Diversity Of Soil Microbial Communities Research Articles

Effects of Land Use Conversion on the Soil Microbial Community Composition and Functionality in the Urban Wetlands of North-Eastern China

Urban wetlands are undergoing intensive conversion from natural wetlands to farmlands, woodlands, and even alkaline land. This study aimed to determine the effects of land conversion on soil microbial communities of urban wetlands in the hinterland of Songnen Plain, Northeastern China. Soil samples were collected from various sites of Longfeng wetland, including swamp wetland (SW), meadow wetland (MW), woodland (WL), farmland (FL), and alkaline land (AL). High-throughput sequencing followed by bioinformatic analysis was conducted to evaluate the structure, composition, and function of soil bacterial and fungal communities. The most dominant bacterial and fungal phylum among the land-use types were Proteobacteria and Ascomycota, respectively. In addition, the bacterial diversity and functions varied significantly across different land-use types. However, no remarkable differences in fungal communities were observed under various land-use types. Edaphic parameters, including exchange sodium percent (ESP) and total nitrogen (TN), remarkably influenced the abundance and diversity of soil microbial communities. These results show that land-use type shapes various aspects of soil microbial communities, including soil physicochemical properties, microbial taxa structure, potential functional genes, and correlation with environmental factors. This study provides reliable data to guide land use management and supervision by decision-makers in this region.

The Effects of Biochar on Microbial Community Composition in and Beneath Biological Soil Crusts in a Pinus massoniana Lamb. Plantation

Biological soil crusts (BSCs) hold promise for reducing soil erosion in subtropical forest plantations, and microorganisms profoundly affect the formation and development of BSCs. The effects of biochar as a soil conditioner on the diversity and structure of soil microbial communities in BSCs are largely unknown. Therefore, our aim was to determine how biochar might improve microbial community composition and BSC function. Herein, a field experiment was conducted in a P. massoniana plantation; the addition of biochar was the treatment, and no biochar addition was the control (CK). Soil microbial communities associated with moss BSCs (in and beneath BSCs) with and without the addition of biochar were analyzed by Illumina sequencing technology. The results showed that Acidobacteria (28.35%), Proteobacteria (22.53%), Actinobacteria (17.41%), and Chloroflexi (16.74%) were the dominant bacterial phyla, whereas Basidiomycota (70.00%) and Ascomycota (22.76%) were the dominant fungal phyla in BSCs. The soil bacterial and fungal OTU number and richness in BSCs were higher than those beneath BSCs. The relative abundances of Acidobacteria, Chloroflexi, and Basidiomycota were higher in BSCs than beneath BSCs, whereas the relative abundances of Actinobacteria, Firmicutes, Ascomycota, and Chytridiomycota showed the opposite trend. Beneath BSCs, biochar addition increased the soil bacterial OTU number and richness (ACE index and Chao1) but decreased the soil fungal OTU number and richness. Biochar had little effect on soil microbial community structures in BSCs; however, beneath BSCs, it significantly increased the relative abundances of Acidobacteria, Chloroflexi, and Basidiomycota and significantly decreased the relative abundances of Actinobacteria, Firmicutes, Ascomycota, and Chytridiomycota. Biochar-induced changes in soil microbial communities were related to soil environmental factors, especially urease activity, organic matter content, pH, total nitrogen content, and sucrase activity. We demonstrated the different effects of biochar on soil microbial communities in and beneath the BSCs of subtropical forest plantations; these findings provided new insights into soil stabilization with BSCs below the forest canopy in subtropical regions.

Bisphenol S degradation in soil and the dynamics of microbial community associated with degradation

Bisphenol S (BPS) has been widely applied as a replacement for BPA in industrial application, leading to the frequent detection in the environment. However, its impact on soil microbial communities has not been well reported. Here, effects of BPS exposure on soil microbial communities in the presence of polystyrene (PS) microplastics were revealed. Rapid degradation of BPS occurred with a degradation rate of up to 98.9 ± 0.001 % at 32 d. The presence of BPS reduced the diversity of soil microbial communities, and changed community structures. After BPS treatment, Proteobacteria, and its members Methylobacillus, Rhodobacteraceae and Mesorhizobium became dominant, and were considered as potential biomarkers indicating BPS contamination. Co-occurrence network analysis revealed the increased relationships of certain groups of microbes after BPS treatment. The resultant low stability and resilience towards environment disturbance of microbial community networks implied the biotoxicity of BPS towards soil ecosystems. The degradation and biotoxicity of BPS (p > 0.05) in soil was not affected by the presence of PS. Our findings showed that exposure to BPS could reshape soil microbial communities and impair the robustness of microbial co-occurrence networks.

Litter decomposition and its effects on soil microbial community in Shapotou area, China

We investigated the decomposition characteristics of Eragrostis minor, mosses, and leaves of Artemisia ordosica with litterbag method in the sand-binding revegetation area, southeastern edge of the Tengger Desert, and further examined their effects on soil microbial communities using the Illumina MiSeq sequencing method. The results showed that the decomposition duration and litter types significantly affected litter decomposition rate. Mosses had the lowest decomposition rate, with a mass loss ratio of only 15.4% after decomposition for 13 months. The average decomposition rates of E. minor and leaves of A. ordosica were 4.9 and 3.4-fold of that of mosses, respectively. During decomposition for 11 months, the dominant bacterial phyla were Actinomycota and Proteobacteria, while that of the fungal community was Ascomycota. Moss decomposition significantly increased the relative abundance of Bacteroidetes and Chloroflexi, but remarkedly decreased the abundance of Basidiomycetes. The diversity and richness of bacterial and fungal communities significantly increased after litter decomposition. The compositional changes of fungal community were significant among litters, but that of bacterial community was not. There was a negative correlation between decomposition rate and the diversity and richness of bacterial and fungal communities. Plant polysaccharides, total phosphorus, soil pH, microbial biomass nitrogen, and soil ammonium content were the main factors affecting microbial community structure. Litter decomposition changed the composition and interspecific similarity within microbial communities, as well as increased the diversity and richness of soil microbial communities, and thus would promote the restoration of soil habitat.

Changes in soil microecology of gangue reclamation areas after 10 years of in situ restoration with herbaceous plants (Artemisia sacrorum and Imperata cylindrica) and trees (Populus spp.)

Changes in the soil ecological microenvironment of coal gangue contaminated areas were evaluated after 10 years of in situ restoration with Artemisia sacrorum, Imperata cylindrica, and Populus spp. The changes in soil enzyme activity, ion spectrum, bacterial community structure and function, and metabolic spectrum were analyzed in an unrestored coal gangue pollution area (Control), an Artemisia sacrorum + Imperata cylindrica remediation area (T1), and a Populus remediation area (T2). Phytoremediation significantly increased the soil acid phosphatase activity by 4.62–7.36 times, and decreased the electrical conductivity by 6.2–85.5%. The overall reduction trend for heavy metals in the soil was shallow layer > middle layer > deep layer, with significant reductions seen for Cs, As, Co, Pb, Ni, U, and Cr. The number and diversity of shallow soil microbial communities increased significantly, with Actinobacteria, which participate in the carbon and nitrogen cycles, and Proteobacteria, which can tolerate/metabolize multiple heavy metals, becoming the dominant species in the restoration area. Microbial genes for glycosyltransferase, transcriptional regulators, and toluene degradation changed significantly. Phytoremediation by both remediation strategies significantly changed the metabolic level of lipids and lipid-like molecules in the soil, while significantly enriching the pathways of ABC transporters and galactose metabolism, which are essential for soil detoxification, ion transport, and carbon cycling. Bacteria such as Thiobacillus and Pseudarthrobacter were important drivers of soil metabolism. In general, the in situ phytoremediation of soil contaminated by coal gangue improved the overall soil ecological microenvironment.

Effects of biochar on karst lime soil nutrients, soil microbial communities and physiology of Sichuan pepper plants

AbstractThe effects of biochar on karstic lime soil physicochemical properties, soil microbial community diversity and plant physiology are poorly understood. To clarify these effects of biochar application, we applied biochar on the soil surface of Sichuan pepper (Zanthoxylum schinifolium) stands. One year later, leaf gas exchange and chemicals as well as soil physicochemical properties and microbial community composition were assessed. Biochar significantly increased photosynthesis, stomatal conductance, transpiration rate and total nitrogen and phosphorus in leaves, but it did not significantly affect total chlorophyll content and malondialdehyde. Total nitrogen and phosphorus as well as available phosphorus and potassium in the soil were significantly increased by biochar. However, soil pH, water content, bulk density, abundance of soil microbes (actinomycetes, bacteria, fungi and Gram negative and positive bacteria), and soil microbial community structure did not exhibit significant increases. Soil total phosphorus, available nitrogen, available phosphorus and available potassium positively correlated with the abundance of soil bacteria, fungi and actinomycetes. These results indicate that biochar enhanced main plant nutrients and improved gas exchange of pepper plants and physicochemical properties of karstic lime soil.

14 year applications of chemical fertilizers and crop straw effects on soil labile organic carbon fractions, enzyme activities and microbial community in rice-wheat rotation of middle China

Traditional fertilization management can damage soil structure and lead to severe soil erosion. The practice of crop straw returning to the field reduces the negative impact of straw burning and improves soil quality. We investigated the effects of these agricultural practices on soil organic carbon components, enzyme activities, and soil microorganisms over 14 years of field experiments. Specifically, we studied four management strategies: no fertilizer or crop straw returning (CK), traditional chemical fertilization (NPK), crop straw returning (S), and crop straw returning with chemical fertilizer (NPKS). We found NPKS treatments significantly (P < 0.05) increased the dissolved organic carbon (DOC), microbial biomass carbon (MBC), particulate organic carbon (POC) and readily oxidized organic carbon (ROC) concentrations by 79.32 %, 82.16 %, 92.46 %, and 104.32 % relative to CK. Furthermore, under NPKS, the activities of soil enzymes related C, N, and P (α-glucosidase (αG), β-glucosidase (βG), cellulase (CBH), xylanase (βX), acetyl β-glucosaminidase (NAG), leucine aminopeptidase (LAP), and acid phosphate (AP)) were increased by 54.66 %, 113.26 %, 76.73 %, 52.41 %, 45.74 %, 56.69 %, and 68.92 % relative to CK, respectively. Redundancy analysis and structural equation modelling showed that straw returning had positive effects on soil microbial community diversity and richness, and also improved microbial activity which is favorable in the degradation of soil carbon. Furthermore, we found that soil fungi were more sensitive than bacteria to changes in soil carbon composition and enzyme activities following straw returning. These results suggest that straw returning combined with chemical fertilizer can be an effective strategy to improve soil labile organic carbon components, enzyme activities, and ecological function of microorganisms.

Diversity and distribution of CO2-fixing microbial community along elevation gradients in meadow soils on the Tibetan Plateau

Soil CO2-fixing microbes play a significant role in CO2-fixation in the terrestrial ecosystems, particularly in the Tibetan Plateau. To understand carbon sequestration by soil CO2-fixing microbes and the carbon cycling in alpine meadow soils, microbial diversity and their driving environmental factors were explored along an elevation gradient from 3900 to 5100 m, on both east and west slopes of Mila Mountain region on the Tibetan Plateau. The CO2-fixing microbial communities were characterized by high-throughput sequencing targeting the cbbL gene, encoding the large subunit for the CO2-fixing protein ribulose 1, 5-bisphosphate carboxylase/oxygenase. The overall OTU (Operational Taxonomic Unit) abundance is concentrated at an altitude between 4300 and 4900 m. The diversity of CO2-fixing microbes is the highest in the middle altitude area, and on the east slope is higher than those on the west slope. In terms of microbial community composition, Proteobacteria is dominant, and the most abundant genera are Cupriavidus, Rhodobacter, Sulfurifustis and Thiobacillus. Altitude has the greatest influence on the structural characteristics of CO2-fixing microbes, and other environmental factors are significantly correlated with altitude. Therefore, altitude influences the structural characteristics of CO2-fixing microbes by driving environmental factors. Our results are helpful to understand the variation in soil microbial community and its role in soil carbon cycling along elevation gradients.

Effects of afforestation on soil microbial diversity and enzyme activity: A meta-analysis

Afforestation is thought to be one of the key measures for mitigating climate change by capturing atmospheric carbon. However, despite the importance of afforestation in ecosystem functioning, its effects on soil microbial diversity and enzyme activity remain unclear. In this study, we conducted a meta-analysis of these effects, using a newly compiled dataset of soil microbial diversity and enzyme activity before and after afforestation collected from 80 sites worldwide. Soil fungal diversity and soil enzyme activities increased significantly after afforestation, but soil bacterial diversity did not change significantly. Among these soil enzymes, the activities of β-1,4-glucosidase (BG), urease (UREA), alkaline phosphatase (AP), dehydrogenase (DEH), and catalase (CAT) increased by 104.7%, 84.0%, 101.7%, 199.2%, and 58.3%, respectively. The responses of soil microbial diversity and enzyme activities varied across afforestation durations, climate zones, prior land use types, and species. Specifically, soil bacterial diversity and the activity of BG increased significantly with afforestation duration, and the increase in BG activity was higher in tropical than in temperate zones. In degraded sites, both soil microbial diversity and enzyme activities significantly increased after afforestation. In addition, structural equation models showed that soil carbon content, nitrogen content, and soil pH value were significant driving factors for the soil microbial community diversity and soil enzyme activities. Overall, our results provided a comprehensive understanding of the changes in soil microbial diversity and enzyme activity under different afforestation conditions, as well as scientific bases for locally adapted afforestation in the future.

Response of Soil Microbial Community Structure Mediated by Sulfur-Induced Resistance Against Kiwifruit Bacterial Canker.

Kiwifruit bacterial canker caused by Pseudomonas syringae pv. actinidiae (Psa) is a major threat to kiwifruit worldwide, and effective control measures are still lacking. Sulfur, as a mineral, has been proved to improve plants' resistance to pathogens. It is of great significance to study the effect of sulfur on rhizosphere microorganisms in kiwifruit planting areas infected by Psa for controlling kiwifruit canker. In this study, the sulfur powder and organic fertilizer were mixed as base fertilizer to treat the soil in the area where kiwifruit bacterial canker occurs. We investigated the incidence of kiwifruit bacterial canker in 2018 and 2019 after sulfur application and the changes in microbial characteristics and community composition structure in the kiwifruit rhizosphere by using the plate-counting method and high-throughput sequencing technology. Fertilization treatments of kiwifruit roots with sulfur and organic fertilizer reduced kiwifruit bacterial canker severity. The diversity of soil microbial communities increased significantly after sulfur application in the range of 1.0~2.0 kg/m3. In particular, the bacterial genera level showed a high diversity after 2 years of sulfur application, reaching more than 516 genera. Furthermore, sulfur treatment resulted in a significant increase in specific microbial taxa, including members of the Acidothermus, norank_f__HSB_OF53-F07, and norank_f __Acidobacteriaceae__Subgroup_1. Moreover, the proportion of the dominant bacteria Acidothermus in the population showed an increasing trend. Altogether, the sulfur application is the key factor leading to microbial differences in kiwifruit rhizosphere soil. Appropriate sulfur can improve microbial structure characteristics of kiwifruit rhizosphere soil, increase bacterial diversity index, and change bacterial community composition structure.

Plant Interaction Patterns Shape the Soil Microbial Community and Nutrient Cycling in Different Intercropping Scenarios of Aromatic Plant Species.

Intercropping systems improve the soil nutrient cycle through microbial community activity and then land productivity. However, their interactions mechanism underlying that the mixed aromatic plant species intercropping regulate the soil microbiome and nutrient cycling on the perennial woody orchard is still uncovered. We designed treatments with 0, 1, and 3 aromatic plant species intercropped in two scenarios of clean tillage (T model, T1, T2, and T4) and natural grass (G model, G1, G2, and G4) in apple orchards, and investigated intercrops effects at the branch growing stage (BGS) and fruit development stage (FDS), respectively. Compared with T model, G model in FDS increased alpha diversity of bacterial community and Shannon index fungal community, the relative abundance of dominant taxa, such as Acidobacteria and Actinobacteria, and also the numbers of up and down-regulated OTUs, the most of indices of co-occurrence network in both bacterial and fungal community, and then improved invertase activity and available nitrogen content. Relative to G1, G2 and G4 reduced diversity bacterial community in FDS, the relative abundance of dominant taxa, the most of indices of co-occurrence network, and then improved soil invertase activity and total phosphorus content in soil. Moreover, Shannon index of fungal community, the altered number of OTUs and the most indices of co-occurrence network were higher in G4 than those in G2 in FDS. These changes above in FDS were more markedly than those in BGS, suggesting that chemical diversity of litter from mixed species of aromatic plants in natural grass scenario led to diversity, complexity, and stability of soil microbial community and then nutrient cycling. It provided a novel highlight and method to modulate biocenosis and then improve the soil nutrient cycling.

Effects of Soil Properties and Microbiome on Highbush Blueberry (Vaccinium corymbosum) Growth

Blueberry has high nutritional value and is favored by consumers, so the planting area is increasing. However, due to the influence of climate conditions and the edaphic environment, achieving high production and the healthy growth of blueberries has become a major problem. In this study, we collected soil and blueberry plants which had normal and limited growth to determine the underlying causes of poor growth by characterizing soil pH, EC, enzyme activities and the microbiome, plant growth properties, and root metabolites. The results showed that the pH of the blueberry rhizosphere soil was less than 6.0 in the case of plants growing well, and higher than 6.0 in case of plants growing poorly. The activities of acid phosphatase and invertase were significantly higher in the rhizosphere soil of the normally growing than growth-limited blueberry plants. The relative abundance of Proteobacteria and Saccharibacteria was higher in the rhizosphere soil of normally growing than growth-limited blueberry plants and they were positively correlated with activity of soil acid phosphatase. Ascomycota, as the dominant fungi, had the highest relative abundance in the rhizosphere soil of growth-limited blueberry plants. The six metabolites showing enrichment in the KEGG pathway analysis were thymidine, cholic acid, raffinose, p-salicylic acid, astaxanthin, and inosine. It was found that flavonoids were correlated positively with soil fungi abundance. The contents of flavonoids apin, rutin and epigallocatechin were significantly higher in roots of growth-limited than normally growing blueberry plants. The content of the flavonoid daidzin was significantly higher in the roots of poorly growing blueberries compared to normally growing ones. In conclusion, the growth of blueberry was significantly related to soil organic matter, soil enzyme activity and soil microbial community diversity.

Immobilization of Cd and Pb in soil facilitated by magnetic biochar: metal speciation and microbial community evolution.

The preparation of magnetic biochar from sewage sludge and rice straw for heavy metal contaminated soil remediation has greater application prospects, but its remediation mechanism was rarely considered by combining soil physicochemical properties with microbial community. In this study, the effects of magnetic sewage sludge biochar (SSB) and rice straw biochar (RSB) on Cd and Pb immobilization in paddy soil were compared and analyzed by 60-day soil incubation experiments. The results illustrated that DTPA-Cd and DTPA-Pb were reduced by 51.53% (43.07%) and 53.57% (50.47%), while the percentage of residual fraction of the BCR procedure was enhanced by 31.27% (30.78%) of Cd and 27.25% (23.22%) of Pb in the SSB (RSB) treatment, respectively. Fe was detected on both SSB and RSB surfaces, but SSB had rougher and a larger specific surface area compared to RSB. The addition of SSB and RSB in paddy soil increased soil pH and TOC content, and affected the diversity and species of soil microbial community. Compared with the CK group, the relative abundance of Proteobacteria, Bacteroidota, and Lysobacter decreased, and the relative abundance of Actinobacteriota, Pontibacter, and Alkaliphilus increased with SSB and RSB treatments, all of which reflected the bioavailability of Cd and Pb reduction.

Variation in Root Exudate Composition Influences Soil Microbiome Membership and Function

Root exudation is one of the primary processes that mediate interactions between plant roots, microorganisms, and the soil matrix, yet the mechanisms by which exudation alters microbial metabolism in soils have been challenging to unravel. Here, utilizing distinct sorghum genotypes, we characterized the chemical heterogeneity between root exudates and the effects of that variability on soil microbial membership and metabolism. Distinct exudate chemical profiles were quantified and used to formulate synthetic root exudate treatments: a high-organic-acid treatment (HOT) and a high-sugar treatment (HST). To parse the response of the soil microbiome to different exudate regimens, laboratory soil reactors were amended with these root exudate treatments as well as a nonexudate control. Amplicon sequencing of the 16S rRNA gene illustrated distinct microbial diversity patterns and membership in response to HST, HOT, or control amendments. Exometabolite changes reflected these microbial community changes, and we observed enrichment of organic and amino acids, as well as possible phytohormones in the HST relative to the HOT and control. Linking the metabolic capacity of metagenome-assembled genomes in the HST to the exometabolite patterns, we identified microorganisms that could produce these phytohormones. Our findings emphasize the tractability of high-resolution multiomics tools to investigate soil microbiomes, opening the possibility of manipulating native microbial communities to improve specific soil microbial functions and enhance crop production. IMPORTANCE Decrypting the chemical interactions between plant roots and the soil microbiome is a gateway for future manipulation and management of the rhizosphere, a soil compartment critical to promoting plant fitness and yields. Our experimental results demonstrate how soil microbial community and genomic diversity is influenced by root exudates of differing chemical compositions and how changes in this microbiome result in altered production of plant-relevant metabolites. Together, these findings demonstrate the tractability of high-resolution multiomics tools to investigate soil microbiomes and provide new information on plant-soil environments useful for the development of efficient and precise microbiota management strategies in agricultural systems.

Changes in diversity, composition and assembly processes of soil microbial communities during Robinia pseudoacacia L. restoration on the Loess Plateau, China

Changes in diversity, composition and assembly processes of soil microbial communities during Robinia pseudoacacia L. restoration on the Loess Plateau, China

Nitrogen addition enhanced the polycyclic aromatic hydrocarbons dissipation through increasing the abundance of related degrading genes in the soils

High concentrations of Polycyclic Aromatic Hydrocarbons (PAHs) in the soils cause significant threats to human health. Since nitrogen plays a crucial role in controlling microbial composition and functions in terrestrial ecosystems, bio-stimulation based on nitrogen has been used in PAHs contaminated environments remediation. Recent studies show that microbial community composition and organic pollutants dissipation correlate with nitrogen addition. Here, we investigated the effect of nitrogen addition on the abundance of microbial community, degrading genes, and their relationship to PAHs dissipation. After a 32-day experiment, PAHs residues in nitrogen treatment soil were reduced by 23.23%−34.21%. The application of 80 mg·kg−1 nitrate and ammonium nitrogen resulted in higher PAHs removal efficiency, and the dissipation rate of PAHs was 59.61% and 62.09%, respectively. Nitrogen application could improve the abundance and the diversity of soil microbial community. Degrading genes involved in PAH detoxification were enhanced after nitrogen addition, particularly those encoding ring-hydroxylating and catechol dioxygenases such as nahAc and nidA, thus, accelerating PAH dissipation in the soil. The results will facilitate the development of beneficial microbiome-based remediation strategies and improve agricultural production safety in PAHs-contaminated soils.

Variation of Soil Microbial Community and Sterilization to Fusarium oxysporum f. sp. niveum Play Roles in Slightly Acidic Electrolyzed Water-Alleviated Watermelon Continuous Cropping Obstacle.

It is critical to exploit technologies for alleviating watermelon continuous cropping obstacle which frequently occurs and results in the limiting production and economic losses of watermelon. This study aimed to explore the effects of slightly acidic electrolyzed water (SAEW) on watermelon continuous cropping obstacles. The results showed that SAEW significantly improved the growth of watermelon seedlings cultivated in continuous cropping soil and caused a mass of changes to the diversity of the soil microbial community. Compared with Con, SAEW decreased the diversity index of bacteria by 2%, 0.48%, and 3.16%, while it increased the diversity index of fungus by 5.68%, 10.78%, and 7.54% in Shannon, Chao1, and ACE index, respectively. Besides, the enrichment level of Fusarium oxysporum f. sp. niveum (FON) was remarkably downregulated by 50.2% at 14 days of SAEW treatment, which could decrease the incidence of Fusarium wilt disease. The wet and dry weights of FON mycelia in the fluid medium were depressed more than 93%, and the number of FON colonies in continuous cropping soil was reduced by 83.56% with SAEW treatment. Additionally, a strong correlation between watermelon, FON, and SAEW was presented by correlation analysis. Furthermore, the content of endogenous reactive oxygen species (ROS) was over quadruply increased by SAEW, which may contribute to the sterilizing effect of SAEW on FON. Taken together, our findings demonstrated that exogenous SAEW could alter the soil microbial diversity and decrease the accumulation of FON, which improved the growth of watermelon seedlings and finally alleviated continuous cropping obstacles of watermelon.

Rice Root Exudation: Signalling and Behavior of Shaping the DNRA Microbiome

In natural ecosystems, plant health is mainly dependent on interactions with diverse and dynamic soil microbial communities. The microbial communities particularly those associated with nitrogen (N) cycling pathway inhabiting in rice field ecosystem have been described previously. Although, little is known about the taxonomic microbial players involved with dissimilatory nitrate reduction to ammonium (DNRA), a short-circuit N retention pathway in terrestrial N cycle. Therefore, we have to focus on how rice plants shape DNRA bacteria and how they alter over the course of several rice growth stages. Besides, we also shed lights on rice root physiology and the role of root exudates to address plant physiological aspects that may influence plant-microbe interactions.

Composition and Diversity of Soil Microbial Community Associated With Land Use Types in the Agro-Pastoral Area in the Upper Yellow River Basin.

The microorganisms of soil are sensitive to their living microenvironment, and their community structure and function will change with the environmental conditions. In the agro–pastoral area on the Qinghai–Tibet Plateau, revealing the diversity of the soil microbial communities and its response to different soil physicochemical properties and environmental factors are important for ecosystem management. The microbial (bacteria and archaea) community composition and diversity under different land use types (cultivated land, grazing grassland and planted forest) were analyzed by 16S rRNA (V4 region) method in a typical agro–pastoral region in the upper Yellow River basin. Also, the soil nutrients were studied and correlated with the microbial community. The results showed that the soil nutrient contents in grassland were low, but the available nutrients were relatively high. There was a great spatial variability under different distances to the river. The microbial community diversity was lower in the grassland than the cultivated land and forest land closer to the river. For all land uses, the dominant phyla of soil microorganisms included Proteobacteria, Actinobacteria, and Bacteroidetes, while the abundance of Clostridia was significantly higher than that of the other groups, indicating that Clostridia dominated the Firmicutes and affected soil microbial community composition. The linear discriminant analysis (LDA) effect size (LefSe) analysis showed different biomarkers were more abundant in grassland than other land use types, suggesting that the structure and diversity of soil microorganisms in grassland were significantly different compared with cultivated land and forest land. The distance-based redundancy analysis (db-RDA) results showed that the total phosphorus (TP) and calcium (Ca) were the key environmental factors affecting the diversity and abundance of the soil microbial community in cultivated land and forestland, respectively. However, the microbial diversity in grassland was more related to spatial distance of the river. These results provided a theoretical basis for the changes in the composition, structure, and function of soil microbial communities in agro–pastoral areas.

Greenhouse gas fluxes response to autumn freeze-thaw period in continuous permafrost region of Daxing'an Mountains, Northeast China.

Autumn freeze-thaw period significantly influenced the soil temperature, moisture, nutrients, and then affected the structure and diversity of soil microbial community. In this paper, three types of wetlands in the permafrost region of Daxing'an Mountains were selected to investigate the greenhouse gas fluxes during the autumn freeze-thaw period. CO2, CH4, and N2O fluxes during the autumn freeze-thaw period ranged from 24.76 to 124.06mgm-2h-1, - 249.10 to 968.87μgm-2h-1, and - 4.21 to 12.86μgm-2h-1. CO2 fluxes were mainly influenced by soil temperature and moisture. CH4 fluxes were mainly influenced by temperature and soil moisture. And N2O fluxes were significantly affected by temperature, soil moisture, ammonia nitrogen, and nitrate nitrogen. Environmental factors could explain 64-73.2%, 51-85.4%, and 60.3-93.3% of temporal variation of CO2, CH4, and N2O fluxes, respectively. Comparing different wetlands, the soil temperature was the significant factor to affect the CH4 flux. The global warming potentials during the autumn freeze-thaw period ranged from 717.83 to 775.57kg CO2-eq hm-2.