Abstract:Accumulating conditions of vermicular red earth in South China have been explored for decades,but its origin and sedimentary environment are still unknown. Based on the analysis of physico-chemical properties of 130 samples which were sampled from Jiujiang Xinzi,and Shahe in Jiangxi Province,Jinhua and Anji in Zhejiang Province,and Zhuzhou in Hunan Province,the authors try to have a better understanding of how vermicular red earth(VRE)was accumulated. Particle size of the soil samples was measured using the Malvern 2000,major elements using XRF,REE using ICP-MS,and isotope ratios of Sr and Nd using TIMS.

Abstract:Spatial prediction is always facing challenges of uncertainty because it is almost impossible for any model to represent exactly the real world. Since the 1990s,more and more attention has been given to analysis and evaluation of uncertainties in output of spatial soil prediction. Visualization can be a way to increase communication between uncertainty analysis and decision making,since it can help expose and express reality more intuitively. First of all,different techniques or ways to visualize uncertainty were briefly reviewed. And a case study was conducted of the statistics-based spatial prediction of total N content in the topsoil of peri-urban Beijing. Relative errors were deemed as expression of uncertainty in the prediction. A Hue Saturation Intensity(HSI)color model,which is a psychologically appealing color model,was recommended to visualize simultaneously soil attribute prediction results and uncertainties therein. The HIS model uses hue to visualize prediction values and whiteness to visu alize uncertainty. A two dimensional legend was designed to supplement the visualization.This case study indicated that visualization of both prediction and prediction uncertainty offers a possibility to enhance visual exploration of data uncertainty and compare different prediction methods or predictions of totally different variables. The whitish area of the visualized output can be simply interpreted as unsatisfactory predictions,where additional samples may be needed for a better prediction. The limitation of using the two dimensional legend is that it is not easy to match the colors between the HSI coded image and the legend because the pale colors are always difficult to distinguish.

Abstract:At present,most of studies about the two-region model(TRM)are all focused on modeling solute transport in laboratory short soil column at small scale. The objective of this study was to investigate the validity and parameters of the two-region model(TRM)describing solute transport across a long range of travel distances in heterogeneous soil. We used the TRM, the convection-dispersion equation(CDE)and the fractional advection-dispersion equation(FADE)to characterize the solute transport process in a 1250-cm long one-dimensional heterogeneous soil column. Comparing to CDE and FADE,the break-through curves(BTCs)at different travel distances can be better fitted by using TRM,and TRM is better to capture the full evolution of the BTCs,especially for the early and long tailing part. It implies that TRM is a highly effective approach to describe the evolution of solute transport at relatively large-scale domain in heterogeneous soil. We found that TRM had similar scale-depen-dent dispersion as CDE. However,the dispersion coefficient of TRM was less scale-dependent than that of CDE. It was also found that the mass transfer coefficient of TRM decreased with the advection time in a power law function indicating the presence of multiple timescales of solute mass transfer between immobile and mobile regions,and the mobile water fraction of TRM can be determined with the ratio of effective porosity and total porosity of soil.

Abstract:The laser diffraction technique(LD method)has been regarded as an effective means of measuring soil particle size distribution(PSD)in recent years. To assess feasibility of applying the LD method to red soil high in clay fraction,soil samples collected from various layers of 6 forestry ferrisol profiles(clay fraction>40%)were analyzed using the LD and traditional pipette methods for comparison. It was found that the LD method is more efficient and effective and capable of providing PSD in formation of more particle size fractions,particularly of the clay fraction(<2μm),but it might "underrate" clay fraction while "overrate" silt fraction. Significant liner-relationship was found between the two methods in measured data of silt fraction and sand fraction,but not of clay fraction,because it is high in content but narrow in distribution. Modification of their models has significantly narrowed the difference between the two methods in measurement,which means the LD method can be used for PSD analysis of clayey ferrisol. However,its measurements or PSD dada are not yet ready to be used directly in the current sedimentation based triangular texture diagram to define soil texture before certain data transformation. It is an inevitable trend for LD technique to be used widely in analyzing soil PSD in the future,thus,it is urgent and significant to conduct systematical and standardized comparison studies of various typical soils,so as to improve the reliability and practicability of the LD technique,and build up a new LD-based triangular texture diagram,which will further application of the LD technique in soil science.

Abstract:Laser diffraction(LD)technique and pipette method were used to measure particle size distributions(PSD)of 60 ferrosol samples. Based on the measurements,mass fractal dimension,D_m,and volume fractal dimension,D_v,were calculated and compared. Results show that D_v is lower than D_m because the laser diffraction technique "underestimated" the clay fraction compared to the pipette method. As significant linear correlations were observed between D_v and D_m as well as between D_v and its measured clay fraction,D_v could also be used to characterize some basic soil properties. The LD method could divide soil particle size into more classes with distinctive D_v value. Further division of particle size classes might lead to slight decrease in D_v.

Abstract:A groundwater-fluctuating region is a region where the groundwater varies sharply in water table and radiation range. With the aid of the geostatistics theory and GIS technology,study was carried out of a groundwater-fluctuating region in the lower reaches of the Heihe River. Based on the data collected from 64 sampling sites,Cross-Validation method and geostatistics method were adopted to select optimum interpolation method and fitted theoretic semivariogram models. Results show 1)spatial heterogeneity of soil salinity was very obviously in the groundwater-fluctuating region of the lower reaches of the Heihe River. That is,salt content in the soil increased gradually along the direction of the flowing water in the area. And the salt content should decrease gradually with the increasing vertical distance from the trunk course of the river,which was controlled by ground-water,but the decrease was replaced by regional variation. The regional variation was more distinct in the radiation range of East River than West Riverπs,which related to the source of replenishment of two rivers and chemical properties of the water;and 2)the range of variation is a measure of spatial heterogeneity. Based on the active variation ranges of the salt elements,7 km is supposed to be the maximum sampling scale in the study. This study is aimed at providing theoretic basis for regional ecological restoration,vegetation re-establishment,and rational arrangement of sampling sites in related studies.

Abstract:Since 1992 when polders began to appear along the coast for aquaculture,a long-term experiment has been carried on to study dynamic variation of salts in the water and bottom mud of the polders as affected by aquaculture in Defang region. Results of the monitoring between 1996 and 2005 show 1)salt concentration in the waterbody decreased from 3.67 to 2.28 g L^-1 in the aquaculture system with river water high in mineralization(Na-Cl>3.5 g L^-1)and rainfall as water sources for replenishment;2)total soluble salts in the pond mud decreased year by year,from 3.22 to 1.06 g kg^-1;and,a significant linear relationship was observed between total soluble salts and Cl^-1 content in pond mud;and 3)an exponential curve model could be used to predict desalinization trend of the mud;and the predicted values of the years to follow are δ₂₀₀₇=0.824 g kg^-1 and δ₂₀₀₉=0.638 g kg^-1,respectively,which may serve as a scientific basis for future reclamation of the polder into farmland.

Abstract:Non-point source pollution in the Fuxianfu Lake catchment,Yunnan has been the main cause of eutrophication of the Fuxianfu Lake.Leaching loss of nutrients from the soil is not only one of the most important agricultural problems,but also the main factor causing nitrogen and phosphorus pollution of the water environment.Four soil columns sampled in the region were used in the laboratory experiment,which was designed to have four different rainfall intensities,to investigate migration and leaching loss of nutrients. Based on the obtained experimental data,characteristics of migration of total nitrogen,total phosphorus,nitrate-N and ammonia-N were analyzed,and cumulative leaching losses were calculated. Results show that nitrate-N moves relatively easily with water movement in the soil profile while ammonia-N can hardly do. A natural logarithm relationship was found existing between cumulative rainfall amount and cumulative leaching losses of nutrients in all the experimental conditions. Leaching loss of total nitrogen was mainly affected by rainfall intensity,while leaching loss of total phosphorus was not significantly related to rainfall intensity. The findings of this paper may help explore distribution and migration of nutrients in agricultural lands,and mechanism of agricultural activities polluting groundwater.

Abstract:Colloid transport in porous media is controlled,to a large extent,by surface properties of the colloid perse and physical and chemical factors,like ionic strength,pore water velocity,etc. An outflow experiment using saturated quartz column was conducted and designed to have three level of ionic-strength(i.e. 0.001 5,0.01 and 0.03 mol L^-1)and two pore water velocities(i.e. 21 and 5 cm h^-1)to analyze deposition and transport process of Kaolinite and SiO₂. Results show that deposition processes of Kaolinite and SiO₂ were distinctly enhanced with increasing ionic strength,while higher pore water velocity tended to facilitate movement of Kaolinite and SiO₂,thus covering a much longer transport distance.Further analysis indicates that ionic strength and pore water velocity had a more significant impact on transport of Kaolinite(≥500 nm in particle size)than of SiO₂ (190 nm in diameter).The findings may further understanding of the mechanism of colloid promoting transport of pollutants,and are of some guiding significance to overall objective assessment of pollution risks of the underground environment.

Abstract:Comparison was conducted between four different virus extraction methods in recovery efficiency of bacteriophage MS2 and φX.74. The method of 3% beef extract plus 0.04M sodium pyrophosphate(pH=9.4)was the most effective one, with virus recovery efficiency ranging from 62.9% to 97.7% for red earth,red clay and fluvo-aquic soil. But the recovery efficiency reached only about 30%,which might be attributed to its high content of amorphous iron oxide and amorphous aluminium oxide. It was also found that type of viruses had little effect on the recovery efficiency. The findings could be cited as a platform for the research on fate and behavior of virus in most soils in our country.

Abstract:Distribution and soil physical properties of water-stable aggregates in red soils different in land use and soil fertility were studied. Results show that the content of soil water-stable aggregates >0.25 mm is consistently affected by land use, and is the lowest in upland soil and the highest in woodland soil. When they are >5 mm,their content is affected by soil fertility. The higher the fertility,the higher the content,which suggests that with increasing soil fertility,the content of soil organic matter increased,thus facilitating formation of more water-stable soil aggregates. Mean weight diameter(MWD)is positively related to content of water-stable aggregates >0.25 mm,which is,therefore,the major factor affecting stability of soil aggregates. Soil physical properties(bulk density,particle density,porosity)differ sharply from pattern to pattern of land use and so do the rules of their variation. However,soil bulk density and soil porosity are favorable related to content of water-stable aggregates >0.25 mm.

Abstract:In greenhouse,three different simulated constructed wetland systems were built up with slag,zeolite and paddy soil,respectively,as substrate,and with Oenanthe javanica,Lolium mutliflorum and Vetiveria zizanioides,respectively,as vegetation. Efficiencies of the three wetland systems removing nitrogen and phosphorus from domestic sewage were studied as compared with that of the floating-bed plant system(no substrate). Results showed that when nitrogen and phosphorus load was low and the hydraulic retention time was 6 days,the constructed wetlands of slag,zeolite and paddy soil displayed high efficiency in removing total nitrogen(TN),ammonia nitrogen(NH₄⁺-N)and total phosphorus(TP),with an average removal rate of over 91.0% for all the three,but low efficiency in removing nitrate nitrogen(NO₃^--N)with a rate ranging from 58.0% to 85.5%. When nitrogen and phosphorus load was high,the floating-bed plant system was much lower than the three simulated ones in removing efficiency. In terms of removal amount,the paddy soil system was lower than the slag and zeolite ones. In the floatingbed plant systems,negative increase in NO₃^--N removal amounts led to decrease in TN removal amounts,but its NH₄⁺-N removal amounts was significantly higher than those in the three simulated wetland systems. The removal amounts of TP in the Oenan the javanica and Vetiveria zizanioides floating-bed systems were also higher than those in all the three simulated wetland systems. Different plants were different in ability to assimilate nitrogen and phosphorus. The four wastewater purifying systems with Lolium mutliflorum as vegetation regardless of substrate,assimilation of TN and TP by the plant was the main mechanism for TN and TP removal. TN and TP uptake by Oenanthe javanica and Vetiveria zizanioides were much smaller than those by Lolium mutliflorum in the three simulated wetland systems,suggesting that Oenanthe javanica and Vetiveria zizanioides assimilation of TN and TP contributed partly to TN and TP removal in the three systems. However,the assimilation of P by Oenanthe javanica and Vetiveria zizanioides was the main mechanism for TP removal in the floating-bed plant systems.

Abstract:Soil samples,collected from farmlands and woodlands in different areas of the Loess Plateau,were incubated aerobically in the lab for 35 days. Results show that the concentration of soluble organic carbon(SOC)in the samples decreased, while the concentration of soluble organic nitrogen(SON)increased significantly during incubation. Typ-Eum-Orthic Anthrosols was much higher than Typic Hapli-Ustic Argosols and Typ-Isohumosols in SOC and SON at the beginning of and throughout the incubation. In the case of Typ-Ishumisols,woodland was significantly higher than farmland in SOC and SON. Incubation significantly increased UV-80 and HIX_em values of soluble organic matter. The rising trend of the latter was especially significant on the 8th day and the 35th day. The SOC/SON ratio of the samples gradually declined with the incubation going on. It was discovered through correlation analysis that the increase in UV-80 value was positively correlated with the decrease in SOC on the 35th day, and that remarkable negative relationship between initial HIX_em and the decrease in SOC on the 8th day,which suggests that UV-80 and HIX_em are suitable indicators that may to a certain extent reflect changes in types and structures of SOM in the soil.

Abstract:Plant growth and pollutants uptake by ryegrass(Lolium perenne L.)grown in a Pb and B[a]P polluted acidic soil developed from red sandstone was studied in a pot experiment.Soil samples treated with Pb at the rates of 0,500,1 000 and 2 000 mg kg^-1 (on a basis of oven dried soil)and B[a]P at 0,12.5,25 and 50 mg kg^-1 were planted with or without ryegrass. The plants were harvested 61 days'after its growth.The contents of Pb and B[a]P in the soil and in the plant shoots and roots as well as plant height and dry mass of ryegrass were determined.Results show ryegrass biomass decreased substantially due to Pb toxicity.In the planted soil 4.7% of the Pb applied and 0.023% of the B[a]P applied was taken up by ryegrass,and about 42.6% of the B[a]P applied was left as residue,whereas in unplanted control soil,50.9% was.The findings suggest that cultivation of ryegrass may help remedy Pb 2B[a]P mixed polluted acidic sandy soil.

Abstract:Soil pollution mixed by persistent organic pollutants(POPs)and heavy metals is widely distributed in farmland. However,little attention has been paid to their interaction in soil.Surface soil samples were collected from a typical copper contaminated farmland in Fuyang of Zhejiang province and analyzed for organochlorine pesticides(OCPs),such as HCB,HCHs and DDTs.The results showed that soil total content of DDT increased with the degree of copper contamination in soil probably as a result of an inhabitat ion from DDT metabolized to DDE or to DDD by the high copper content.Correlation analysis indicated a closer relationship between the content of OCPs and the content of organic matter in the copper contaminated soil,implying that copper pollution might have promoted combination of DDTs and HCHs with organic matter in the soil.This result also likely accounted for the higher content of DDTs in paddy soil than that in upland soil since higher content of copper were generally found in paddy field in this investigation area.

Abstract:Effects of cadmium(Cd)on activities of key nitrogen metabolism enzymes in leaves of Arabis paniculata F. were studied.Arabis paniculata F.,a newly identified hyperaccumulator,was grown in soils varying in Cd content(0,10,20,40,80,160 and 240 mg kg^-1)for 135 days.Plants were analyzed for contents of NO₃^--N,NH₄⁺-N,soluble protein,proline and activities of nitrate reductase(NR),glutamine synthetase(GS),glutamate synthase(GOGAT),glutamate dehydrogenase (GDH).Results show that the biomass of Arabis paniculata F.increased with the Cd concentration in the soil and reached the highest in the treatment of 240 mg kg^-1.In the treatments with Cd content varying from 10 to 80 mg kg^-1,the contents of NO₃^--N and NH₄⁺-N in plant shoots were lower than in the control but did not show any significant variance(p>0.05),while in the treatments above 80 mg kg^-1 Cd,both the contents of NO₃^--N and NH₄⁺-N increased with the Cd concentration.Compared with the control,the treatments of Cd varying between 10～160 mg kg^-1 did not show any significant variance(p>0.05)in NR activity,but NR activity reduced sharply to 67% of the control in Treatment 240 mg kg^-1 Cd.Furthermore,the activities of GS, GOGAT and soluble protein in all the Cd treatments showed no significant variance(p>0.05)from the control.The GDH activity increased with the Cd concentration from 10 to 80 mg kg^-1 and then decreased dramatically when above 80 mg kg^-1.Compared with that of the control,the contents of free proline increased obviously in the Cd treatments except in treatment 10 mg kg^-1 Cd.

Abstract:Following the promulgation of the standards for arsenic(As)in environment and food people are getting more and more concerned about As pollution and the issue of food safety.It is still controversial over effect of phosphorus(P)supply on uptake and accumulation of As in plant and its mechanism.A hydroponic experiment of tomato(Lycopersicon esculentum,cv. Micro tom)was conducted to verify the effect of P mitigating As stress on plant growth.Addition of 50 mol L^-1 arsenate(AsO₄^3-)significantly decreased the growth of both root and shoot of the tomato plant with P supply ranging from 0.025 to 0.4 mmol L^-1,however,both As concentration in the plant and its inhibitory effect were reduced as P supply rose in level.The roots contained much more As than the shoots.Inhibitory effect of As on P uptake was observed also only at low P supply levels (0.025 and/or 0.05 mmol L^-1 of P).In addition,As had little influence on the expression of the two phosphate transporter genes(LePT1 and LePT2)in tomato.In conclusion,increase in P supply could decrease concentration of As in the plant,thus mitigating the adverse effects of As stress on tomato growth.

Abstract:Soil samples were collected of eroded Ultisols,varying in extent of erosion(slight,medium and severe),in the subtropical China.Organo-mineral complexing status of the samples was determined with the method modified by Fu Jiping and its relationship with soil nutrients was analyzed.Results show that with the extent of erosion rising from slight,medium to severe, the content of soil nutrients(OM,total N and total P)decreased gradually.Tightly-combined and loosly-combined humus dominated in the soils,and the content of stably-combined was the least.With erosion of the soil getting serious,both the contents of combined humus and organo-mineral complexes reduced,but the organo-mineral complexing degree of the soil did not change much.The content of soil complexes was positively related to combined humus and water-stable aggregates,so was the organo-mineral complexing degree.The contents of total N,total P and OM were closely related to combined humus,but the contents of total K and CEC were not.Among the three types of humus,tightly-combined humus was the most closely related to soil nutrients (total N,total P and organic matter).

Abstract:Vegetation restoration is a key measure to improve eco-environment in the Loess Plateau of China.To explore characteristics of the evolution of soil microbes after closure of hillsides for management of eroded hilly Loess Plateau,biomass and respiration of soil microbes and physico-chemical properties of the soils under natural shrubs(Sophora davidii,mixed boskage)different in history of the closure in Zhifanggou Catchment were studied systematically by means of substituting temporal serial with spatial serial.In addition,two pieces of grazing field and natural secondary forest(Platycladus orientailis,Quercus liaotungensis)each were chosen as contrast.Results show that soil quality,including biomass,respiration and metabolic quotient of soil microbes and physical and chemical properties of the soil,was gradually improved along the chronosequence of vegetation restoration.Microbial biomass C,N and P(SMBC,SMBN and SMBP)increased remarkably after 5 years of closure and management and kept on increasing gradually with each passing year in the southern slope.

Abstract:Out of 19 different genotypes of soybeans(Glycine max),Variety Zhechun No.2(Al-resistant)and Variety Zhechun No.3(Al-sensitive)were screened and selected as subjects in this study,which was designed to have 5 different aluminum(Al³⁺)treatments 0,0.2,0.4,0.6,and 0.8 g kg^-1,(i.e.0.293,0.493,0.693,0.893,and 1.093 g kg^-1,respectively,in soil total Al³⁺)and 3 parallel treatments(non-rhizospheric soils,rhizospheric soils and bulk soils with exogenous soybean exudation).Thirty days after the treatment,respiration rate,cellulose hydrolysis efficiency,ammonification rate,nitri-fication rate of the soils,and activities of acid phosphatase,catalase,and sucrase were measured.Results indicate that in treatments low in soil Al(0.2 and 0.4 g kg^-1),irritated secretion from the soybean roots increased the population of soil microbes, strengthened their capability of material transformation and stimulated the activity of soil enzymes,whereas in treatments high in soil Al(0.8 g kg^-1),root exudation was restrained comparatively,result ing in inhibition of the activity of microorganisms and soil enzymes.The results also demonstrated that exogenous root exudation could also influence the microbial ecosystem,triggering changes in activity of the soil enzymes and in major biochemical functions of the soil,thus mitigating aluminum poison to soybean,which is convincing evidence that root exudation obviously affects the microbial ecosystem.

Abstract:In aquatic and soil systems,trace metals exist in a number of forms,soluble or particulate,that determine their effect on ecosystems.It is accepted that based on the content of total heavy metal alone,it is not feasible to make any good prediction of its biological effect.Consequently,in establishing environmental criteria for and executing risk assessment of heavy metals,more and more attention is being given to taking into account their bioavailability.Metal bioavailability and toxicity have long been recognized as a function of water chemistry.And models were proposed to describe its mechanisms,such as Free Ion Activity Model(FIAM),Gill Site Interaction Model(GSIM)and Biotic Ligand Model(BLM).Based on FIAM and GSIM,by taking into account the effects of chemical speciation of heavy metals in water and their competition with cations for biotic lig-ands,BLM was successfully used to predict bioavailability and toxicity of metals in waterbody.USEPA has recently adopted BLM in developing its water quality criteria for copper.In this paper,a complete introduction is presented to the conceptual model of BLM in aquatic environment,its development and application of software,and a review made of extrapolating BLM to the sediment and soil environments,with emphasis on the terrestrial biotic ligand models(t-BLM)for plants,soil animals and microor-ganisms.A conceptual model of t-BLM was proposed and its methodology discussed.T-BLM which integrates soil physicochemical properties,metal speciation,bioaccumulation and toxicity response,will serve as a new tool to develop the more rational soil quality criteria and to conduct risk assessment of heavy metals.

Abstract:空间变异及其尺度问题在土壤学、地理学、水文学和生态学中均处于十分重要的地位,是当前研究热点之一^[1~5]。变异结果使得不同景观斑块间的交换过程在从田块到流域的不同空间尺度上产生^[6]。因此要实现景观生态过程中的尺度转换,关键是从实测到预测模型的复杂转变^[7,8]。在土壤学研究中,观测尺度和模型尺度均包含尺度的三因素,即采样间隔、采样幅度和支撑效应,这三个因素是界定观测或模型空间尺度的必要条件^[3]。而随采样尺度变化,土壤水分的表观变异与真实变异出现偏差,这种偏差是观测尺度的函数,可以采用地统计学中的半变异函数进行有效地尺度转化^[9]。国内外学者对土壤水分的空间尺度问题作了大量研究。

Abstract:土壤水分是影响黄土高原植被生长和生态环境建设的主要因素。已有对黄土高原土壤的持水性能、水分有效性能与移动性能、黄土高原环境的旱化与黄土中水分关系等方面的深入研究^[1,2],也有小流域内土壤水分物理性状与地形和利用条件之间关系的具体分析^[3,4]。但是这些工作所涉及的土壤剖面深度多为2 m或3 m,深层土壤水分物理参数研究还少有报道。而对于具有深厚土层的黄土塬区,高产农田与多年生林草地在土壤深层产生了不同程度的干燥化^[5~7],土壤干燥化的深入探讨需要与剖面土壤物理性质相关联。

Abstract:蔬菜中硝酸盐因其对人类健康有不利影响而受到广泛的关注^[1~4]。沈其荣等^[5]认为植物液泡作为临时的无机离子和养分离子的储存库,在维持细胞质离子浓度的动态稳定的过程中有着很重要的作用。硝态氮是液泡中储存大量离子的成分之一,当外源硝态氮供应不足时,储存于液泡中的硝态氮能被调配出来维持细胞质中硝酸盐浓度的稳定而满足植物对氮的需求。同样也有人提出不同的观点,认为细胞液泡内的硝酸盐离子是不容易被植物再调动的^[5],植物在细胞质中同化硝酸盐离子的速度远远超过了硝酸盐离子从液泡中释放进而被植物再利用的速率,仅仅通过调动液泡内的硝酸盐是不能够维持植物的正常生长的。

Abstract:我国水资源稀缺,人均淡水资源正以惊人速度减少,而咸水、微咸水量则不断增长。但目前这类水资源基本上未得到利用,浪费严重,若能加以利用、转化增值将对区域生态经济产生不可估量的效益^[1]。

Abstract:DNA是所有生物的遗传物质基础。在土壤生态系统中,动植物和微生物主动分泌或细胞死亡裂解释放的DNA分子可迅速被土壤黏粒吸附固定,从而对核酸酶降解产生抗性而在土壤中持久存在,并能被某些合适的宿主细胞所接受^[1]。土壤胶体固定的DNA被称作是“环境中的隐性基因”,对微生物的生态、生物多样性及遗传进化有着重要的影响^[2~4]。

Abstract:红壤是我国南方14省(区)的重要土壤类型和耕作土壤,主要分布在湖南、江西、浙江、云南等中国南部地区,总面积约218万hm²,约占全国总土地面积的22.7%,占全国耕地面积的28%^[1]。红壤区自然条件十分优越,是我国粮食、经济作物和肉类产品等的主要生产基地,其生产的粮食占全国粮食总产量54.8%。由于土壤发育完全,淋溶强烈,红壤呈盐基不饱和状态,土壤呈酸性。

Abstract:土壤中矿物的种类与土壤的粒级有关,随着粒级变粗,矿物组成趋于简单,次生矿物类型及含量减少,而原生矿物种类及含量增加^[1]。土壤钾素含量、有效性及其转化又与土壤矿物组成密切相关,存在于黏粒部分的含钾矿物(黏粒矿物)因直接影响钾的生物有效性而备受关注。土壤中钾素的研究较多^[2,3],关于不同粒级的土壤钾素释放的差异已有报道^[4~6],但长期定位施肥对不同粒级的土壤颗粒中钾素行为的影响研究得较少,笔者在这方面做了一系列的工作^[7~9]。因此研究长期定位施肥中土壤粒级与土壤钾素释放行为的关系不仅能丰富土壤矿物风化和黏土矿物形成理论,而且对全面认识土壤中钾素状况、供钾能力、钾素的相互转化及合理利用有限的