Prescribed burning can alter soil microbial activity and spatially redistribute soil nutrient elements.However,no systematic,in-depth studies have investigated the impact of prescribed burning on the spatial patterns ...Prescribed burning can alter soil microbial activity and spatially redistribute soil nutrient elements.However,no systematic,in-depth studies have investigated the impact of prescribed burning on the spatial patterns of soil microbial biomass in temperate forest ecosystems in Northeast China.The present study investigated the impacts of prescribed burning on the small-scale spatial heterogeneity of microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN)in the upper(0–10 cm)and lower(10–20 cm)soil layers in Pinus koraiensis and Quercus mongolica forests and explored the factors that infl uence spatial variations of these variables after prescribed burning.Our results showed that,MBC declined by approximately 30%in the 10–20 cm soil layer in the Q.mongolica forest,where there were no signifi cant eff ects on the soil MBC and MBN contents of the P.koraiensis forest(p>0.05)after prescribed burning.Compared to the MBC of the Q.mongolica forest before the prescribed burn,MBC spatial dependence in the upper and lower soil layers was approximately 7%and 2%higher,respectively.After the prescribed burn,MBN spatial dependence in the upper and lower soil layers in the P.koraiensis forest was approximately 1%and 13%lower,respectively,than that before the burn,and the MBC spatial variability in the 0–10 cm soil layer in the two forest types was explained by the soil moisture content(SMC),whereas the MBN spatial variability in the 0–10 cm soil layer in the two forests was explained by the soil pH and nitrate nitrogen(NO_(3)^(–)-N),respectively.In the lower soil layer(10–20 cm)of the Q.mongolica forest,elevation and ammonium nitrogen(NH 4+-N)were the main factors aff ecting the spatial variability of MBC and MBN,respectively.In the 10–20 cm soil layer of the P.koraiensis forest,NO_(3)^(–)-N and slope were the main factors aff ecting the spatial variability of MBC and MBN,respectively,after the burn.The spatial distributions of MBC and MBN in the two forests were largely structured with higher spatial autocorrelation(relative structural variance C/[C 0+C]>0.75).However,the factors infl uencing the spatial variability of MBC and MBN in the two forest types were not consistent between the upper and lower soil layers with prescribed burning.These fi ndings have important implications for developing sustainable management and conservation policies for forest ecosystems.展开更多
The present study was conducted to see the short term impact of organic and inorganic fertilizers on soil microbial biomass both in spring and summer. Also aimed to observe the correlation between soil microbial bioma...The present study was conducted to see the short term impact of organic and inorganic fertilizers on soil microbial biomass both in spring and summer. Also aimed to observe the correlation between soil microbial biomass and soil DNA. The study concluded that type of fertilizer might alter the soil microbial biomass and DNA contents. In soil treated with organic fertilizers resulted in higher concentrations of microbial biomass and DNA contents in summer as compared to spring dute to increase in temperature. Correspondingly, in case of inorganic fertilizer, concentrations of soil microbial biomass and DNA detected higher in summer instead of spring. The statistical correlation between soil microbial biomass, DNA and ODR in spring and summer along with organic and inorganic fertilizers were calculated highly significant(p>0.01). This study demonstrated the impact of fertilizers and seasonal variations on soil microbial biomass and also revealed significant correlation between soil microbial biomass and soil DNA.展开更多
Soil salinization has become a global issue. Saline and alkaline arable land was taken as research object in this paper and four salt gradients were set(S1: 0.1%; S2:0. 5%; S3:0.9%; S4:1.3%). Through the addition of d...Soil salinization has become a global issue. Saline and alkaline arable land was taken as research object in this paper and four salt gradients were set(S1: 0.1%; S2:0. 5%; S3:0.9%; S4:1.3%). Through the addition of different substrates( CK: no addition of substrate; N: addition of nitrogen source; C: addition of glucose,C + N: addition of glucose and nitrogen source) to soil,it analyzed the influence of salt content on the soil microbial biomass carbon( SMBC) for the purpose of surveying the response mechanism of soil carbon turnover to salt stress. Results indicated that after addition of different substrates,the SMBC in high salt content(S3 and S4) is obviously lower than that in low salt content( S1 and S2). The decline rate of S3 and S4 is 5. 4% and 14. 2% for no addition of substrate; the decline rate is 9.0% and 24.0% for addition of nitrogen source; the decline rate is 11.5% and 28.0% for addition of carbon source; the decline rate is 19.5% and 39.5% for addition of carbon source + nitrogen source. Compared with no addition of substrates,addition of nitrogen source could not increase the SMBC. Addition of carbon source and carbon + nitrogen can significantly increase the SMBC,and the increase in low salt content soil( 80.0%- 81.0% and 58.0%- 59.0%) is obviously higher than high salt content soil( 52.0%- 69.0%and 34.0%- 50.0%). Generally,when the soil salt content is low( 0.5%),the influence of different substrate treatment is little on the SMBC,and increasing the soil salt content can obviously reduce the SMBC.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
Introduction:The availability of essential nutrients,such as nitrogen(N)and phosphorus(P),can feedback on soil carbon(C)and the soil microbial biomass.Natural cycles can be supplemented by agricultural fertiliser addi...Introduction:The availability of essential nutrients,such as nitrogen(N)and phosphorus(P),can feedback on soil carbon(C)and the soil microbial biomass.Natural cycles can be supplemented by agricultural fertiliser addition,and we determined whether the stoichiometry and nutrient limitation of the microbial biomass could be affected by an unbalanced nutrient supply.Methods:Samples were taken from a long-term trial(in effect since 1968)with annual applications of 0,15 and 30 kg P ha^(−1) with constant N and potassium.Soil and microbial biomass CNP contents were measured and nutrient limitation assessed by substrate-induced respiration.Linear regression and discriminant analyses were used to identify the variables explaining nutrient limitation.Results:Soil and biomass CNP increased with increasing P fertiliser,and there was a significant,positive,correlation between microbial biomass P and biomass C,apart from at the highest level of P fertilisation when the microbial biomass was over-saturated with P.The molar ratios of C:N:P in the microbial biomass remained constant(homeostatic)despite large changes in the soil nutrient ratios.Microbial growth was generally limited by C and N,except in soil with no added P when C and P were the main limiting nutrients.C,N and P,however,did not explain all the growth limitation on the soils with no added P.Conclusions:Increased soil C and N were probably due to increased net primary production.Our results confirm that C:N:P ratios within the microbial biomass were constrained(i.e.homeostatic)under near optimum soil conditions.Soils with no added P were characterised by strong microbial P limitation and soils under high P by over-saturation of microorganisms with P.Relative changes in biomass C:P can be indicative of nutrient limitation within a site.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
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 salinization has adverse effects on the soil physical-chemical characteristics.However,little is known about the changes in soil salt ion concentrations and other soil physical-chemical characteristics within the...Soil salinization has adverse effects on the soil physical-chemical characteristics.However,little is known about the changes in soil salt ion concentrations and other soil physical-chemical characteristics within the Qarhan Salt Lake and at different soil depths in the surrounding areas.Here,we selected five sampling sites(S1,S2,S3,S4,and S5)alongside the Qarhan Salt Lake and in the Xidatan segment of the Kunlun Mountains to investigate the relationship among soil salt ion concentrations,soil physical-chemical characteristics,and environmental variables in April 2019.The results indicated that most sites had strongly saline and very strongly saline conditions.The main salt ions present in the soil were Na^(+),K^(+),and Cl^(-).Soil nutrients and soil microbial biomass(SMB)were significantly affected by the salinity(P<0.05).Moreover,soil salt ions(Na^(+),K^(+),Ca2+,Mg^(2+),Cl^(-),CO_(3)^(2-),SO_(4)^(2-),and HCO_(3)^(-))were positively correlated with electrical conductivity(EC)and soil water content(SWC),but negatively related to altitude and soil depth.Unlike soil salt ions,soil nutrients and SMB were positively correlated with altitude,but negatively related to EC and SWC.Moreover,soil nutrients and SMB were negatively correlated with soil salt ions.In conclusion,soil nutrients and SMB were mainly influenced by salinity,and were related to altitude,soil depth,and SWC in the areas from the Qarhan Salt Lake to the Xidatan segment.These results imply that the soil quality(mainly evaluated by soil physical-chemical characteristics)is mainly influenced by soil salt ions in the areas surrounding the Qarhan Salt Lake.Our results provide an accurate prediction of how the soil salt ions,soil nutrients,and SMB respond to the changes along a salt gradient.The underlying mechanisms controlling the soil salt ion distribution,soil nutrients,and SMB in an extremely arid desert climate playa should be studied in greater detail in the future.展开更多
Soil microorganisms play a key role in soil organic matter dynamics, nutrient cycling, and soil fertility maintenance in forest ecosystems, and they are influenced by stand age and soil depth. However, few studies hav...Soil microorganisms play a key role in soil organic matter dynamics, nutrient cycling, and soil fertility maintenance in forest ecosystems, and they are influenced by stand age and soil depth. However, few studies have simultaneously considered these two factors. In this study, we measured soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), soil basal respiration (SBR) rate, and potential extracellular enzyme activity (EEA) in soil to a depth of 60 cm under 10-, 30-, and 40-year-old Scots pine (Pinus sylvestris var. mongolica) stands (Y10, Y30, and Y40, respectively) in plantations in northern China in 2011. Soil water content (SWC), soil pH, soil organic carbon (SOC), and soil total nitrogen (STN) were also measured to explore their effects on soil microbial indices across different stand ages and soil depths. Our results showed that SMBC, SMBN, and the SBR rate were generally higher for the Y30 stand than for the Y10 and Y40 stands. Potential EEA, except forα-glucosidase, decreased significantly with increasing stand age. Soil organic carbon,STN, SWC, and soil pH explained 67%of the variation in soil microbial attributes among the three stand ages. For the same stand age, soil microbial biomass and the SBR rate decreased with soil depth. Lower microbial biomass, lower SBR rate, and lower EEA for the mature Y40 stand indicate lower substrate availability for soil microorganisms, lower soil quality, and lower microbial adaptability to the environment. Our results suggest that changes in soil quality with stand age should be considered when determining the optimum rotation length of plantations and the best management practices for afforestation programs.展开更多
Artemisia sacrorum communities with different growth years were selected to analyse soil nutrient characteristics,the variation in soil microbial properties,and their relationships in the loess hilly region.The result...Artemisia sacrorum communities with different growth years were selected to analyse soil nutrient characteristics,the variation in soil microbial properties,and their relationships in the loess hilly region.The results showed that with an increase in the number of growth years,soil microbial biomass carbon and nitrogen contents as well as soil phosphatase and urease activities initially decreased and then increased in the A.sacrorum communities.The soil organic carbon,organic nitrogen,and total nitrogen contents as well as soil respiration rate showed an increasing trend and reached a maximum at age(a)37.The soil available phosphorus content first decreased and then increased,with the lowest level observed at 18 a.By contrast,soil available potassium initially increased and then decreased.Soil microbial biomass carbon had a significant positive correlation with soil organic carbon,total nitrogen and organic nitrogen,while soil respiration had a significant positive correlation with organic nitrogen,soil phosphatase and organic carbon.Soil respiration had a highly significant positive correlation with organic carbon and total nitrogen,while soil phosphatase had a highly significant positive correlation with total nitrogen and organic nitrogen.In the A.sacrorum communities,the soil organic carbon and total nitrogen contents were mainly affected by soil respiration,soil available potassium content was mainly affected by soil urease activity,and soil organic nitrogen content was mainly affected by soil phosphatase activity.These findings indicate that soil basal respiration,urease activity and phosphatase activity were the major microbial factors affecting the characteristics of the soil nutrients in the A.sacrorum communities.In conclusion,the natural restoration process of A.sacrorum communities can enhance soil microbial activity and improve soil quality.展开更多
Background:Nitrogen(N)deposition alters litter decomposition and soil carbon(C)sequestration by influencing the microbial community and its enzyme activity.Natural atmospheric N deposition comprises of inorganic N(IN)...Background:Nitrogen(N)deposition alters litter decomposition and soil carbon(C)sequestration by influencing the microbial community and its enzyme activity.Natural atmospheric N deposition comprises of inorganic N(IN)and organic N(ON)compounds.However,most studies have focused on IN and its effect on soil C cycling,whereas the effect of ON on microbial enzyme activity is poorly understood.Here we studied the effects of different forms of externally supplied N on soil enzyme activities related to decomposition in a temperate steppe.Ammonium nitrate was chosen as IN source,whereas urea and glycine were chosen as ON sources.Different ratios of IN to ON(Control,10:0,7:3,5:5,3:7,and 0:10)were mixed with equal total amounts of N and then used to fertilize the grassland soils for 6 years.Results:Our results show that IN deposition inhibited lignin-degrading enzyme activity,such as phenol oxidase(POX)and peroxidase(PER),which may restrain decomposition and thus induce accumulation of recalcitrant organic C in grassland soils.By contrast,deposition of ON and mixed ON and IN enhanced most of the C-degrading enzyme activities,which may promote the organic matter decomposition in grassland soils.In addition,theβ-N-acetyl-glucosaminidase(NAG)activity was remarkably stimulated by fertilization with both IN and ON,maybe because of the elevated N availability and the lack of N limitation after long-term N fertilization at the grassland site.Meanwhile,differences in soil pH,soil dissolved organic carbon(DOC),and microbial biomass partially explained the differential effects on soil enzyme activity under different forms of N treatments.Conclusions:Our results emphasize the importance of organic N deposition in controlling soil processes,which are regulated by microbial enzyme activities,and may consequently change the ecological effect of N deposition.Thus,more ON deposition may promote the decomposition of soil organic matter thus converting C sequestration in grassland soils into a C source.展开更多
Introduction:In Central Himalaya,anthropogenic activities have led to the widespread replacement of Banj oak(Quercus leucotrichophora)forest by Chir pine(Pinus roxburghii)for decades.This study was conducted to determ...Introduction:In Central Himalaya,anthropogenic activities have led to the widespread replacement of Banj oak(Quercus leucotrichophora)forest by Chir pine(Pinus roxburghii)for decades.This study was conducted to determine how natural Banj oak,Chir pine,and mixed oak-pine forest would differ in soil microbial biomass and soil nutrients.Soil microbial biomass nitrogen(SMBN)and phosphorus(SMBP),soil organic carbon(SOC)total nitrogen(TN),and total phosphorus(TP)in the 0 to 15 cm soil layer were investigated in the Central Himalayan region in the stands of Banj oak,mixed oak-pine,and Chir pine forest.Results:The SMBN and SMBP were significantly higher in Banj oak and mixed oak-pine forest as compared to Chir pine forest.The ratios of SMBN to TN(SMBN/TN)and SMBP to TP(SMBP/TP)were significantly higher in the Chir pine forest,indicating that in this forest,the proportion of microbial biomass N and P to total soil N and P was higher as compared to Banj oak forest.A similar pattern of variation was found in relation to season across the forests,all with an apparent peak in the rainy season.Conclusion:These results indicate that low microbial biomass N and P may be one of the reasons to create a nutrient poor site in Chir pine forest.The collection of pine litter by local people also impairs the return of nutrients to the soil and makes it difficult for Banj oak to re-invade areas occupied by Chir pine.This calls for cautions in large-scale conversions of the Banj oak forests to coniferous plantations as a forest management practice on concerns of sustaining soil productivity.展开更多
Anthropogenic activities have increased nitrogen(N)deposition in terrestrial ecosystems,which directly and indirectly affects soil biogeochemical processes,including soil respiration.However,the effects of the increas...Anthropogenic activities have increased nitrogen(N)deposition in terrestrial ecosystems,which directly and indirectly affects soil biogeochemical processes,including soil respiration.However,the effects of the increases in N availability on soil respiration are not fully understood.In this study,soil respiration was measured using an infrared gas analyzer system with soil chambers under four N treatments(0,5,15,and 30 g Nm^-2 year^-1 as control,low N(LN),moderate N(MN),and high N(HN),respectively)in camphor tree and slash pine forests in subtropical China.Results showed that soil respiration rates decreased by 37% in the camphor tree forest and 27% in the slash pine forest on average on an annual base,respectively,in the N-fertilized treatments when compared with the control.No significant differences were found in the soil respiration rate among the LN,MN,and HN treatments in both forest types as these fertilized plots reached an adequate N content zone.In addition,soil microbial biomass carbon(C)content and fine root biomass declined in N-treated plots compared to the control.Our results indicated that elevated N deposition might alter the tree growth pattern,C partitioning,and microbial activity,which further affect soil C sequestration by reducing soil respiration in subtropical forests of China.展开更多
Soil soluble organic nitrogen(SON)is one of the most active components in soil nitrogen pools;however,limited information is available with regard to its driving factors,as well as their pathways and degrees of influe...Soil soluble organic nitrogen(SON)is one of the most active components in soil nitrogen pools;however,limited information is available with regard to its driving factors,as well as their pathways and degrees of influence.In this study,structural equation modeling was used to analyze the driving factors,their significance,and pathways that affected SON dynamics in a waterlogged experiment of two typical paddy soils incubated for 80 d after green manure application.Soil p H,Eh,microbial biomass,enzyme activity,and SON dynamics were used to construct the structural equation model.Results showed that soil microbial biomass carbon(MBC),protease,glutamine,and initial organic matter(OM)directly and significantly affected soil SON with path coefficients corresponding to 0.405,0.547,0.523,and-0.623(P<0.01),respectively.Soil microbial biomass carbon and initial OM affected the SON dynamics indirectly through protease and glutamine activity.In addition,pH indirectly affected SON dynamics by glutamine activity.It is implied that soil MBC,protease,glutamine,and initial OM are the key factors affecting SON dynamics in the waterlogged paddy soils after green manure application.Our research indicated that structural equation modeling could provide an effective method to clearly recognize the impact,significance,and pathways of multiple factors on SON dynamics in paddy soils.展开更多
In non-flooded lowland rain forests with low soil phosphorus(P)in parts of Amazonia,P cycling largely occurs via leaf litter recycling by arbuscular mycorrhizal(AM)fungal symbionts.Occasional high input of P into thes...In non-flooded lowland rain forests with low soil phosphorus(P)in parts of Amazonia,P cycling largely occurs via leaf litter recycling by arbuscular mycorrhizal(AM)fungal symbionts.Occasional high input of P into these ecosystems occurs during drought years with increased litterfall.As the length and frequency of drought events are projected to increase in the region,a single-dose nutrient addition experiment was carried out to test how this would impact P cycling.An application rate of 4 kg P ha^(-1) was used,which corresponds to twice the amount of litter-derived P in an average year.It was hypothesized that i)the added mineral P would be immobilized by soil microorganisms,leading to measurable increase in soil microbial biomass carbon(C)and P and ii)AM colonization rate would be reduced by the pulse in mineral P available for plant uptake.The results did not support either of our hypotheses.The addition of P did not have an effect on AM root colonization,nor was P immobilized by soil microbiota during the experimental period.The lack of a difference between the control and treatment at our study site could be attributed to the relatively low one-off dose of P applied that did not change either the colonization rate of roots by AM fungi or the amount of soil available labile P.To obtain a mechanistic understanding of the availability,capture,and use of P by plant-symbiont associations in tropical rain forest ecosystems,further integrated studies of the soil-plant system combining long-term nutrient manipulations,modeling,and experimental approaches are required.展开更多
TTie Ultisols in the Rana de Canamero area in Southwest Spain showed aluminum(Al)phytotoxicity,and the clearance of natural vegetation and decades of intensive conventional agriculture caused the deplation of soil org...TTie Ultisols in the Rana de Canamero area in Southwest Spain showed aluminum(Al)phytotoxicity,and the clearance of natural vegetation and decades of intensive conventional agriculture caused the deplation of soil organic matter(SOM).Therefore,we studied the long-term effects of no tillage and liming using sugar beet foam(SF)and red gypsum(RG),alone or in combination,on the restoration of Ultisols affected by acidification,Al phytotoxicity,and SOM depletion.We measured the main soil chemical properties,soil microbial biomass,soil enzyme activities involved in carbon,nitrogen,phosphorus,and sulfur mineralization,and the emission of volatile organic compounds(VOCs).The results indicated that liming effectively neutralized the soil acidity in the long term and,in combination with no tillage,significantly increased soil microbial biomass and enzyme activities.Twenty-three VOCs were detected using the proton transfer reaction-time of flight(PTR-ToF)technique,and both liming and tillage changed the VOC emission patterns.The greatest difference in VOC emission pattern was observed between no-tilled un-amended soils and tilled lime-amended soils,suggesting the activation of different metabolic pathways within the microbial communities of soils under different management.Differences in VOC emission patterns could be attributed to the decomposition of carbohydrates,which were also sustained by the higher enzyme activities in the lime-amended soils.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.32001324,32071777)Youth Lift Project of China Association for Science and Technology(Grant No.YESS20210370)Heilongjiang Province Outstanding Youth Joint Guidance Project(No.LH2021C012).
文摘Prescribed burning can alter soil microbial activity and spatially redistribute soil nutrient elements.However,no systematic,in-depth studies have investigated the impact of prescribed burning on the spatial patterns of soil microbial biomass in temperate forest ecosystems in Northeast China.The present study investigated the impacts of prescribed burning on the small-scale spatial heterogeneity of microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN)in the upper(0–10 cm)and lower(10–20 cm)soil layers in Pinus koraiensis and Quercus mongolica forests and explored the factors that infl uence spatial variations of these variables after prescribed burning.Our results showed that,MBC declined by approximately 30%in the 10–20 cm soil layer in the Q.mongolica forest,where there were no signifi cant eff ects on the soil MBC and MBN contents of the P.koraiensis forest(p>0.05)after prescribed burning.Compared to the MBC of the Q.mongolica forest before the prescribed burn,MBC spatial dependence in the upper and lower soil layers was approximately 7%and 2%higher,respectively.After the prescribed burn,MBN spatial dependence in the upper and lower soil layers in the P.koraiensis forest was approximately 1%and 13%lower,respectively,than that before the burn,and the MBC spatial variability in the 0–10 cm soil layer in the two forest types was explained by the soil moisture content(SMC),whereas the MBN spatial variability in the 0–10 cm soil layer in the two forests was explained by the soil pH and nitrate nitrogen(NO_(3)^(–)-N),respectively.In the lower soil layer(10–20 cm)of the Q.mongolica forest,elevation and ammonium nitrogen(NH 4+-N)were the main factors aff ecting the spatial variability of MBC and MBN,respectively.In the 10–20 cm soil layer of the P.koraiensis forest,NO_(3)^(–)-N and slope were the main factors aff ecting the spatial variability of MBC and MBN,respectively,after the burn.The spatial distributions of MBC and MBN in the two forests were largely structured with higher spatial autocorrelation(relative structural variance C/[C 0+C]>0.75).However,the factors infl uencing the spatial variability of MBC and MBN in the two forest types were not consistent between the upper and lower soil layers with prescribed burning.These fi ndings have important implications for developing sustainable management and conservation policies for forest ecosystems.
基金Supported by the University Science and Technology Innovation Team Construction Projects of Heilongjiang Province(2013 TD003)
文摘The present study was conducted to see the short term impact of organic and inorganic fertilizers on soil microbial biomass both in spring and summer. Also aimed to observe the correlation between soil microbial biomass and soil DNA. The study concluded that type of fertilizer might alter the soil microbial biomass and DNA contents. In soil treated with organic fertilizers resulted in higher concentrations of microbial biomass and DNA contents in summer as compared to spring dute to increase in temperature. Correspondingly, in case of inorganic fertilizer, concentrations of soil microbial biomass and DNA detected higher in summer instead of spring. The statistical correlation between soil microbial biomass, DNA and ODR in spring and summer along with organic and inorganic fertilizers were calculated highly significant(p>0.01). This study demonstrated the impact of fertilizers and seasonal variations on soil microbial biomass and also revealed significant correlation between soil microbial biomass and soil DNA.
基金Supported by Key Sci-tech Project for Prevention and Control of Major Safe Production Accidents by State Administration of Work Safety in 2015(Shandong-0017-2015AQ)Scientific Research Foundation of Binzhou University(BZXYG1414)Key Research and Development Program of Shandong Province(2015GNC111018)
文摘Soil salinization has become a global issue. Saline and alkaline arable land was taken as research object in this paper and four salt gradients were set(S1: 0.1%; S2:0. 5%; S3:0.9%; S4:1.3%). Through the addition of different substrates( CK: no addition of substrate; N: addition of nitrogen source; C: addition of glucose,C + N: addition of glucose and nitrogen source) to soil,it analyzed the influence of salt content on the soil microbial biomass carbon( SMBC) for the purpose of surveying the response mechanism of soil carbon turnover to salt stress. Results indicated that after addition of different substrates,the SMBC in high salt content(S3 and S4) is obviously lower than that in low salt content( S1 and S2). The decline rate of S3 and S4 is 5. 4% and 14. 2% for no addition of substrate; the decline rate is 9.0% and 24.0% for addition of nitrogen source; the decline rate is 11.5% and 28.0% for addition of carbon source; the decline rate is 19.5% and 39.5% for addition of carbon source + nitrogen source. Compared with no addition of substrates,addition of nitrogen source could not increase the SMBC. Addition of carbon source and carbon + nitrogen can significantly increase the SMBC,and the increase in low salt content soil( 80.0%- 81.0% and 58.0%- 59.0%) is obviously higher than high salt content soil( 52.0%- 69.0%and 34.0%- 50.0%). Generally,when the soil salt content is low( 0.5%),the influence of different substrate treatment is little on the SMBC,and increasing the soil salt content can obviously reduce the SMBC.
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.
基金BSG is supported by Science Foundation Ireland grant no.07/SK/B1236b.
文摘Introduction:The availability of essential nutrients,such as nitrogen(N)and phosphorus(P),can feedback on soil carbon(C)and the soil microbial biomass.Natural cycles can be supplemented by agricultural fertiliser addition,and we determined whether the stoichiometry and nutrient limitation of the microbial biomass could be affected by an unbalanced nutrient supply.Methods:Samples were taken from a long-term trial(in effect since 1968)with annual applications of 0,15 and 30 kg P ha^(−1) with constant N and potassium.Soil and microbial biomass CNP contents were measured and nutrient limitation assessed by substrate-induced respiration.Linear regression and discriminant analyses were used to identify the variables explaining nutrient limitation.Results:Soil and biomass CNP increased with increasing P fertiliser,and there was a significant,positive,correlation between microbial biomass P and biomass C,apart from at the highest level of P fertilisation when the microbial biomass was over-saturated with P.The molar ratios of C:N:P in the microbial biomass remained constant(homeostatic)despite large changes in the soil nutrient ratios.Microbial growth was generally limited by C and N,except in soil with no added P when C and P were the main limiting nutrients.C,N and P,however,did not explain all the growth limitation on the soils with no added P.Conclusions:Increased soil C and N were probably due to increased net primary production.Our results confirm that C:N:P ratios within the microbial biomass were constrained(i.e.homeostatic)under near optimum soil conditions.Soils with no added P were characterised by strong microbial P limitation and soils under high P by over-saturation of microorganisms with P.Relative changes in biomass C:P can be indicative of nutrient limitation within a site.
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jointly supported by the National Natural Science Foundation of China(41621001,32061123006)the Fund of Ningxia Independent Innovation on Agriculture Science and Technology,China(NGSB-2021-14-04).
文摘Soil salinization has adverse effects on the soil physical-chemical characteristics.However,little is known about the changes in soil salt ion concentrations and other soil physical-chemical characteristics within the Qarhan Salt Lake and at different soil depths in the surrounding areas.Here,we selected five sampling sites(S1,S2,S3,S4,and S5)alongside the Qarhan Salt Lake and in the Xidatan segment of the Kunlun Mountains to investigate the relationship among soil salt ion concentrations,soil physical-chemical characteristics,and environmental variables in April 2019.The results indicated that most sites had strongly saline and very strongly saline conditions.The main salt ions present in the soil were Na^(+),K^(+),and Cl^(-).Soil nutrients and soil microbial biomass(SMB)were significantly affected by the salinity(P<0.05).Moreover,soil salt ions(Na^(+),K^(+),Ca2+,Mg^(2+),Cl^(-),CO_(3)^(2-),SO_(4)^(2-),and HCO_(3)^(-))were positively correlated with electrical conductivity(EC)and soil water content(SWC),but negatively related to altitude and soil depth.Unlike soil salt ions,soil nutrients and SMB were positively correlated with altitude,but negatively related to EC and SWC.Moreover,soil nutrients and SMB were negatively correlated with soil salt ions.In conclusion,soil nutrients and SMB were mainly influenced by salinity,and were related to altitude,soil depth,and SWC in the areas from the Qarhan Salt Lake to the Xidatan segment.These results imply that the soil quality(mainly evaluated by soil physical-chemical characteristics)is mainly influenced by soil salt ions in the areas surrounding the Qarhan Salt Lake.Our results provide an accurate prediction of how the soil salt ions,soil nutrients,and SMB respond to the changes along a salt gradient.The underlying mechanisms controlling the soil salt ion distribution,soil nutrients,and SMB in an extremely arid desert climate playa should be studied in greater detail in the future.
基金This study was supported by projects of the National Natural Science Foundation of China(Nos.31972939,31630009 and 31670325)the National Basic Research Pro-gram of China(No.2016YFC0500701)+1 种基金the Research Fund of the State Key Laboratory of Soil and Sustainable Agri-culture,Nanjing Institute of Soil Science,Chinese Academy of Sciences(No.Y412201439)the University Con-struction Projects from the Central Authorities in Beiing of China.
文摘Soil microorganisms play a key role in soil organic matter dynamics, nutrient cycling, and soil fertility maintenance in forest ecosystems, and they are influenced by stand age and soil depth. However, few studies have simultaneously considered these two factors. In this study, we measured soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), soil basal respiration (SBR) rate, and potential extracellular enzyme activity (EEA) in soil to a depth of 60 cm under 10-, 30-, and 40-year-old Scots pine (Pinus sylvestris var. mongolica) stands (Y10, Y30, and Y40, respectively) in plantations in northern China in 2011. Soil water content (SWC), soil pH, soil organic carbon (SOC), and soil total nitrogen (STN) were also measured to explore their effects on soil microbial indices across different stand ages and soil depths. Our results showed that SMBC, SMBN, and the SBR rate were generally higher for the Y30 stand than for the Y10 and Y40 stands. Potential EEA, except forα-glucosidase, decreased significantly with increasing stand age. Soil organic carbon,STN, SWC, and soil pH explained 67%of the variation in soil microbial attributes among the three stand ages. For the same stand age, soil microbial biomass and the SBR rate decreased with soil depth. Lower microbial biomass, lower SBR rate, and lower EEA for the mature Y40 stand indicate lower substrate availability for soil microorganisms, lower soil quality, and lower microbial adaptability to the environment. Our results suggest that changes in soil quality with stand age should be considered when determining the optimum rotation length of plantations and the best management practices for afforestation programs.
基金Financial support was provided by the Talent Training Program of the West of the Chinese Academy of Sciences(2008DF02)National Chinese Medicine Resources Survey Project[Finance and Social Work(2017)66].
文摘Artemisia sacrorum communities with different growth years were selected to analyse soil nutrient characteristics,the variation in soil microbial properties,and their relationships in the loess hilly region.The results showed that with an increase in the number of growth years,soil microbial biomass carbon and nitrogen contents as well as soil phosphatase and urease activities initially decreased and then increased in the A.sacrorum communities.The soil organic carbon,organic nitrogen,and total nitrogen contents as well as soil respiration rate showed an increasing trend and reached a maximum at age(a)37.The soil available phosphorus content first decreased and then increased,with the lowest level observed at 18 a.By contrast,soil available potassium initially increased and then decreased.Soil microbial biomass carbon had a significant positive correlation with soil organic carbon,total nitrogen and organic nitrogen,while soil respiration had a significant positive correlation with organic nitrogen,soil phosphatase and organic carbon.Soil respiration had a highly significant positive correlation with organic carbon and total nitrogen,while soil phosphatase had a highly significant positive correlation with total nitrogen and organic nitrogen.In the A.sacrorum communities,the soil organic carbon and total nitrogen contents were mainly affected by soil respiration,soil available potassium content was mainly affected by soil urease activity,and soil organic nitrogen content was mainly affected by soil phosphatase activity.These findings indicate that soil basal respiration,urease activity and phosphatase activity were the major microbial factors affecting the characteristics of the soil nutrients in the A.sacrorum communities.In conclusion,the natural restoration process of A.sacrorum communities can enhance soil microbial activity and improve soil quality.
基金supported by the National Natural Science Foundation of China(32022054,31901137)China Postdoctoral Science Foundation(2018M640263)+2 种基金Instrument Developing Project of CAS(YJKYYQ20190079)Strategic Priority Research Program of CAS(Grant No.XDA28120100)Youth Innovation Promotion Association of CAS(2019198)。
文摘Background:Nitrogen(N)deposition alters litter decomposition and soil carbon(C)sequestration by influencing the microbial community and its enzyme activity.Natural atmospheric N deposition comprises of inorganic N(IN)and organic N(ON)compounds.However,most studies have focused on IN and its effect on soil C cycling,whereas the effect of ON on microbial enzyme activity is poorly understood.Here we studied the effects of different forms of externally supplied N on soil enzyme activities related to decomposition in a temperate steppe.Ammonium nitrate was chosen as IN source,whereas urea and glycine were chosen as ON sources.Different ratios of IN to ON(Control,10:0,7:3,5:5,3:7,and 0:10)were mixed with equal total amounts of N and then used to fertilize the grassland soils for 6 years.Results:Our results show that IN deposition inhibited lignin-degrading enzyme activity,such as phenol oxidase(POX)and peroxidase(PER),which may restrain decomposition and thus induce accumulation of recalcitrant organic C in grassland soils.By contrast,deposition of ON and mixed ON and IN enhanced most of the C-degrading enzyme activities,which may promote the organic matter decomposition in grassland soils.In addition,theβ-N-acetyl-glucosaminidase(NAG)activity was remarkably stimulated by fertilization with both IN and ON,maybe because of the elevated N availability and the lack of N limitation after long-term N fertilization at the grassland site.Meanwhile,differences in soil pH,soil dissolved organic carbon(DOC),and microbial biomass partially explained the differential effects on soil enzyme activity under different forms of N treatments.Conclusions:Our results emphasize the importance of organic N deposition in controlling soil processes,which are regulated by microbial enzyme activities,and may consequently change the ecological effect of N deposition.Thus,more ON deposition may promote the decomposition of soil organic matter thus converting C sequestration in grassland soils into a C source.
文摘Introduction:In Central Himalaya,anthropogenic activities have led to the widespread replacement of Banj oak(Quercus leucotrichophora)forest by Chir pine(Pinus roxburghii)for decades.This study was conducted to determine how natural Banj oak,Chir pine,and mixed oak-pine forest would differ in soil microbial biomass and soil nutrients.Soil microbial biomass nitrogen(SMBN)and phosphorus(SMBP),soil organic carbon(SOC)total nitrogen(TN),and total phosphorus(TP)in the 0 to 15 cm soil layer were investigated in the Central Himalayan region in the stands of Banj oak,mixed oak-pine,and Chir pine forest.Results:The SMBN and SMBP were significantly higher in Banj oak and mixed oak-pine forest as compared to Chir pine forest.The ratios of SMBN to TN(SMBN/TN)and SMBP to TP(SMBP/TP)were significantly higher in the Chir pine forest,indicating that in this forest,the proportion of microbial biomass N and P to total soil N and P was higher as compared to Banj oak forest.A similar pattern of variation was found in relation to season across the forests,all with an apparent peak in the rainy season.Conclusion:These results indicate that low microbial biomass N and P may be one of the reasons to create a nutrient poor site in Chir pine forest.The collection of pine litter by local people also impairs the return of nutrients to the soil and makes it difficult for Banj oak to re-invade areas occupied by Chir pine.This calls for cautions in large-scale conversions of the Banj oak forests to coniferous plantations as a forest management practice on concerns of sustaining soil productivity.
基金supported financially by the Chinese Forestry Specific Research Fund for Public Benefits (No.200804030)New Century Excellent Youth Program of the Ministry of Education of China (No.NCET-10-0151)+1 种基金‘100-Talents’ Scholar Program of Hunan Province, ChinaCentral South University of Forestry and Technology, China (No.0842)
文摘Anthropogenic activities have increased nitrogen(N)deposition in terrestrial ecosystems,which directly and indirectly affects soil biogeochemical processes,including soil respiration.However,the effects of the increases in N availability on soil respiration are not fully understood.In this study,soil respiration was measured using an infrared gas analyzer system with soil chambers under four N treatments(0,5,15,and 30 g Nm^-2 year^-1 as control,low N(LN),moderate N(MN),and high N(HN),respectively)in camphor tree and slash pine forests in subtropical China.Results showed that soil respiration rates decreased by 37% in the camphor tree forest and 27% in the slash pine forest on average on an annual base,respectively,in the N-fertilized treatments when compared with the control.No significant differences were found in the soil respiration rate among the LN,MN,and HN treatments in both forest types as these fertilized plots reached an adequate N content zone.In addition,soil microbial biomass carbon(C)content and fine root biomass declined in N-treated plots compared to the control.Our results indicated that elevated N deposition might alter the tree growth pattern,C partitioning,and microbial activity,which further affect soil C sequestration by reducing soil respiration in subtropical forests of China.
基金supported by the National Natural Science Foundation of China(No.41671490)the Science and Technology Innovation Fund Project of Fujian Agriculture and Forestry University,China(No.KF2105074)
文摘Soil soluble organic nitrogen(SON)is one of the most active components in soil nitrogen pools;however,limited information is available with regard to its driving factors,as well as their pathways and degrees of influence.In this study,structural equation modeling was used to analyze the driving factors,their significance,and pathways that affected SON dynamics in a waterlogged experiment of two typical paddy soils incubated for 80 d after green manure application.Soil p H,Eh,microbial biomass,enzyme activity,and SON dynamics were used to construct the structural equation model.Results showed that soil microbial biomass carbon(MBC),protease,glutamine,and initial organic matter(OM)directly and significantly affected soil SON with path coefficients corresponding to 0.405,0.547,0.523,and-0.623(P<0.01),respectively.Soil microbial biomass carbon and initial OM affected the SON dynamics indirectly through protease and glutamine activity.In addition,pH indirectly affected SON dynamics by glutamine activity.It is implied that soil MBC,protease,glutamine,and initial OM are the key factors affecting SON dynamics in the waterlogged paddy soils after green manure application.Our research indicated that structural equation modeling could provide an effective method to clearly recognize the impact,significance,and pathways of multiple factors on SON dynamics in paddy soils.
基金a M.Sc.grant from the Brazilian Coordination for the Improvement of Higher Education Personnel(CAPES)a post-doctoral grant from the Portuguese Foundation for Science and Technology(No.SFRH/BPD/77795/2011)。
文摘In non-flooded lowland rain forests with low soil phosphorus(P)in parts of Amazonia,P cycling largely occurs via leaf litter recycling by arbuscular mycorrhizal(AM)fungal symbionts.Occasional high input of P into these ecosystems occurs during drought years with increased litterfall.As the length and frequency of drought events are projected to increase in the region,a single-dose nutrient addition experiment was carried out to test how this would impact P cycling.An application rate of 4 kg P ha^(-1) was used,which corresponds to twice the amount of litter-derived P in an average year.It was hypothesized that i)the added mineral P would be immobilized by soil microorganisms,leading to measurable increase in soil microbial biomass carbon(C)and P and ii)AM colonization rate would be reduced by the pulse in mineral P available for plant uptake.The results did not support either of our hypotheses.The addition of P did not have an effect on AM root colonization,nor was P immobilized by soil microbiota during the experimental period.The lack of a difference between the control and treatment at our study site could be attributed to the relatively low one-off dose of P applied that did not change either the colonization rate of roots by AM fungi or the amount of soil available labile P.To obtain a mechanistic understanding of the availability,capture,and use of P by plant-symbiont associations in tropical rain forest ecosystems,further integrated studies of the soil-plant system combining long-term nutrient manipulations,modeling,and experimental approaches are required.
基金We are grateful to the Comunidad de Madrid(Spain)and European Structural and Investment Funds for the financial support(No.AGRISOST-CM S2013/ABI-2717)to maintain the field experiment.
文摘TTie Ultisols in the Rana de Canamero area in Southwest Spain showed aluminum(Al)phytotoxicity,and the clearance of natural vegetation and decades of intensive conventional agriculture caused the deplation of soil organic matter(SOM).Therefore,we studied the long-term effects of no tillage and liming using sugar beet foam(SF)and red gypsum(RG),alone or in combination,on the restoration of Ultisols affected by acidification,Al phytotoxicity,and SOM depletion.We measured the main soil chemical properties,soil microbial biomass,soil enzyme activities involved in carbon,nitrogen,phosphorus,and sulfur mineralization,and the emission of volatile organic compounds(VOCs).The results indicated that liming effectively neutralized the soil acidity in the long term and,in combination with no tillage,significantly increased soil microbial biomass and enzyme activities.Twenty-three VOCs were detected using the proton transfer reaction-time of flight(PTR-ToF)technique,and both liming and tillage changed the VOC emission patterns.The greatest difference in VOC emission pattern was observed between no-tilled un-amended soils and tilled lime-amended soils,suggesting the activation of different metabolic pathways within the microbial communities of soils under different management.Differences in VOC emission patterns could be attributed to the decomposition of carbohydrates,which were also sustained by the higher enzyme activities in the lime-amended soils.
