Soil Microbial Community Composition Research Articles

Increased soil bacteria-fungus interactions promote soil nutrient availability, plant growth, and coexistence

Tree species and interkingdom relationships in the belowground metacommunity are key factors in determining soil microbial diversity and community composition. However, how bacterial-fungal interactions mediate soil nutrient and plant growth remains largely unexplored in the coniferous forests. Here, we selected three types of naturally growing coniferous forests on the Loess Plateau—pure stands of Platycladus orientalis, mixed stands of Platycladus orientalis and Pinus tabuliformis, and pure stands of Pinus tabuliformis—to compare the differences in soil properties, microbial diversity and community composition, soil enzymatic activity, and plant growth conditions across these stand types. We found that tree species mixing significantly alters soil microbial community diversity and composition, increasing the positive associations between bacteria and fungi. Compared to pure stands, mixed stands exhibit significantly higher bacterial diversity, whereas fungal diversity shows no significant difference. Additionally, available soil nutrients (ammonium nitrogen and available phosphorus) are significantly increased in mixed stands, along with their associated soil enzymatic activities. The partial least squares path model suggests that higher bacterial diversity enhances bacterial-fungal positive interactions, increasing the relative abundance of ectomycorrhizal fungi and the decomposition rate of organic matter in mixed stands, thereby boosting soil nutrient availability and plant growth. These results highlight the importance of positive bacterial-fungal associations for soil nutrient availability and plant growth, deepen the understanding of the role of soil microbial interactions in mediating plant species coexistence. Most importantly, our results implied a stable coexistence of the pioneer P. orientalis and the late successional species P. tabuliformis in the Loess Plateau region and provided a microbiological interpretation.

Differential effects of urbanization-induced heavy metal pollution on soil microbial communities under evergreen and deciduous trees

Urbanization has significantly increased heavy metal contamination in urban soils, adversely affecting soil microorganisms, which are vital indicators of soil quality. However, the effects of urbanization-induced metal pollution on soil microbial communities remains largely underestimated. This study examines soil microbial communities and properties beneath the canopy of three deciduous and three evergreen trees in urban parks, situated at varying distances from the city center. The results demonstrated that urbanization consistently alters soil physicochemical properties, including pH, soil moisture, and specific heavy metal contents (e.g., Zn, Mn, Cr). The α-diversity of soil bacterial community was significantly influenced by pH and specific heavy metals (e.g., Cr, Cd), whereas the α-diversity of fungal community was affected by pH, independent of heavy metal concentrations. The response of heavy metal content to urbanization exhibited a consistent pattern across both deciduous and evergreen trees, although the effect differed between these tree types. Furthermore, urbanization impacts the diversity, structure, composition and network of soil microbial communities. Notably, the Shannon index of soil fungal communities under deciduous species shows an initial increase, followed by a decline as urbanization intensifies. In contrast, the Simpson index of soil bacteria under evergreen tree species decreases with increased urbanization. Moreover, urbanization alters soil bacterial networks, with higher network density observed in less urbanized areas. It may also affect microbial functions, such as xenobiotic and lipid metabolism. This study provided a theoretical basis for urban park soil management, which is crucial for enhancing urban soil ecosystem services and mitigating the adverse effects of urbanization.

Detection of Nitrate-Reducing/Denitrifying Bacteria from Contaminated and Uncontaminated Tallgrass Prairie Soil: Limitations of PCR Primers.

Contamination of soil by spills of crude oil and oilfield brine is known to affect the species composition and functioning of soil microbial communities. However, the effect of such contamination on nitrogen cycling, an important biogeochemical cycle in tallgrass prairie soil, is less well known. Detecting nitrate-reducing (NR) and denitrifying (DN) bacteria via PCR amplification of the genes essential for these processes depends on how well PCR primers match the sequences of these bacteria. In this study, we enriched for NR and DN bacteria from oil/brine tallgrass prairie soil contaminated 5-10 years previously versus those cultured from uncontaminated soil, confirmed the capacity of 75 strains isolated from the enrichments to reduce nitrate and/nitrite, then screened the strains with primers specific to seven nitrogen cycle functional genes. The strains comprised a phylogenetically diverse group of NR and DN bacteria, with proportionately more γ-Proteobacteria in oil-contaminated sites and more Bacilli in brine-contaminated sites, suggesting some residual effect of the contaminants on the NR and DN species distribution. Around 82% of the strains shown to reduce nitrate/nitrite would not be identified as NR and DN bacteria by the battery of NR and DN primers used. Our results indicate an urgent need to expand the NR/DN functional gene primer database by first identifying novel NR/DN strains through their capacity to reduce nitrate/nitrite.

Differential Effects of Sulfur Fertilization on Soil Microbial Communities and Maize Yield Enhancement

Sulfur (S) is an essential nutrient for plant growth, influencing not only crop yields but also the composition and function of soil microbial communities. However, the differential effects of S fertilization on abundant and rare taxa in agricultural soils remain poorly understood. This study investigates the impact of different S fertilizer types on maize yield and the structure and stability of soil microbial communities, with a particular focus on abundant and rare taxa. S fertilization led to significant increases maize yield on two typical soils (black soil and sandy soil) (5.3–24.3%) and altered soil properties, including reducing pH (0.04–0.20) and increasing the available sulfur (AS) content (3.8–8.0 mg kg−1), with ammonium sulfate having a more pronounced effect than elemental sulfur. Microbial analysis revealed distinct impacts on the diversity and community structure of both abundant and rare taxa. Elemental sulfur reduced the alpha diversity of abundant taxa more than ammonium sulfate, while NMDS indicated significant shifts in community structures, particularly among abundant taxa. Network analysis showed that S fertilization decreased the complexity of microbial interactions among rare taxa, with ammonium sulfate leading to simpler networks and elemental sulfur resulting in higher modularity. SEM highlighted that the diversity of rare taxa played a crucial role in influencing maize yield, alongside direct effects from soil properties such as AS and SAR (aryl sulfatase). Functional predictions demonstrated that amino acid metabolism and xenobiotic biodegradation and metabolism pathways were enriched in rare taxa, suggesting significant implications for soil health and crop productivity. This study provides new insights into the roles of abundant and rare bacterial taxa under S fertilization, emphasizing their importance in optimizing fertilization strategies for enhanced crop yield in specific soil types.

Soil microbial community construction under revegetation in newly created land

Revegetation represents the primary method for restoring the ecological balance of the Loess Plateau. The assessment of revegetation efficacy on degraded lands can be facilitated through the utilization of soil microorganisms as indicators. We chose Medicago sativa L. (MX), Trifolium repens L. (BSY), Festuca arundinacea Schreb. (GYM), Elymus dahuricus Turcz. (PJC) and natural grass (CK) as the research objects, the soil microbial community composition, function and co-occurrence patterns of the five treatments were analyzed. The results showed that the microbial community composition was similar among the different vegetation types, but there were differences in abundance. Bacteria were significantly correlated with OM, BD and sand. Fungi were significantly correlated with sand and BD. Notably, BD showed highly significant correlation with microbial communities (P < 0.001). Microbial function prediction was dominated by metabolism at the bacterial level, and fungal function was predicted with eight trophic types dominated by parthenogenetic trophic types, and the microbial function prediction analyses showed that in bacteria, BSY had a high abundance of gene functions, and in fungi, PJC had a high abundance of gene functions. Network analysis revealed that the microbial community had small-world characteristics, a modular structure and a non-random co-occurrence pattern. Bacterial interactions included both competition and cooperation, further suggesting that growing raw grass increased the stability of the bacterial community. Overall, our results elucidated the changes in microbial communities and their correlations after raw grass cultivation, which could provide a more comprehensive perspective on microbial community assembly, and provide a theoretical basis for future ecological restoration on the Loess Plateau.

Comparative evaluation of the impacts of different microplastics on greenhouse gas emissions, microbial community structure, and ecosystem multifunctionality in paddy soil

Although the increasing accumulation of microplastics (MPs) in terrestrial soil ecosystems has aroused worldwide concern, research remains limited on their potential impacts on soil processes and ecosystem functionality. Here, through a 41-day microcosm experiment, we found that polylactic acid (PLA), low-density polyethylene (LDPE), and polypropylene (PP) MPs consistently increased soil carbon nutrients and pH but had varying effects on soil nitrogen nutrients and the chemodiversity of dissolved organic matter (DOM). Different treatments led to notable shifts in the α-diversity and composition of soil microbial community, with phyla Proteobacteria and Ascomycota consistently enriched by MPs regardless of polymer type. The emissions of CO2 and N2O were suppressed by MPs in most cases, which in combination led to a decline in global warming potential. LDPE and 1 – 1.5% of PLA MPs significantly improved the multifunctionality of the soil ecosystem, while PP and 0.5% of PLA MPs exerted an opposite effect. Soil total organic carbon, pH, DOM molecular mass and condensation degree, and CO2 emissions were identified as the most important variables for predicting soil ecosystem multifunctionality. Results of this study can extend the current understanding of the impacts of MPs on soil biogeochemical cycling and ecosystem functionality. Environmental ImplicationSoils are the largest recipient of MPs. Due to their diverse origins, MPs in the soil are typically present in different polymer types, shapes, and concentrations, which may induce complex impacts on soil ecosystem. This study highlighted that polymer types and concentrations were two important factors influencing the specific impacts of MPs on soil carbon and nitrogen turnover, microbial community composition, and ecosystem multifunctionality. Biodegradable MPs can also profoundly affect soil processes and functionality, raising questions about their ecological benefits. Results of this study can improve the current understanding of the ecological risks of MPs contamination in the soil.

Combined Effects of Nitrogen Addition and Warming on Shrub Growth and Nutrient Uptake through Microbially Mediated Soil Fertility

Plant restoration strategies are ubiquitously employed for the purposes of soil and water conservation and ecological improvement in forest ecosystems. Despite N and temperature being acknowledged as pivotal factors affecting plant restoration outcomes, their effects on soil fertility, microbial communities, and shrub biomass remain underexplored, particularly in the loess hilly regions of China. Here, we examined the growth patterns and nutrient acquisition abilities of three shrub species, Periploca sepium, Amorpha fruticosa, and Vitex negundo, along with the attendant alterations in soil properties and microbial community composition under controlled greenhouse conditions. Specifically, we imposed three levels of N fertilization (200, 400, and 600 kg ha−1; designated as N1, N2, and N3, respectively) and temperature regimes (18–23, 25–30, and 32–37 °C; labeled T1, T2, and T3, respectively). The results indicated a significant interplay between the combination of N fertilization and temperature significantly affecting shrub growth. Optimal growth conditions, as evidenced by the highest dry biomass accumulation, were identified as N3T1 for A. fruticosa, N1T1 for P. sepium, and N2T2 for V. negundo, with these conditions differentially influencing roots, stems, and leaves. Furthermore, soil microorganisms also responded significantly to the N fertilization and temperature. However, this was largely dependent on shrub species and soil nutrients. For A. fruticosa under N3T1 conditions, Actinobacteria and Basidiomycota abundances correlated strongly with soil C, N, and P contents, while leaf N uptake significantly correlated with the structure of both bacterial and fungal communities. For P. sepium at N1T1, Acidobacteriota was dominant in response to soil N and C, while leaf C uptake and leaf and stem N uptake positively correlated with bacterial and fungal communities, respectively. For V. negundo at N2T2, Chloroflexi had the greatest abundance, responding to the greatest variation in soil N and C, while its stem N uptake was significantly related to the structure of the fungal communities. Thus, our findings underscored the intricate interplay between abiotic factors, shrub growth, soil fertility, and microbial community dynamics, providing insights into the optimization of plant restoration efforts in ecologically sensitive regions.

Changes in soil microbial community and function across stand age of Cryptomeria japonica var. sinensis plantations in subtropical China

Microbial communities are important influencing factors in soil biogeochemical cycling. Differences in stand age can affect microbial communities and functions by altering soil biochemical characteristics. Studying the changes in soil microbial communities and functions at different ages of Cryptomeria japonica var. sinensis can provide a theoretical basis for the scientific management of plantations. Therefore, we collected soil samples from different soil depths from 7- (7a), 13- (13a), 24- (24a), 33- (33a), and 53-year (53a) C. japonica var. sinensis plantations, to assess the differences in soil biochemical characteristics, soil bacterial and fungal communities, soil enzyme activity, and soil respiration rate. Results showed that as the stand age increases, the ACE and Shannon indices of fungal communities showed an initial increase followed by a decrease, whereas the Chao 1 index showed an increasing trend. The ACE and Shannon indices of bacterial communities did not change with stand age, but the Chao1 index decreased with an increase in stand age. In addition, the fungal ACE and Chao1 indices and bacterial Shannon index were higher at the 0–15 cm depth than at the 15–30 cm depth. Soil microbial community composition varied with stand age and soil depth, including Proteobacteria and Unclassified_k_Fungi relative abundances, and their functional groups' (nitrogen cycling-related bacteria, saprophytic fungi, pathogens, and ectomycorrhizal fungi) relative abundances. In addition, stand age will indirectly affect soil microbial function by influencing soil biochemical characteristics and microbial communities at the 0–15 cm depth, whereas at the 15–30 cm depth, there is no direct or indirect impact on the above indicators. In summary, significant variations exist in soil microbial communities and their functions across stand ages, and these differences will further vary between soil depths. Our research contributes to a better understanding of the impact of different ages of afforestation on soil biogeochemical cycling, providing valuable microbial information for the sustainable management of C. japonica var. sinensis forests in the future.

Diversified crop rotations improve soil microbial communities and functions in a six-year field experiment

Diversified crop rotations can help mitigate the negative impacts of increased agricultural intensity on the sustainability of agroecosystems. However, the impact of crop rotation diversity on the complexity of soil microbial association networks and ecological functions is still not well understood. In this study, a 6-year field experiment was conducted to evaluate how six different crop rotations change the composition and network complexity of soil microbial communities, as well as their related ecological functions. Microbial traits were measured in six crop rotations with different crop diversity index (CDI) during 2016–2022, including winter wheat–summer maize (CDI 1, WM) as the control, sweet potato→winter wheat–summer maize (CDI 1.5, SpWM), peanut→winter wheat–summer maize (CDI 1.5, PWM), soybean→winter wheat–summer maize (CDI 1.5, SWM), spring maize→winter wheat–summer maize (CDI 1.5, SmWM), and ryegrass–sweet sorghum→winter wheat–summer maize (CDI 2, RSWM). The study findings indicated that diversified crop rotations significantly increased ASV richness of both bacterial and fungal communities after 6-year treatments, and the β-diversity profiles of bacterial and fungal communities significantly distinguished at the year of 2022 from 2016. The relative abundance of Acidobacteria and Chloroflexi was significantly enriched in SpWM rotation at 2022, while Basidiomycota significantly declined in five diversified rotations compared to WM. Diversified crop rotations at 2022 increased the complexity and density of bacterial and fungal networks than 2016. SpWM and PWM rotations had the highest functional groups involved in chemoheterotrophy and saprotroph, respectively. Structural equation modelling (SEM) also revealed that diversified crop rotations increased soil nutrients through improving the composition of bacterial communities and the augmented intricacy of the interconnections within both bacterial and fungal communities. This research underscores the importance of preserving the diversity and ecological functions of soil microorganisms in the nutrient-recycling processes for efficient agricultural practices.

The Composition and Diversity of Soil Microbial Communities Associated With the Invasive Plant Solidago canadensis Vary Across Locations and Time Since Invasion

ABSTRACTAimPrevious local‐scale research (within plots or landscapes) has shown that invasive plants can alter the composition and diversity of soil microbial communities, with potential feedback effects on their own invasion success. However, the broader ecological patterns of these interactions across different invasion timescales and geographic regions remain poorly understood. This study investigated whether the composition and diversity of soil microbial communities associated with Solidago canadensis (Canada goldenrod) invasion vary across both population residence times and geographic locations.LocationSouth‐eastern China.TaxonSoil fungal and bacterial communities and S. canadensis.MethodsWe collected rhizospheric soil of S. canadensis, nonrhizospheric soil and adjacent uninvaded soil from each of 36 populations of S. canadensis with varying residence times (8–89 years), totalling 108 samples. We extracted DNA from these samples and sequenced the V3–V4 region of the bacterial 16S rRNA gene and the ITS2 region of the fungal rDNA. We analysed the DNA sequences to assess whether variation in α‐diversity, β‐diversity, arbuscular mycorrhizal fungi (AMF) richness and the ratio of AMF to plant pathogens in the soil microbial communities varied with S. canadensis population residence time, latitude and longitude.ResultsThe α‐diversity and β‐diversity of soil fungal and bacterial communities significantly varied with S. canadensis residence times, latitude and longitude. In locations where S. canadensis had been established for longer periods, there was an increase in AMF richness and a decrease in plant pathogens in the rhizospheric soil. Fungal diversity in rhizospheric soils was positively correlated with longitude, while bacterial diversity in rhizospheric and nonrhizospheric soils was positively correlated with both latitude and longitude.Main ConclusionsThese findings indicate that the time since invasion and geographical location can both significantly influence the composition and diversity of soil microbial communities associated with invasive plant species.

Influence of thinning on carbon storage mediated by soil physicochemical properties and microbial community composition in large Chinese fir timber plantation

BackgroundThinning practices are useful measures in forest management and play an essential role in maintaining ecological stability. However, the effects of thinning on the soil properties and microbial community in large Chinese fir timber plantations remain unknown. The purpose of this study was to investigate the changes in soil physicochemical properties and microbial community composition in topsoil (0–20 cm) under six different intensities (i.e., 300 (R300), 450 (R450), 600 (R600), 750 (R750) and 900 (R900) trees per hectare and 1650 (R1650) as a control) in a large Chinese fir timber plantation.ResultsCompared with the CK treatment, thinning significantly altered the contents of soil organic carbon (SOC) and its fractions but not in a linear fashion; these indicators were highest in R900. In addition, thinning did not significantly affect the soil microbial community diversity indices but significantly affected the relative abundance of the core microbial community. Proteobacteria, Acidobacteria, and Actinobacteria were the dominant bacterial phyla; the relative abundances of Proteobacteria and Acidobacteria were highest in R900, and that of Actinobacteria was lowest in R900. The dominant fungal phyla were Ascomycota, Basidiomycota and Mucoromycota; the relative abundance of Ascomycota was lowest in R900, and that of Mucoromycota was highest in R900. The fungal microbial community composition was more sensitive than the bacterial community composition. The activity of the carbon-cycling genes was not linearly correlated with thinning, and the abundance of C-cycle genes was highest in R900.ConclusionsThese findings are important because they show that SOC and its fractions and the abundance of the soil microorganism community in large Chinese fir timber plantations can be significantly altered by thinning, thus affecting the capacity for carbon storage. These results may advance our understanding of how the density of large timber plantations could be modified to promote soil carbon storage.

Maize/soybean intercropping with nitrogen supply levels increases maize yield and nitrogen uptake by influencing the rhizosphere bacterial diversity of soil.

Intercropping practices play a crucial role in enhancing and maintaining the biodiversity and resiliency of agroecosystems, as well as promoting stable and high crop yields. Yet the relationships between soil nitrogen, microbes, and yield in maize cultivated under maize/soybean intercropping systems remain unclear. To fill that knowledge gap, here we collected maize rhizosphere soil at the staminate stage after 6 consecutive years of maize/soybean intercropping, to investigate how intercropping and nitrogen application rates affected nitrogen utilization by crops and soil microbial community composition and function. We also examined correlations of those responses with yields, to clarify the main ways that yield is enhanced via intercropping and by nitrogenous fertilizer gradient changes generated by different nitrogen application rates. The amount of applied fertilizer was 240 kg N ha-1 was best for obtaining a high maize yield and also led to the greatest nitrogen-use efficiency and bacterial diversity. Under the same N application rate, intercropping increased the maize yield by 31.17% and soil nitrogen (total, ammonium and nitrate nitrogen) by 14.53%, on average, in comparison to monocropping. The enrichment of Gemmatimonas and Bradyrhizobium significantly increased the soil nitrogen content, and a greater relative abundance of Sphingomonas and Gemmatimonas increased the maize yield, whereas enrichment of Candidatus_Udaeobacter and Bradyrhizobium decreased it. The benefits of intercropping mainly arise from augmenting the abundance of beneficial microorganisms and enhancing the efficiency of N use by crop plants. This study's findings are of key importance to bolster the stability of agro-ecosystems, to guide the scientific rational use of nitrogen fertilizers, and to provide a sound theoretical basis for achieving the optimalmanagement of intensive crop-planting patterns and green sustainable development.

Drying-rewetting alters arsenic ecotoxicity: From the perspective of enzyme-based functional diversity

Drying-rewetting (DW) cycles can significantly influence soil properties and microbial community composition, leading to direct or indirect changes in arsenic (As) toxicity, which inturn affects soil ecological functions. Despite this, there has been insufficient focus on accurately evaluating As ecotoxicity and its impact on soil ecological function under DW conditions. This study seeks to address this gap by examining the effects of DW on As toxicity and the characteristics of soil ecological function, specifically from the perspective of enzyme-based functional diversity. Our results reveal that compared to constant moisture conditions, DW treatment significantly increased the toxicity of As on alkaline phosphatase and β-glucosidase, with maximum inhibition rates observed at 46.29% and 21.54%, respectively. Conversely, for other tested enzymes including invertase, fluorescein diacetate hydrolase, and dehydrogenase, DW treatment decreased As toxicity, possibly be due to the different stability of these enzymes under varying soil moisture conditions. From an enzyme functional diversity perspective, DW treatment reduced the As toxicity, as evidenced by the reduced inhibition rates and a lower coefficient of variation. In conclusion, DW appears to enhance soil functional resilience against arsenic pollution. These findings contribute to a better understanding of changes in ecological functions in heavy metal-contaminated soils under dynamic environmental conditions, offering insights for improved monitoring and mitigation strategies for metalloids toxicity in natural environments.

Impact of nitrogen and phosphorus amendments on nitrogen‐cycling microbial abundances and potentials: A meta‐analysis

AbstractThe rapid increase in nitrogen (N) and phosphorus (P) availabilities in terrestrial ecosystems has led to sustained shifts in soil microbial communities and microbially‐mediated N‐cycling. However, the specific effects of N and P amendments on N‐cycling microbes are poorly understood. This meta‐analysis synthesizes the effects of N and/or P amendments on the abundances and functional potentials of N‐cycling genes involved in N₂ fixation, organic N mineralization, nitrification, and denitrification across natural ecosystems and diverse soil conditions in China. Our findings indicate that ammonia‐oxidizing bacteria (AOB) showed greater responsiveness to N amendment than ammonia‐oxidizing archaea (AOA), and AOB amoA abundance increased while AOA amoA abundance decreased with P amendments. Additionally, the abundance of nirS declined, while nirK abundance remained unresponsive to both N and P amendments. These findings highlight the distinct ecological niches occupied by microbial groups with equivalent functions in response to N and P amendments. Moreover, our findings indicate that soil N and P availabilities, along with soil acidification induced by N additions and microbial biomass carbon content, are key factors regulating N‐cycling gene abundances and potentials. The driving mechanisms for N‐cycling genes and their corresponding potentials appear to be distinct, with gene abundance showing only a limited influence on functional potentials. This suggests that factors such as soil properties and microbial community compositions may be more critical determinants of N‐cycling processes than functional gene abundances with regard to scenarios of increasing N and P deposition.

Nitrogen deposition in the middle-aged and mature coniferous forest: Impacts on soil microbial community structure and function

The impact of nitrogen (N) deposition on soil microbial community structure and function has been a focal point of research; however, the influence of forest age and N form on the microbial response to N deposition has yet not to be fully understood. To address this gap, metagenomic sequencing was utilized to explore the responses of soil microbial community structure and functional genes to five years of N addition in middle-aged and mature coniferous forests in southwest China. Adopting a randomized block design, the experiment included two N forms ((NH4)2SO4 and KNO3) across four levels of addition (0, 10, 20 and 40 kg N ha−1 yr−1). Our findings reveal that the composition of the microbial community structure and functional genes involved in the carbon (C), N, phosphorus (P), and sulphur (S) cycling varied significantly between middle-aged and mature forest (P < 0.001). At the phylum level, the soil microbial community in the mature forest were dominated by Proteobacteria (30.4–38.8 %), Acidobacteriota (8.5–24.1 %), and Chloroflexota (8.1–21.5 %), and the soil microbial community in the middle-aged forest showed a greater presence of Acidobacteriota (28.9–34.0 %) and Actinobacteriota (13.3–19.2 %) with a lower proportion of Chloroflexota (0.4–1.2 %). In both middle-aged and mature forests, functional gene abundance, and the composition of microbial community and functional genes were unaffected by N addition rate (P = 0.793) and N form (P = 0.725). The taxonomic composition of soil microbial community in the mature forest showed a significant positive correlation with soil pH, soil organic carbon (SOC) and total nitrogen (TN) (P < 0.01), while the microbial community composition in the middle-aged forests was not significant correlated with soil pH, SOC and TN (P > 0.05). These findings underscore that N addition in the middle-aged and mature coniferous forest does not significantly impact the soil microbial community structure and function across different N forms and N addition rate, suggesting that soil microorganisms of the forest ecosystem exhibit strong resilience to increased N supply.

Soil microbial community composition and nitrogen enrichment responses to the operation of electric power substation.

The surge in global energy demand mandates a significant expansion of electric power substations. Nevertheless, the ecological consequences of electric power substation operation, particularly concerning the electromagnetic field, on soil microbial communities and nitrogen enrichment remain unexplored. In this study, we collected soil samples from six distinct sites at varying distances from an electric power substation in Xintang village, southeastern China, and investigated the impacts of electromagnetic field on the microbial diversity and community structures employing metagenomic sequencing technique. Our results showed discernible dissimilarities in the fungal community across the six distinct sites, each characterized by unique magnetic and electric intensities, whereas comparable variations were not evident within bacterial communities. Correlation analysis revealed a diminished nitrogen fixation capacity at the site nearest to the substation, characterized by low moisture content, elevated pH, and robust magnetic induction intensity and electric field intensity. Conversely, heightened nitrification processes were observed at this location compared to others. These findings were substantiated by the relative abundance of key genes associated with ammonium nitrogen and nitrate nitrogen production. This study provides insights into the relationships between soil microbial communities and the enduring operation of electric power substations, thereby contributing fundamental information essential for the rigorous environmental impact assessments of these facilities.

Farm dairy effluent application

Dairy intensification produces a large amount of farm dairy effluents (FDE). The final disposal of FDE is generally to the soil as fertilizer. While this use of FDE as fertilizer has numerous benefits, such as reducing the application of synthetic fertilizers or improving soil quality, there are concerns about the environmental and health risks associated with microbial pathogens from animal waste, the spread of antibiotic resistance genes, nutrient losses and greenhouse gases (GHG) emissions. Furthermore, how this agricultural practice impacts the composition and functionality of soil microbial communities has not yet been elucidated. This thesis aimed to evaluate the impact of FDE applications on soil GHG emissions, the composition, activity and diversity of its microbial community, and health risks. The FDE were collected raw and from a two-stage stabilization lagoon. The N application rate normalized to 200 kg N ha−1 was divided into four seasonal applications compared to urea fertilization or a no-aggregate control. Soil samples were taken after each application for microbial and physicochemical characterization and GHG fluxes were measured up to twenty days after each application. The pasture was harvested according to typical grazing management. Repeated application of both types of FDE increased the soil nutrient status and enhanced microbial activity. Higher fescue pasture production and macronutrient content with FDE than the control positioned FDE application to soil as an alternative disposal. However, N2O emissions increased after applying both FDE’s, most notably with raw FDE. Soil microbial community composition was not significantly influenced by FDE applications, but functional diversity shifted with raw FDE. Lagoon storage effectively reduced organic C and total N along with pathogenic indicator bacteria and changed the bacterial community composition except in winter. Beta-lactam resistance genes were detected in both FDEs, but not in the soil after repeated applications.

Effects of Long-Term Application of Nitrogen Fertilizer on Soil Acidification and Biological Properties in China: A Meta-Analysis.

Soil acidification is a global environmental problem with significant impacts on agricultural production, environmental protection, and ecosystem health. Soil acidification is widespread in China, affecting crop yields, agricultural product quality, and biodiversity. Since the 1980s, much work has been done on acidic soils in China, but it is controversial whether excessive nitrogen fertilizer application can lead to soil acidification mechanisms. To address the above issues, we conducted a meta-analysis of 115 published papers to integrate and analyze the effects of N fertilizer application on soil acidification and biological properties from 1980 to 2024. We also quantified the effect of nitrogen fertilization on soil acidification and biological changes under different climatic conditions. The results showed that under long-term application of nitrogen fertilizers in China from 1980 to 2024, soil pH decreased by an average of 15.27%, and the activities of soil urease, nitrate reductase, nitrite reductase, catalase, glutamate dehydrogenase, and glutamate synthetase decreased by an average of 9.82-22.37%. The soil microbial community richness (Chao1 index) increased by 6.53%, but the community diversity (Shannon index) decreased by 15.42%. Among the dominant soil microorganisms, the relative abundance of bacteria decreased by an average of 9.67-29.38% and the abundance of gene expression of nifH, amoA-AOA, amoA-AOB, and qnorB decreased by 9.92-19.83%. In addition, we found that the mean annual temperature and rainfall impacted soil acidification via their effect on soil microbial diversity and community composition. This study provides a scientific basis for an in-depth understanding of the spatial and temporal variation of soil acidification and biological properties in China.

The influence of plant traits on soil microbial communities varies between arid and mesic grasslands

Abstract Background and aims Both soil properties and plant traits shape the diversity, composition and functions of plant-associated soil microbial communities. However, the relative influence of these factors is poorly understood, as are interactive effects between factors and the degree to which their influence varies among climate zones. Methods To address this gap, we compared the diversity and composition of soil microbial communities associated with co-occurring C3 and C4 grasses from arid and mesic environments, and plant traits influencing them. Results Climate emerged as the main determinant of plant traits and microbial community properties. Within each climatic region, above- and below-ground traits and soil properties differentially affected microbial community composition, and their relative influence varied among communities. In both mesic and arid environments aboveground traits related to quantity and quality of leaf litter (e.g., specific leaf area, leaf C content) and nutrient availability were the most influential variables for community composition. However, in arid regions, belowground traits (i.e., root tissue density and specific root area) significantly contributed to structure the eukaryotic community, supporting the role of roots as important driver of eukaryotic differentiation in constrained environments. Further, the presence of C4 plants in the arid region resulted in higher relative abundance of ciliate protists and higher recruitment of potentially beneficial microbial community members from green algae mediated by drought adaptation traits (e.g. decreased abundance of fine roots). Conclusions Overall, our study revealed a differential response of microbial communities to environmental conditions, suggesting that soil microbial community composition is influenced by trade-offs between host adaptive traits across distinct climatic regions.

Synergistic changes in bacterial community composition, function, and soil characteristics of tomato rhizosphere soil under long-term monoculture conditions

Tomato is widely cultivated all over the world, and long-term monoculture has resulted in decreased tomato yields and stunted plant growth. Soil bacterial communities have a profound effect on plant growth and health, and the effect of different planting years on rhizosphere soil microorganisms of tomato is not clear. In this study, metagenomic sequencing was used to analyze the rhizosphere soil microorganisms of tomatoes cultivated continuously for 3, 6 years (short-term continuous cropping), 9, and 12 years (long-term continuous cropping) (LZ3, LZ6, LZ9, LZ12). The results showed that the pH in LZ9 was significantly higher than that in the other treatments, the relative abundance of Planctomycetes and Candidatus Rokubacteria in LZ3 were higher than those in the other treatments, the relative abundance of Proteobacteria was significantly higher in LZ6 and LZ9 than that in the other treatments, and the relative abundance of Chloroflexi and Bacteroidetes in LZ12 were higher than those in the other treatments. At the genus level, the relative abundance of Nocardioides, Sphingomonas, Pseudolabrys were lower in LZ3 than that in other treatments, and the relative abundance of Gaiella was significantly higher in short-term continuous cropping than that in LZ9. The pH, hydrolyzable nitrogen (HN), and available potassium (AK) were the most important factors driving the changes in microbial communities. The relative abundance of amino acid metabolism, terpenoid and polyketide metabolism decreased significantly with years of continuous cropping, and that total nitrogen (TN), HN, and available phosphorus (AP) were significantly correlated with translation, amino acid metabolism, and cell growth and death. Continuous cropping leads to nutrient imbalance in tomato soils, which affects the structure and functional composition of soil microbial communities, providing insights into microbial community response to continuous tomato cropping, but further in-depth studies are needed.