Changes In Soil Bacterial Community Research Articles

Microplastics alter cadmium accumulation in different soil-plant systems: Revealing the crucial roles of soil bacteria and metabolism

Cadmium (Cd) and microplastics (MPs) gradually increased to be prevalent contaminants in soil, it is important to understand their combined effects on different soil-plant systems. We studied how different doses of polylactic acid (PLA) and polyethylene (PE) affected Cd accumulation, pakchoi growth, soil chemical and microbial properties, and metabolomics in two soil types. We found that high-dose MPs decreased Cd accumulation in plants in red soil, while all MPs decreased Cd bioaccumulation in fluvo-aquic soil. This difference was primarily attributed to the increase in dissolved organic carbon (DOC) and pH in red soil by high-dose MPs, which inhibited Cd uptake by plant roots. In contrast, MPs reduced soil nitrate nitrogen and available phosphorus, and weakened Cd mobilization in fluvo-aquic soil. In addition, high-dose PLA proved detrimental to plant health, manifesting in shortened shoot and root lengths. Co-exposure of Cd and MPs induced the shifts in bacterial populations and metabolites, with specific taxa and metabolites closely linked to Cd accumulation. Overall, co-exposure of Cd and MPs regulated plant growth and Cd accumulation by driving changes in soil bacterial community and metabolic pathways caused by soil chemical properties. Our findings could provide insights into the Cd migration in different soil-plant systems under MPs exposure. Environmental ImplicationMicroplastics (MPs) and cadmium (Cd) are common pollutants in farmland soil. Co-exposure of MPs and Cd can alter Cd accumulation in plants, and pose a potential threat to human health through the food chain. Here, we investigated the effects of different types and doses of MPs on Cd accumulation, plant growth, soil microorganisms, and metabolic pathways in different soil-plant systems. Our results can contribute to our understanding of the migration and transport of Cd by MPs in different soil-plant systems and provide a reference for the control of combined pollution in the future research.

A novel Zr-P-modified nanomagnetic herbal biochar immobilized Cd and Pb in water and soil and enhanced the relative abundance of metal-resistant bacteria: Biogeochemical and spectroscopic investigations to identify the governing factors and potential mechanisms

Remediation of toxic metals contaminated water and soil using engineered biochar is of great concern. This study introduces a novel zirconium-phosphate-modified nanomagnetic biochar (ZMBC) synthesized from traditional Chinese herbal residues as a potential adsorbent for remediation of Cd2+ and Pb2+ contaminated water and soil. The impact of co-existing ions, ionic strength, metal concentrations, pH, and contact time on the adsorption/immobilization efficiency/mechanisms of ZMBC for Cd2+ and Pb2+ in water and soil were investigated together with the induced changes in soil bacterial community for the first time. The governing factors and potential mechanisms for the interaction between metals and ZMBC have been investigated using biogeochemical, microscopic, and spectroscopic techniques. The adsorption capacity of ZMBC for Pb2+ (357.1 mg g−1) and Cd2+ (136.2 mg g−1) was significantly higher than that of pristine biochar (BC) and nanomagnetic biochar (MBC) (<5 mg g−1). The adsorption behavior for Pb2+ and Cd2+ followed the pseudo-second-order, intra-particle diffusion and Langmuir model, and was minimally affected by ionic strength. Co-existence of Ca2+, Cu2+ and Zn2+ ions at lower concentrations (<10 mg L–1) promoted the adsorption of Pb2+ but inhibited it at higher concentrations (50–200 mg L–1). Conversely, the co-existence of those ions at 10–200 mg L–1, particularly Cu2+ and Zn2+ significantly inhibited Cd2+ adsorption. Adsorption of Pb2+ and Cd2+ on ZMBC was dominated by functional group complexation, co-precipitation, metal-π electronic coordination, and ion exchange. Addition of ZMBC to the contaminated soil altered the mobile fraction of Cd2+ and Pb2+ to the residual fractions and thus significantly reduced the DTPA-extractable Pb2+ by 51.3% and Cd2+ by 56.1%, and also reduced the Cd and Pb in the wheat roots (by 64.0% and 36.1%, respectively) and shoots (by 73.5% and 62.2%, respectively), as compared to the untreated soil. The analysis of the soil 16S rDNA gene showed that the addition of ZMBC increased soil bacteria suitable for bioremediation of Pb2+ and Cd2+ contaminated soil. Those findings conclude that ZMBC can be used as a promising amendment for remediation of water and soils co-polluted with Cd and Pb.

A preliminary study characterizing temporal changes in soil bacterial communities after dismembered bones were buried.

Determining the burial time of skeletal remains is one of the most important issues of forensic medicine. We speculated that the microbiome of gravesoil may be a promising method to infer burial time by virtue of time-dependent. As we know, forensic scientists have established various models to predict the postmortem interval of a decedent based on the changes in body and soil microbiome communities. However, limited data are available on the burial time prediction for bones, especially dismembered bones. In this exploratory study, we initially conducted 16S rRNA amplicon high-throughput sequencing on the burial soil of 10 porcine femurs within a 120-day period and analyzed the changes in soil microbial communities. Compared with the control soil, a higher Shannon index in the microbial diversity of burial soil containing bones was observed. Correlation analysis identified 61 time-related bacterial families and the best subset selection method obtained best subset, containing Thermomonosporaceae, Clostridiaceae, 0319-A21, and Oxalobacteraceae, which were used to construct a simplified multiple linear regression model with a mean absolute error (MAE) of 56.69 accumulated degree day (ADD). An additional random forest model was established based on indicators for the minimum cross-validation error of Thermomonosporaceae, Clostridiaceae, 0319-A21, Oxalobacteraceae, and Syntrophobacteraceae, with an MAE of 55.65 ADD. The produced empirical data in this pilot study provided the evidence of feasibility that the microbial successional changes of burial soil will predict the burial time of dismembered bones and may also expand the current knowledge of the effects of bone burial on soil bacterial communities.

Light-dark cycles may influence insitu soil bacterial networks and diurnally-sensitive taxa.

Soil bacterial taxa have important functional roles in ecosystems (e.g. nutrient cycling, soil formation, plant health). Many factors influence their assembly and regulation, with land cover types (e.g. open woodlands, grasslands), land use types (e.g. nature reserves, urban green space) and plant-soil feedbacks being well-studied factors. However, changes in soil bacterial communities insitu over light-dark cycles have received little attention, despite many plants and some bacteria having endogenous circadian rhythms that could influence soil bacterial communities. We sampled surface soils insitu across 24-h light-dark cycles (at 00:00, 06:00, 12:00, 18:00) at two land cover types (remnant vegetation vs. cleared, grassy areas) and applied 16S rRNA amplicon sequencing to investigate changes in bacterial communities. We show that land cover type strongly affected soil bacterial diversity, with soils under native vegetation expressing 15.4%-16.4% lower alpha diversity but 4.9%-10.6% greater heterogeneity than soils under cleared vegetation. In addition, we report time-dependent and site-specific changes in bacterial network complexity and between 598-922 ASVs showing significant changes in relative abundance across times. Native site node degree (bacterial interactions) at the phylum level was 16.0% higher in the early morning than in the afternoon/evening. Our results demonstrate for the first time that light-dark cycles have subtle yet important effects on soil bacterial communities insitu and that land cover influences these dynamics. We provide a new view of soil microbial ecology and suggest that future studies should consider the time of day when sampling soil bacteria.

Combined effects of mulch film-derived microplastics and pesticides on soil microbial communities and element cycling

Pesticides and microplastics (MPs) derived from mulch film in agricultural soil can independently impact soil ecology, yet the consequences of their combined exposure remain unclear. Therefore, the effects of simultaneous exposure to commonly used pesticides (imidacloprid and flumioxazin) and aged mulch film-derived MPs on soil microorganisms and element cycles in cotton fields were investigated. The combined exposure influenced soil microorganisms, alongside processes related to carbon, nitrogen, and phosphorus cycles, exhibiting effects that were either neutralized or enhanced compared to individual exposures. The impact of pesticides in combined exposure was notably more significant and played a dominant role than that of MPs. Specifically, combined exposure intensified changes in soil bacterial community and symbiotic networks. The combined exposure neutralized NH4+, NO3-, DOC, and A-P contents, shifting from 0.33 % and 40.23 % increase in MPs and pesticides individually to a 40.24 % increase. Moreover, combined exposure resulted in the neutralization or amplification of the nitrogen-fixing gene nifH, nitrifying genes (amoA and amoB), and denitrifying genes (nirS and nirK), the carbon cycle gene cbbLG and the phosphorus cycle gene phoD from 0.48 and 2.57-fold increase to a 2.99-fold increase. The combined exposure also led to the neutralization or enhancement of carbon and nitrogen cycle functional microorganisms, shifting from a 1.53-fold inhibition and 10.52-fold increase to a 6.39-fold increase. These findings provide additional insights into the potential risks associated with combined pesticide exposure and MPs, particularly concerning soil microbial communities and elemental cycling processes.

PH-Related Changes in Soil Bacterial Communities in the Sanjiang Plain, Northeast China.

Soil bacteria are crucial components of terrestrial ecosystems, playing an important role in soil biogeochemical cycles. Although bacterial community diversity and composition are regulated by many abiotic and biotic factors, how soil physiochemical properties impact the soil bacteria community diversity and composition in wetland ecosystems remains largely unknown. In this study, we used high-throughput sequencing technology to investigate the diversity and composition of a soil bacterial community, as well as used the structural equation modeling (SEM) method to investigate the relationships of the soil's physicochemical properties (i.e., soil pH, soil organic carbon (SOC), total nitrogen (TN), ammonium nitrogen (NH4+N), electrical conductivity (EC) and nitrate nitrogen (NO3-N)), and soil bacterial community structures in three typical wetland sites in the Sanjiang Plain wetland. Our results showed that the soil physicochemical properties significantly changed the α and β-diversity of the soil bacteria communities, e.g., soil TN, NH4+N, NO3-N, and SOC were the main soil factors affecting the soil bacterial α-diversity. The soil TN and pH were the key soil factors affecting the soil bacterial community. Our results suggest that changes in soil pH indirectly affect soil bacterial communities by altering the soil nitrogenous nutrient content.

Biochar drives changes in soil bacterial communities and cotton growth by improving nutrients availability under saline conditions

AbstractApplying biochar to saline soil is a novel strategy for improving soil quality. However, how biochar addition amount affects soil nutrients, bacterial communities, and cotton growth at different stages remains unclear. Three biochar treatments, no biochar (BC0), 1% biochar (BC1, w/w), 3% biochar (BC3), and two cotton varieties, salt‐sensitive (SS) and salt‐tolerant (ST), were used in pot experiments, analyzing biochar effects on saline soil nutrients, bacterial communities, and cotton growth. The study found that biochar increased only organic carbon (SOC), total nitrogen (TN), and available potassium (AK) at the seedling stage. However, at the flowering‐boll stage, biochar also increased nitrate () and available phosphorus (AP) and reduced soil salt content. Biochar did not affect α‐diversity at the seedling stage, but BC3 reduced α‐diversity at the flowering‐boll stage. The principal coordinate analysis revealed changes in the soil bacterial community composition that were closely associated with biochar added. From the redundancy analyses, SOC and AK were the leading environmental factors for soil bacterial community composition changes. SOC, TN, and AK correlated positively with Proteobacteria, which increased their relative abundance through biochar addition and correlated negatively with Bacteroidetes, Chloroflexi, and Acidobacteria, which decreased their relative abundance due to biochar. Furthermore, the random forests analysis showed that SOC, Shannon index, and β‐diversity were significant predictors of cotton biomass. In summary, biochar drives changes in bacterial communities in saline soils by increasing nutrients such as SOC and AK, which affect cotton growth. This study provides data to support the application of biochar on saline soils.

Soil Bacterial Community Structure and Physicochemical Influencing Factors of Artificial Haloxylon ammodendron Forest in the Sand Blocking and Fixing Belt of Minqin, China

Microbial activity plays a crucial role in upholding the functional stability of vegetation–soil ecosystems. Nevertheless, there exists a paucity of studies concerning the impact of sand-fixing vegetation (Haloxylon ammodendron) on the structure and functional attributes of soil microbial communities. We employed Illumina high-throughput sequencing and PICRUSt2 functional prediction technology to investigate the characteristics of soil bacterial community structure, diversity, and metabolic functions in an artificial H. ammodendron forest, and RDA analysis and the Mantel test were used to reveal the main environmental factors affecting the structure and ecological functions of soil bacterial communities. The findings revealed a significant increase in the principal nutrient contents (organic matter, total nitrogen, total phosphorus) in the H. ammodendron forest soil compared to the mobile dune soil, while a reduction of 17.17% in the surface soil water content was observed. The H. ammodendron forest exhibited a significant enhancement in the diversity and richness index of soil bacteria. Specifically, Actinobacteria (24.94% ± 11.85%), Proteobacteria (29.99% ± 11.56%), and Chloroflexi (11.14% ± 4.55%) emerged as the dominant bacterial phyla, with Actinobacteria displaying significantly higher abundance compared to the mobile dune soil. PICRUSt2 analyses revealed that the predominant secondary metabolic functions of soil bacteria were carbohydrate metabolism, amino acid metabolism, and the metabolism of cofactors and vitamins. Additionally, the tertiary metabolic pathways exhibited greater activity in relation to enzyme function, nucleotide metabolism, energy metabolism, and antibiotics. The RDA results demonstrated that SOM, AK, and pH collectively accounted for 82.4% of the cumulative contribution, significantly influencing the bacterial community. Moreover, the Mantel test revealed that the metabolic function of soil bacteria primarily relied on five environmental factors, namely SOM, TN, AK, pH, and EC. This study significantly advances our understanding of the structural and functional changes in soil bacterial communities during the reclamation of sandy land through the establishment of artificial H. ammodendron forests.

Changes in Soil Bacterial Community and Function in Winter Following Long-Term Nitrogen (N) Deposition in Wetland Soil in Sanjiang Plain, China.

N deposition is a key factor affecting the composition and function of soil microbial communities in wetland ecosystems. Previous studies mainly focused on the effects of N deposition in the soil during the growing season (summer and autumn). Here, we focused on the response of the soil microbial community structure and function in winter. Soil from the Sanjiang Plain wetland, China, that had been treated for the past 11 years by using artificial N deposition at three levels (no intervention in N0, N deposition with 4 g N m-2 yr-1 in N1, and with 8 g N m-2 yr-1 in N2). Soil characteristics were determined and the bacterial composition and function was characterized using high-throughput sequence technology. The N deposition significantly reduced the soil bacterial diversity detected in winter compared with the control N0, and it significantly changed the composition of the bacterial community. At the phylum level, the high N deposition (N2) increased the relative abundance of Acidobacteria and decreased that of Myxococcota and Gemmatimonadota compared with N0. In soil from N2, the relative abundance of the general Candidatus_Solibacter and Bryobacter was significantly increased compared with N0. Soil pH, soil organic carbon (SOC), and total nitrogen (TN) were the key factors affecting the soil bacterial diversity and composition in winter. Soil pH was correlated with soil carbon cycling, probably due to its significant correlation with aerobic_chemoheterotrophy. The results show that a long-term N deposition reduces soil nutrients in winter wetlands and decreases soil bacterial diversity, resulting in a negative impact on the Sanjiang plain wetland. This study contributes to a better understanding of the winter responses of soil microbial community composition and function to the N deposition in temperate wetland ecosystems.

Soil Bacterial Communities Across Seven Rhizoma Peanut Cultivars (Arachis glabrata Benth.) Respond to Seasonal Variation.

Soil microorganisms play key roles in soil nutrient transformations and have a notable effect on plant growth and health. Different plant genotypes can shape soil microbial patterns via the secretion of root exudates and volatiles, but it is uncertain how a difference in soil microorganisms induced by crop cultivars will respond to short-term seasonal variations. A field experiment was conducted to assess the changes in soil bacterial communities of seven rhizoma peanut (Arachis glabrata Benth, RP) cultivars across two growing seasons, April (Spring season) and October (Fall season). Soils' bacterial communities were targeted using 16S rRNA gene amplicon sequencing. Bacterial community diversity and taxonomic composition among rhizoma peanut cultivars were significantly affected by seasons, cultivars, and their interactions (p < 0.05). Alpha diversity, as estimated by the OTU richness and Simpson index, was around onefold decrease in October than in April across most of the RP cultivars, while the soils from Arblick and Latitude had around one time higher alpha diversity in both seasons compared with other cultivars. Beta diversity differed significantly in April (R = 0.073, p < 0.01) and October (R = 0.084, p < 0.01) across seven cultivars. Bacterial dominant taxa (at phylum and genus level) were strongly affected by seasons and varied towards more dominant groups that have functional potentials involved in nutrient cycling from April to October. A large shift in water availability induced by season variations in addition to host cultivar's effects can explain the observed patterns in diversity, composition, and co-occurrence of bacterial taxa. Overall, our results demonstrate an overriding effect of short-term seasonal variations on soil bacterial communities associated with different crop cultivars. The findings suggest that season-induced shifts in environmental conditions could exert stronger impacts on soil microorganisms than the finer-scale rhizosphere effect from crop cultivars, and consequently influence largely microbe-mediated soil processes and crop health in agricultural ecosystems.

Changes in grassland soil types lead to different characteristics of bacterial and fungal communities in Northwest Liaoning, China.

Soil microbial communities are critical in regulating grassland biogeochemical cycles and ecosystem functions, but the mechanisms of how environmental factors affect changes in the structural composition and diversity of soil microbial communities in different grassland soil types is not fully understood in northwest Liaoning, China. We investigated the characteristics and drivers of bacterial and fungal communities in 4 grassland soil types with 11 sites across this region using high-throughput Illumina sequencing. Actinobacteria and Ascomycota were the dominant phyla of bacterial and fungal communities, respectively, but their relative abundances were not significantly different among different grassland soil types. The abundance, number of OTUs, number of species and diversity of both bacterial and fungal communities in warm and temperate ecotone soil were the highest, while the warm-temperate shrub soil had the lowest microbial diversity. Besides, environmental factors were not significantly correlated with soil bacterial Alpha diversity index. However, there was a highly significant negative correlation between soil pH and Shannon index of fungal communities, and a highly significant positive correlation between plant cover and Chao1 index as well as Observed species of fungal communities. Analysis of similarities showed that the structural composition of microbial communities differed significantly among different grassland soil types. Meanwhile, the microbial community structure of temperate steppe-sandy soil was significantly different from that of other grassland soil types. Redundancy analysis revealed that soil total nitrogen content, pH and conductivity were important influencing factors causing changes in soil bacterial communities, while soil organic carbon, total nitrogen content and conductivity mainly drove the differentiation of soil fungal communities. In addition, the degree of connection in the soil bacterial network of grassland was much higher than that in the fungal network and soil bacterial and fungal communities were inconsistently limited by environmental factors. Our results showed that the microbial community structure, composition and diversity of different grassland soil types in northwest Liaoning differed significantly and were significantly influenced by environmental factors. Microbial community structure and the observation of soil total nitrogen and organic carbon content can predict the health changes of grassland ecosystems to a certain extent.

Changes in soil bacterial communities and functional groups beneath coarse woody debris across a subalpine forest successional series

Changes in soil bacterial communities and functional groups beneath coarse woody debris across a subalpine forest successional series

Effects of Simulated Acid Rain and Nitrogen Deposition on Soil Bacterial Community Structure and Diversity in the Masson Pine Forest

By analyzing the effects of acid rain and nitrogen deposition on the structure and diversity of soil bacterial communities, the response mechanism of Masson pine forests to environmental stress was investigated, providing a theoretical reference basis for resource management and conservation in Tianmu Mountain National Nature Reserve. Four treatments of the simulated acid rain and nitrogen deposition were set up in 2017 to 2021 in Tianmu Mountain National Nature Reserve (pH value of 5.5 and 0 kg·(hm2·a)-1, CK; pH value of 4.5 and 30 kg·(hm2·a)-1, T1; pH value of 3.5 and 60 kg·(hm2·a)-1, T2; pH value of 2.5 and 120 kg·(hm2·a)-1, T3). The differences in soil bacterial community composition and structure among treatments and their influencing factors were analyzed by collecting soils from four treatments, using the Illumina MiSeq PE300 second-generation high-throughput sequencing platform. The results showed that acid rain and nitrogen deposition significantly reduced soil bacterial α-diversity (P<0.05) in a Masson pine forest. The Masson pine forest soils consisted of 36 phylum groups of mycota, with Acidobacteria, Proteobacteria, Actinobacteria, and Chloroflexi as the main bacterial phyla (relative abundance>1%) in the Masson pine forest soils. Flavobacterium, Nitrospira, Haliangium, Candidatus_Koribacter, Bryobacter, Occallatibacter, Acidipla, Singulisphaera, Pajaroellobacter, and Acidothermus, which showed significant changes in relative abundance under the four treatments, could be used as indicator species for changes in soil bacterial communities under acid rain and nitrogen deposition stress. Soil pH and total nitrogen were influential factors in the diversity of soil bacterial communities. As a result, acid rain and nitrogen deposition increased the potential ecological risk, and the loss of microbial diversity will change the ecosystem function as well as reduce the stability of the ecosystem.

Effect of Rice Straw and Stubble Burning on Soil Physicochemical Properties and Bacterial Communities in Central Thailand.

Rice straw and stubble burning is widely practiced to clear fields for new crops. However, questions remain about the effects of fire on soil bacterial communities and soil properties in paddy fields. Here, five adjacent farmed fields were investigated in central Thailand to assess changes in soil bacterial communities and soil properties after burning. Samples of soil prior to burning, immediately after burning, and 1 year after burning were obtained from depths of 0 to 5 cm. The results showed that the pH, electrical conductivity, NH4-N, total nitrogen, and soil nutrients (available P, K, Ca, and Mg) significantly increased immediately after burning due to an increased ash content in the soil, whereas NO3-N decreased significantly. However, these values returned to the initial values. Chloroflexi were the dominant bacteria, followed by Actinobacteria and Proteobacteria. At 1 year after burning, Chloroflexi abundance decreased remarkably, whereas Actinobacteria, Proteobacteria, Verrucomicrobia, and Gemmatimonadetes abundances significantly increased. Bacillus, HSB OF53-F07, Conexibacter, and Acidothermus abundances increased immediately after burning, but were lower 1 year after burning. These bacteria may be highly resistant to heat, but grow slowly. Anaeromyxobacter and Candidatus Udaeobacter dominated 1 year after burning, most likely because of their rapid growth and the fact that they occupy areas with increased soil nutrient levels after fires. Amidase, cellulase, and chitinase levels increased with increased organic matter levels, whereas β-glucosidase, chitinase, and urease levels positively correlated with the soil total nitrogen level. Although clay and soil moisture strongly correlated with the soil bacterial community's composition, negative correlations were found for β-glucosidase, chitinase, and urease. In this study, rice straw and standing stubble were burnt under high soil moisture and within a very short time, suggesting that the fire was not severe enough to raise the soil temperature and change the soil microbial community immediately after burning. However, changes in soil properties due to ash significantly increased the diversity indices, which was noticeable 1 year after burning.

Bacterial community assembly and antibiotic resistance genes in soils exposed to antibiotics at environmentally relevant concentrations.

Understanding how bacterial community assembly and antibiotic resistance genes (ARGs) respond to antibiotic exposure is essential to deciphering the ecological risk of anthropogenic antibiotic pollution in soils. In this study, three loam soils with different land management (unmanured golf course, dairy-manured pasture, and swine-manured cornfield) were spiked with a mixture of 11 antibiotics at the initial concentration of 100 and 1000 μg kg-1 for each antibiotic and incubated over 132 days, mimicking a scenario of pulse disturbance and recovery in soils, with unspiked soil samples as the control treatment. The Infer Community Assembly Mechanisms by Phylogenetic-bin-based null model (iCAMP) analysis demonstrated that drift and dispersal limitation contributed to 57%-65% and 16%-25%, and homogeneous selection 12%-16% of soil bacterial community assembly. Interestingly, antibiotic exposure to 1000 μg kg-1 level significantly increased the contribution of drift to community assembly, largely due to the positive response from Acidobacteria-6 in the golf course and pasture soilsand from Chthoniobacteraceae in the cornfield soil to the antibiotic exposure. However, ARG abundance and diversity in the three soils exhibited antibiotics-independent temporal fluctuations, but were associated with the changes in soil bacterial communities over time. This study provides the first insight into the relative contributions of different bacterial community assembly processes in soils upon antibiotic exposure at environmentally relevant concentrations.

The Effects of Oil and Gas Produced Water on Soil Bacterial Community Structure in the Arid Desert Area.

The safe utilization and risk assessment of produced water (PW) from oil and gas fields for desert irrigation have received increasing attention in recent years. In this context, this study aimed to analyze structural changes in soil bacterial community, and assess the environmental impact of PW discharge and irrigation over time. High-throughput sequencing technology was employed to examine the structure of the soil bacterial community in the constructed wetland and its surrounding desert vegetation irrigation region where PW was released for a considerable amount of time (30 years). The results revealed that long-term discharge of PW and irrigation significantly reduced the abundance of the soil bacterial community but did not significantly alter the richness and diversity of the soil bacterial community. Proteobacteria was the dominant bacterial phyla in soil, but in irrigated and drained areas, the dominant bacterial phyla changed from Alphaproteobacteria to Gammaproteobacteria, the Firmicutes abundance was significantly reduced.

Effects of paddy field non-grainization consolidation on sustainable eco-functions protection of soil bacterial: Empirical evidence from Zhejiang province, China

The increasing “non-grainization” of paddy fields affecting large-scale grain cultivation and impacting the sustainable eco-functions protection of soil bacterial in China. The same problem of “non-grainization” has threatened food security and farmland soil ecological functions in other areas of the world. Although previous research has demonstrated that soil microorganisms are strongly affected by land use change, little is known about the effects of paddy field non-grainization consolidation (NGC) on soil microorganisms. This study examined soil samples before and after paddy field NGC in Zhejiang province, China, measured soil environmental factors and performed 16S rDNA amplicon sequencing to analyze the changes in soilbacterial communities and ecosystem functions before and after NGC. Results show that NGC increased the relative abundances of Proteobacteria (27.89%) and Actinobacteria (25.25%) in the project zones. Total soil bacteria increased in all samples after NGC implementation in terms of absolute soil bacterial community content, but there were large differences. NGC improved the alpha diversity indices, including Ace, Chao1, Coverage, and Shannon indices (p &amp;lt; 0.01) in terms of soil bacterial community diversity. The data analysis of RDA and the significance test showed that the environmental factors which were close-knitted with the soil bacterial diversity and structure of the sample sites were TN, AP, pH, SOM, FIQ, and AK. Wilcoxon rank sum test results showed that NGC also significantly enhanced the amino acid transport and metabolic functions of soil bacterial. Our findings suggest that NGC is beneficial to improve the paddy field soil bacterial diversity, enhance the versatility of soil ecosystems, and promote sustainable arable land soil ecosystem protection. The quantitative results would be useful for better studying the use of land remediation engineering measures to the remediation and maintenance of bacterial diversity and sustainable eco-functions protection in paddy fields.

Comparison of Soil Bacterial Communities under Canopies of Pinus tabulaeformis and Populus euramericana in a Reclaimed Waste Dump

To compare the effects of different remediation tree species on soil bacterial communities and provide a theoretical basis for the selection of ecosystem function promotion strategies after vegetation restoration, the characteristic changes in soil bacterial communities after Pinus tabulaeformis and Populus euramericana reclamation were explored using high-throughput sequencing and molecular ecological network methods. The results showed that: (1) With the increase in reclamation years, the reclaimed soil properties were close to the control group, and the soil properties of Pinus tabulaeformis were closer to the control group than those of P. euramericana. (2) The dominant bacteria under the canopies of P. tabulaeformis and P. euramericana was the same. Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi, Gemmatimonadetes, Planctomycetes, Bacteroidetes, and Cyanobacteria were the dominant bacteria in the restored soil, accounting for more than 95% of the total abundance. The average values of the Shannon diversity index, Simpson diversity index, Chao 1 richness estimator, and abundance-based coverage estimator of the bacterial community in the P. euramericana reclaimed soil were higher than those in the P. tabulaeformis reclaimed soil. The influence of reclamation years on the bacterial community of samples is greater than that of species types. (3) The results of ecological network construction showed that the total number of nodes, total number of connections, and average connectivity of the soil bacterial network under P. euramericana reclamation were greater than those under P. tabulaeformis reclamation. The bacterial molecular ecological network under P. euramericana was more abundant. (4) Among the dominant bacteria, the relative abundance of Actinobacteria was negatively correlated with soil pH, soil total nitrogen content, and the activities of urease, invertase, and alkaline phosphatase, while the relative abundance of Proteobacteria and Bacteroidetes was positively correlated with these environmental factors. The relationship between the soil bacterial community of P. tabulaeformis and P. euramericana and the environmental factors is not completely the same, and even the interaction between some environmental factors and bacteria is opposite.

Changes in soil bacterial community along a gradient of permafrost degradation in Northeast China

Spatial fragmentation of permafrost alters soil hydrothermal conditions and physicochemical properties that control microbial activity responsible for the decomposition of organic matter. Due to climate warming, there is a need to identify changes in microbial community and diversity to predict altered soil function along permafrost degradation gradient. To determine the drivers of soil bacterial community at regional (across permafrost regions) and local scales (across habitats, within permafrost region), the method of “space instead of time” was adopted. The soil samples were collected from forest and wetland ecosystems in three types of west-east permafrost regions (including discontinuous, sporadic and isolated patches permafrost regions, which represent the primary degenerate sequence) in Northeast China. The results showed that Chloroflexi, Proteobacteria, Actinobacteria, and Acidobacteria were the most abundant phyla. The effect of permafrost degradation on bacterial relative abundance varied by species and habitats. The response of soil bacterial α-diversity (the observed OTU richness and phylogenetic diversity) in forests and wetlands to permafrost degradation were inconsistent. It was significantly correlated with mean annual temperature (MAT), mean annual precipitation (MAP), soil pH, soil microbial biomass carbon (MBC) and nitrogen (MBN) contents. The structure of soil bacterial community became increasingly dissimilar with degradation, indicating that permafrost degradation significantly changed the bacterial community structure. Climate conditions and edaphic factors jointly contribute to 92 % of the variance in the soil bacterial diversity and 40 % in community composition. The results are valuable for understanding the dynamics of soil microbial community and potential carbon feedback to future climate warming in permafrost regions.

Increased Soil Bacterial Abundance but Decreased Bacterial Diversity and Shifted Bacterial Community Composition Following Secondary Succession of Old-Field

Plant secondary succession is a very effective approach for the rejuvenation of degraded ecosystems. In order to comprehend alterations and driving mechanisms of soil bacterial communities under secondary succession of old-field and reveal their subsequent impacts on the decomposition and accumulation of soil organic carbon (SOC) and nitrogen (SON), we investigated changes in soil bacterial communities following ~160 years of old-field succession on the Loess Plateau of China through analyses of quantitative polymerase chain reaction (qPCR) and Illumina MiSeq DNA sequencing of 16S rRNA genes. Our results revealed that subsequent to secondary succession of old-field, soil bacterial abundance progressively increased, while bacterial richness and diversity significantly decreased. Principal component analysis and Bray–Curtis similarity index showed that bacterial community composition gradually shifted following old-field succession. Specifically, the relative abundances of Proteobacteria, Rokubacteria, and Verrucomicrobia progressively increased, while Actinobacteria and Firmicutes slightly decreased following old-field succession. The most enriched of Proteobacteria (e.g., Rhizobiales, Xanthobacteraceae, Gammaproteobacteria, Bradyrhizobium, Rhizobiaceae, and Mesorhizobiur) were found in a climax forest, while Chloroflexi and Gemmatimonadetes had the lowest relative abundances. Further, the most enriched members of Actinobacteria, including Geodermatophilaceae, Frankiales, Blastococcus, Micrococcales, Micrococcacea, Propionibacteriales, Nocardioidaceae, Nocardioide, and Streptomycetaceae, were exhibited in the farmland stage. Our results suggested that secondary succession of old-field greatly modified soil bacterial communities via the transformation of soil nutrients levels, altering plant biomass and soil physiochemical properties. Soil bacterial community composition was transformed from oligotrophic groups to copiotrophic Proteobacteria following old-field succession, which may promote SOC and SON accumulation through increasing the utilization of labile organic carbon (C) and nitrogen (N), while decreasing decomposition of recalcitrant organic C and N from the early- to late-successional stages.