Abstract:On the basis of dynamics principle for soil water and solutes transport,the numerical modeling is used for analyzing the regularity of the transport of water and Cl^- in the soil with clay layer under evaporation in this paper.The layered soils used for simulation are composed of loam and two kinds of clay layer respectively.The depth of groundwater is 1.5 m.The differences and causes in the effects of the position and thickness of the clay layer on the transport of soil water and solute between two kinds of clay layer are focused.The results show that the degree of the effects depends on the soil hydraulic properties of the clay and loam in the layered soil.In case 1 where the layered soil is composed of loam and heavy clay Y,the basic condition is,the higher the position of the clay layer and the thicker the clay layer are,the lower the evaporation,up-inflow rate and the accumulation of Cl^- in soil are.In case 2,where the layered soil is composed of the same loam as above and light clay R,the highest evaporation and up-inflow rate and accumulation of Cl^- appear in the layered soil with clay layer at the top position.The next higher level appears in the case where the clay layer locates in the bottom of the soil and the lowest appears in the soil with clay layer in the middle position.The causes of above differences are resulted from the different hydraulic properties of the two clays.The hydraulic conductivity curves(K versus h) of clay R and loam cross at about -1000 cm of h.Therefore,when the surface soil is drying and h drops to less than -1000 cm,the K of clay R will be higher than that of loam.But the h value of the intersecting point for clay Y and loam is rather lower than above value.The accumulation position of Cl^- in soil profile under evaporation is mainly at the soil surface,clay layer in soil profile only plays the role of retardation in the transport of solutes to the surface and of temporal accumulation place.

Abstract:The processes and characteristics of nitrogen mineralization in paddy soils of the Shanghai Region were studied with 120 days anaerobic incubation at 25℃ and 35℃.Results showed that the organic nitrogen mineralized amounted to 4.0% to 9.4% of total N(60 to 241 mg kg^-1) and the mineral nitrogen was only correlated with total N(partial correlation analysis).pH changed greatly and was related to the mineral nitrogen contents during the mineralization.Temperature was one of the main factors influencing the mineralization of nitrogen.Four models,(1) effective cumulated temperature model;(2) a one-component,first order exponential model(one-pool model);(3) a two-component,first order exponential model(two-pool model) and (4) a two-component,mixed first and zero order exponential model including a constant term(special model),were fitted to the observed mineral-N vs incubation days using a non-linear regression procedure.The two-pool model and the special model gave the best fits amongst the four models.The special model was the unique one that could appropriately reflect the responses of organic nitrogen mineralization to incubation temperature in all studied paddy soils.All results showed the special model made the best prediction of nitrogen mineralization under flooded conditions.

Abstract:The black soil region is an important food base of China It plays a crucial role in food safety and national economy But few studies on spatial characteristics of environmental capacity of black soil were reported In this article spatial characteristics of the environment capacity of the black soil region in Heilongjiang Province are studied based on GIS The results show that the relative environment capacity of a single element and the comprehensive environment capacity of the region are both quite high,generally above 0.45 and even over 0.75 in quite a number of areas In terms of the comprehensive environment capacity,the area high in capacity(Rc>0.75) amounts to 19132.48 km² or 26.84% of the total region,the area moderate in capacity(0.45 Rc 0.75) to 49605.00 km² or 69.74% of the total,the area low in capacity(0 Rc<0.45) to 2112.09 km² or 2.97% of the total and the area overloaded in capacity(Rc<0) to 316.62 km² or 0.45% of the total These are indicators revealing that the geochemistry environment of the black soil region is quite advantageous to sustainable development of the agriculture and the development of green food in the region.

Abstract:Scientific determination of index areas and participating factors is the premise and foundation for accurate farmland gradation.On the basis of the analysis of the purposes,principles and requirements of the determination of index areas and participating factors for farmland gradation,Yixing County of Jiangsu Province was cited as a case study.Division of index areas for farmland gradation and determination of the principal gradation participating factors for every index area were attempted by the cluster analysis method and the principal component analysis method.The results indicated that with the quantitative analysis method,gradation index areas could be divided and their gradation principal part icipating factors determined objectively and scientifically,which made the final gradation more accurate.

Abstract:Dynamic information of soil water,temperature,thermal properties and other physical parameters is vital for de-scribing the physical,chemical,and biological processes in the vadose zone.Recent development of the thermo-Time Domain Reflectometry(Thermo-TDR) opens up an opportunity for such purposes.In this study,the Thermo-TDR technique is applied to simultaneously determine water content,electrical conductivity,heat capacity,thermal conductivity,and thermal diffusivity in soils of various textures.Soil bulk density,air-filled porosity,and degree of saturation are then obtained from the dependence of soil heat capacity on water content and bulk density.The results indicate that the Thermo-TDR measured soil water,electrical,and thermal properties,as well as other physical parameters,agree well with the results from theoretical models or gravimetric measurements.Further improvement in probe design,waveform interpretation,and determination of the effective probe length will increase the measurement accuracy of the Thermo-TDR technique.

Abstract:Owing to the fact that Mn availability in soils varying in pH and Eh,the values of available Mn determined through soil tests tend to be an irreliable indicator for the actual Mn availability to crops in the field In literature,however,there is some incorrect interpretation and confusion in discussion of the relationships between soil pH and Mn availability This study examined the solubility of manganese dioxide,in the form of birnessite(MnO₂),in three acids(HCl,HNO₃ and H₂SO₄) varying in concentration and its mechanism,and the reduction powers of three halides(KCl,KBr and KI) under two different pH conditions The effect of pH on the solubility of MnO₂ was elucidated in theory and experiment Results showed that MnO₂ could be dissolved instantly by HCl high in concentration In concentrated HNO₃ and H₂SO₄,however,this was not observed A process of reduction by water took place slowly in the two acids and the reaction was still not completed in a two-year standing When the three acids were low in concentration,none noticeably dissolved the MnO₂ with the H⁺ ion strength <0.5 mol L^-1 HCl significantly dissolved much more MnO₂ than HNO₃ or H₂SO₄ when the H⁺ ion strength reached>1.0 mol L^-1 The reduction powers of the three halides were observed as KI>KBr>KCl and further enhanced by a decrease in pH and an increase in concentration KCl had a very weak reducing power at pH>3,while KI showed a very strong reducing power even at the very low concentration(0.001 mol L^-1) regardless of pHs under the test The above results further indicate that H⁺ perse,regardless of its concentration,cannot reduce MnO₂ in the absence of reductant or e^--donor On the contrary,MnO₂ can be reduced in large quantity in the presence of strong reductant even at a higher pH Low Eh and pH are most favorable to reduction of MnO₂ to Mn²⁺.

Abstract:Energy characteristics of the reaction kinet ics of H⁺ -Ca²⁺ on red soil surface under acidic conditions were investigated by using a home-made dynamic device.The results showed that Ca²⁺ adsorption could be divided into rapid and slow reactions.The maximal Ca²⁺ adsorption fitted by the first order equation remarkably decreased with increase in acidity and reached equilibrium in advance with increase in temperature.A two-constant equation could be used to describe unevenness of the energy distribution of Ca²⁺ adsorption on the sites of the soil surface.Activation energy(Eb) of Ca²⁺ diffusion was calculated by using b value of the rate constant of Parabolic Diffusion Low and increased with increase in acidity,which reflected that the energy barrier to be overcome by Ca²⁺ diffusion would rise up and the rate of diffusion in Ca²⁺ adsorption decrease accordingly.Enthalpy of activation(H) was positive in value and rising temperature could contribute to Ca²⁺ diffusion.Entropy of activation(S*) was nagative in all cases,suggesting that system could improve its degree of order.pH of effluent drast ically dropped when the influent solution was pH 4.5 and pH 5.6.H⁺ release could be best described by the first order equation and the power-function equation,which were followed by Elovich equation,Parabolic Diffusion Low and zero order equation.Energy barrier to be overcome by H⁺ (Al³⁺) diffusion in pH 5.6 treatment was lower than that in pH 4.5 treatment.△H values of H⁺ diffusion were positive indicating an endothermic reaction and the increase in temperature speeded up H⁺ diffusion.There was the consumption process of H⁺ ion by using influent of pH 3.5,which was attributed to soil buffer mechanism and specific adsorption of SO₄^2-.The energy of activation of H⁺ consumption was lower than that of H⁺ release,showing that more H⁺ was diffused to the surface of soil particles than H⁺ released to bulk solution when the amount of H⁺ in the bulk solution exceeded a certain quantity.H⁺ consumption was rapid at the initial stage of the reaction.△H of H⁺ consumption,in comparison with that of H⁺ release,could contribute to H⁺ adsorption.Since H⁺ dissolution of minerals became a controlling process,it could be best described by Elovich equation and Parabolic Diffusion Low.

Abstract:Mineralization of soil organic carbon is an important biochemical process closely related to release and supply of nutrients,formation of greenhouse gases,and maintenance of soil quality.In incubation experiments and chemical analysis of soil samples of Udic Isohumisols,Udic Cambosols,Hapli-Stagnic Anthrosols No.1 and No.2,Fe-leach-Stagnic Anthrosols,Feaccumul-Stagnic Anthrosols gathered in East China,dynamics of soluble organic carbon content and soil organic carbon mineralization under different moisture treatments were investigated to determine difference in soluble organic carbon content between aerobic and submersion conditions as related to change in mineralization of soil organic carbon.Soluble organic C(SOC) was linearly and significantly related to wate-rsoil ratios ranging from 1:1 to 10:1,with different correlation coefficients(R²) in the soils(Udic Isohumisols 0.908^**,Udic Cambosols 0.973^**,Hapli-Stagnic Anthrosols No.20.933^**,Fe-leach-Stagnic An-hrosols 0.901^**,Fe-accumul-Stagnic Anthrosols 0.865^**).Cumulative SOC increased with the extracting time and SOC from a single event decreased with the frequency of the extraction.During the 8 weeks incubation,soluble organic C in the submergence treatments was 46% ~117% (p<0 05) for Hapl-i Stagnic Anthrosols No.1,112% ~285% (p<0 001) for Hapli-Stagnic Anthrosols No.2,and 21% ~73% (p<0 05) for Fe-accumul-Stagnic Anthrosols,higher than those in the aerobic treatments.In the first 3 weeks(for Hapli-Stagnic Anthrosols No.1) or 4 weeks(for Hapl-i Stagnic Anthrosols No.2) of incuba- tion,the daily mineralization of soil organic C was significantly different between moisture treatments(p<0 01),and tended to be similar thereafter;and the cumulative mineralization of soil organic C was significantly higher in the submergence treatment than in the aerobic treatment for the whole incubation period(p<0.01).Dynamics of the mineralization of soil organic C and trend of the change in content of soluble organic C tended to be similar,especially for Hapli-Stagnic Anthrosols No.2,which showed significant correlation coefficients(r) between soil organic C mineralization and soluble organic C content(0.942 in the aerobic treatment and 0.975 in the submergence treatment).Results also showed that difference in soil organic C mineralization(including daily and cumulative mineralization) between Hapli-Stagnic Anthrosols No.1 and No.2 was mainly related to their significant difference in content of soluble organic C,not the total soil organic C content.Significant increase in soluble organic C content as a result of submergence might be the main cause for a higher mineralization of soil organic C under the submersion condition than under the aerobic condition.

Abstract:Effects of Fe deficiency and P type ATPase inhibitor on Cu uptake by C.communis were investigated in this study.The results showed that Cu accumulation in C.communis was increased with the drop in Fe concentration in the nutrient solution.Cu uptake by C.communis was significantly enhanced by Fe deficiency in solutions with different Cu concentrations,which suggested that there was an inherent relationship between Cu uptake and element Fe.Cu concentrations in Fe deficient plants in Treatments EDTA Cu,NTA Cu,oxalate-Cu,and citrate-Cu,were lower than that in Treatment Cu.But Cu uptake,no matter what form of Cu,by Fe deficient plants was higher than that by Fe sufficient plants.Fe deficiency could lead to acidification of the rhizosphere of C.communis.Cu uptake was inhibited by P-type ATPase inhibitor Na₃VO₄.The promotion of Cu up take by Fe deficiency perhaps had nothing to do with the activity of P-type ATPase.

Abstract:The effects of organic acids on Cd²⁺ sorption desorption in testing soil colloids were studied by batch meth ods.The results showed the maximum amount of Cd²⁺ sorption by yellow brown soil,red soil and latosol was 43.7,16.8 and 1.58 mmol kg^-1 respectively.At the same concentration of Cd²⁺ added,the amount of Cd²⁺ sorption was generally characterized as peak like curves with the increase of organic acids concentration.When organic acids and Cd²⁺ simultaneously were intro duced in testing systems(competitive sorption),lower concentration of oxalic acid(<0.5~2 mmol L^-1) or citric acid(<0.025~0.2 mmol L^-1) promoted Cd²⁺ sorption,and higher concentration of them decreased the Cd²⁺ sorption amount.The effect of Cd²⁺ sequential sorption on the soil colloids previously adsorbed organic acids(sequential sorption) was almost same as that of competitive sorption,however,the variation of both amount of Cd²⁺ competitive sorption and sequential sorption were not same.Its reason was related to content of residual organic acids in both sorption systems.The results of desorption tests demonstrated that the concentration of oxalic acid impacted total amount and total rate of Cd²⁺ desorption as well as distribution ratio of Cd²⁺ desorbed by KNO₃ and by DTPA on surfaces of testing soil colloids.

Abstract:In order to elucidate carbon cycling in the forest ecosystem,respiration of soils under deciduous(Quercus acutissima,Acer palmatum Thunberg and Fraxinus rhynchophylla Hance),coniferous(Pinus koraiensis) and mixed(Pinus koraiensis,Quercus acutissima and Acer palmatum Thunberg) forests and its environmental factors were investigated in Kwangneung Experimental Forest,Pochun-gun,Gunggi-do,Korea. In situ soil respiration was being measured for a 16-month period between August 2001 and December 2002 using Pp-systens EGM-4(IRGA). For each measurement,soil temperature,gravimetric water content,soil organic matter content,total organic carbon,total nitrogen and carbon to nitrogen ratio in the subsoil 10cm depth were also determined. Relations between soil respiration and their environmental factors were analyzed,and causes leading to difference between three forests were found out. Results indicated that soil respiration rates from the forest soil were strongly related to soil temperature. The highest correlation was found with the soil temperature at the depth of 10 cm,and soil respiration rates increased exponentially with increase in soil temperature. Thus,soil temperature was the primary abiotic determinant of soil respiration rates in this study. Q₁₀ model was used to figure out the Q₁₀ value of the decidous,coniferous and mixed forest soils,being 3.6(r²=0.66),3.8(r²=0.63) and 3.2(r²=0.63),respectively. The daily mean soil respiration rate was CO₂ 15.12,15.10 and 13.99 g m^-2 d^-1,respectively. No difference was found between deciduous and coniferous forests,but difference did exist between mixed forest and the others. Other than that no environmental factors had any significant effect. However,when temperature was not a limiting factor,soil water content had some effect on forest soil CO₂ efflux. A modeling examination showed in summer(20℃),soil respiration rates increased exponentially with increase in soil water content,whereas in winter(4℃),soil respiration rates decreased exponentially with increase in soil water content. In spring and autumn(10℃),there was no apparent effect of soil water content.

Abstract:Rice is one of the main crops in China and needs a lot of nitrogen fertilizer to ensure high yields Thus,nitrogen take up and utilization efficiency by rice is an important issue in agricultural production Due to inhibited nitrificaton in the bulk soil of lowland rice field,researches on nitrogen nutrition of rice mainly focus much more on ammonium(NH₄⁺) than on nitrate(NO₃^-) Much evidence has shown that rice can take up not only NH₄⁺-N but also NO₃^--N,but is different in capacity which varies with its genotype The responses of rice to different nitrogen forms and their physiological effects are poorly understood Hydroponic culture experiments were carried out to study the response of rice to different nitrogen forms(NH₄⁺/NO₃^- ratios of 100:0,50:50,and 0:100) Best growth of rice plants of all genotypes tested was found in the mixed solution of NH₄⁺ and NO₃^- but crops different in genotypes responded differently Based on the rice growth in two nitrogen solutions,i.e.,NH₄⁺/NO₃^- ratios of 100:0 and 50:50,the 40 varieties of rice tested could be divided into three groups,such as high response to NO₃^-,intermediate response to NO₃^- and non-response to NO₃^-Rice with high response to NO₃^- had much higher root dry weight and nitrogen accumulation in the mixed solution of ammonium and nitrate than in the single ammonium solution Thus,the root dry weight and nitrogen accumulation could be used as physiological indices for screening rice of genotypes with different responses to nitrate.

Abstract:All the physical and chemical properties of soil are ascribed to surface charge of soil particles.Many processes taking place in the soil system are influenced by surface charge.Therefore,parameters of its electrochemical properties,especially the surface potent ial and the surface charge density,are of the most importance.However,there is no reliable method available in accurately determining these parameters until recently.Li Hang solved this issue in his study by deducing the relationship between average potential and surface potential in the double layer.By using his method,surface charge properties of acidic,neutral and calcareous purplish soils were studied in this paper.The total charge volume,surface potential,surface charge density,electric field strength on surface and SSA(specific surface area) were determined.The effect of electrolyte concentration,cation variety,temperature and pH on the surface charge properties was also studied.The experimental results show that:(1) in 2B1 type electrolyte system(Mg(NO₃) ₂),the surface potential is-0.16~-0.18 V,-0.17~-0.19 V and -0.18~-0.19 V and the surface charge density is -0.26~-0.44 cm^-2,-0.37~-0.59 cm^-2 and -0.58~ -0.67 cm^-2 for acidic,neutral and calcareous purple soil samples,respectively;(2) the surface potential of the samples decreases with the electrolyte concentration increasing,but the surface charge density,and the electric field strength increase slowly;(3) the surface potential in 2:1 type electrolyte system is about 50 percent as much as the one in 1:1 type(KNO₃),however,there is little difference found in the surface charge density,the electric field strength and SSA between the two types of electrolyte system;(4) the surface potential,surface charge density and electric strength decrease with the temperature rising.

Abstract:Changes in the microbial biomass C(MB-C) and P(MB-P),Olsen-P,and fixed inorganic P fractions in red-earth soil under flood-drought cultivation were invest igated after amendment of organic materials(glucose and rice straw) and incubation at 25℃ and 100% humidity.Results showed that soil MB-C increased by 215%,74% and 163%,respect ively,by 3 days for the treatments of adding glucose(G5,at 5 g kg^-1 soil) and straw(S5,at 5 g kg^-1 soil;S10,at 10 g kg^-1 soil).Thereafter,soil MB-C in Treatments G5 and S10 underwent a decreasing process for a period of 3~14 days and 3~7 days,respectively,and then leveled off,but in Treatment S5,it remained relatively constant till the end of the incubation.However,soil MB-P in the former increased considerably during the early phase(by 3 or 7 days),and followed by a stable trend throughout the remaining incubation period.Soil MB-P in Treatment S5 remained relat ively constant during the entire incubation period,and by the end was about 2 times greater than that in the control(without amendment) as soil MB-P in it decreased significantly during the period.A significant decrease(3.5 mg kg^-1 soil) in Olsen-P occurred in Treatment G5 during the first 3 days.Differences between the content of Olsen-P in Treatments S5 and S10 and that in the control were limited(generally under 1 mg kg^-1 soil).It was found that,by the end of the 43 d incubation,the contents of A-l and Fe-bonded P,and total fixed inorganic P in the soil of Treatment G5 were significantly lower than those in the control.It was concluded that the amendment of organic materials enhanced the microbial biomass and MB-P in the soil under flood-drought cultivation,and consequently act ivated some fixed inorganic P(mainly Fe-bonded P) for utilization.A further analysis of the data obtained suggests that a considerable part(over 30% ) of the P used by the microbial biomass was transformed into organic P pool,and that P released from decomposing straws could preferentially be used by microbial biomass and generally filled up its need.Thus,the influence of straw incorporation on soil P availability may be limited.

Abstract:Degradation dynamics of Abamectin in different soils were studied by in cubation method.The result shows that soil organic matter,soil temperature and pesticide concentration can obvio usly affect Abamectin degradation,maybe which contributes to microorganism in soil.The dominant bacteria which can effect ively degrade Abamectin was isolated from experimental soil,and it was identified by 16SrDNA as Stenotrophomonas maltrophilia.After the inoculation of dominant bacteria into soil Abamectin degradation was further augmented.

Abstract:Soil microflora,soil enzyme activity and soil biochemical function were studied under different types of vegetation and analyzed the changes of soil microbial activities during the process of forest succession in Maolan Karst Nature Reserve,in Guizhou Province.The results showed that,along with Karst forest degradation being intensified,the total population of major soil microbes was declining;the numbers of major physiological groups,including ammonifiers,cellulose decomposing microbes,nitrogen fixing bacteria were decreasing;the activity of soil enzymes,including urease,sucrase,proteinase,alkaline phosphatase,peroxidase,and polyphenol oxidase were weakening;soil biochemical functions,including ammonification,nitrification,nitrogen fixation and cellulose decomposition were being impaired.Soil microbes activities were sensit ive to the process of forest degradation and could be deemed as microbial indicators of Karst forest ecology system.Soil microbes and enzyme activity were recommended as one of the major characteristics of ecological functions of Karst forest.

Abstract:Field experiments were carried out to investigate effects of combined application of organic manure and inorganic fert ilizer on chemical and biological characterist ics of the degraded soil and soil fertility restoration in Central Tibet.The results showed that changes in chemical or biological characteristics of the degraded soil were quite similar among different treatments,i.e.a declining trend for organic matter,total N and total P in the plough layer,but total K and available K in different depths of the soil profile dropped significantly in the non-fert ilization treatment.Processes of soil fertility restoration were not affected in the organic manure treatment.Combined application of organic manure and inorganic fertilizer had a significant and prompt effect on harmonizing the soil environment,promoting the process of bacteria-dominated propagation of soil microorganism,enhancing the accumulation of soil organic matter and improving the structure of humic compounds,and increasing the pool of N,P and CEC,exchangeable bases as compared with the treatment of non-fertilization.Although K was applied to the soil,K deficiency was still quite obvious in all treatments.The annual changes in soil total N,available P and available K were correlated with the annual balance of N,P and K to a varying extent,and the changes in soil nutrient contents coincided with that in nutrient balance.On the basis of continuous application of organic manure,application of an increased rate of nitrogenous fertilizer,an appropriate rate of phosphates fertilizer and a high rate of potassium fertilizer had an important promoting effect on fertility restoration of the degraded soil.

Abstract:Several molecular biotechniques which have been used for study on microbial diversity in polluted soils were reviewed.These approaches include analysis of mol% (G₊C) abundance of DNA,nucliec acid hybridisation,DNA reassociation kenitics and DNA fingerprints pattern based on PCR technique and so on.Both of the advantages and limitations of these approaches were also discussed.

Abstract:Soil organic carbon has been regarded as one of the most important pools that retain CO₂,and a binding agent influencing soil structure formation and stability.This paper reviews latest researches on soil structure hierarchy and different soil organic carbon pools contributing to soil structure formation and stability,mechanisms of soil structure hierarchy and stability being affected by the quantity and quality of soil active organic carbon pools,such as particulate organic matter and dissolved organic matter,and effects of hydrophobic organic matter on soil structure stability and soil properties.In the end,the authors pro pose researches in future to elucidate the relationship between soil organic carbon pools and soil structure stability under different land uses and soil managements;to quantify the formation processes of soil organic carbon pools and soil structure hierarchy;to investigate the relationship between soil organic carbon pools,soil structure stability and soil resiliency;to clarify effect of the quality of soil organic carbon on water infiltration and to consummate the models of soil organic carbon and water recycling.

Abstract:土壤侵蚀是世界上头号环境问题,已得到越来越多国家的普遍重视.中国是土壤侵蚀较严重的国家之一,侵蚀面积多达492万km²,占国土面积的51.2%^[1].土壤侵蚀机理仍是一个正在研究的问题.关于我国土壤侵蚀的状况已有不少详细研究,认为北方主要发生在黄土地区,南方侵蚀的对象主要是红壤和紫色土,而对花岗岩地区加速侵蚀的研究则少见报道.关于土壤侵蚀的影响因素一般认为不外乎降雨、地貌、土壤、植被及人类活动等5个方面,前3个因素纯粹是自然力所控制,与人类活动的关系不大,只有植被分布是自然因素和人类活动共同作用的产物^[2].

Abstract:中国的黄土高原地区,由于其土壤质地均一,颗粒细小,颗粒间粘结力弱,结构松散,稳定性差等性质,极易遭受水蚀以及风蚀.据统计,黄土高原水土流失面积达45.4万km²,年侵蚀模数大于15000tkm^-2的剧烈水蚀面积为3.67万km²,占全国同等强度侵蚀面积的89%^[1].每年进入黄河的泥沙约为16亿t,其中约有13亿t来源于坡耕地,约占土壤侵蚀总量的81%^[2].

Abstract:五十多年以前,Ellison^[1]将土壤侵蚀的过程分为四个基本过程:降雨冲击引起的剥蚀,降雨飞溅引起的剥蚀,地表径流引起的剥蚀,及径流迁移引起的剥蚀.最近,Kinnell^[1]根据土壤侵蚀中雨滴和径流的相互作用建立了土壤侵蚀的四个输沙系统:雨滴剥蚀和溅蚀迁移系统,雨滴剥蚀和雨滴引发的水流迁移系统,雨滴剥蚀和水流的迁移系统,水流剥蚀和水流迁移系统.这些系统可能是独自起作用,也可能是共同的作用.在不算太长的研究历史进程中,学者们对土壤侵蚀中雨滴的溅蚀作用、结皮的形成及细沟的侵蚀作用等分别进行了很好的深入研究,并对各自的机理获得了深入的了解而且取得了许多好的成果^[3,4].

Abstract:在可变电荷土壤上,植物生长期间对磷肥的利用效率很低^[1,2],这是由P的专性吸附所决定^[3,4].Easterwood和Sarfain^[5]报道了减少土壤对P素固定的磷肥与有机质配合施用技术.无机磷肥与有机肥配合施用,植物能有效地吸收肥料中的磷,其原因可能是降低了土壤对磷的吸附能力,进而提高了土壤溶液中磷的浓度^[6~8].相反,Li等^[9]发现,施用含磷低的有机质降低了土壤磷的活性.石灰物质能有效缓解土壤的酸化.然而,对酸性土壤在同时施用石灰物质和有机物质的情况下,土壤对磷的吸附-解吸特性的研究少见报道,更重要的是此类问题与酸性土壤的改良关系密切.

Abstract:有关水分胁迫改变水稻生长形态、组织结构与生理代谢方面的研究已有不少报道,但试验结果间颇有差异^[1～9].在以往水分胁迫的植物效应研究中,往往只讨论水分胁迫处理本身对试验结果的影响,较少涉及处理前水稻生长环境的影响.至今尚未见有作物对全程和阶段性非充分灌溉反应差异的试验报道.本研究拟通过作物体对水分胁迫较为敏感的叶片水分含量、叶绿素含量和丙二醛(MDA)含量、根系活力、叶片气孔阻抗和光合速率等指标进行测定,探讨抽穗后(即阶段性)与全程非充分灌溉影响水稻产量形成的差异及其生理机制,为发展水稻节水栽培技术提供理论依据.

Abstract:金属采矿产生的尾矿不但粒度小、重量轻、表面积大,堆放时易流动和形成塌漏,而且含有高浓度的重金属,对附近的村镇、农田、水源等构成极大威胁^[1～3].因此,为保护环境、减小矿业开发对自然生态的破坏,金属尾矿库的土地复垦将非常必要^[4,5].早期的结果表明,重金属的毒性和营养物质的缺乏是矿区植物定植的主要限制因子^[6,7].添加改良剂和化学肥料来改变矿砂性质从而改善植物生长条件,实现尾矿库的植被恢复是一个可行的途径^[8,9].

Abstract:大量研究表明,固定态钱的含量与土壤质地有关.李生秀等人的研究表明^[1],西北地区土壤的固定态铵含量与粘粒含量呈显著正相关,与砂粒含量呈显著负相关;Feigin和Yaalon的测定证明,以色列129种钙质土固定态钱含量与粘粒(< 0.002 mm)含量显著正相关(r=0.63,p<0.01)^[2];施书莲等人^[3]报道,棕壤、栗钙土、黑土、棕钙土和红壤带土壤中的固定态铵含量与粘粒、粘粒及细粉砂含量之和的相关均达到0.01显著水准.这些结果说明,固定态铵主要存在于粘粒和粉粒中,而砂粒中几乎没有^[4].

Abstract:马尾松(Pinus massoniana)是我国南方的主要用材树种,具有适应性强、主根明显、用途广、速生丰产等优点.然而营造的人工马尾松纯林,树种层次单一,结构简单,针叶化明显,弱点逐渐暴露出来,导致林地地力衰退、林分抗逆性差、火灾频率增加,已引起人们的广泛关注[1].研究表明,大力营造混交林,增加森林生态系统中生物类群的多样性、多层性,就能从根本上改善林分的生态环境,提高生产力.营造马尾松混交林不仅是一项重要的营林技术措施,而且涉及到对树种生物学和生态学特征,尤其是种间关系的全面了解.