Response Of Microbial Community Structure Research Articles

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

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

Identification of key microbial communities and intracellular metabolic pathways to response micro-aerobic environment for enhancing degradation of N, N-dimethylformamide in refractory membrane-making wastewater

Enhanced sludge hydrolysis in micro-aerobic environment with dissolved oxygen (DO) regulation could degrade stubborn refractory N, N-dimethylformamide (DMF) in membrane-making wastewater. However, investigations on how micro-aerobic condition affects DMF conversion and microbial metabolism in biological system are still inadequate. Herein, the responses of microbial community to micro-aerobic environment, and the consequent variations of metabolic pathways in DMF degradation were unraveled. Results indicated that low concentration of DO (0.2–0.4 mg/L) could significantly enhance the ammonification rate (from 21.8 % to 52.8 %) and COD removal efficiency (from 65.2 % to 82 %) by breaking C–N and CO bonds of amide group in macromolecular organics, which help it degraded into micromolecular organics. 16S rRNA and metagenomic analysis further revealed that low DO contents prompted the changes of microbial community structure. Specifically, toxicity-tolerant fermentation bacteria (e.g. Desulfomicrobium and unclassified_c_ Deltaproteobacteria) gradually became the dominant species in micro-aerobic environment, showing positive connections with COD removal and ammonification functions. Additionally, functional genes analysis further revealed the intracellular metabolic pathways of DMF, where the upregulation of tricarboxylic acid (TCA) cycle and oxidative phosphorylation pathway was observed in micro-aerobic environment. Such regulation led to the massive synthesis of adenosine triphosphate (ATP) and NADH, which are needful in oxidative demethylation process, and thus promoting the conversion from DMF to formamide, CH4 and NH3 in Methanolobus step-by-step. Therefore, this study provided vital insights into the responses of microbial community structure and DMF intracellular metabolic pathways to micro-aerobic environment, and profoundly discussed their contributions to the efficient treatment effect on membrane-making wastewater.

Response of soil microbial community structure, carbon and nitrogen cycling to drying and rewetting

Global change scenarios predict that precipitation regimes will become more variable in many parts of the world, extending drought periods and increasing rainfall intensity. Under these conditions, soil microbial community composition will likely change in ways that have implications for microbially-mediated nutrient cycling. Understanding these responses is key to predicting consequential changes in ecosystem functions. A 30 day incubation experiment was used to investigate the response of microbial community structure to three different soil moisture treatments, namely, constantly moist (CM), constantly dry (CD), and drying-rewetting (DRW), in soils of three different land condition types (Remnant, Restored, and Old-field) from Para Woodlands Nature Reserve, South Australia. Soil respiration and inorganic N transformations were approximately the same across soils, despite fundamental differences in physicochemical properties, vegetation communities, and land-use history. Soil microbial community structure changed in response to the different soil moisture treatments; responses of taxa was divergent among soils. These results demonstrate that changes to soil moisture regimes under climate projections will almost certainly have consequences for soil microbial communities and C and N dynamics. The results highlight the need for further research to understand the mechanisms driving divergent responses to soil moisture, particularly in areas of different land-use types.

Synergistic Removal of β-Hexachlorocyclohexane from Water via Microorganism–Plant Technology and Analysis of Bacterial Community Characteristics

In recent years, β-Hexachlorocyclohexane (β-HCH) has been detected frequently in water, seriously threatening human health and ecological balance. To explore the effects of different treatment groups on the removal of β-HCH in experimental water and the response of microbial community structure in the system, three strains of β-HCH-degrading bacteria—Ochrobactrum sp. (Och1, Och2) and Pseudomonas sp. (Pse1)—combined with Canna were selected for microbial, plant, and microbe–plant repair hydroponic experiments, respectively. Solid-phase extraction combined with GC-ECD and high-throughput sequencing determined the β-HCH content and bacterial community in water and Canna tissues. The results showed that when β-HCH stress concentrations were 10 μg·L−1 and 100 μg·L−1, Och1 and Pse1 showed the best degradation performance (33.49% and 60.02%, respectively). Following this, the three degrading strains were combined with Canna. Under the two β-HCH stress concentrations, the combination of Och1–Canna showed the highest β-HCH removal efficiency (96.74% and 99.06%). At the same time, we measured the concentration of β-HCH in Canna tissues and found that Och1 had a better removal effect on β-HCH in water and that the addition of Pse1 may significantly improve the absorption capacity of β-HCH in Canna roots. In addition, the relative abundance of Methophilic bacteria in experimental water and Canna root samples increased significantly after the inoculation of degrading bacteria, suggesting that Methophilic bacteria may be vital in degrading benzene-ring-containing substances. The results of this research can provide a theoretical basis and technical support for the prevention and control of the non-point source pollution of organic pesticides.

Soil nutrients and the responses of microbial community structure to pine bark and vinegar residues in blueberry cultivation

The addition of suitable acidic organic materials to improve the soil for blueberry (Vaccinium spp.) cultivation is the foundation for ensuring the sustainable development of blueberry industry in China. However, the effects of managing orchards with different inputs of organic material to improve the soil nutrients varied substantially. To unearth the best types of organic material to improve the soil fertility for blueberry cultivation and the rates to use in their application, a cultivation experiment used rooting zone restriction container and one-year-old seedlings of highbush blueberry (Vaccinium corymbosum L. variety “Legacy”) as the test materials and pure soil as the control (CK) in this study. We compared the effects of three rates of application of pine bark and vinegar residue on the soil nutrients and microbial community structures, three concentrations of 1884, 3768, and 5652 m3 km−2 of pine bark and three of 2826, 5652, and 8478 m3 km−2 vinegar residue were designed to add to the soil, and they were designated PB1, PB2, and PB3 and VR1, VR2, and VR3, respectively. Surface soil samples were collected for analysis after the blueberry shrubs had been planted for one year. The results showed that compared with the CK, the PB1 treatment significantly increased the total potassium (TK), alkaline hydrolyzed nitrogen (AN) and available phosphorus (AP) contents in the soil. The PB2 and PB3 treatments significantly enhanced the soil organic matter (SOM), total phosphorus (TP), AN, and AP contents but significantly reduced the microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial biomass phosphorus (MBP) contents. The VR1, VR2 and VR3 treatments significantly increased the contents of soil pH, total nitrogen (TN), available potassium (AK), SOM, AN, MBC and MBP. The PB1, PB2, VR1, VR2, and VR3 treatments markedly enhanced the bacterial Shannon index. However, the VR3 treatment markedly reduced the number of fungal species and the Chao 1, ACE, Simpson, and Shannon indices when compared with those of the CK. The soil fungal diversity was more easily regulated by soil nutrients than the bacterial diversity. A redundancy analysis showed that the dominant bacterial phyla were primarily regulated by the soil AN, while the dominant fungal phyla were primarily regulated by the SOM and MBN. In conclusion, the vinegar residue was more effective than the pine bark at improving the soil nutrients. The VR2 treatment not only significantly improved the soil nutrients but also maintained the soil microbial diversity, which rendered it the best organic material to improve the cultivation of blueberry soil.

Field investigation on the change process of microbial community structure in large-deep reservoir during the initial impoundment

During the initial impoundment of large-deep reservoir, the aquatic environment changed dramatically in various aspects such as water level, hydrological regime, and pollutants, which could alter microorganisms’ community structure, break the balance of the aquatic ecosystem and even endanger the aquatic ecosystem. However, the interaction of microbial communities and water environment during the initial impoundment process of a large-deep reservoir remained unclear. To this end, in-situ monitoring and sampling analysis on water quality and microbial communities during the initial impoundment process of a typical large-deep reservoir named Baihetan were conducted so as to explore the response of microbial community structure to the changes of water environmental factors during the initial impoundment of large deep reservoir and reveal the key driving factors affecting microbial community structure. The spatio-temporal variation in water quality was analyzed, and the microbial community structure in the reservoir was investigated based on high-throughput sequencing. The results showed that the COD of each section increased slightly, and the water quality after impoundment was slightly poorer than that before the impoundment. Water temperature and pH were proved to be the key factors affecting the structure of bacterial and eukaryotic communities respectively during the initial impoundment. The research results revealed the role of microorganisms and their interaction with biogeochemical processes in the large-deep reservoir ecosystem, which was crucial for later operation and management of the reservoir and the protection of the reservoir water environment.

The content of PAEs in field soils caused by the residual film has a periodical peak

The wide use of plastic film mulch has led to the release of phthalate esters (PAEs), which seriously threatens the soil environment and the safety of crop production. However, it is unknown whether there is a maximum threshold of soil PAEs accumulation induced by plastic film residue, and the dynamic changes of soil PAEs under field conditions are still unclear. To address these issues, a field experiment was conducted to investigate the temporal fluctuations of soil PAEs content and the response of microbial community structure in the field with plastic film residue. Results showed that the content of soil PAEs fluctuated during an observation period of one year, had a periodical peak in winter and summer, and was exacerbated by the increase in the aging degree and residual amount of plastic films. The PAEs content in soil with black films was higher than the US soil allowable criteria. High-throughput sequencing analysis showed that the addition of residual film significantly increased the alpha diversity of bacterial communities, changed the structure of bacterial community, and generated significant disturbances in bacterial function. Besides, the residual film recruited more microbiota related to plastic film and PAEs degradation. Results of the present study provide insight into the dynamic variation of soil PAEs caused by plastic film residue in one year, which is important to help evaluate the pollution risk of PAEs on soils and crops caused by residual plastic film.

Response of microbial community structure to chromium contamination in Panax ginseng-growing soil.

Chromium (Cr) contamination in soil poses a serious security risk for the development of medicine and food with ginseng as the raw material. Microbiome are critical players in the functioning and service of soil ecosystems, but their feedback to Cr-contaminated ginseng growth is still poorly understood. To study this hypothesis, we evaluated the effects of microbiome and different Cr exposure on the soil microbial community using Illumina HiSeq high-throughput sequencing. Our results indicated that 2467 OTUs and 1785 OTUs were obtained in 16S and ITS1 based on 97% sequence similarity, respectively. Bacterial and fungal diversity were affected significantly in Cr-contaminated soil. Besides, Cr contamination significantly changed the composition of the soil bacterial and fungal communities, and some biomarkers were identified in the different classification level of the different Cr-contaminated treatments using LEfSe. Finally, a heatmap of Spearman's rank correlation coefficients and canonical discriminant analysis (CDA) indicated that Chloroflexi, Gemmatimonadetes, Acidobacteria, Verrucomicobia, and Parcubacteria in phylum level and Acidimicrobiia, Gemmatimonadetes, and Deltaproteobacteria in class level were positively correlated with AK, AP, and NO3--N (p < 0.05 or p < 0.01), but negatively correlated with total Cr and available Cr (p < 0.05 or p < 0.01). Similarly, in the fungal community, Tubaria, Mortierellaceae, and Rhizophagus in the phylum level and Glomeromycetes, Agaricomycetes, and Exobasidiomycetes in the class level were positively correlated with AK, AP, and NO3--N (p < 0.05 or p < 0.01), but negatively correlated with total Cr and available Cr (p < 0.05 or p < 0.01). Our findings provide new insight into the effects of Cr contamination on the microbial communities in ginseng-growing soil.

Relationships Between Soil Microbial Diversities Across an Aridity Gradient in Temperate Grasslands : Soil Microbial Diversity Relationships.

Soil microbes assemble in highly complex and diverse microbial communities, and microbial diversity patterns and their drivers have been studied extensively. However, diversity correlations and co-occurrence patternsbetween bacterial, fungal, and archaeal domains and between microbial functional groups in arid regions remain poorly understood. Here we assessed the relationships between the diversity and abundance of bacteria, fungi, and archaea and explored how environmental factors influence these relationships. We sampled soil along a 1500-km-long aridity gradient in temperate grasslands of Inner Mongolia (China) and sequenced the 16S rRNA gene of bacteria and archaea and the ITS2 gene of fungi. The diversity correlations and co-occurrence patterns between bacterial, fungal, and archaeal domains and between different microbial functional groups were evaluated using α-diversity and co-occurrence networks based on microbial abundance. Our results indicate insignificant correlations among the diversity patterns of bacterial, fungal, and archaeal domains using α-diversity but mostly positive correlations among diversity patterns of microbial functional groups based on α-diversity and co-occurrence networks along the aridity gradient. These results suggest that studying microbial diversity patterns from the perspective of functional groups and co-occurrence networks can provide additional insights on patterns that cannot be accessed using only overall microbial α-diversity. Increase in aridity weakens the diversity correlations between bacteria and fungi and between bacterial and archaeal functional groups, but strengthens the positive diversity correlations between bacterial functional groups and between fungal functional groups and the negative diversity correlations between bacterial and fungal functional groups. These variations of the diversity correlations are associated with the different responses of microbes to environmental factors, especially aridity. Our findings demonstrate the complex responses of microbial community structure to environmental conditions (especially aridity) and suggest that understanding diversity correlations and co-occurrence patternsbetween soil microbial groups is essential for predicting changes in microbial communities under future climate change in arid regions.

Linkages Among Dissolved Organic Matter Export, Dissolved Metabolites, and Associated Microbial Community Structure Response in the Northwestern Sargasso Sea on a Seasonal Scale.

Deep convective mixing of dissolved and suspended organic matter from the surface to depth can represent an important export pathway of the biological carbon pump. The seasonally oligotrophic Sargasso Sea experiences annual winter convective mixing to as deep as 300 m, providing a unique model system to examine dissolved organic matter (DOM) export and its subsequent compositional transformation by microbial oxidation. We analyzed biogeochemical and microbial parameters collected from the northwestern Sargasso Sea, including bulk dissolved organic carbon (DOC), total dissolved amino acids (TDAA), dissolved metabolites, bacterial abundance and production, and bacterial community structure, to assess the fate and compositional transformation of DOM by microbes on a seasonal time-scale in 2016–2017. DOM dynamics at the Bermuda Atlantic Time-series Study site followed a general annual trend of DOC accumulation in the surface during stratified periods followed by downward flux during winter convective mixing. Changes in the amino acid concentrations and compositions provide useful indices of diagenetic alteration of DOM. TDAA concentrations and degradation indices increased in the mesopelagic zone during mixing, indicating the export of a relatively less diagenetically altered (i.e., more labile) DOM. During periods of deep mixing, a unique subset of dissolved metabolites, such as amino acids, vitamins, and benzoic acids, was produced or lost. DOM export and compositional change were accompanied by mesopelagic bacterial growth and response of specific bacterial lineages in the SAR11, SAR202, and SAR86 clades, Acidimicrobiales, and Flavobacteria, during and shortly following deep mixing. Complementary DOM biogeochemistry and microbial measurements revealed seasonal changes in DOM composition and diagenetic state, highlighting microbial alteration of the quantity and quality of DOM in the ocean.

An attempt to stimulate aniline degrading bioreactor by exogenous auto-inducer: Decontamination performance, sludge characteristics, and microbial community structure response

To break the contradiction between aniline and nitrogen metabolism in activated sludge reactor by influencing microbial interspecific communication, Auto-inducer C6-HSL and 3-oxo-C8-HSL were selected in this study to interfere with aniline degradation system. The two Auto-inducers enhanced the aniline degradation rate and ammonia removal efficiency of the systems, especially C6-HSL. Meanwhile, the main ammonia removal way was assimilation. Exogenous Auto-inducer effectively stabilized the sludge structure and activity from the destruction of aniline, and promoted EPS secretion. Microbial diversity analysis showed that most of functional microflora of seed sludge gradually deactivated with the operation of the reactor, while Rhodococcus, Leucobacter, g_norank_f_Saprospiraceae proliferated wildly under the action of Auto-inducer. Additionally, the interspecific relationship also demonstrated a different trend. Exogenous Auto-inducer was proved to exert positive effects on aniline degradation system to a certain extent, providing new insights in the field of aniline wastewater bio-degradation.

Soil Nutrients and the Responses of Microbial Community Structure to Pine Bark and Vinegar Residues in Blueberry Cultivation

Soil Nutrients and the Responses of Microbial Community Structure to Pine Bark and Vinegar Residues in Blueberry Cultivation

Response of microbial succession of Anammox granular sludge (AnGS) and essential abundance under salty stress and temperature reduction

This study explored the adaptive response of microbial community structure of anammox granular sludge (AnGS) and the recovery effect of biomass addition strategy under dual inhibitions of high salinity and low temperature. The results showed that, anammox process stable operated in a high-salt environment (18 g-NaCl L-1) at 35 °C, and the nitrogen removal rate (NRR) reached 0.60 kg-N m-3 d-1. The high salinity tolerance and recovery performance were attributed to the dominant functional bacteria genus Unclassified Candidatus Brocadiaceae selected by salinity. When the temperature dropped to 17 ℃, nitrogen accumulation (especially nitrite) could not be alleviated by simply reducing the substrate concentration. After adding 6 mL L-1 of sludge per day with an activity of 0.09 kg-N kg-VSS-1 d-1, nitrogen removal performance quickly recovered to 0.42 kg-N m-3 d-1 and reached 0.54 kg-N m-3 d-1 as the temperature recovered to 32 ℃. The abundance of 7.75E+10 copies g-SS-1 may be the primary value required by anammox bacteria in the adverse environment of high-salty and low-temperature.

Passive Treatment for Acid Mine Drainage Partially Restores Microbial Community Structure in Different Stream Habitats

The assessment of the degree to which biological communities in streams impaired by acid mine drainage (AMD) are restored by passive treatment has focused primarily on eukaryotic-cell organisms and microbial processes. The responses of microbial community structure to passive treatment have received much less attention, even though functional processes such as nutrient cycling and organic matter decomposition depend on taxonomic composition. Our objective was to determine the degree to which passive treatment restored microbial communities in three types of habitats: aqueous, leaf, and sediment. To assess their recovery, we compared the community composition in these habitats based on 16S rRNA gene sequencing at three different stream sites: an untreated AMD site (U), a remediated site below AMD passive treatment (T), and an unimpaired reference site (R). The acidity, conductivity, and soluble metal concentrations at T were found to be elevated compared to R, but generally 1–2 orders of magnitude less than at U. Microbial community composition was found to be synergistically affected by habitat type and AMD impact, with the similarity among communities in the three habitats increasing with the severity of the AMD. Sediment- and leaf-associated microbial communities at U were characterized by taxa that are tolerant to severe AMD. The absence of the nitrogen oxidizing bacterium Nitrospira in sediment communities at T and U was found to correspond to higher NH4+ concentrations compared to R, possibly because of the presence of iron oxyhydroxide precipitate. In contrast, the microbial composition was found to be similar between the T and R sites for both aqueous and leaf communities, indicating that passive treatment was more able to restore these communities to the reference condition than sediment communities. The remediation of AMD streams should consider the habitat-specific responses of microbial community composition and be guided by future studies that empirically couple changes in taxonomic composition to measured functional processes.

Impacts of municipal wastewater treatment plant discharge on microbial community structure and function of the receiving river in Northwest Tibetan Plateau

Wastewater treatment plant (WWTP) effluents carrying plenty of nutrients and micropollutants pose serious threats to receiving rivers, however, the response of microbial community structure and function to WWTP effluents discharge is still poorly understood. To address this knowledge gap, paired water and sediment samples from 17 sites of the Huangshui River, and effluents from 6 WWTPs were collected to investigate the effect of WWTP discharge on riverine microbial communities. Our results revealed that WWTP effluents exerted significant effects on planktonic rather than sedimentary microorganisms in the receiving river. Notably, lower diversity and richness of planktonic communities were observed in the effluent-influenced section (WRW) than other river sections (RW) along the urban river. Meanwhile, network analysis potentially revealed lower stability of co-occurrence patterns of microbial communities in WRW. The remarkably higher antibiotics, nitrate-nitrogen, and water temperature in WRW samples caused by WWTPs played essential roles in shaping the structure and function of planktonic microbial communities. This study suggested the enrichment of multiple-drug resistance genes and destruction of energy metabolisms were caused by sewage effluents, and highlighted the importance of effective management strategies for protecting the ecological health of the receiving river.

The response of microbial community structure and sediment properties to anthropogenic activities in Caohai wetland sediments

This study aimed to investigate the response of sediment microbial communities (including bacteria and archaeal groups) in Caohai Lake to anthropogenic activities. The sediment samples were collected from the regions with high anthropogenic interference and low anthropogenic interference. Their physicochemical properties and enzyme activities were analyzed, and the bacterial and archaeal communities were investigated using high-throughput sequencing technology. The results showed that the physicochemical characters changed by anthropogenic activities were the important factors that influenced enzyme activities, alpha diversity, key functional taxa, and community structure. And the impact of anthropogenic activities on microbial communities might follow a non-linear pattern. Furthermore, few significant differences of alpha indices between the high and low disturbed areas, but clear differences of microbial community composition analysis and beta-diversity analysis were observed. The hypothesis was proved that the intensity of anthropogenic impacts in Caohai had not reached the potential thresholds. The best distinguish biomarkers between the two areas and the most related key nodes among the network did not always have a high microbial abundance. The anthropogenic activities might influence the microbial community by affecting a small number of the key taxon in the ecological network. These findings provided a valuable understanding of how sediment microorganisms respond to anthropogenic activities in Caohai Lake.

Inconsistent responses of soil microbial community structure and enzyme activity to nitrogen and phosphorus additions in two tropical forests

Soil microorganisms play an important role in biogeochemical cycles in terrestrial ecosystems. Increasing nitrogen (N) and phosphorus (P) deposition are likely to regulate microbial growth by altering soil nutrient availability in tropical forests, yet their impacts on microbial community structure and function between primary forests and secondary forests are not well understood. To investigate how nutrient availability affects microbial community structure and function in tropical forests, we measured soil phospholipid fatty acids and enzyme activities in a seven-year N and P fertilization experiment in two tropical montane rainforests, China. In N addition plots, fungal biomass, arbuscular mycorrhizal fungal biomass and fungi to bacteria ratio (F/B) decreased in the secondary forest, but had moderate changes in the primary forest. In P and N plus P addition plots, microbial biomass showed minor changes, but the F/B increased significantly in both forests. However, hydrolytic enzyme activities did not show a significant change in the secondary forest, while they decreased significantly in the primary forest. Microbial P limitation in the primary forest decreased under P addition and N plus P addition. Our findings suggest inconsistent responses of microbial community structure and enzyme activity to N and P additions in tropical soils depending on forest type.

氮磷添加对杉木根叶分解残余物微生物群落结构及酶活性的影响

为揭示根、叶分解残余物对生态系统养分循环相关过程的影响，研究了分解第3年杉木根残余物（凋_R）和叶残余物（凋_L）中的微生物群落结构（环丙基脂肪酸/前体结构，Cy/pre；单不饱和脂肪酸/饱和脂肪酸，Mono/sat；真菌/细菌，F/B；革兰氏阳性菌/革兰氏阴性菌，G⁺/G^-）、酶活性（β-葡萄糖苷酶，βG；β-N-乙酰氨基葡糖苷酶，NAG；酸性磷酸酶，AP）、化学元素含量及计量比对氮磷添加的响应。结果表明：（1）与凋_R相比，凋_L中的Cy/pre、F/B、G⁺/G^-低，Mono/sat高。氮磷添加对分解残余物微生物群落结构影响不显著。（2）与凋_R相比，凋_L中的βG和NAG活性高、βG/AP大。氮磷添加抑制了AP活性，提高了βG/NAG及βG/AP。且氮磷添加对凋_R的AP活性抑制作用更强，对凋_L的βG/NAG提升幅度更大。（3）分解残余物中的Mono/sat、G+/G、F/B分别与锰含量、磷/钙、氮含量正相关；AP、βG/NAG分别与氮/磷、磷/铁正相关；βG/AP、NAG、βG分别与氮/锰、磷/镁、氮/钙负相关。表明根、叶分解残余物仍可对生态系统养分循环相关过程产生不同影响，考虑分解残余物类型可提高全球变化背景下生态系统养分循环过程预报精度。;Root and leaf litters are two important litter sources in ecosystems, providing carbon sources and nutrients for microorganisms. The decompositions of root and leaf litters are highly sensitive to the environmental availability of nutrients. The simultaneous deposition of nitrogen and phosphorus is one of the most critical challenges in ecosystems worldwide. Changes of nitrogen and phosphorus inputs can affect both the decomposition rates of root and leaf litter and other responses of the ecosystem. The long-term patterns of mass loss during leaf and root litter decomposition are well documented, but the responses of microbial community structure and enzyme activity in root and leaf debris to the simultaneous deposition of exogenous nitrogen and phosphorus are not known. Understanding the influence of simultaneous inputs of exogenous nitrogen and phosphorus on the microbial community structure and enzyme activity in root and leaf debris can help us to precisely predict shifts in ecosystem processes in nitrogen and phosphorus deposition enriched regions. We investigated the responses of microbial community structure (cyclopropyl fatty acids/precursor structure, Cy/pre; monounsaturated fatty acids/saturated fatty acid, Mono/sat; fungus/bacteria, F/B; Gram-positive bacteria/Gram-negative bacteria, G⁺/G^-), enzyme activity (glucosidase, βG; β-N-Acetylglucosaminidase, NAG; acid phosphatase, AP), chemical element content and stoichiometry in root and leaf debris (3 years after decomposition) of Cunninghamia lanceolata to nitrogen and phosphorus additions. Results showed that Cy/pre, F/B, G⁺/G^- were lower and Mono/sat was higher in the leaf debris than those in the root debris. However, nitrogen and phosphorus additions had no significant effect on the microbial community structure of the debris. The leaf debris had higher βG and NAG activity and βG/AP compared with the root debris. Nitrogen and phosphorus additions decreased the AP activity and increased βG/NAG and βG/AP. Moreover, nitrogen and phosphorus additions resulted in a greater decrease in root debris' AP activity but a more significant increase in βG/NAG of leaf debris. Multiple stepwise regression showed that Mono/sat, G⁺/G^- and F/B positively correlated with manganese content, phosphorus/calcium, and nitrogen content, respectively. AP and βG/NAG were positively correlated with nitrogen/phosphorus and phosphorus/iron, respectively; and βG/AP, NAG, and βG were negatively correlated with nitrogen/manganese, phosphorus/magnesium, and nitrogen/calcium, respectively. Our results found that the effects of nitrogen and phosphorus additions on microbial community structure and enzyme activity were generally inconsistent between root and leaf debris, thereby underlining that leaf and root litters need to be considered separately when evaluating the response of decomposers to their substrates in the context of global change to improve the prediction accuracy of ecosystem nutrient cycling processes.

Bacterial community dynamics and functional profiling of soils from conventional and organic cropping systems

Soil microbiomes play an integral role in agricultural production systems. Understanding of the complex microbial community structure and responses to conventional compared to organic cropping systems is crucial for sustainable production and ecosystems health. This study investigated soil microbial community structure responses based on a four year long field experiment. Bacterial communities characterizing conventional and organic cropping systems were evaluated using Illumina MiSeq high-throughput sequencing targeting the V4-V5 variable region of the 16S rRNA gene. Soil bacterial community structure showed a cropping system dependant distribution, with nitrogen cycling taxa (Bacillus, Niastella, Kribbella, and Beijerinckia) dominant in conventional cropping systems, while carbon cycling taxa (Dokdonella, Caulobacter, Mathylibium, Pedobacter, Cellulomonas and Chthoniobacter and Sorangium) were abundant in organic cropping systems. Functional prediction of the bacterial biomes showed conventional cropping systems to harbour a community adapted to carbon-limited environments, with organic cropping systems dominated by those involved in the degradation of complex organic compounds. These findings suggest the existence of niche specific communities and functional specialization between cropping systems with potential use in soil management through selective promotion of organisms beneficial to soil health.

The effect of chemical and organic N inputs on N2O emission from rain-fed crops in Eastern Mediterranean

Nitrogen has a significant contribution to global warming and its reduction in agriculture is expected to reduce N2O emissions having however adverse effects on the productivity of agricultural ecosystems. Maintaining systems productivity with alternative N sources i.e manure and composts could be a strategy also to mitigate N2O emissions. In this paper, we present the effect of different N sources (organic and chemical) on field N2O emissions and how these emissions are associated with soil available N forms (NH4+ and NO3−) in three different rain-fed crops namely barley, pea and vetch grown in Cyprus for two growing seasons. The daily emissions ranged from −3.11 to 12.3 g N–N2O/ha/day, while cumulative emissions ranged from 119 g N–N2O/ha to 660 g N–N2O/ha depending on crop and nitrogen source type. The emissions showed a seasonal pattern and WFPS has been identified as a critical soil parameter controlling daily N2O emissions. The daily N2O fluxes in the current study derives mainly from nitrification irrespectively crop type or nitrogen source type. Specific emission factors for each crop cultivated under different N source type were calculated and ranged from 0.03% ± 0.02–0.34% ± 0.09. The application of manure and chemical fertilizers cause similar intensity of N2O emissions while compost exhibited the lower emission factors. These findings suggest that composts could be integrated in a nutrient management strategy of rain-fed crops with less N2O emissions. The high background emissions found suggest also that other factors than external inputs are associated with N2O emissions and further studies including the response of microbial community structure and their contribution and association with N2O emissions.