Abstract:An experiment was carried out in Dianchi catchment,a severely eroded region,in Kunming,Yunnan Province,Southwest China.In the experiment,the technique of ¹³⁷Cs tracer is introduced as a new approach to the study of soil erosion,though it has already been extensively used in this field the world over and yield numerous fruits in the study on deposition,erosion and transportation of silts in the process of soil erosion.The method of using ¹³⁷Cs as soil tracer makes it feasible to study soil erosion on the catchment scale,moreover,it is reliable and time-and labor-saving.The Yun-Gui Plateau,squatting in Southwest China,is one of the most severely eroded regions in the southern part of the country.Owing to lack of historic data,it is hard to predict the mid-long term(ca.50 a) mean soil erosion rate,just by measuring for a short term.In this experiment the technique was used to study distribution of soil erosion intensity in the D ianchi Catchment.Results show that soil erosion rate along a slope followed a decreasing order of mid-slope > lower-slope > upper slope;and among the lands different in land use,cultivated land > uncultivated land.The research also revealed that the average soil erosion rate in the catchment was 1 280 t km^-2 a^-1,and in the category of light erosion.Position in the landform,slope and land use pattern are major factors affecting soil erosion.

Abstract:Based on the rule of wind friction decomposition on the rough wall in the turbulent boundary layer,threshold velocity of soil erosion,sand transport rate and wind erosion rate were studied to explore effect of roughn essele ments on soilwind erosion,and thus a soil erosion theory was derived,from which some theoretical results were developed that the exponential relation between threshold velocity and coverage,the exponential relation between threshold velocity and stubble height for farm lands after harvesting,and the theoretical formulas of the effect of wind velocity and coverage(or stubble height) on sand tran sportrate and wind erosion rate.They were applied to and verified in a series of experiments on wind erosion of natural land and farmland,and found to be extensively applicable.

Abstract:The study on loess collapsib ility has long ignored role of CaCO₃ W ith the a id of scann ing electron microscope(SEM) and X ray energy dispersivemicroanalys is(EDX or EDS),CaCO₃ distribution in loess was explored.Some indoor expermi en ts were carried out to smiulate loess collapse and study b eh aviors o f CaCO₃ in the process.Results show that bewt een loess particles exists plenty of CaCO₃,which is easily leached with irrigation water and lost in the process Its loss th rough movement is much greater than th rough leach ing,and increas ing with the percolation rate of irrigation water.Then CaCO₃ accumu lates in the subsoil layer.

Abstract:Spatial heterogeneities of soil hydraulic characteristics and soil physical properties,and their relat ionship maybe differentat different scales Scaling analysis of soil hyd raulic characteristics(field capacity,wilting point and saturated hydraulic conductivity) and physical properties(particle size distributions,bulk density and organic carbon content) was carried out using the Detrended Fluctuation.Analysis(DFA) method Results showth at spatial variability analysis and scaling transformation(e.g.up-scaling) could be performed only with in a certain range of scales.The fluctuation pattern cannot be up scaled.when the scale is too small,because it can not get free from spatial in terdependency and hence reflects local scale features only.But when the scale is too large scale,it is hard to define dominant factors,including those with certa in characteristic length scale.For the sandy loam cinnam on soil in the study,the ranges of up scaling for field capacity,hydraulic conductivity,bulk density and organic carbon content are relatively large,being 55~155,50~125,50~125,and 50~135m,respectively,but small for sand,silt and clay con tents,being 50~85 m,indicating that it is essential to determine the range of up scaling before spatial scaling transformation is performed.

Abstract:An in-lab unidimensional soil-column venting experiment was conducted with sandy soil to investigate mass transfer process of non-aqueous phase liquid(benzene) in the soil vapor extraction system composed of gas,water,oil and solid substances at four moisture levels(0%,21.9%,36.6% and 51.2%).Results of the experiment were compared with those of the prediction using the Local Phase Equilibrium Model(LPEM) and Non-Equilibrium Kinetic Model(NEKM).When the moisture level was 0%,the LEM model fitted well the ventilation process of the soil column;but with the moisture level rising,its prediction seriously deviated from the experiment results.However,in this case,the prediction of the NEKM model fitted better with the experiment results.The findings show that moisture level of the soil affects Gas-NAPL mass transfer.The LPEM model may be used to describe the process of SVE remediation in dry soil,whereas the NEKM model should be used in soils higher in moisture content.

Abstract:Delayed geochemical hazard(DGH) of soil elements in soil will do serious harm to the environment.Base on the mathematical model of DGH,DGH characteristics of Cu element in the soils of Daxing Town and Yicheng.Town of Hefei were studied and compared.Results show that Cu element in the soil of Daxing Towntends to shift from release of TRCP_Cu(total releasable content of Cu element) to that of Cu_E+C(effective content of Cu element),and its DGH model was y=0.005 6x³-0.436.1x²+ 11.28x-90.803.In the soil of about 38% of the land area of Daxing Town,DGH of Cu element is very likely to break out,because Daxing Town is an important industrial town of Hefei.But the Cu element in the soil of Yicheng Town is not likely to break in to DGH,because the town is dominated with agriculture and livestock breeding.The study of DGH is of great significance to early warning of soil heavy metal pollution.

Abstract:Diversity of the soils and variability of the soil properties of karst microrelieves were exp lored through survey and sampling analysis of the soils in micro-habitats of the karst forest ecosystem of Maolan,South Guizhou.Results show that soil distribution and soil properties varied sharp ly spatially with the micro-habitats,like pit,gully,crevice,cavern and flat land.Cavern was obviously higher than pit,gully,crevice and flat land in sand content,> 5 mm aggregate content and bulk density of the soil,but lower in < 1 mm aggregate content,aeration porosity,humic acid,total nitrogen,total phosphorus and available N;Pit was higher than the others in < 1 mm aggregate content,aeration porosity,organic carbon,humic acid,total nitrogen,available P,available K,available Cu and Zn,but lower in clay content,> 5 mm aggregate content,and bulk density than earthy flat land,gully,and crevice.Gully was markedly lower than flatland and crevice in clay content,but higher in 1 mm aggregate content,organic carbon,humic acid and total N.Crevice was obviously lower than earthy flatland,and gully in organic carbon and available K.Therefore,the soils in microrelieves of the karst region can primarily be divided into four types,i.e.cavern soil,crevice soil,earthy-flatland-gully soil,and pitsoil,of which flatland-gully soil is most extensively distributed and followed by crevice soil.

Abstract:In this study,physical protection of soil organic carbon(SOC) in particle size fractions of paddy soils was investigated using cross-site study of top soil samples from three sites of long-term soil-agro-ecosystem experiments from South China.Undisturbed top soil samp les collected at 0～15 cm were used for size factions of micro-aggregates by low-energy ultra-sonic dispersion procedure.SOC content and its distribution in particle-size fractions under different fertilization and cultivation treatments were analyzed to address the relationship between SOC accumulation and physical protection of aggregates.The results were as follows:the distribution of particle-size fractions of three tested paddy soils was dominated by 200～20 μm and 20～2μm fractions(22%～43% and 27%～44%),showing prominent micro-aggregation in these paddy soils.SOC content was higher in fractions of 2 000～200μm and < 2μm than in the other fractions,while labile organic carbon(LOC) content and LOC/SOC ration higher in the coarse fraction of 2 000～200 μmonly.The newly accumulated young SOC found its fate mainly in the coarse fraction of 2 000～200 μmin active response to tillage and fertilization treatments.Of the three studied paddy soils,SOC and LOC in the red-earth derived paddy soil showed most intense response to fertilization treatments,exerting a most prominent trend of SOC accumulation under well management practices.Furthermore,statistic analysis indicated significant parabola relationship between SOC accumulation in bulk soil and in 2 000～200 μm coarse fraction.Therefore,it is inferred that accumulation of young SOC of top soil may reach a saturation controlled by the physical protection in the coarse particle-size fractions.However,as shown by the calculation using the curve obtained,the maximum protection capacity by the coarse micro-aggregates of the three tested paddy soils had not yet realized,still possessing obviously a potential of carbon sequestration.The higher potential in the red-earth derived paddy soil suggests that C sequestration had been mostly obvious in paddy soils from South China especially those in the Red soil region.Physical protection in soil aggregates and carbon sequestration of paddy soil may also involve the binding of physically protected SOC in aggregates and chemical stabilization of SOC in the paddy soils rich in iron oxy-hydrates.

Abstract:Studies were carried out on B radford reactive soil protein(BRSP) concentrations in aggregates different in particle size and relations of BRSP with soil organic C and total N in fields of long-term fertilization experiment under a continuous rice-rice cropp ing system.At the same time,in order to simplify the process of the soil BRSP test,attempts were made to exp lore feasibility of determining soil BRSP concentration using whole soil passed through 1 mm sieve instead of 1～2 mm soil aggregates.Results show that long-term fertilization significantly affected concentrations of soil total BRSP(T-BRSP) and easily extractable BRSP(EE-BRSP) in 1～2 mm aggregate.Soil BRSP was increased sharply by application of inorganic fertilizer p lus organic manure,especially in the treatment of N,P,K p lus rice straw.After 25 years of continuous fertilization,regardless of treatments,both T-BRSP and EE-BRSP in 1～2 mm aggregates were highly correlated with SOC and TN.It was found in the experiment that BRSP existed in < 1 mm aggregates and showed a tendency similar to what the aggregates did in variation from treatment to treatment.It was also discovered that it is feasible to determine soil BRSP using the whole soil passed through 1 mm sieve,because both T-BRSP and EE-BRSP in the whole soil are highly correlated not only with those in 1～2 mm aggregates,but also with SOC and TN in the soil.

Abstract:Effects of soil moisture contents and phosphorus(P) application rate on form of soil inorganic P in red paddy soil were investigated through pot and field experiments.Results show in terms of percen tage against the total P,in organic P of different forms were lined in a decreasing order of O-P > Fe-P > Al-P> Ca-P.In the pot expermient,with increasing days of rice growth or increasing soil moisture and Papplication rate,contents of Al-P,Fe-P and Ca-P decreased,but content of O-P increased,whereas,in the field experiment,the effect of soil moisture content was markedly observed only on Ca-P in the early and late rice growth periods and on O-P in the mid grwoth period,and nothing was on Al-P and Fe-P Compostion of soil in organic P was closed related with P application rate.In the pot experiment,the effect of soil moisture on soil inorganic P,regard less of form,was not as significant,while the effect of P application rate wassign ificantly positive on Al-P and Fe-P in the early rice growth periods,and on Ca-P in the mid growth period,but little on O-P and Ca-P in the late growth period.Furthermore,the effect of interaction between soil moisture and P application rate was distinct on the four forms of in organic P.

Abstract:Changshu County in Jiangsu Province was chosen as a typical region in investigating variation of soil fertility between 2000 and 2006 in the Yangtze River Delta.Two sets of soil chemical property data were compared and the in tegrated soil fertility index(IFI) method was also used to evaluate soil fertility as a whole.Results show that soil organic matter(SOM),tolal nitrogen(TN),total phosphorus(TP),total potassium(TK),CEC,available phosphorus(AP),available potassium(AK) all increased in the fields after 6 years of cultivation,while pH decreased.Among all the changes,TN,TK and AP in creased most significantly.In this study,the increment of TN,TK and AP varied in the range of 0~4 g kg^-1,1~2 g kg^-1 and 0~5 mg kg^-1,respectively.The IFIs obtained in soil surveys of both 2006 and 2000 were mainly scattered in the 2 top grades,excellent and good,and the in tegrated soil fertility in 2006 displayed an increasing trend as compared to that in 2000,indicating that the soil fertility was improved during the cultivation.

Abstract:In an experiment using the flat-stand method,11 strains of bacteria antagonistic against Verticillium dahliae Kleb(Vd) were isolated from healthy cotton plants growing in cotton fields seriously infected with verticillium wilt.Their verticilliuminhabiting rates ranged from 70% to 87.4%.Cotton Verticillium wilt disease was effectively suppressed by 57% over the control by app lication of a mixture of the antagonistic bacteria along with organic fertilizer.Microbial communities were significantly changed in cotton rhizospheric soils in Treatment VS(app lication of mixed antagonistic strain solution),Treatment VF(organic manure),and Treatment VFS(strain solution plus organic manure),among which Treatment VFS was the highest in disease inhabiting rate,reaching 57%.Significant increase in population of bacteria and actinomyces and decrease in population of pathogen microsclerotia were found in these treatments,as compared with that in the control.Based on the physiological and biochemical determination and the 16S rDNA sequence analysis,HJ-5 and DF-15 strains were identified as Bacillus vallism ortis,while DF-14 strain as Bacillus subtilis.This is the first paper that reports Bacillus vallismortis is antibiotic against Verticillium dahliae.

Abstract:Effects of complex heavy metal pollution on biomass and community structure of soil microbes in paddy soil were studied with the aid of the chloroform fumigation-extraction,diluted agar plate cultivation and phospholip idfatty acid(PLFA) techniques,using soil samples collected from paddy fields in the vicinity of a small smeltery in Fuyang County,Zhejiang Province.Results show that soil microbial biomass was reduced in paddy fields polluted by Cu,Zn,Cd and Pb together.Soil microbial community structure was also affected by complex pollution and about 41.82% of the change was attributed to the pollution.Soils high in heavy metal pollution were dominated with microbes high in fatty acids of 12:0,i15:0,i17:0,18:0,i16:0 and 19:0,while soils low in heavy metal pollution with microbes high in fatty acids of 20:ω6,9c,20:0,16:1ω9c,a15:0,a16:0,18:1ω7,10Me16:0 and 10Me19:01.With pollution rising in degree,soil microbes decreased in C_mic/N_mic,fungi increased relatively,and the amount of actinomyce and G-bacteria decreased relatively.

Abstract:Dynamics of soil microorganism s in stipa pu rpurea alp ine steppes different in degradation intensity in North Tibet Plateau were studied.Four p lots were selected,coincident in parent rock and soil texture,but different in degradation intensity,i.e.non-degraded(ND),slightly degraded(SD),moderately degraded(MD) and severely degraded(VD).Soil samp les were taken using the grid method from the four p lots in both warm and cold seasons.Results indicate that under alp ine arid conditions,both degradation intensity and seasonal variation have significant influences on soil microbial activities in alp ine steppe.A similar trend of variation of soil bacteria population,microbial biomass(carbon(C) and nitrogen(N)) and soil enzyme(cellulase,urease and alkaline phosphatase) activities as a whole was found in both warm and cold seasons,and so was high correlation between the two.In the warm season,the steppes were in the order of SD > ND >MD > VD in soil microbial activity.The numbers of fungi and actinomycetes were positively correlated with soil microbial biomass,but negatively with soil enzyme activity to a varying extent in warm season,while an opposite trend was found in cold season.The soil microbial activities in cold season declined significantly,compared with those in warm season.The ratio of soil bacteria in warm season to that in cold season in the four grades of steppes was 206 10,251.7,18.4 and 87.4,respectively,of fungi,14.7,1.132,0.6 and 0.9 and of actinomycetes,0.1,10.5,10.0 and 14.9.With respect to ratio of B_C(microbial biomass C) and B_N(microbial biomass N) in warm-season to those in cold-season,SD was the highest and followed by ND,MD,and then VD.and sharp variation of B_N was observed between sea-sons.The ratios of B_C/B_N in cold season and in warm season were more or less the same in variation,but the B_C/B_N.ratio was much higher in cold season than in warm season.However,the values of B_C/T_C and B_N/T_N were higher in cold season than in warm season for all of the four grasslands,except VD,which showed a reverse trend.Soil urease was much higher than other soil enzymes in activity in warm season.The ratio of soil urea activity in warm season to that in cold season ranged from 31.5 to 781.5.The activity of soil cellulolytic enzyme,especially alkaline phosphatase,were higher in cold season than in warm season,and the ratio of the activity in warm season to that in cold season ranged from 0.46 to 1.01 for soil cellulolytic enzyme and 0.40 to 1.37 for alkaline phosphatase.

Abstract:In view of the particularity of the environmental conditions and management model,of the Tarim desert highway shelter forest,and the important roles of the forest in development of the socio economy of South Xinjiang,an experiment was carried out using sampled soils from four layers,0~5 cm,5~15 cm,15~30 cm,30~50 cm,in the forest lands dripirrigated with ground water,2.58,5.75,8.90 and 13.99 g/L^-1 in minera lization degree,respectively.Results showth at there are obvious canonical correlation variab les between soil nutrient,microbe quantity and enzyme activity,which basically represents general correlation between variables;the correlation between soil nutrients and soil microbial biomass is mainly attributed to total N,available N,organic matter,total P of nutrient factors and actinomycetes quantity,microbial biomass C and microbial biomass P,while the correlation between soil nutrients and soilenzyme activity is to organic carbon,available K of soil nutrient factors and catalase activity,phosphatase activity of soil enzyme activity factors;and the correlation between soil microbial biomass and soil enzyme activity is to microb ial biomass P,microbial biomass N,invertase activity,and phosphatase activity of soil enzymes Moreover,vertical differences between these three groups of comprehensive factors were found So,the effects of mineralization degree of ground water used as irrigation water on soil nutrients and microbial biomass in the Tarim desert highway shelter forest land are remarkab le,and ground water,high in mineralization degree goes against soil nutrien taccumulation and microbe survival.

Abstract:A pot experiment was carried out using soils,1.2 and 1.5 g cm^-3 in bulk den ity,was experimented to study effects of soil compaction on soil respiration intensity and CO₂ concen tration in various soil layers,and responses of cucumber to soil compaction in plant growth and fruit quality.Results show that CO₂ concentration and respiration in tensity in the soil layers below the surface in the compacted soil(CS) were higher than in the loose soil(LS).The extension of roots was hindered in CS,leading to significantly lower dry weight of the roots,decreased root/shoot ratio,and lower fresh weight and dry weight of shoots,too,but certain increase in drymatter content.Fewer extended leaves,more yellow leaves and earlier senescence were found of the plants in CS that in LS A nd further more,fruit expansion rate suppressed,soluble sugar content in fruit lowered,contents of soluble protein and organic acid significantly in creased,sugar/acid ratio declined sharply,and fruit flavor worsened.

Abstract:A method for rap id analysis onsite of organic matter in sediment and soil is recommended.It is based on researches on the phenomenon of chemiluminescence of organic matter in sediment and soil reacting with ozone.A curve of chemiluminescence regularity was obtained by using an experimental prototype instrument,and used to analyze content and characteristics of the organic matter in sediment and soil,such as active organic carbon,hardly-oxidized organic matter,etc.Effectiveness of the method was verified comparing its results with those of the existing detection method.Based on the finding that sediments and soils varied sharply in chemiluminescence feature from type to type,a concept of "soil finger-print" or coding of soil properties is recommended.

Abstract:A rbuscular mycorrhiza(AM) is a kind of mycorhiza,most extensively distributed in nature and very common in polluted soils of various types,such as heavy metal contaminated soils,organic contaminated soils,and combined pollutant contaminated soils.It has been demonstrated that AM fungi contribute to quality safety of farm products produced in contaminated soils through 1) promoting degradation and transformation of organic pollutants,thus reducing their residues in the soil and farm products therefrom;2) enhancing crop tolerance to heavy metals,thus inhibiting its accumulation in farm products;3) improving crop nutrition,thus strengthening cropresistance to disease,thus calling for less fertilizers and pesticides and hence leaving less residues in the soil and farm products therefrom.So the potential of AM fungi in improving quality safety of farm products is significant.In the years to come,more efforts should be devoted in the following fields:1) screen and domesticate AM fungal strains that are capable of reducing residues of pollutants in farm products;2) explore effects and mechanisms of AM fungi improving quality safety of farm products;3) prove up interaction between AM fungi and other biofertilizers and biopesticides;and 4) conduct basic research on app lication of AM fungi in farming production.

Abstract:Abstract Soil organic matter(SOM) is a kind of natura lorganic matter,extremely complex in composition and important in soil chemistry.Interms of its chemical nature,SOM consists of twoma in portions,that is,humic substances(HS) and non-humic substances.HS is the princ ipal body of SOM,and plays a vital role in soil nutrient recycling and carbon sequestration.SOM attracts numerous scientists for itps importance and complexity.To better understand soil HS and find new research area,this review sums up status quo of the study on form ation-transformation and itps stability(including formation sequences of huminc fractions,inter-transformation,driving factors,isotope discrimination and thermodynamic stability,etc.),chemical composition and structural characteristics(including extraction,purification and structure characterization,etc.) of soil HS and its response to human factors(includ ing the effects of tillage,fertilization and land use,etc.) and puts forth suggestions that further efforts should be made to apply advanced technology to the study,and resume the study of chemical fractionation and structural characteristics of HS and relat ionship between HS formationtransformation and agricultural practices.

Abstract:环境地球化学基线(Environmental geochemicalbaseline)一词出现在国际地质对比计划的国际地球化学填图项目(IGCP259)和全球地球化学基线项目(IGCP360)中,在国际地球化学填图计划中,环境地球化学基线的定义为地球表层物质中化学物质(元素)浓度的自然变化^[1].但随着人们对环境地球化学基线问题研究的深入,环境地球化学基线的定义也不断明确:地球化学基线将某一地区或数据集合作为参照时某一元素在特定物质中(土壤、沉积物、岩石)的自然丰度,并可以表述为区分地球化学背景和异常的单一的极限^[2].基线与取样时间、取样地点、取样方法、测试方法、分析技术等有关^[3].

Abstract:多环芳烃(Polycyclic Aromatic Hydrocarbons,PAHs)是具有“三致作用”的持久性有机污染物,是污泥土地利用时重点控制的有机污染物之一^[1,2].国外关于污泥中多环芳烃的研究比较深入^[3~7],我国关于污泥中多环芳烃的研究报道并不多^[8~9].随着污水处理率的提高,上海污泥的量也越来越大,污泥土地利用是上海今后污泥处理处置的有效途径之一^[10,11].为了解上海污泥中多环芳烃的分布特征,为污泥土地合理利用提供科学依据,我们应用索氏提取法和GC/MS技术对上海主要的14个污水处理厂中污泥中的多环芳烃化合物进行测定,并分析了其分布特征.

Abstract:多环芳烃(Polycyclic Aromatic Hydrocarbons,PAHs)是一类重要的土壤有机污染物,其在土壤中半衰期为2个月至2年^[1],很多PAHs具有毒性、致癌、致畸和致突变的作用^[2,3].但由于单靠化学分析难以评价PAHs的毒性^[4],因此,PAHs污染土壤的生物生态风险评价成为人们关注的热点.高等植物是陆地生态系统的主要组成部分,仅在近十年来开始被利用来评价生态环境风险.平衡、稳定、健康的土壤生态系统可生长出优良的植物,反之,不稳定或受污染的土壤生态系统则会对植物正常生长发育带来负面影响.根据高等植物的生长情况可以监测和判断土壤的污染程度,评价土壤质量^[5,6].

Abstract:土壤动物在分解植物残体、改变土壤理化性质、促进土壤物质循环和转化过程中起着重要作用,同时土壤环境因子也影响着土壤动物的生存与活动.近年来国内外学者已从生理学、生态学、分子生物学等方面^[1,2],研究了土壤动物与环境的密切关系,并采用试验模拟的方法,研究不同处理水平土壤动物群落的动态变化^[3,4].土壤pH是土壤动物群落的重要影响因子,对土壤动物的影响因环境条件的特异性而结果不尽一致^[5,6],一般而言,酸碱度适宜的土壤环境土壤动物相对较丰富^[7,8].大兴安岭北部地区,由于气温低,降水少,物质分解缓慢,凋落物累积较多,构成火灾和虫灾的隐患.

Abstract:21世纪以来,由于其良好的生态环境效应、及市场对绿色安全稻米的需求,稻田种养复合生态系统的应用范围不断扩大,模式多种多样,在我国南方地区主要以稻田养鸭、养鱼、养虾为主.同时对稻田种养复合生态系统的机理及其效应也进行了较为广泛的研究.相关研究表明:稻鸭共生可利用鸭子的活动、觅食产生中耕除虫的效果^[1,2],减少农药对环境的污染;稻鸭共生有利于稻田通风透光,改善水稻群体结构;提高土壤肥力^[3~5];还能减少稻田中的产甲烷菌数量,减少甲烷排放^[6~9]等方面作用.然而对于稻田养鸭、养鱼后对土壤微生物数量及多样性方面的研究还很少,甘德欣等^[10]研究表明稻田养鸭后能增加土壤微生物的数量,但对土壤微生物数量,但对土壤微生物多样性影响的研究还有待深入.

Abstract:土壤团聚体是由单个土粒与有机物质胶结而成的复杂结构,是构成土壤结构的基本单位,在很大程度上决定土壤的质量特征^[1].其形状、大小和稳定性直接影响土壤中水和空气的含量,决定土壤孔隙的大小分布,并由此影响土壤的其他属性以及作物生长^[2].目前对各种不同土壤团聚体的研究已受到专家们的普遍重视.土壤微生物是土壤有机组分和生态系统中最活跃的部分,被认为是最敏感的土壤质量生物学指标^[3].Bearden等^[4]和Degens等^[5]发现土壤团聚体中菌丝将砂粒联结在一起,证实真菌菌丝可有效提高土壤结构和土壤团聚体的稳定性;同时,在土壤团聚体形成过程中,许多菌丝体还通过分泌胶结物质(多糖类物质)使微团聚体粘结在一起.

Abstract:我国几乎所有大的湖泊均面临富营养化问题,究其原因主要是由于氮、磷的过量输入,而P又是内陆水体富营养化的限制因素^[1~4].有关资料表明^[5],在排除工业点源污染后,太湖流域各种面源污染中每年从农田进入水体的磷素相对贡献率不足10%,而生活污水、人畜排泄物及淡水养殖业等的磷素相对贡献率达90%左右.稻田土壤是水网地区一种特定的土地利用方式,农田管理方式直接影响着周围水体的环境状况,因此有关稻田土壤的农田排水和径流损失方面也一直是环境学家关注的热点问题.目前有关稻田土壤磷素损失机制,磷素在稻田土壤中向下迁移的可能性及渗漏通量还没有比较明确的定论.

Abstract:土壤中氮(N)的矿化过程是森林生态系统中的重要动态过程,影响着生态系统的生产力、结构及功能^[1].氮的矿化过程会受到许多因素的影响,并且在不同的空间与时间上表现出不同的变化特征^[2,3].随海拔高度的变化,土壤的温度水分均会随之改变,很多研究发现^[3~5]土壤中氮的矿化会随海拔高度的升高而增加,可能原因是(1)高海拔的枯落物可促进矿化,(2)低海拔土壤的低pH会抑制矿化,(3)高海拔氮库较大,(4)低海拔土壤水分含量相对较低,(5)土壤质地的差异以及(6)生物族群的差异.然而目前的证据还不足以很好解释高海拔土壤中高的氮矿化速率^[6].

Abstract:埋藏于土壤中的种子是植物群落再生的物质基础,识别这些种子的种类与数量特征是很多植物群落学、恢复生态学等相关学科领域的重要内容.将采集土壤样品置于温室内,保持最佳的萌发环境让尽量多的物种种子萌发,通过鉴定这些萌发幼苗的种类与数量来推断土壤种子库的种类组成与密度是最重要的种子库检测方法之一^[1~3],国内的研究者也基本采用这一方法^[4~11].该方法在检测的精度和准确度上具有不可替代的优越性^[1,12,13].即使在同一生态系统内,不同的植物种子所需要的萌发条件可能由于休眠^[2]、种子对策差异^[3,14],对光照、温度^[14~16]等的需求差异而存在巨大差别,作为种子存贮与萌发介质的土壤层的厚度和土壤质地对种子萌发会产生重要影响.

Abstract:土地盐碱化是影响世界农业生产最主要的非生物胁迫之一,已成为阻碍作物高产的一个主要因素^[1~3].我国松嫩平原是世界三大苏打盐碱土集中分布区之一,也是我国盐碱化程度最严重和对农业影响最大的地区之一^[4].由于苏打盐碱土中Na₂CO₃和NaHCO₃的水解作用,植物在这些土壤中的生长不仅受Na⁺的毒害作用,同时也受高pH胁迫的影响.某些植物之所以能够在这种极端不良环境胁迫下得以生存和繁衍,主要是因为它们在胁迫来临时能够及时启动内部防御体系主动适应环境的变化.同样,对于不同种类的盐碱胁迫而言,植物间可能存在类似或不同的适应机制,进而维持自身的正常生长和发育.

Abstract:苏云金芽胞杆菌(Bacillus thuringiensis,简称Bt)近缘于蜡状芽胞杆菌,革兰氏染色阳性,在其芽孢形成过程中产生Bt杀虫晶体蛋白.Bt是目前应用最广的生物杀虫剂之一,其杀虫原理也被广泛应用于转基因抗虫育种实践中.转Bt基因作物的外源基因表达产物Bt杀虫晶体蛋白可通过根系分泌物或作物残茬等方式进入土壤^[1,2],其残留会影响土壤生态系统平衡^[3].纯化的Bt毒蛋白可被黏土矿物、腐殖酸和有机矿质复合体等活性颗粒快速吸附,且不易解吸^[3~5].吸附后毒素蛋白仍具有杀虫活性,毒性甚至较游离态的还强^[6];红外光谱和X射线衍射表明,吸附后毒素蛋白结构仅有微小变化^[4].