand how interannual changes in different years and seasonal changes in one year affect soil fertility restoration and sustainable forest plantation management. It is a meaningful exploration of soil microbial communities and provides new information for further research.

Maize/Soybean Intercropping with Straw Return Increases Crop Yield by Influencing the Biological Characteristics of Soil.

With mounting demand for high-quality agricultural products and the relentless exploitation of arable land resources, finding sustainable ways to safely cultivate food crops is becoming ever more important. Here, we investigated the effects of the integrated cropping technique "straw return + intercropping" on the soil aggregates as well as the microbial biomass carbon (MBC) content, enzyme activities and microbial diversity in soils of maize and soybean crops. Our results show that in comparison to straw removal and monoculture, straw return and intercropping increase the rhizosphere's MBC content (59.10%) of soil, along with urease (47.82%), sucrase (57.14%), catalase (16.14%) and acid phosphatase (40.66%) activities as well as the microbial diversity under maize and soybean. Under the same straw treatment, the yield of maize when intercropped surpassed that when grown in monoculture, with the land equivalent ratio of the intercropping treatment under straw return being highest. Overall, the intercropping of maize and soybean is beneficial for the healthy development of sustainable agriculture in the black soil region of northeast China, especially when combined with straw return to fields.

Vermicompost Supply Enhances Fragrant-Rice Yield by Improving Soil Fertility and Eukaryotic Microbial Community Composition under Environmental Stress Conditions.

Heavy-metal contamination in agricultural soil, particularly of cadmium (Cd), poses serious threats to soil biodiversity, rice production, and food safety. Soil microbes improve soil fertility by regulating soil organic matter production, plant nutrient accumulation, and pollutant transformation. Addressing the impact of Cd toxicity on soil fungal community composition, soil health, and rice yield is urgently required for sustainable rice production. Vermicompost (VC) is an organic fertilizer that alleviates the toxic effects of Cd on soil microbial biodiversity and functionality and improves crop productivity sustainably. In the present study, we examined the effects of different doses of VC (i.e., 0, 3, and 6 tons ha-1) and levels of Cd stress (i.e., 0 and 25 mg Cd kg-1) on soil biochemical attributes, soil fungal community composition, and fragrant-rice grain yield. The results showed that the Cd toxicity significantly reduced soil fertility, eukaryotic microbial community composition and rice grain yield. However, the VC addition alleviated the Cd toxicity and significantly improved the soil fungal community; additionally, it enhanced the relative abundance of Ascomycota, Chlorophyta, Ciliophora, Basidiomycota, and Glomeromycta in Cd-contaminated soils. Moreover, the VC addition enhanced the soil's chemical attributes, including soil pH, soil organic carbon (SOC), available nitrogen (AN), total nitrogen (TN), and microbial biomass C and N, compared to non-VC treated soil under Cd toxicity conditions. Similarly, the VC application significantly increased rice grain yield and decreased the Cd uptake in rice. One possible explanation for the reduced Cd uptake in plants is that VC amendments influence the soil's biological properties, which ultimately reduces soil Cd bioavailability and subsequently influences the Cd uptake and accumulation in rice plants. RDA analysis determined that the leading fungal species were highly related to soil environmental attributes and microbial biomass C and N production. However, the relative abundance levels of Ascomycota, Basidiomycota, and Glomeromycta were strongly associated with soil environmental variables. Thus, the outcomes of this study reveal that the use of VC in Cd-contaminated soils could be useful for sustainable rice production and safe utilization of Cd-polluted soil.

Prairie restoration promotes the abundance and diversity of mutualistic arbuscular mycorrhizal fungi.

Predicting how biological communities assemble in restored ecosystems can assist in conservation efforts, but most research has focused on plants, with relatively little attention paid to soil microbial organisms that plants interact with. Arbuscular mycorrhizal (AM) fungi are an ecologically significant functional group of soil microbes that form mutualistic symbioses with plants and could therefore respond positively to plant community restoration. To evaluate the effects of plant community restoration on AM fungi, we compared AM fungal abundance, species richness, and community composition of five annually cultivated, conventionally managed agricultural fields with paired adjacent retired agricultural fields that had undergone prairie restoration 5-9 years prior to sampling. We hypothesized that restoration stimulates AM fungal abundance and species richness, particularly for disturbance-sensitive taxa, and that gains of new taxa would not displace AM fungal species present prior to restoration due to legacy effects. AM fungal abundance was quantified by measuring soil spore density and root colonization. AM fungal species richness and community composition were determined in soils and plant roots using DNA high-throughput sequencing. Soil spore density was 2.3 times higher in restored prairies compared to agricultural fields, but AM fungal root colonization did not differ between land use types. AM fungal species richness was 2.7 and 1.4 times higher in restored prairies versus agricultural fields for soil and roots, respectively. The abundance of Glomeraceae, a disturbance-tolerant family, decreased by 25% from agricultural to restored prairie soils but did not differ in plant roots. The abundance of Claroideoglomeraceae and Diversisporaceae, both disturbance-sensitive families, was 4.6 and 3.2 times higher in restored prairie versus agricultural soils, respectively. Species turnover was higher than expected relative to a null model, indicating that AM fungal species were gained by replacement. Our findings demonstrate that restoration can promote a relatively rapid increase in the abundance and diversity of soil microbial communities that had been degraded by decades of intensive land use, and community compositional change can be predicted by the disturbance tolerance of soil microbial taxonomic and functional groups.

Consistent community assembly but contingent species pool effects drive ß-diversity patterns of multiple microbial groups in desert biocrust systems.

One of the key goals of ecology is to understand how communities are assembled. The species co-existence theory suggests that community ß-diversity is influenced by species pool and community assembly processes, such as environmental filtering, dispersal events, ecological drift and biotic interactions. However, it remains unclear whether there are similar ß-diversity patterns among different soil microbial groups and whether all these mechanisms play significant roles in mediating ß-diversity patterns. By conducting a broad survey across Chinese deserts, we aimed to address these questions by investing biological soil crusts (biocrusts). Through amplicon-sequencing, we acquired ß-diversity data for multiple microbial groups, that is, soil total bacteria, diazotrophs, phoD-harbouring taxa, and fungi. Our results have shown varying distance decay rates of ß-diversity across microbial groups, with soil total bacteria showing a weaker distance-decay relationship than other groups. The impact of the species pool on community ß-diversity varied across microbial groups, with soil total bacteria and diazotrophs being significantly influenced. While the contributions of specific assembly processes to community ß-diversity patterns varied among different microbial groups, significant effects of local community assembly processes on ß-diversity patterns were consistently observed across all groups. Homogenous selection and dispersal limitation emerged as crucial processes for all groups. Precipitation and soil C:P were the key factors mediating ß-diversity for all groups. This study has substantially advanced our understanding of how the communities of multiple microbial groups are structured in desert biocrust systems.