Soil microorganisms play important roles in nitrogen transformation. The aim of this study was to characterize changes in the activity of nitrogen transformation enzymes and the abundance of nitrogen function genes in...Soil microorganisms play important roles in nitrogen transformation. The aim of this study was to characterize changes in the activity of nitrogen transformation enzymes and the abundance of nitrogen function genes in rhizosphere soil aerated using three different methods(continuous flooding(CF), continuous flooding and aeration(CFA), and alternate wetting and drying(AWD)). The abundances of amoA ammonia-oxidizing archaea(AOA) and ammonia-oxidizing bacteria(AOB), nirS, nirK, and nifH genes, and the activities of urease, protease, ammonia oxidase, nitrate reductase, and nitrite reductase were measured at the tillering(S1), heading(S2), and ripening(S3) stages. We analyzed the relationships of the aforementioned microbial activity indices, in addition to soil microbial biomass carbon(MBC) and soil microbial biomass nitrogen(MBN), with the concentration of soil nitrate and ammonium nitrogen. The abundance of nitrogen function genes and the activities of nitrogen invertase in rice rhizosphere soil were higher at S2 compared with S1 and S3 in all treatments. AWD and CFA increased the abundance of amoA and nifH genes, and the activities of urease, protease, and ammonia oxidase, and decreased the abundance of nirS and nirK genes and the activities of nitrate reductase and nitrite reductase, with the effect of AWD being particularly strong. During the entire growth period, the mean abundances of the AOA amoA, AOB amoA, and nifH genes were 2.9, 5.8, and 3.0 higher in the AWD treatment than in the CF treatment, respectively, and the activities of urease, protease, and ammonia oxidase were 1.1, 0.5, and 0.7 higher in the AWD treatment than in the CF treatment, respectively. The abundances of the nirS and nirK genes, and the activities of nitrate reductase and nitrite reductase were 73.6, 84.8, 10.3 and 36.5% lower in the AWD treatment than in the CF treatment, respectively. The abundances of the AOA amoA, AOB amoA, and nifH genes were significantly and positively correlated with the activities of urease, protease, and ammonia oxidase, and the abundances of the nirS and nirK genes were significantly positively correlated with the activities of nitrate reductase. All the above indicators were positively correlated with soil MBC and MBN. In sum, microbial activity related to nitrogen transformation in rice rhizosphere soil was highest at S2. Aeration can effectively increase the activity of most nitrogen-converting microorganisms and MBN, and thus promote soil nitrogen transformation.展开更多
Soil microbial biomass nitrogen(MBN)contains the largest proportion of biologically active nitrogen(N)in soil,and is considered as a crucial participant in soil N cycling.Agronomic management practices such as crop ro...Soil microbial biomass nitrogen(MBN)contains the largest proportion of biologically active nitrogen(N)in soil,and is considered as a crucial participant in soil N cycling.Agronomic management practices such as crop rotation and monocropping systems,dramatically affect MBN in agroecosystems.However,the influence of crop rotation and monocropping in agroecosystems on MBN remains unclear.A meta-analysis based on 203 published studies was conducted to quantify the effect of crop rotation and mono-cropping systems on MBN under synthetic N fertilizer application.The analysis showed that crop rotation significantly stimulated the response ratio(RR)of MBN to N fertilization and this parameter reached the highest levels in upland-fallow rotations.Upland mono-cropping did not change the RR of MBN to N application,however,the RR of MBN to N application in paddy mono-cropping increased.The difference between crop rotation and mono-cropping systems appeared to be due to the various cropping management scenarios,and the pattern,rate and duration of N addition.Crop rotation systems led to a more positive effect on soil total N(TN)and a smaller reduction in soil pH than mono-cropping systems.The RR of MBN to N application was positively correlated with the RR of mineral N only in crop rotation systems and with the RR of soil pH only in mono-cropping systems.Combining the results of Random Forest(RF)model and structural equation model showed that the predominant driving factors of MBN changes in crop rotation systems were soil mineral N and TN,while in mono-cropping systems the main driving factor was soil pH.Overall,our study indicates that crop rotation can be an effective way to enhance MBN by improving soil N resources,which promote the resistance of MBN to low pH induced by intensive synthetic N fertilizer application.展开更多
In this study, seasonal variation characteristics of surface soil microbial biomass carbon （MBC） and soil microbial biomass nitrogen （MBN） of an artificial vegetation area located in Shapotou for different time pe...In this study, seasonal variation characteristics of surface soil microbial biomass carbon （MBC） and soil microbial biomass nitrogen （MBN） of an artificial vegetation area located in Shapotou for different time periods were studied using the chloroform fumigation method, and the results were compared with those of near-natural vegetation areas and mobile dunes. Results showed that the MBC and MBN levels in the 0-5 cm soil layer were higher in autumn than in summer and spring. As the prolongation of vegetation restoration raised the MBC and MBN levels in summer and autumn, no clear variation was found in spring. However, the MBC and MBN in 5-20 cm had no obvious seasonal variation. During summer and autumn, the variation trend of MBC and MBN in the vertical direction was shown to be 0-5 〉 5-10 〉 10-20 cm in the vegetation area, while for mobile dunes, the MBC and MBN levels increased as the depth increased. The natural vegetation area was shown to possess the highest MBC and MBN levels, and yet mobile dunes have the lowest MBC and MBN levels. MBC and MBN levels in artificial sand-binding vegetation increased with the prolongation of vegetation restoration, indicating that the succession of sand-binding vegetation will result in the ac- cumulation of soil carbon and nitrogen, as well as the restoration of soil fertility.展开更多
The change of freeze-thaw pattern of the Tibetan Plateau under climate warming is bound to have a profound impact on the soil process of alpine grassland ecosystem;however,the research on the impact of the freeze-thaw...The change of freeze-thaw pattern of the Tibetan Plateau under climate warming is bound to have a profound impact on the soil process of alpine grassland ecosystem;however,the research on the impact of the freeze-thaw action on nitrogen processes of the alpine grassland ecosystem on the Tibetan Plateau has not yet attracted much attention.In this study,the impact of the freezing strength on the soil nitrogen components of alpine grassland on the Tibetan Plateau was studied through laboratory freeze-thaw simulation experiments.The 0–10 cm topsoil was collected from the alpine marsh meadow and alpine meadow in the permafrost region of Beilu River.In the experiment,the soil samples were cultivated at –10℃,–7℃,–5℃,–3℃ and –1℃,respectively for three days and then thawed at 2℃ for one day.The results showed that after the freeze-thaw process,the soil microbial biomass nitrogen significantly decreased while the dissolved organic nitrogen and inorganic nitrogen significantly increased.When the freezing temperature was below –7℃,there was no significant difference between the content of nitrogen components,which implied a change of each nitrogen component might have a response threshold toward the freezing temperature.As the freeze-thaw process can lead to the risk of nitrogen loss in the alpine grassland ecosystem,more attention should be paid to the response of the soil nitrogen cycle of alpine grasslands on the Tibetan Plateau to the freeze-thaw process.展开更多
Soil salinization can limit the development of agriculture in the Yellow River Delta.In this paper,saline and alkaline farmland in the Yellow River Delta was chosen as the research object,and effects of soil salinity ...Soil salinization can limit the development of agriculture in the Yellow River Delta.In this paper,saline and alkaline farmland in the Yellow River Delta was chosen as the research object,and effects of soil salinity on soil microbial biomass nitrogen(SMBN) under different conditions were investigated to study the response of soil nitrogen turnover to salt stress.There were four salinity gradients(S1:0.1%;S2:0.5%;S3:0.9%;S4:1.3%),and four substrates were added to the soil.The results showed that after the addition of various substrates,SMBN in treatments with high soil salinity(S3 and S4) was obviously lower than that in treatments with low soil salinity(S1 and S2).In comparison with treatment S1,the average of SMBN in treatments S3 and S4 decreased by 35.8% and 46.7% respectively when there was no substrate added to them;it declined by 55.6% and 56.1% respectively as the carbon source was added to them;it reduced by 24.6% and 28.3% when the nitrogen source was added to them;it dropped by 43.8% and 57.0% respectively as the carbon and nitrogen source were added to them.Compared with treatments without substrates,the addition of the nitrogen source could not improve SMBN;the addition of the carbon source or carbon and nitrogen source could enhance SMBN obviously,and it increased by 60.9% and 66.1%(or 110.8% and 140.2%) in treatments with low soil salinity(S1 and S2),while it changed slightly in treatments with high soil salinity(S3 and S4).In order to increase SMBN,it is needed to apply organic fertilizer or chemical fertilizer and organic fertilizer to maintain or improve soil fertility.展开更多
[Objectives]To comprehensively and deeply explore the effects of different land cover types in the lower reaches of Niyang River on soil microbial biomass carbon and nitrogen,and to provide a scientific basis for the ...[Objectives]To comprehensively and deeply explore the effects of different land cover types in the lower reaches of Niyang River on soil microbial biomass carbon and nitrogen,and to provide a scientific basis for the rational use and sustainable management of land resources in this area.[Methods]Taking the 3 types of land cover(cultivated land,grass land and forest land)in the lower reaches of Niyang River in Tibet as the research object,the contents,distribution characteristics and relationships of soil organic carbon,organic nitrogen,microbial biomass carbon,microbial biomass nitrogen and readily oxidizable organic carbon,and their relationships were studied in 0-10,10-20,20-40,40-60,and 60-100 cm soil depth.[Results]The soil organic carbon content of forest land was higher than that of grass land and cultivated land;the vertical change trend of soil organic carbon content decreased with the increase of depth(P<0.05),and it was mainly concentrated in the soil with a depth of 0-20 cm.The soil organic carbon content was significantly different among forest land,grass land and cultivated land(P<0.05),but there was no significant difference between cultivated land and grass land(P>0.05).The soil organic nitrogen content was significantly different among cultivated land,grass land,and forest land(P<0.05),but there was no significant difference between grass land and forest land(P>0.05).The readily oxidizable organic carbon,microbial biomass carbon and nitrogen in forest land were higher than that in cultivated land and grass land.The change trend of soil readily oxidizable organic carbon,microbial biomass carbon and microbial biomass nitrogen was similar to the change of soil organic carbon content,showing a significant positive correlation.In addition to being subject to land cover,soil microbial biomass carbon and nitrogen content were also subject to the interaction of factors such as soil temperature,humidity,pH and vegetation types.[Conclusions]Changes in land cover significantly affect soil organic carbon and nitrogen,readily oxidizable organic carbon,microbial biomass carbon and nitrogen content.展开更多
The impulse to remain profitable by increasing agricultural production levels in view of the greater demand for food, provided impetus to production intensification. The aim of this review is to summarise current lite...The impulse to remain profitable by increasing agricultural production levels in view of the greater demand for food, provided impetus to production intensification. The aim of this review is to summarise current literature, reporting specifically on the impact of production intensification on habitats and yield constraints caused by weeds. Secondly, in alleviating these effects over the short term, ecological measures that enhance species diversity in conserved habitats and promote semi-natural habitats in the agricultural landscape, are discussed. In large-scale intensive agriculture, weed control is predominantly rooted in agrochemical applications in the form of herbicides. Long lasting intensive agricultural practices show discord both with the promotion of the biodiversity of microbes belowground and aboveground and with organisms involved in the breaking down of plant material. The presence of native species in the surroundings, in combination with hedgerows and field margins, with a comparatively intricate and balanced variety of plants in a sheltered environment, are essential for settlement of benign insects, particularly in the face of intensive agricultural production. The promising tactic of advantageous seed predators enables decreased herbicide applications. Crop mosaics arranged to advance compatibility at the landscape scale are important to bolster pollination services and insect management, while ecological variety in the surroundings acts as a safety net for habitat diversity. Weed control in combination with different tactics of vegetation use, comprising cover cropping, hedgerows and field margins, sets up safe havens in the landscape, and improves the diffusion of complementary life forms. Field margins perform a meaningful natural function as point of provision for forage, safe havens and distribution passageways for pollinators and insect predators. Production practices that promote more heterogeneity and combine high density semi-natural safe havens and habitat conservation in agro ecosystems are beneficial to species diversity across trophic levels and contribute to agricultural production stability and food safety.展开更多
Soluble organic nitrogen （SON） is recognized as a sensitive indicator of soil nitrogen status. The present work was conducted in the temperate forests of northeast China where soils are typically characterized by hi...Soluble organic nitrogen （SON） is recognized as a sensitive indicator of soil nitrogen status. The present work was conducted in the temperate forests of northeast China where soils are typically characterized by high organic matter and high organic nitrogen content, and soil sampling was made in early spring just after the freeze-thaw period. The water extracted SON pools in the organic layer of forest soils were measured within the range from 156.0 mg·kg^-1 to 292.6 mg·kg^-1, a similar magnitude of salt solution extracted SON pools reported in literatures. However, the water soluble SON pools in 0-15 cm mineral soils in present study were much higher （3-10 times） than any other reports, ranging from 58.6 mg·kg^-1 to 125.2 mg·kg^-1. Water soluble SON varied markedly among the soils under different forests and at different sites. The SON in water extracts were positively and significantly correlated to soil organic matter and total nitrogen contents, but negatively correlated to microbial biomass nitrogen （MBN）. The reasons of the abnormally large SON pools and the negative correlations between SON and MBN in the 0-15cm mineral soils in this study were specially discussed.展开更多
Soil microbial biomass is an important indicator to measure the dynamic changes of soil carbon pool.It is of great signifi cance to understand the dynamics of soil microbial biomass in plantation for rational manageme...Soil microbial biomass is an important indicator to measure the dynamic changes of soil carbon pool.It is of great signifi cance to understand the dynamics of soil microbial biomass in plantation for rational management and cultivation of plantation.In order to explore the temporal dynamics and infl uencing factors of soil microbial biomass of Keteleeria fortunei var.cyclolepis at diff erent stand ages,the plantation of diff erent ages(young forest,5 years;middle-aged forest,22 years;mature forest,40 years)at the Guangxi Daguishan forest station of China were studied to examine the seasonal variation of their microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN)by chloroform fumigation extraction method.It was found that among the forests of diff erent age,MBC and MBN diff ered signifi cantly in the 0–10 cm soil layer,and MBN diff ered signifi cantly in the 10–20 cm soil layer,but there was no signifi cant diff erence in MBC for the 10–20 cm soil layer or in either MBC or MBN for the 20–40 cm soil layer.With increasing maturity of the forest,MBC gradually decreased in the 0–10 cm soil layer and increased fi rstly and then decreased in the 10–20 cm and 20–40 cm soil layers,and MBN increased fi rstly and then decreased in all three soil layers.As the soil depth increased,both MBC and MBN gradually decreased for all three forests.The MBC and MBN basically had the same seasonal variation in all three soil layers of all three forests,i.e.,high in the summer and low in the winter.Correlation analysis showed that MBC was signifi cantly positively correlated with soil organic matter,total nitrogen,and soil moisture,whereas MBN was signifi cantly positively correlated with soil total nitrogen.It showed that soil moisture content was the main factor determining the variation of soil microbial biomass by Redundancy analysis.The results showed that the soil properties changed continuously as the young forest grew into the middle-aged forest,which increased soil microbial biomass and enriched the soil nutrients.However,the soil microbial biomass declined as the middle-age forest continued to grow,and the soil nutrients were reduced in the mature forest.展开更多
To show the vegetation succession interaction with soil properties, microbial biomass, basal respiration, and enzyme activities in different soil layers （0-60 cm） were determined in six lands, i.e., 2-, 7-, 11-, 20-...To show the vegetation succession interaction with soil properties, microbial biomass, basal respiration, and enzyme activities in different soil layers （0-60 cm） were determined in six lands, i.e., 2-, 7-, 11-, 20-, and 43-year-old abandoned lands and one native grassland, in a semiarid hilly area of the Loess Plateau. The results indicated that the successional time and soil depths affected soil microbiological parameters significantly. In 20-cm soil layer, microbial biomass carbon （MBC）, microbial biomass nitrogen （MBN）, MBC/MBN, MBC to soil organic carbon ratio （MBC/SOC）, and soil basal respiration tended to increase with successional stages but decrease with soil depths. In contrast, metabolic quotient （qCO2） tended to decrease with successional stages but increase with soil depths. In addition, the activities of urease, catalase, neutral phosphatase, β-fructofuranosidase, and earboxymethyl cellulose （CMC） enzyme increased with successional stages and soil depths. They were significantly positively correlated with microbial biomass and SOC （P 〈 0.5）, whereas no obvious trend was observed for the polyphenoloxidase activity. The results indicated that natural vegetation succession could improve soil quality and promote ecosystem restoration, but it needed a long time under local climate conditions.展开更多
Monitoring of soil nitrogen （N） cycling is useful to assess soil quality and to gauge the sustainability of management practices. We studied net N mineralization, nitrification, and soil N availability in the 0-10 c...Monitoring of soil nitrogen （N） cycling is useful to assess soil quality and to gauge the sustainability of management practices. We studied net N mineralization, nitrification, and soil N availability in the 0-10 cm and 11-30 cm soil horizons in east China during 2006-2007 using an in situ incubation method in four subtropical evergreen broad-leaved forest stands aged 18-, 36-, 48-, and 65-years. The properties of surface soil and forest floor varied between stand age classes. C：N ratios of surface soil and forest floor decreased, whereas soil total N and total organic C, available P, and soil microbial biomass N increased with stand age. The mineral N pool was small for the young stand and large for the older stands. NO3^--N was less than 30% in all stands. Net rates of N mineralization and nitrification were higher in old stands than jn younger stands, and higher in the 0-10 cm than in the 11-30 cm horizon. The differences were significant between old and young stands （p 〈 0.031） and between soil horizons （p 〈 0.005）. Relative nitrification was somewhat low in all forest stands and declined with stand age. N trans- formation seemed to be controlled by soil moisture, soil mierobial biomass N, and forest floor C：N ratio. Our results demonstrate that analyses of N cycling can provide insight into the effects of management disturbances on forest ecosystems.展开更多
Recent advancements in constructed wetlands(CWs)have highlighted the imperative of enhancing nitrogen(N)removal efficiency.However,the variability in influent substrate concentrations presents a challenge in optimizin...Recent advancements in constructed wetlands(CWs)have highlighted the imperative of enhancing nitrogen(N)removal efficiency.However,the variability in influent substrate concentrations presents a challenge in optimizing N removal strategies due to its impact on removal efficiency and mechanisms.Here we show the interplay between influent substrate concentration and N removal processes within integrated vertical-flow constructed wetlands(IVFCWs),using wastewaters enriched with NO_(3)^(-)-N and NH4þ-N at varying carbon to nitrogen(C/N)ratios(1,3,and 6).In the NO_(3)^(-)-N enriched systems,a positive correlation was observed between the C/N ratio and total nitrogen(TN)removal efficiency,which markedly increased from 13.46±2.23%to 87.00±2.37%as the C/N ratio escalated from 1 to 6.Conversely,in NH4þ-N enriched systems,TN removal efficiencies in the A-6 setup(33.69±4.83%)were marginally 1.25 to 1.29 times higher than those in A-3 and A-1 systems,attributed to constraints in dissolved oxygen(DO)levels and alkalinity.Microbial community analysis and metabolic pathway assessment revealed that anaerobic denitrification,microbial N assimilation,and dissimilatory nitrate reduction to ammonium(DNRA)predominated in NO_(3)^(-)-N systems with higher C/N ratios(C/N 3).In contrast,aerobic denitrification and microbial N assimilation were the primary pathways in NH4þ-N systems and low C/N NO_(3)^(-)-N systems.A mass balance approach indicated denitrification and microbial N assimilation contributed 4.12-47.12%and 8.51e38.96%in NO_(3)^(-)-N systems,respectively,and 0.55e17.35%and 7.83e33.55%in NH4þ-N systems to TN removal.To enhance N removal,strategies for NO_(3)-N dominated systems should address carbon source limitations and electron competition between denitrification and DNRA processes,while NH4þ-N dominated systems require optimization of carbon utilization pathways,and ensuring adequate DO and alkalinity supply.展开更多
As per randomized block design, the research had different fertilizer treatments, and the organic matter, respiration, enzyme activity and microbial carbon and nitrogen in reclaimed soil were studied. Fertilization sc...As per randomized block design, the research had different fertilizer treatments, and the organic matter, respiration, enzyme activity and microbial carbon and nitrogen in reclaimed soil were studied. Fertilization schemes were as follows： The treatment without fertilizers（CK）, the treatment with chemical fertilizers（C）, the treatment with chemical fertilizers and bacterial fertilizer（CB）, the treatment with organic fertilizer and chemical fertilizers（CM）, and the treatment with chemical fertilizers, organic fertilizer and bacterial fertilizer（CMB）. The results showed： Four fertilization treatments could improve the content of soil organic matter. CMB, CM and CB could significantly improve the soil respiration. Organic fertilizer and fertilizer could significantly improve soil enzyme activity, In different growth stages the CMB treatment had highest urease and phosphatase.The most significant in the treatment content of sucrose was CM. Organic fertilizer and microbial fertilizer can significantly improve the microbial carbon and nitrogen in soil. For the microbial biomass carbon, the CMB treatment increased by 11%-34% than CB treatment, and 35%-63% than C treatment. In terms of microbial nitrogen CMB, CM respectively increased by 31%-51% than CB treatment, and 52%-100% compared with C. In the process of land reclamation, we should combine the organic fertilizer, microbial fertilizer and inorganic fertilizer. Only in this way can soil biological activity be accelerated, soil microbial environment improved, and the ripening increased soil nutrient and soil cultivation be enhanced.展开更多
Aims Natural secondary forest(NSF)and larch plantation are two of the predominant forest types in Northeast China.However,how the two types of forests compare in sustaining soil quality is not well understood.This stu...Aims Natural secondary forest(NSF)and larch plantation are two of the predominant forest types in Northeast China.However,how the two types of forests compare in sustaining soil quality is not well understood.This study was conducted to determine how natural secondary forest and larch plantation would differ in soil microbial biomass and soil organic matter quality.Methods Microbial biomass carbon(MBC),microbial biomass nitrogen(MBN),soil organic carbon(SOC)and total nitrogen(TN)in the 0-to 15-cm and 15-to 30-cm soil layers were investigated by making chemical and biological measurements in the montane region of eastern Liaoning Province,Northeast China,during the growing season of 2008 in stands of NSF and Larix olgensis plantation(LOP).Important Findings We found that soil MBC and MBN were significantly lower in the LOP than in the NSF.Both MBC and MBN declined significantly with increasing soil depth in the two types of stands.The ratios of MBC to SOC(MBC/SOC)and MBN to TN(MBN/TN)were also significantly lower in the LOP than in the NSF.Moreover,the values of MBC,MBC/SOC,and MBN/TN significantly varied with time and followed a similar pattern during the growing season,all with an apparent peak in summer.Our results indicate that NSF is better in sustaining soil microbial biomass and nutrients than larch plantation in the temperate Northeast China.This calls for cautions in large-scale conversions of the native forests to coniferous plantations as a forest management practice on concerns of sustaining soil productivity.展开更多
Dissolved organic nitrogen（DON）extracted from Lake Shankou sediments using KCl was isolated into hydrophobic and hydrophilic fractions.The bioavailabilities of the hydrophobic and hydrophilic fractions to three type...Dissolved organic nitrogen（DON）extracted from Lake Shankou sediments using KCl was isolated into hydrophobic and hydrophilic fractions.The bioavailabilities of the hydrophobic and hydrophilic fractions to three types of bacterial communities collected from sediments,activated sludge and compost products were examined.The DON recoveries obtained by DAX-8 and cation exchange resins treatment were 96.17% ± 1.58% and 98.14% ±0% for the samples obtained from N4 and N14 stations,respectively.After 25 days of incubation at 25℃,most DON（59% to 96%）was degraded.Hydrophilic DON exhibited a higher reduction rate than hydrophobic DON during the growth phase.Untreated wastewater from Changshuihe town was the main degradable DON source to station N4,and 93% of hydrophilic DON and 80% of hydrophobic DON were degraded.Station N14 received a large amount of refractory DON from forest soils and exhibited DON degradation rates of 82% and 71% for the hydrophilic and hydrophobic fractions,respectively.Amino acid contents and fluorescence intensities were also analyzed.Approximately 27% to 74% of amino acids were taken up by day 5,and their concentration gradually increased in the following days due to the decomposition of dissolved proteins.Parallel factor analysis resulted in identification of tryptophan-like proteins,tyrosine-like proteins and FA-like substances.During the growth phase,40%–51% of the tryptophan-like proteins were taken up by bacteria,and the accumulation of tyrosine-like proteins was attributed to the release of biotic substances.The concentration of the FA-like substances decreased due to microbial decomposition.展开更多
Microbial fuel cells（MFCs） have become a promising technology for wastewater treatment accompanying electricity generation. Carbon and nitrogen removal can be achieved by utilizing the electron transfer between the ...Microbial fuel cells（MFCs） have become a promising technology for wastewater treatment accompanying electricity generation. Carbon and nitrogen removal can be achieved by utilizing the electron transfer between the anode and cathode in an MFC. However,large-scale power production and high removal efficiency must be achieved at a low cost to make MFCs practical and economically competitive in the future. This article reviews the principles, feasibility and bottlenecks of MFCs for simultaneous carbon and nitrogen removal, the recent advances and prospective strategies for performance improvement, as well as the involved microbes and electron transfer mechanisms.展开更多
Substituting chemical fertilizers with manure is an important method for efficient nutrient management in rice cropping systems of China.Labile nitrogen(N)is the most active component of the soil N pool and plays an e...Substituting chemical fertilizers with manure is an important method for efficient nutrient management in rice cropping systems of China.Labile nitrogen(N)is the most active component of the soil N pool and plays an essential role in soil fertility.However,the effects of manure substitution on soil labile N in rice cropping systems and their relationships with soil properties,fertilization practices,and climatic conditions remain unclear and should be systematically quantified.Here,we investigated rice grain yield and four types of soil labile N that have been widely reported,including available nitrogen(AN),ammonium nitrogen(NH_(4)^(+)-N),nitrate nitrogen(NO_(3)^(−)-N),and microbial biomass nitrogen(MBN).We reviewed 187 published articles and performed a meta-analysis to quantify the effects of manure substitution on yield and soil labile N.The results showed that manure substitution increased AN,MBN,NH+4-N,and NO−3-N by 11.3%,38.5%,5.9%,and 8.1%,respectively.Partial substitution significantly increased the yield by 1.4%–5.9%,but full substitution significantly decreased the yield by 2.9%.The positive effects of manure substitution on yield and AN were stronger with long-term fertilization.The differences in responses varied across specific manure types,N application rates,soil properties,and climatic factors.In conclusion,manure substitution can increase soil labile N and is regarded as an efficient strategy for improving soil N fertility and a recommended measure for applying both chemical and organic fertilizers in rice systems.This study provides evidence of the effects of manure substitution on yield enhancement by increasing soil labile N.展开更多
Taking surrounding woodland soils of Cedrus deodara(Roxb.)G.Don,Prunus ceraifera cv.Pissardii,Ginkgo biloba L.and Ligustrum lucidum in Zhoushan Forest Park of Henan Province as the research objects,the physicochemical...Taking surrounding woodland soils of Cedrus deodara(Roxb.)G.Don,Prunus ceraifera cv.Pissardii,Ginkgo biloba L.and Ligustrum lucidum in Zhoushan Forest Park of Henan Province as the research objects,the physicochemical properties of sample plots were investigated,and the contents of soil microbial biomass carbon,nitrogen,phosphorus and total soil nutrients were determined.The results showed that the carbon-nitrogen ratios and carbon–phosphorus ratios were 8.0-11.4 and 17.1-25.3,respectively;the percentages of carbon,nitrogen and phosphorus in soil organic carbon(SOC),total nitrogen(TN)and total phosphorus(TP)were 2.84%-5.1%,2.69%-4.44%and 2.19%-5.62%,respectively.The carbon–nitrogen ratio and carbon-phosphorus ratio of P.ceraifera,G.biloba and L.lucidum forests were signifi cantly lower than that of C.deodara forest(P<0.05).The MBC/SOC,MBN/TN and MBP/TP ratios of G.biloba forest were the highest,which had signifi cant difference with those of other tree species(P<0.05).The contents of carbon,nitrogen and phosphorus were extremely or signifi cantly correlated with SOC,TN,TP,tree species and human disturbance,but had no correlation with soil pH,slope,slope direction,etc.Tree species and human disturbance also significantly affected the physical and chemical properties closely related to soil microbial biomass.展开更多
A successful design, previously adapted for treatment of complex wastewaters in a microbial fuel cell （MFC）, was used to fabricate two MFCs, with a few changes for cost reduction and ease of construction. Performanc...A successful design, previously adapted for treatment of complex wastewaters in a microbial fuel cell （MFC）, was used to fabricate two MFCs, with a few changes for cost reduction and ease of construction. Performance and electrochemical characteristics of MFCs were evaluated in different environmental conditions （in complete darkness and presence of light）, and different flow patterns of batch and continuous in four hydraulic retention times from 8 to 30 h. Changes in chemical oxygen demand, and nitrate and phosphate concentrations were evaluated. In contrast to the microbial fuel cell operated in darkness （D-MFC） with a stable open circuit voltage of 700 mV, presence of light led to growth of other species, and consecutively low and unsteady open circuit voltage. Although the performance of the MFC subjected to light （L-MFC） was quite low and unsteady in dynamic state （internal resistance = 100 Ω, power density = 5.15 W.m-3）. it reached power density of 9.2 W.m-3 which was close to performance of D-MFC （internal resistance = 50 d, power density = 10.3 W.m-3）. Evaluated only for D-MFC, the coulombic efficiency observed in batch mode （30%） was quite higher than the maximum acquired in continuous mode （9.6%） even at the highest hydraulic retention time. In this study, changes in phosphate and different types of nitrogen existing in dairy wastewater were investigated for the first time. At hydraulic retention time of 8 h, the orthophosphate concentration in effluent was 84% higher compared to influent. Total nitrogen and total Kjeldahl nitrogen were reduced 70% and 99% respectively at hydraulic retention time of 30 h, while nitrate and nitrite concentrations increased. The microbial electrolysis cell （MEC）, revamped from D-MEC, showed the maximum gas production of 0.2 m3 H2·m-3·d-1 at 700 mV applied voltage.展开更多
In order to improve the anaerobic digestion efficiency of waste activated sludge（WAS）,a pretreatment procedure should be carried out so as to disrupt the microbial cell structure,thus releasing intracellular organic...In order to improve the anaerobic digestion efficiency of waste activated sludge（WAS）,a pretreatment procedure should be carried out so as to disrupt the microbial cell structure,thus releasing intracellular organic matters.In this paper,a corona discharge triggered by a DC voltage was employed to pre-treat WAS for various time periods under different temperatures.The magnitude of the DC voltage was 4 k V at both negative and positive polarities.The changes in the soluble chemical oxygen demand,phosphorus and nitrogen content,and p H value within the WAS were utilized to estimate the pretreatment performance of the DC corona.It was found that with increasing treatment time,the pretreatment efficiency tends to be reduced.With increased temperature,the pretreatment efficiency appears to be better.It is suggested that the oxidative species and the active particles generated in the corona discharge play an important role in disrupting the microbial cell structure,which is dependent upon the treatment time and the temperature.展开更多
基金supported by the Key Research and Development Program of Zhejiang Province,China(2022C02008)the National Natural Science Foundation of China(31401343)+1 种基金the earmarked fund for China Agriculture Research System(CARS-01)the Agricultural Science and Technology Innovation Program of Chinese Academy of Agricultural Sciences(CAASZDRW202001)。
文摘Soil microorganisms play important roles in nitrogen transformation. The aim of this study was to characterize changes in the activity of nitrogen transformation enzymes and the abundance of nitrogen function genes in rhizosphere soil aerated using three different methods(continuous flooding(CF), continuous flooding and aeration(CFA), and alternate wetting and drying(AWD)). The abundances of amoA ammonia-oxidizing archaea(AOA) and ammonia-oxidizing bacteria(AOB), nirS, nirK, and nifH genes, and the activities of urease, protease, ammonia oxidase, nitrate reductase, and nitrite reductase were measured at the tillering(S1), heading(S2), and ripening(S3) stages. We analyzed the relationships of the aforementioned microbial activity indices, in addition to soil microbial biomass carbon(MBC) and soil microbial biomass nitrogen(MBN), with the concentration of soil nitrate and ammonium nitrogen. The abundance of nitrogen function genes and the activities of nitrogen invertase in rice rhizosphere soil were higher at S2 compared with S1 and S3 in all treatments. AWD and CFA increased the abundance of amoA and nifH genes, and the activities of urease, protease, and ammonia oxidase, and decreased the abundance of nirS and nirK genes and the activities of nitrate reductase and nitrite reductase, with the effect of AWD being particularly strong. During the entire growth period, the mean abundances of the AOA amoA, AOB amoA, and nifH genes were 2.9, 5.8, and 3.0 higher in the AWD treatment than in the CF treatment, respectively, and the activities of urease, protease, and ammonia oxidase were 1.1, 0.5, and 0.7 higher in the AWD treatment than in the CF treatment, respectively. The abundances of the nirS and nirK genes, and the activities of nitrate reductase and nitrite reductase were 73.6, 84.8, 10.3 and 36.5% lower in the AWD treatment than in the CF treatment, respectively. The abundances of the AOA amoA, AOB amoA, and nifH genes were significantly and positively correlated with the activities of urease, protease, and ammonia oxidase, and the abundances of the nirS and nirK genes were significantly positively correlated with the activities of nitrate reductase. All the above indicators were positively correlated with soil MBC and MBN. In sum, microbial activity related to nitrogen transformation in rice rhizosphere soil was highest at S2. Aeration can effectively increase the activity of most nitrogen-converting microorganisms and MBN, and thus promote soil nitrogen transformation.
基金Financial supports were received from the Agro-scientific Research in the Public Interest of China(201503122)。
文摘Soil microbial biomass nitrogen(MBN)contains the largest proportion of biologically active nitrogen(N)in soil,and is considered as a crucial participant in soil N cycling.Agronomic management practices such as crop rotation and monocropping systems,dramatically affect MBN in agroecosystems.However,the influence of crop rotation and monocropping in agroecosystems on MBN remains unclear.A meta-analysis based on 203 published studies was conducted to quantify the effect of crop rotation and mono-cropping systems on MBN under synthetic N fertilizer application.The analysis showed that crop rotation significantly stimulated the response ratio(RR)of MBN to N fertilization and this parameter reached the highest levels in upland-fallow rotations.Upland mono-cropping did not change the RR of MBN to N application,however,the RR of MBN to N application in paddy mono-cropping increased.The difference between crop rotation and mono-cropping systems appeared to be due to the various cropping management scenarios,and the pattern,rate and duration of N addition.Crop rotation systems led to a more positive effect on soil total N(TN)and a smaller reduction in soil pH than mono-cropping systems.The RR of MBN to N application was positively correlated with the RR of mineral N only in crop rotation systems and with the RR of soil pH only in mono-cropping systems.Combining the results of Random Forest(RF)model and structural equation model showed that the predominant driving factors of MBN changes in crop rotation systems were soil mineral N and TN,while in mono-cropping systems the main driving factor was soil pH.Overall,our study indicates that crop rotation can be an effective way to enhance MBN by improving soil N resources,which promote the resistance of MBN to low pH induced by intensive synthetic N fertilizer application.
基金supported by the Chinese National Natu-ral Scientific Foundation(41171077,40801002,40971031)
文摘In this study, seasonal variation characteristics of surface soil microbial biomass carbon （MBC） and soil microbial biomass nitrogen （MBN） of an artificial vegetation area located in Shapotou for different time periods were studied using the chloroform fumigation method, and the results were compared with those of near-natural vegetation areas and mobile dunes. Results showed that the MBC and MBN levels in the 0-5 cm soil layer were higher in autumn than in summer and spring. As the prolongation of vegetation restoration raised the MBC and MBN levels in summer and autumn, no clear variation was found in spring. However, the MBC and MBN in 5-20 cm had no obvious seasonal variation. During summer and autumn, the variation trend of MBC and MBN in the vertical direction was shown to be 0-5 〉 5-10 〉 10-20 cm in the vegetation area, while for mobile dunes, the MBC and MBN levels increased as the depth increased. The natural vegetation area was shown to possess the highest MBC and MBN levels, and yet mobile dunes have the lowest MBC and MBN levels. MBC and MBN levels in artificial sand-binding vegetation increased with the prolongation of vegetation restoration, indicating that the succession of sand-binding vegetation will result in the ac- cumulation of soil carbon and nitrogen, as well as the restoration of soil fertility.
基金funded by the National Natural Science Foundation of China (31100337)the Scientific Research Foundation of Nanjing University of Information Science & Technology (2243141301132)
文摘The change of freeze-thaw pattern of the Tibetan Plateau under climate warming is bound to have a profound impact on the soil process of alpine grassland ecosystem;however,the research on the impact of the freeze-thaw action on nitrogen processes of the alpine grassland ecosystem on the Tibetan Plateau has not yet attracted much attention.In this study,the impact of the freezing strength on the soil nitrogen components of alpine grassland on the Tibetan Plateau was studied through laboratory freeze-thaw simulation experiments.The 0–10 cm topsoil was collected from the alpine marsh meadow and alpine meadow in the permafrost region of Beilu River.In the experiment,the soil samples were cultivated at –10℃,–7℃,–5℃,–3℃ and –1℃,respectively for three days and then thawed at 2℃ for one day.The results showed that after the freeze-thaw process,the soil microbial biomass nitrogen significantly decreased while the dissolved organic nitrogen and inorganic nitrogen significantly increased.When the freezing temperature was below –7℃,there was no significant difference between the content of nitrogen components,which implied a change of each nitrogen component might have a response threshold toward the freezing temperature.As the freeze-thaw process can lead to the risk of nitrogen loss in the alpine grassland ecosystem,more attention should be paid to the response of the soil nitrogen cycle of alpine grasslands on the Tibetan Plateau to the freeze-thaw process.
基金Sponsored by Science and Technology Project of Key Technology for Control of Major Production Accidents in 2015(shandong-0017-2015AQ)National Natural Science Foundation of Shandong Province,China(ZR2015PC022)
文摘Soil salinization can limit the development of agriculture in the Yellow River Delta.In this paper,saline and alkaline farmland in the Yellow River Delta was chosen as the research object,and effects of soil salinity on soil microbial biomass nitrogen(SMBN) under different conditions were investigated to study the response of soil nitrogen turnover to salt stress.There were four salinity gradients(S1:0.1%;S2:0.5%;S3:0.9%;S4:1.3%),and four substrates were added to the soil.The results showed that after the addition of various substrates,SMBN in treatments with high soil salinity(S3 and S4) was obviously lower than that in treatments with low soil salinity(S1 and S2).In comparison with treatment S1,the average of SMBN in treatments S3 and S4 decreased by 35.8% and 46.7% respectively when there was no substrate added to them;it declined by 55.6% and 56.1% respectively as the carbon source was added to them;it reduced by 24.6% and 28.3% when the nitrogen source was added to them;it dropped by 43.8% and 57.0% respectively as the carbon and nitrogen source were added to them.Compared with treatments without substrates,the addition of the nitrogen source could not improve SMBN;the addition of the carbon source or carbon and nitrogen source could enhance SMBN obviously,and it increased by 60.9% and 66.1%(or 110.8% and 140.2%) in treatments with low soil salinity(S1 and S2),while it changed slightly in treatments with high soil salinity(S3 and S4).In order to increase SMBN,it is needed to apply organic fertilizer or chemical fertilizer and organic fertilizer to maintain or improve soil fertility.
基金Natural Science Foundation of Tibet Autonomous Region(XZ2019ZRG-60).
文摘[Objectives]To comprehensively and deeply explore the effects of different land cover types in the lower reaches of Niyang River on soil microbial biomass carbon and nitrogen,and to provide a scientific basis for the rational use and sustainable management of land resources in this area.[Methods]Taking the 3 types of land cover(cultivated land,grass land and forest land)in the lower reaches of Niyang River in Tibet as the research object,the contents,distribution characteristics and relationships of soil organic carbon,organic nitrogen,microbial biomass carbon,microbial biomass nitrogen and readily oxidizable organic carbon,and their relationships were studied in 0-10,10-20,20-40,40-60,and 60-100 cm soil depth.[Results]The soil organic carbon content of forest land was higher than that of grass land and cultivated land;the vertical change trend of soil organic carbon content decreased with the increase of depth(P<0.05),and it was mainly concentrated in the soil with a depth of 0-20 cm.The soil organic carbon content was significantly different among forest land,grass land and cultivated land(P<0.05),but there was no significant difference between cultivated land and grass land(P>0.05).The soil organic nitrogen content was significantly different among cultivated land,grass land,and forest land(P<0.05),but there was no significant difference between grass land and forest land(P>0.05).The readily oxidizable organic carbon,microbial biomass carbon and nitrogen in forest land were higher than that in cultivated land and grass land.The change trend of soil readily oxidizable organic carbon,microbial biomass carbon and microbial biomass nitrogen was similar to the change of soil organic carbon content,showing a significant positive correlation.In addition to being subject to land cover,soil microbial biomass carbon and nitrogen content were also subject to the interaction of factors such as soil temperature,humidity,pH and vegetation types.[Conclusions]Changes in land cover significantly affect soil organic carbon and nitrogen,readily oxidizable organic carbon,microbial biomass carbon and nitrogen content.
文摘The impulse to remain profitable by increasing agricultural production levels in view of the greater demand for food, provided impetus to production intensification. The aim of this review is to summarise current literature, reporting specifically on the impact of production intensification on habitats and yield constraints caused by weeds. Secondly, in alleviating these effects over the short term, ecological measures that enhance species diversity in conserved habitats and promote semi-natural habitats in the agricultural landscape, are discussed. In large-scale intensive agriculture, weed control is predominantly rooted in agrochemical applications in the form of herbicides. Long lasting intensive agricultural practices show discord both with the promotion of the biodiversity of microbes belowground and aboveground and with organisms involved in the breaking down of plant material. The presence of native species in the surroundings, in combination with hedgerows and field margins, with a comparatively intricate and balanced variety of plants in a sheltered environment, are essential for settlement of benign insects, particularly in the face of intensive agricultural production. The promising tactic of advantageous seed predators enables decreased herbicide applications. Crop mosaics arranged to advance compatibility at the landscape scale are important to bolster pollination services and insect management, while ecological variety in the surroundings acts as a safety net for habitat diversity. Weed control in combination with different tactics of vegetation use, comprising cover cropping, hedgerows and field margins, sets up safe havens in the landscape, and improves the diffusion of complementary life forms. Field margins perform a meaningful natural function as point of provision for forage, safe havens and distribution passageways for pollinators and insect predators. Production practices that promote more heterogeneity and combine high density semi-natural safe havens and habitat conservation in agro ecosystems are beneficial to species diversity across trophic levels and contribute to agricultural production stability and food safety.
基金National Nature Science Foundation of China (30571476, 30771703)
文摘Soluble organic nitrogen （SON） is recognized as a sensitive indicator of soil nitrogen status. The present work was conducted in the temperate forests of northeast China where soils are typically characterized by high organic matter and high organic nitrogen content, and soil sampling was made in early spring just after the freeze-thaw period. The water extracted SON pools in the organic layer of forest soils were measured within the range from 156.0 mg·kg^-1 to 292.6 mg·kg^-1, a similar magnitude of salt solution extracted SON pools reported in literatures. However, the water soluble SON pools in 0-15 cm mineral soils in present study were much higher （3-10 times） than any other reports, ranging from 58.6 mg·kg^-1 to 125.2 mg·kg^-1. Water soluble SON varied markedly among the soils under different forests and at different sites. The SON in water extracts were positively and significantly correlated to soil organic matter and total nitrogen contents, but negatively correlated to microbial biomass nitrogen （MBN）. The reasons of the abnormally large SON pools and the negative correlations between SON and MBN in the 0-15cm mineral soils in this study were specially discussed.
文摘Soil microbial biomass is an important indicator to measure the dynamic changes of soil carbon pool.It is of great signifi cance to understand the dynamics of soil microbial biomass in plantation for rational management and cultivation of plantation.In order to explore the temporal dynamics and infl uencing factors of soil microbial biomass of Keteleeria fortunei var.cyclolepis at diff erent stand ages,the plantation of diff erent ages(young forest,5 years;middle-aged forest,22 years;mature forest,40 years)at the Guangxi Daguishan forest station of China were studied to examine the seasonal variation of their microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN)by chloroform fumigation extraction method.It was found that among the forests of diff erent age,MBC and MBN diff ered signifi cantly in the 0–10 cm soil layer,and MBN diff ered signifi cantly in the 10–20 cm soil layer,but there was no signifi cant diff erence in MBC for the 10–20 cm soil layer or in either MBC or MBN for the 20–40 cm soil layer.With increasing maturity of the forest,MBC gradually decreased in the 0–10 cm soil layer and increased fi rstly and then decreased in the 10–20 cm and 20–40 cm soil layers,and MBN increased fi rstly and then decreased in all three soil layers.As the soil depth increased,both MBC and MBN gradually decreased for all three forests.The MBC and MBN basically had the same seasonal variation in all three soil layers of all three forests,i.e.,high in the summer and low in the winter.Correlation analysis showed that MBC was signifi cantly positively correlated with soil organic matter,total nitrogen,and soil moisture,whereas MBN was signifi cantly positively correlated with soil total nitrogen.It showed that soil moisture content was the main factor determining the variation of soil microbial biomass by Redundancy analysis.The results showed that the soil properties changed continuously as the young forest grew into the middle-aged forest,which increased soil microbial biomass and enriched the soil nutrients.However,the soil microbial biomass declined as the middle-age forest continued to grow,and the soil nutrients were reduced in the mature forest.
基金Project supported by the National Key Basic Research Program (973 Program) of China (No. 2007CB106804)the PhD candidate Training Program (No. 20060730027)+1 种基金the "111" Project from the State Administration of Foreign Experts Affairs (SAFEA)the Ministry of Education of China
文摘To show the vegetation succession interaction with soil properties, microbial biomass, basal respiration, and enzyme activities in different soil layers （0-60 cm） were determined in six lands, i.e., 2-, 7-, 11-, 20-, and 43-year-old abandoned lands and one native grassland, in a semiarid hilly area of the Loess Plateau. The results indicated that the successional time and soil depths affected soil microbiological parameters significantly. In 20-cm soil layer, microbial biomass carbon （MBC）, microbial biomass nitrogen （MBN）, MBC/MBN, MBC to soil organic carbon ratio （MBC/SOC）, and soil basal respiration tended to increase with successional stages but decrease with soil depths. In contrast, metabolic quotient （qCO2） tended to decrease with successional stages but increase with soil depths. In addition, the activities of urease, catalase, neutral phosphatase, β-fructofuranosidase, and earboxymethyl cellulose （CMC） enzyme increased with successional stages and soil depths. They were significantly positively correlated with microbial biomass and SOC （P 〈 0.5）, whereas no obvious trend was observed for the polyphenoloxidase activity. The results indicated that natural vegetation succession could improve soil quality and promote ecosystem restoration, but it needed a long time under local climate conditions.
基金supported by National Natural Science Foundation of China (NSFC Nos. 30771719 and 30471386)
文摘Monitoring of soil nitrogen （N） cycling is useful to assess soil quality and to gauge the sustainability of management practices. We studied net N mineralization, nitrification, and soil N availability in the 0-10 cm and 11-30 cm soil horizons in east China during 2006-2007 using an in situ incubation method in four subtropical evergreen broad-leaved forest stands aged 18-, 36-, 48-, and 65-years. The properties of surface soil and forest floor varied between stand age classes. C：N ratios of surface soil and forest floor decreased, whereas soil total N and total organic C, available P, and soil microbial biomass N increased with stand age. The mineral N pool was small for the young stand and large for the older stands. NO3^--N was less than 30% in all stands. Net rates of N mineralization and nitrification were higher in old stands than jn younger stands, and higher in the 0-10 cm than in the 11-30 cm horizon. The differences were significant between old and young stands （p 〈 0.031） and between soil horizons （p 〈 0.005）. Relative nitrification was somewhat low in all forest stands and declined with stand age. N trans- formation seemed to be controlled by soil moisture, soil mierobial biomass N, and forest floor C：N ratio. Our results demonstrate that analyses of N cycling can provide insight into the effects of management disturbances on forest ecosystems.
基金supported by the National Natural Science Foundation of China(21972036)the State Key Laboratory of Urban Water Resource and Environment(Harbin Institute of Technology)(No.2022TS07,No.2022ES202210 and No.2022QG202226)+1 种基金support from the National Natural Science Foundation of China(52300199)the Fundamental Research Funds for the Central Universities(FRFCU5710010522).
文摘Recent advancements in constructed wetlands(CWs)have highlighted the imperative of enhancing nitrogen(N)removal efficiency.However,the variability in influent substrate concentrations presents a challenge in optimizing N removal strategies due to its impact on removal efficiency and mechanisms.Here we show the interplay between influent substrate concentration and N removal processes within integrated vertical-flow constructed wetlands(IVFCWs),using wastewaters enriched with NO_(3)^(-)-N and NH4þ-N at varying carbon to nitrogen(C/N)ratios(1,3,and 6).In the NO_(3)^(-)-N enriched systems,a positive correlation was observed between the C/N ratio and total nitrogen(TN)removal efficiency,which markedly increased from 13.46±2.23%to 87.00±2.37%as the C/N ratio escalated from 1 to 6.Conversely,in NH4þ-N enriched systems,TN removal efficiencies in the A-6 setup(33.69±4.83%)were marginally 1.25 to 1.29 times higher than those in A-3 and A-1 systems,attributed to constraints in dissolved oxygen(DO)levels and alkalinity.Microbial community analysis and metabolic pathway assessment revealed that anaerobic denitrification,microbial N assimilation,and dissimilatory nitrate reduction to ammonium(DNRA)predominated in NO_(3)^(-)-N systems with higher C/N ratios(C/N 3).In contrast,aerobic denitrification and microbial N assimilation were the primary pathways in NH4þ-N systems and low C/N NO_(3)^(-)-N systems.A mass balance approach indicated denitrification and microbial N assimilation contributed 4.12-47.12%and 8.51e38.96%in NO_(3)^(-)-N systems,respectively,and 0.55e17.35%and 7.83e33.55%in NH4þ-N systems to TN removal.To enhance N removal,strategies for NO_(3)-N dominated systems should address carbon source limitations and electron competition between denitrification and DNRA processes,while NH4þ-N dominated systems require optimization of carbon utilization pathways,and ensuring adequate DO and alkalinity supply.
基金Supported by Natural Science Foundation of Shanxi Province(2014011001-4)~~
文摘As per randomized block design, the research had different fertilizer treatments, and the organic matter, respiration, enzyme activity and microbial carbon and nitrogen in reclaimed soil were studied. Fertilization schemes were as follows： The treatment without fertilizers（CK）, the treatment with chemical fertilizers（C）, the treatment with chemical fertilizers and bacterial fertilizer（CB）, the treatment with organic fertilizer and chemical fertilizers（CM）, and the treatment with chemical fertilizers, organic fertilizer and bacterial fertilizer（CMB）. The results showed： Four fertilization treatments could improve the content of soil organic matter. CMB, CM and CB could significantly improve the soil respiration. Organic fertilizer and fertilizer could significantly improve soil enzyme activity, In different growth stages the CMB treatment had highest urease and phosphatase.The most significant in the treatment content of sucrose was CM. Organic fertilizer and microbial fertilizer can significantly improve the microbial carbon and nitrogen in soil. For the microbial biomass carbon, the CMB treatment increased by 11%-34% than CB treatment, and 35%-63% than C treatment. In terms of microbial nitrogen CMB, CM respectively increased by 31%-51% than CB treatment, and 52%-100% compared with C. In the process of land reclamation, we should combine the organic fertilizer, microbial fertilizer and inorganic fertilizer. Only in this way can soil biological activity be accelerated, soil microbial environment improved, and the ripening increased soil nutrient and soil cultivation be enhanced.
基金The Academy of Sciences/State Administration of Foreign Experts Affairs(CAS/SAFEA)International Partnership Program for Creative Research Teams(KZCX2-YW-445)National Forestry Scientific Support Program(2006BAD03A0903 and 2006BAD03A0401)Non-commercial Forest Project(200804027-05).
文摘Aims Natural secondary forest(NSF)and larch plantation are two of the predominant forest types in Northeast China.However,how the two types of forests compare in sustaining soil quality is not well understood.This study was conducted to determine how natural secondary forest and larch plantation would differ in soil microbial biomass and soil organic matter quality.Methods Microbial biomass carbon(MBC),microbial biomass nitrogen(MBN),soil organic carbon(SOC)and total nitrogen(TN)in the 0-to 15-cm and 15-to 30-cm soil layers were investigated by making chemical and biological measurements in the montane region of eastern Liaoning Province,Northeast China,during the growing season of 2008 in stands of NSF and Larix olgensis plantation(LOP).Important Findings We found that soil MBC and MBN were significantly lower in the LOP than in the NSF.Both MBC and MBN declined significantly with increasing soil depth in the two types of stands.The ratios of MBC to SOC(MBC/SOC)and MBN to TN(MBN/TN)were also significantly lower in the LOP than in the NSF.Moreover,the values of MBC,MBC/SOC,and MBN/TN significantly varied with time and followed a similar pattern during the growing season,all with an apparent peak in summer.Our results indicate that NSF is better in sustaining soil microbial biomass and nutrients than larch plantation in the temperate Northeast China.This calls for cautions in large-scale conversions of the native forests to coniferous plantations as a forest management practice on concerns of sustaining soil productivity.
基金supported by the Mega-projects of Science Research for Water Environment Improvement(No.2012ZX07101-002)the National Natural Science Foundation of China(No.41303085)
文摘Dissolved organic nitrogen（DON）extracted from Lake Shankou sediments using KCl was isolated into hydrophobic and hydrophilic fractions.The bioavailabilities of the hydrophobic and hydrophilic fractions to three types of bacterial communities collected from sediments,activated sludge and compost products were examined.The DON recoveries obtained by DAX-8 and cation exchange resins treatment were 96.17% ± 1.58% and 98.14% ±0% for the samples obtained from N4 and N14 stations,respectively.After 25 days of incubation at 25℃,most DON（59% to 96%）was degraded.Hydrophilic DON exhibited a higher reduction rate than hydrophobic DON during the growth phase.Untreated wastewater from Changshuihe town was the main degradable DON source to station N4,and 93% of hydrophilic DON and 80% of hydrophobic DON were degraded.Station N14 received a large amount of refractory DON from forest soils and exhibited DON degradation rates of 82% and 71% for the hydrophilic and hydrophobic fractions,respectively.Amino acid contents and fluorescence intensities were also analyzed.Approximately 27% to 74% of amino acids were taken up by day 5,and their concentration gradually increased in the following days due to the decomposition of dissolved proteins.Parallel factor analysis resulted in identification of tryptophan-like proteins,tyrosine-like proteins and FA-like substances.During the growth phase,40%–51% of the tryptophan-like proteins were taken up by bacteria,and the accumulation of tyrosine-like proteins was attributed to the release of biotic substances.The concentration of the FA-like substances decreased due to microbial decomposition.
基金supported by the "Knowledge Innovation" Program of the Chinese Academy of Sciences (Nos. KZZD-EW09-3 and KSCX2-EW-B-1-5)the National Water Pollution Control and Treatment Science and Technology Major Project (No. 2015ZX07206-006)the Key Technologies R&D Program of China (No. 2014BAD14B01)
文摘Microbial fuel cells（MFCs） have become a promising technology for wastewater treatment accompanying electricity generation. Carbon and nitrogen removal can be achieved by utilizing the electron transfer between the anode and cathode in an MFC. However,large-scale power production and high removal efficiency must be achieved at a low cost to make MFCs practical and economically competitive in the future. This article reviews the principles, feasibility and bottlenecks of MFCs for simultaneous carbon and nitrogen removal, the recent advances and prospective strategies for performance improvement, as well as the involved microbes and electron transfer mechanisms.
基金supported by the Major Project for Support System Construction of Agriculture Green Development from the Ministry of Agriculture and Rural Affairs of China(No.NG/LS2020-71-05)the National Major Science and Technology Project of China(No.2014ZX07101-012).
文摘Substituting chemical fertilizers with manure is an important method for efficient nutrient management in rice cropping systems of China.Labile nitrogen(N)is the most active component of the soil N pool and plays an essential role in soil fertility.However,the effects of manure substitution on soil labile N in rice cropping systems and their relationships with soil properties,fertilization practices,and climatic conditions remain unclear and should be systematically quantified.Here,we investigated rice grain yield and four types of soil labile N that have been widely reported,including available nitrogen(AN),ammonium nitrogen(NH_(4)^(+)-N),nitrate nitrogen(NO_(3)^(−)-N),and microbial biomass nitrogen(MBN).We reviewed 187 published articles and performed a meta-analysis to quantify the effects of manure substitution on yield and soil labile N.The results showed that manure substitution increased AN,MBN,NH+4-N,and NO−3-N by 11.3%,38.5%,5.9%,and 8.1%,respectively.Partial substitution significantly increased the yield by 1.4%–5.9%,but full substitution significantly decreased the yield by 2.9%.The positive effects of manure substitution on yield and AN were stronger with long-term fertilization.The differences in responses varied across specific manure types,N application rates,soil properties,and climatic factors.In conclusion,manure substitution can increase soil labile N and is regarded as an efficient strategy for improving soil N fertility and a recommended measure for applying both chemical and organic fertilizers in rice systems.This study provides evidence of the effects of manure substitution on yield enhancement by increasing soil labile N.
基金National Natural Science Foundation of China(31670616).
文摘Taking surrounding woodland soils of Cedrus deodara(Roxb.)G.Don,Prunus ceraifera cv.Pissardii,Ginkgo biloba L.and Ligustrum lucidum in Zhoushan Forest Park of Henan Province as the research objects,the physicochemical properties of sample plots were investigated,and the contents of soil microbial biomass carbon,nitrogen,phosphorus and total soil nutrients were determined.The results showed that the carbon-nitrogen ratios and carbon–phosphorus ratios were 8.0-11.4 and 17.1-25.3,respectively;the percentages of carbon,nitrogen and phosphorus in soil organic carbon(SOC),total nitrogen(TN)and total phosphorus(TP)were 2.84%-5.1%,2.69%-4.44%and 2.19%-5.62%,respectively.The carbon–nitrogen ratio and carbon-phosphorus ratio of P.ceraifera,G.biloba and L.lucidum forests were signifi cantly lower than that of C.deodara forest(P<0.05).The MBC/SOC,MBN/TN and MBP/TP ratios of G.biloba forest were the highest,which had signifi cant difference with those of other tree species(P<0.05).The contents of carbon,nitrogen and phosphorus were extremely or signifi cantly correlated with SOC,TN,TP,tree species and human disturbance,but had no correlation with soil pH,slope,slope direction,etc.Tree species and human disturbance also significantly affected the physical and chemical properties closely related to soil microbial biomass.
基金supported by Sharif University of Technology,Vice President for Research Grant G930111
文摘A successful design, previously adapted for treatment of complex wastewaters in a microbial fuel cell （MFC）, was used to fabricate two MFCs, with a few changes for cost reduction and ease of construction. Performance and electrochemical characteristics of MFCs were evaluated in different environmental conditions （in complete darkness and presence of light）, and different flow patterns of batch and continuous in four hydraulic retention times from 8 to 30 h. Changes in chemical oxygen demand, and nitrate and phosphate concentrations were evaluated. In contrast to the microbial fuel cell operated in darkness （D-MFC） with a stable open circuit voltage of 700 mV, presence of light led to growth of other species, and consecutively low and unsteady open circuit voltage. Although the performance of the MFC subjected to light （L-MFC） was quite low and unsteady in dynamic state （internal resistance = 100 Ω, power density = 5.15 W.m-3）. it reached power density of 9.2 W.m-3 which was close to performance of D-MFC （internal resistance = 50 d, power density = 10.3 W.m-3）. Evaluated only for D-MFC, the coulombic efficiency observed in batch mode （30%） was quite higher than the maximum acquired in continuous mode （9.6%） even at the highest hydraulic retention time. In this study, changes in phosphate and different types of nitrogen existing in dairy wastewater were investigated for the first time. At hydraulic retention time of 8 h, the orthophosphate concentration in effluent was 84% higher compared to influent. Total nitrogen and total Kjeldahl nitrogen were reduced 70% and 99% respectively at hydraulic retention time of 30 h, while nitrate and nitrite concentrations increased. The microbial electrolysis cell （MEC）, revamped from D-MEC, showed the maximum gas production of 0.2 m3 H2·m-3·d-1 at 700 mV applied voltage.
基金financially supported by National Natural Science Foundation of China(Grant No.51677127)
文摘In order to improve the anaerobic digestion efficiency of waste activated sludge（WAS）,a pretreatment procedure should be carried out so as to disrupt the microbial cell structure,thus releasing intracellular organic matters.In this paper,a corona discharge triggered by a DC voltage was employed to pre-treat WAS for various time periods under different temperatures.The magnitude of the DC voltage was 4 k V at both negative and positive polarities.The changes in the soluble chemical oxygen demand,phosphorus and nitrogen content,and p H value within the WAS were utilized to estimate the pretreatment performance of the DC corona.It was found that with increasing treatment time,the pretreatment efficiency tends to be reduced.With increased temperature,the pretreatment efficiency appears to be better.It is suggested that the oxidative species and the active particles generated in the corona discharge play an important role in disrupting the microbial cell structure,which is dependent upon the treatment time and the temperature.
