Abstract:B.B.Mandelbrot enunciated the concepts of fractal and fractal dimension in 1967.They have found application in a variety of fields ever since.Fractal theory is a new method to observe and explain the complexity and mechanism of nature.Although fractal dimensions of lots of phenomena were calculated, related studies on fractal characters of soils of China are seldom seen.This issue is discussed in this paper.Some significant conclusions are drawn: (1) A certain relationship between perimeter and area of soil patches object ively exists for soils in China.(2) Fractal dimensions of soils of China are calculated.It is the biggest with the cold desert soil being 1.9524, and the smallest with the gray desert soil, being 1.1582.(3) The fractal dimensions of soils of China tend to increase from the south to the northeast and northwest of the country, showing a rising trend with the topography rising from southeast to northwest, in the Qinghai-Tibet Plateau.(4) The stability of spatial structure is the highest with the cold desert soil and the smallest with the gray-cinnamonic soil.(5) The stability of spatial structure of soil type declines from South China to Northeast China, but rises from the southeast to the northwest in the Qinghai-Tibet Plateau.(6) Physical mechanism of the spatial fractal structure of the soils of China is also revealed.It is indicated that the average indexes of number and shape of soil patches are the most important factors which influence spatial fractal structure of the soils.In other words, the spatial fractal structures of soils are mainly influenced by geometric characteristic of the spatial pattern of soils.

Abstract:土壤系统分类的检索系统是以定量化特征为主,描述土壤的知识体系,具有严格的逻辑一致性和完整性,是建立土壤信息元数据模型的重要基础。XML是先进的网络语言标准,采用可扩展的标记,能够描述各种数据结构,是网络信息共享的重要工具。本研究分析了目前土壤信息共享中存在的问题,提出了以中国土壤系统分类检索系统为主体,参照中国土壤分类与代码的国家标准和ISO地理信息元数据标准,采用XML为描述语言,建立的土壤信息元数据模型,为实现土壤信息共享提供解决方案。

Abstract:Based on spatial data originating respectively from the TM satellite images of 1984, 1995, 2000 and 2003, a multi time phase successive comparison study was conducted on urbanization and city sprawl in the Nanjing region using RS and GIS techniques.Meanwhile, impacts of city sprawl on the regional soil resources were analyzed based on data from the digital soil map of the city, files of the second nat ional soil survey and supplementary investigations.Results obtained in the study indicate that the urban area of the city increased very fast in the past two decades, suggesting a rapid regional urbanization process.The total built up area of the city increased by nearly 100% during the period from 1984 to 2003.As a result of the rapid urbaniza tion, the soil resources of Nanjing reduced by 7.4% in acreage.Especially, the soil resources with high productivity and favor able facilities in the suburbs were decreasing much faster because of their close contiguity to the expanding city.Finally, it might be concluded that rapid urbanization was posing an increasing pressure on soil resources, of which the impact on regional agricul tural production and food security allows no neglect.

Abstract:The research on soil water infiltration is of great significance to the acquisition of a better knowledge of hydrological circulation of the watershed.A water-wind erosion interlaced region is a place where the most serious soil and water loss happens on the Loess Plateau, and any study on soil infiltration properties and on their spat ial variability of this region will do help to expose process of the soil erosion and improve precision of the watershed hydrological model.Of a natural slope (380 m long) in the Liudaogou catchment, which is typical of the water wind erosion interlaced region, stable infiltration rate, mean infiltration rate and cumulate infiltration capacity within the initial 30 min were measured with a double ring infiltrometer at 57 sampling sites, and the data were analyzed with both the traditional statistical method and the geostatistical method combined with the fractal theory.The results indicate: (1) the coefficient of variation of the above three parameters was respectively 0.48, 0.36 and 0.40 and the spatial variability was medium in degree;(2) the fractal dimension of the three parameters was 1.88, 1.92 and 1.85, respectively, which shows that the difference was rather small between soil samples in values of the soil infiltration properties;and(3) the soil was not a medium with significant theoretical fractal phenomenon, and fractal features existed only in a specific range of space, and the range of spatial autocorrelation for stable infiltration rate, mean infiltration rate and cumulate infiltration capacity within the initial 30 min was 20~120 m, 20~140 m and 40~100 m, respectively.

Abstract:In recent years, nitrate contamination of groundwater has become an increasing concern for the health of people in rural areas who consume groundwater daily in China, ecially in the North China Plain.Usually, a deterministic model with mean hydraulic parameters is used to estimate the nitrate leaching for the whole agricultural field.In fact, the quantities of nitrate leached are variable from place to place in the field because of the parameters are different, so the simulated results by the deterministic model using mean hydraulic parameters could not represent the field-wide nitrate leaching.The objective of this paper is to evaluate the effect of spatial variability of the surface soil saturated hydraulic conductivity (K_s) on nitrate leaching and to assess the risk of nitrate contamination.First, a soil water-heat-nitrogen simulation model was established and verified based on the field data.Second, a sequential Gaussian simulation method was used to get a random field of the surface soil K_s based on 117 observed values in the field.Finally, the joint model was coupled with the random field of the surface soil K_s, which was gained by a conditional simulation method.During the period from March 15 to June 10, 1999, nitrate leaching was stochastically simulated with the irrigation rate being 353.8 mm and the nitrogen fertilizer application rate being 86.25 kg hm^-2.The accumulated quantities of the leached nitrate ranged from N 15.04 kg hm^-2 to 26.04 kg hm^-2 in the soil profile 2 m in depth, account ing for about 17.4% and 30.2% of the fert ilizer used during this period.The area with the probability of nitrate leaching exceeding the value obtained by the conventional method in the control being higher than 70% amounted to about 20%.It was implied that the soil spatial variability could result in change in nitrate leaching.The value obtained with the traditional method in the control could not be used because it obscured the risk of nitrate leaching.

Abstract:Spat ial variability of HCH (HCH_S=α-HCH+β-HCH+γ-HCH+δ-HCH) and DDT (DDX_S=4, 4'- DDE +4,4'-DDD+2, 4'-DDT+4, 4'-DDT) in typical agricultural soils of 7 counties located in the Huang-Huai-Hai Plain, China was examined, and vertical distribution pattern of the residues in 4 soil profiles investigated.Their distribution maps clearly indicated that the residues varied nearly randomly in distribution in these counties.DDT showed stronger variability than HCH.Soils with DDX_S contents exceeding 50 μgkg^-1, the upper limit specified by the Chinese government for the first-class soil quality, all distributed in the east part of Yucheng County.The study revealed the necessity of determining spatial variability in status of organochlorine pesticide for planning a correspondent management programme.The contents of HCH_S at layers deeper than 30 cm were quite similar to what was found in the surface layer 0~30 cm in depth, with β-HCH dominating among its isomers.While, DDX S was concentrated in the surface layer, 0~30 cm in depth, but remained less than the detection limit or decreased markedly with depth.The results indicated that HCH and DDT residues in 0~100 cm soil profiles had declined down to safety level in most sites 20 years after the official ban.

Abstract:The transport and regime of water and salt under crops are a very complex physical chemical biological system.The study of their laws and characteristics is very important to developing water and salt transport models, guiding of sustainable exploitation of salt-affected soils and irrigation management, explaining interaction between sustainable agriculture and environment, and forecasting water and salt transport.Therefore, a soil water and salt transport model (SWSTM) was developed and adopted to describe transport of water and salt under winter wheat crop, numerical simulation of water and salt regime was done, and water and salt transport under different climate conditions and groundwater conditions was predicted and forecast with the SWSTM model.The results show that the simulation is very ideal and it is practicable to do numerical simulation and forecast with this model.So, a new method to forecast water-salt regime is thus brought forth.Furthermore, according to the actually situation, a simplified useful method without complex calculation is expected to be applied to forecasting distribution of salt-affected soil resources and water and salt regime on a large scale.

Abstract:Retarding factors of copper movement in sandy loam, silty clay and loamy sand were determined in an experiment of isothermal static equilibrium adsorption and calculated by using the deterministic convection-dispersion equation and deterministic two region nonequilibrium convection-dispersion equation coupled with the outflowing dynamics of copper ions and tracer ions measured in a miscible displacement experiment.The results indicate that the Langmuir linear isothermal adsorption could accurately describe adsorption behavior of copper;and that retarding factors calculated were close to measured values.In addition, to determine retarding factors, the method of using the miscible displacement experiments coupled with the convection-dispersion equation was both time-consuming and low in accuracy.

Abstract:Polycyclic aromat ic hydrocarbons (PAHs) are supposed to be ubiquitous in the environment.However, researches on PAHs of Hong Kong area used to be focused mainly on sediments, atmosphere and marine organisms in the past, and little was reported on the soils.A total of 53 surface (0~10cm) soil samples consisting of 45 ones from rural areas and 8 from urban areas were collected and analyzed for PAHs with a gas chromatograph in combination with a flame ionization detector (GC/FID).Distributions of PAHs contents in Hong Kong soils were presented with the aid of the geographic information system (GIS), and the origins of PAHs were identified with the method of isomer ratio.The results indicate that all the 16 U.S.EPA priority controlled PAHs except Dibenz(a, h) Anthracene were detected in the soils of Hong Kong.PAHs contents were averaged 34.2±16.0μgkg^-1 in the rural soils and 169±123μgkg^-1 in the urban soils.PAHs patterns varied to some extent as well between the urban and rural soils.Higher molecular PAHs, such as Benzo(b+k) fluoranthene, were found much higher in the former than in the latter.Benzo(a) pyrene, that has been recognized as one of the carcinogenic chemicals by the International Agency for Research on Cancer (IARC), was detected up to 47.2μgkg^-1 in the soil in the Zoology and Botanic Garden of Hong Kong, which was twice the relevant target value of the Soil Protection Guidelines in the Netherlands.As for the PAHs origins, it seemed that the former mainly stemmed from biomass burning, such as hill fires whereas the latter was closely associated with vehicular exhaust.

Abstract:Cluster analysis, anova, and multiple comparison were used to investigate the spat ial distribution pattern of PAHs in the surface soils of Tianjin. It was revealed that the studied area can be categorized into three subarea with similarity in PAH level and profile within each category, i. e. the Tanggu-Hangu area with the hightest in PAH level, the urban-suburb area with the relatively high in PAH level, and the rural area low in PAH level. In addition to PAH contents in the soil, the profile of 16 PAH compounds dist inguished from one area to another. It was demonstrated that coal combustion is the only major source to the PAHs in the rural area, while vehicle emission as well as other industrial activities add more PAHs to the other two area in addition to input from coal combustion.

Abstract:Based on the work of Williams et al in 1992, an inventory of soil NO_X emissions for China was developed.With the aid of a mesoscale meteorological model MM5 and a photochemical model Calgrid, effects of these emissions on tropospheric photochemistry in China were investigated.For the year 2000, it was estimated that the annual soil emissions in China amounted to 22518 Gg N, i.e.7% of the anthropogenic emissions.In summer, this fraction increased up to 23.4%, showing the importance of soil emissions to photochemical reactions.These emissions caused rise in average concentration of NO_X, O₃, HNO₃ and PAN (peroxyacetyl nitrate) and variation of spatial distribution of the pollutants as well.Their maximum increments on average reached 2.37, 26.08, 9.79 and 0.43 Lg m^-3, respectively, and the rising trend was much higher in summer than in any other seasons.The rise variedwith the sources of emission, meteorological conditions and photochemical characteristics.With increasing anthropogenic emissions, the role of NO_X emission from the soil will be more significant in tropospheric photochemistry and can not be neglected.

Abstract:A tract of farmland on a typical mount in Northeast China was selected as a case to study effect of soil erosion and deposition on dynamics of soil organic carbon (SOC) by determining some properties and δ¹³C of the soils at different topographic positions.The results showed that the δ¹³C value of the surface soil was significantly correlated to slope gradient, clay content, soil moisture and pH.The change in δ¹³C with depth in soil profile reflected input of plant residue and accumulation of eroded soil, which helps to identify buried soil surfaces.The slope (β) of linear regression between isotopic composition and SOC concentration was positively related to slope gradient of the landscape and negatively related to clay content, indicating that β could be used as a useful index to describe mineralization of SOC at the erosion position.The contents of C₃-C at the shoulder and back of the slope were significantly less than that at the summit and C₄-C showed no obvious difference between them, indicating the differences in SOC content between erosion sites resulted from C₃-C.The contents of C₄-C at the foot and toe of the slope were significantly less than those at the shoulder and back of the slope, which indicates that the loss of new carbon at deposited sites was greater.

Abstract:An experiment has been conducted in the Experimental Station of the Nanjing Agricultural University since 1999, with the experimental fields separated into plots (2.8 m×1.0 m×0.6 m) by concrete frames.The soil in the plots was sandy loam soil (Orthic aquisols) collected from Rugao County, Jiangsu Province.The experiment was designed to be rice and wheat rotation with five treatments, i.e.application of corn residues (incorporating or mulching) with or without earthworms and control, and 3 replicates for each treatment.The responses of soil microbial biomass carbon (MBC) to earthworm act ivity had been investigated from the rice season of 2001 to the wheat season of 2004.It was found that MBC significantly increased (p<0.05) in the treatments with earthworms.Generally, the MBC was higher at the maturing stage of wheat than that in the rice season in the same year, however, the difference was notably enhanced (p< 0.05) by earthworm and weakened by input of corn straw.Posit ive effect of earthworms on MBC was more distinct in the 0~5 cm soil layer with corn residues incorporated and in the 5~10 cm soil layer with corn residues mulched.The enhancement of MBC by earthworms was similar in the 10~20 cm soil layer whether corn residue was incorporated or mulched.

Abstract:Objectives of the study were to explore forms, quantities and distribution of soil phophorus in profile of paddy soil as affected by different fertilization patterns in a long-term experiment under a rice wheat (or rape) cropping system, and to evaluate potential effects of transformat ion and downward transport of phosphorus on environment.The experiment that has been carrying on since 1980 on a permeable paddy soil (huang ni tu), is designed to have 14 treatments with 3 replicates.Soil samples were collected from the top soil (0~15 cm) and then layers 5 cm apart till 1 m in depth in November 2002.Significant P accumulation was found at the depth of 25 cm for all P treatments but Treatment M_NPK (Manure+fertilizer N+fertilizer P+fertil izer K) where it was detected at the depth of 30 cm.Inorganic P (I-P) concentrations increased significantly in the soil layer of 0~25 cm for most P treatments.Ca₂-P moved beneath 30 cm in soil depth, Al-P, Fe-P and Occluded-P (Oc-P) to 25 cm in depth, and Ca₈-P to 20 cm in depth.Ca₁₀-P contents increased significantly only in treatments with fert ilizer P application, showing manure P keeps available longer than fertilizer P.Changes in O-P were smaller than I-P in range.Merely in the plots with manure plus fert ilizer P or with fert ilizer P and K, the organic P (O-P) concentration in the top soils (0~15 cm) increased significantly.Long term of P application exceeding P removal by crops were not economical because more inactive Oc-P and Ca₁₀-P accumulated, and led to P accumulation in the top soil and hence the potential of P loss via surface runoff and leaching that would threaten the quality of surface water and groundwater.

Abstract:By simulating oxalic acid/oxalate concentrations in forest litter leachate, a series of experiments were conducted including one-time extraction and repeated sequential extraction, with the oxalate loading rate varying from 0 to 200 mmol kg^-1 soil.Oxalic acid loading substantially stimulated soil-P-release from A₁ horizon, showing a linear relationship;but its effect on B horizon soil was relat ively negligible, especially at low oxalic acid concentrations (< 5 mmol L^-1).Oxalate solutions (0.5~20.0 mmol L^-1) oxalic acid adjusted to pH 5.16 with 10.0 mmol L^-1 NaOH) had a much higher (1.51~2.98 times) soil P re lease effect than oxalic acid solut ion the same in oxalate concentration.Therefore, the mechanism of oxalic acid/oxalate triggering release of soil phosphorus is assumed to be dominated by ligand-exchange or complexing reactions of oxalate anion(C₂O₄^2-), but not simply acid-dissolving effect.The effect of oxalate anion on soil phosphorus release was found to be somewhat cumula tive, i.e.the amount of P released was primarily controlled by the cumulative oxalate loading rate, relatively independent of the manner of oxalate addition (one-time or sequential).When oxalate anion was loaded as pH 5.16 sodium oxalate solution, the regression equation between A₁ horizon soil P release (mg kg^-1) and cumulative oxalic loading rate (mmol kg^-1) was: Y=-0.0004X²+0.1766X+0.4253,R²=0.9902.Merely on a quantitative basis of oxalate anion leached from forest litter, the increased soil P release from A₁ horizon (0~20 cm) was estimated to be 2.40 kg hm^-2 a^-1, accounting for 1/3~1/5 of the annual P absorption in middle-aged forests.If other types of organic anion or other react ions producing organic anion were taken into account, the cumulative effect of organic anions on soil P release would be very conspicuous.

Abstract:Ridge tillage is a kind of soil and water conservation tillage used frequently in the rainfed farmland of sandy areas.Through field observat ion and analysis of soil samples, effects of the practice were studied on growing environment of rape.The results indicate that compared with flat tillage, ridge tillage increased soil moisture of the plow layer, reduced moisture fluctuation during the growing season of rape, and altered distribution of soil moisture in the vertical profile, locating wetting front in the plow layer, which alleviated drought stress on rape growth.In addition, it also reduced the content of erodible particles in the soil, increased roughness of the land surface and vertical wind velocity grads, thus efficiently reducing soil erodibility and wind speed near the land surface, which played an important role in preventing soil wind erosion and protecting crop seedling.Comparison between various structures of ridge tillage showed ridge t illage with ridges 15 cm high and a height spacing ratio of 1/12 (T₃) and ridge tillage with ridges 25 cm high and a ratio of 1/24 (T₄) did better in rainfall harvesting during the growing season of rape, while ridge tillage with ridges 25 cm high and a ratio of 1/6 (T₂) did better in preventing soil wind erosion during the fallow period of cropland.So ridge tillage with a reasonable structure is an effect ive measure in adjust ing micro-land-use structure in the rainfed farmland of sandy areas.

Abstract:Pot experiments were conducted in greenhouse on effects of salts different in type and concentration on growth and physiological indexes of crops to find out mechanisms of their adaptability and tolerance to salt.The results showed that plant height, number of effective tillers, yield and biomass of the ground parts of barley dropped along with the increasing soil salt concentration and the growth of spinach was inhibited even more significantly.The content of malondialdehyde(MDA) in barley leaves increased with the increasing NaCl concentration and reached summit under Na₂CO₃ stress.Compared with barley, more Na⁺ was transported through roots to the ground parts and accumulated in spinach leaves under salt stress. Barley has the capability of restraining transportation of salt ions to leaves and sustaining normal function of leaves.Na₂CO₃ is more harmful to leaves of the plants.

Abstract:Because of complex chemical reactions of chromium in soil, the mechanism of electroremediation of Cr-contaminated soil remains unclear up to now.In this paper, effects of voltage drops during electrokinetic treatments on the movement of chromium in a yellow brown soil were studied by evaluating distribution of voltage drops in soil sections, electric energy consumption, change in soil basic properties and total chromium residual in the soil.The results show that electrokinetic currents and electroosmosis flows increased with increasing voltage, and the soil pHs in all soil sections dropped to about 3 after electrokinetics.Redox and precipitat ion reactions occurred in the soil column during the electrokinetic treatments, which led to decrease in ions concentrat ion in the soil solution and uneven distribution of voltage drop in the soil column.The applied electric field and low pH environment strengthened reduction reaction of hexavalent chromium to form hardly-movable trivalent chromium in the soil.Application of 20 V voltage achieved higher Cr removal rate and used up less electric energy.After 576 hours, the treatment removed 41.1% and 77.7%, of soil Cr and Cr (v) respectively, and used up 147 kWh t^-1 of electric energy.It suggests that to control anolyte pH and increase the anolyte electroconductivity is an effective method to increase Cr removal rate from the soil column and reduce electric energy consumption.

Abstract:Adsorption of phthalic and salicylic acids by two variable charge soils, Haplic Acrisol and Rhodic Ferralsol, was investigated in this study.Results show that both soils were high in adsorption capacity for two organic acids and higher in affinity for phthalic acid.The quantities of the two organic acids adsorbed by Rhodic Ferralsol were larger than by Haplic Acrisol and this result consisted with the content of iron and aluminum oxides in the two soils.The iron oxides in these soils played a significant role in the adsorption of organic acids, but the soil minerals such as kaolinite showed a small adsorption capacity for organic acids.The adsorption of organic acids involved two mechanisms: specific adsorption and electrostatic attraction, but the former was the major one for the two organic acids.Little effect of pH on adsorption of the organic acids was observed below pH4.5, whilst the adsorption decreased with the increase in pH beyond pH4 5.

Abstract:Effect of a new pesticide, acetamiprid, on biological activity in upland soil was studied through analysis of soil enzyme activities and soil respiration.The results show that acetamiprid obviously affected soil respiration and phosphatase activity, and the higher the concentration was, the stronger the inhibitive effect was.The activity of dehydrogenase was enhanced in two weeks after acetamiprid application Variance of urease and catalase showed no distinct relationship with the application rate.The activity of proteinase was not significantly affected within the first two weeks after acetamiprid application but was from the 4th week.

Abstract:Nutrients in litters and soils, amount of microorganisms and activity of enzymes in soils of plantations of Cunninghamia lanceolata, Pinus massoniana, Pinus elliottii, Acacia mangium and Eucalyptus urophylla similar in geographic conditions were studied using soil chemical analysis, dilution flat and enzyme analysis methods in order to get a better understanding of influences of some main tree species in South China on soil fertility.The soils of the five plantations were rather strong in acidity.Among the five plantat ions, the Cunninghamia lanceolata plantation had the largest amount of litters, which were also rather rich in nutrient reserve, about 94.08 kg hm^-2.Consequently, its soil fertility was relatively high, with soil organic matter, total N, total P, total K, alkali-hydrolyzable N, available P and available K being 25.54 g^-1, 0.96 g^-1, 0.37 g^-1, 12.04 mg^-1, 64.42 mg^-1, 1.87 mg^-1, 41.88 mg^-1, respectively.However, the soil was low in amount of microorganisms.Pinus massoniana and Pinus elliottii litters were low in nutrient content, and their soils were resultantly low in nutrient contents and soil fertility.The Acacia mangium plantation effectively improved soil chemical properties and its litters had the highest nutrient reserve among the five plantations, about 106.2 kg hm^-2.Its soil fertility was the highest among the five plantations, with organic matter, total N, total P, total K, alkali-hydrolyzable N, available P and available K reaching 23.42 g^-1, 0.93 g^-1,1.28 g^-1, 15.29 mg^-1, 69.32 mg^-1, 1.98 mg^-1and 76.88 mg^-1, respectively, and its amount of soil microorganisms and activity of enzymes were also great.The soil in the Eucalyptus urophylla plantation was high in K, but low in soil organic matter, N, P, amount of soil microorganisms and enzyme act ivity, and thus resulting in low soil fertility.

Abstract:The insecticidal crystal protein gene of Bt (Bacillus thuringiensis) has been the most extensively used one in plant insectresistant genetic engineering.Along with commercialization of large groups of Bt-transgenic crops, the impact of Bt toxins released from transgenic plants on the soil ecosystem has aroused high concerns.In this paper the environmental behavior and biological effects of the Bt toxin are reviewed, addressing ways of Bt toxins released into the soil from transgenic plants, its movement, bond onto soil surface-active particle, degradation, persistence and effects on organisms and enzymes in the soil.

Abstract:西藏地质历史比较年轻,因而土壤的形成也较晚。由于喜马拉雅山造山运动和多次的冰期和间冰期的发生,青藏高原不断加速抬升,气候变干变冷。洪积物、坡积物、冰积物、湖积物和冰水沉积物在气候、生物、物理、化学和人类活动的作用下不断演变,在不同的地型部位形成多种类型的土壤,且具有鲜明的高原特色。耕地是土壤资源的精华,它是在自然土壤的基础上,经过长期的人类耕作、灌溉、施肥等措施逐步演化而成的,由于各地气候、成土母质、成土条件、耕作方式、栽培历史等的不同,耕地的类型、质量、肥力状况差异较大^[1,2]。

Abstract:钾是植物生长必需的大量元素,施入土壤中的钾主要通过扩散作用与作物根系接触而被吸收利用,其在土壤中的扩散受水分、温度,质地等多种因素的影响^[1]。研究钾在土壤中的迁移距离和形态变化有助于了解钾的土壤化学行为,从而指导合理施肥。肥料施入土壤后,特别在集中施用时(条施、穴施、带施等)都会在肥料附近造成一个特殊的环境,在这一微域内,肥料养分的浓度数倍或十几倍于整个土体,它必然会引起一系列特殊的物理、化学、物理化学和生物学的反应。这些反应常常对土壤生产力和植物营养会产生很大影响,研究这一区别于整个土体的特殊区域的特殊反应必然有着巨大的理论和实际意义,鲁如坤把这一微域称为肥际微域^[2]。

Abstract:土壤饱和导水率(K_s)是土壤重要的物理性质之一,是估计土壤非饱和导水率,计算土壤剖面水通量和排水工程设计的一个重要土壤水力参数^[1]。目前,土壤饱和导水率测定方法较多,如定水头测定法、稳态流法、变水头出流仪法等^[2]。已有的研究成果表明,K_s值受土壤水分特性、质地、土壤结构、土壤中阳离子组成与含量、土温、有机质含量、土地利用方式等众多因素的影响^[3~5]。一般而言,土壤质地越粗,K_s值越大;有良好结构体的土壤的Ks值比无结构体的高;土壤中一价阳离子的存在会减弱土壤的导水性能;K_s值随着土温的升高而增大;有机质含量越高,K_s值越大。

Abstract:根据最新的考古发现,中国种植水稻的历史可以追溯到公元前4000多年。据考证,位于长江三角洲的昆山市正仪镇绰墩山古水稻土遗址的地下42~57cm与100~116cm均为古水稻土层,历史耕作时间分别距今约3320a和6280a。硝化细菌在耕作土中的数量及其硝化强度被认为是土壤肥力的指标之一^[1],在土壤氮素循环中起着重要作用。氨氧化细菌在硝化作用过程中将铵氧化为亚硝酸盐,实现亚硝化作用,是硝化过程中必不可少的步骤,同时也是其限速反应^[2]。

Abstract:目前,利用有机固体废弃物生产生物有机肥料已成为一门产业^[1]。生物有机肥料具有的优越性是任何一种化肥都不能代替的。因为生物有机肥中的有机质不但可以作为N、P、K等作物营养元素的主要来源,而且还能促使土壤团粒结构形成,提高土壤保水、保肥的能力,进而提高作物的产量^[2]。同时有机堆肥过程中形成的腐殖酸以及一些低分子量有机物质具有重要的生理功能^[3]。目前阻碍有机固体废弃物堆肥进展的一个重要原因就是至今还没有一个权威的评论方法或统一的指标对堆肥腐熟进行评价^[4],从分子微生态学角度对有机堆肥的微生物多样性和堆肥中腐熟微生物研究鲜见报道。

Abstract:化能自养氨氧化细菌(Ammonia-oxidizing bacteria,AOB)能将氨氧化为亚硝酸盐,这一反应是硝化过程中的限速步骤,在污水氨氮脱除中有着重要作用^[1]。氨氧化细菌主要由Nitrosomonas、Nitrosospira、Nitrosolobus、Nitrosovibrio、Nitrosococcus等种属组成,其中Nitrosomonas为主要的和常见的氨氧化细菌^[2]。由于化能自养菌具有生长速率低和生物量低等特点,使得采用常规的筛选和鉴定方法极为耗时和繁琐。