Abstract:Tropical soils with unique pedogenic processes influenced by warm humid climate are investigated worldwidely.Latosols are zonal soils in tropical areas of China and have been the subject for scientists studying mineralogical and geochemical characteristics.However studies on micromorphological characteristics of the soil are still far and rare.In this study, micromor-phological features and pedogenic processes of three Latosol profiles derioedfrom different parent materials from Hainan Island are studied with soil micromorphological, clay mineralogical and chemical methods.Vermiculated red soils in South China, which were formed in the mid-Pleistocene, are called Latosols in some studies.To provide evidence for the study of palaeoenvironment and archaeology, vermiculated red soils are compared with Latosols in this study.The results indicate that Latosols mainly have two typical micromorphological features.One is the absence of unweatherable minerals and illuvial clay, and the other is the presence of nodules of iron and manganese oxides resulting from weathering and isotropic b-fabric in good drainage conditions.The typical pedogenic processes of latosols are strong weathering, rubification, homogenization, eluviation and remarkable desilication.In poor drainage conditions, some pseudogley features are formed.Resulting from strong chemical weathering under the tropical climate, Latosols are strongly developed.Compared with Latosols, vermiculated red soils are less developed.They cannot be classified as latosols and Oxisols, but tend to be classified as Ultisols in the American Soil Taxonomy, corresponding to red earths in the Chinese Soil Genetic Classification.This indicates wet, warm climate and indeciduous, latifoliate vegetation in the vast areas south of the Yangtze River during the forming period of vermiculated red soils.

Abstract:The Basin Scale Simulation Model for Soil and Water Resources Management-SWRRB, which includes 198 mathematic equations, was used to simulate water yield, sediment yield and other natural processes in the Lianshui Basin, 579.3 km² in area in Jiangxi Province, China.A good result was obtained.Successful simulation depends on: (1) dividing the basin into more subareas; (2) elaborately and thoroughly preparing input parameters; (3) fully conducting simulation experiments and adjusting parameters one by one according to the order of magnitude of the influences of input parameters on output parameters, to the optimal effect.More attention was paid to subareas dividing and values assigning to topographical elements, air temperature, rainfall, soil properties and RCN.

Abstract:There is no doubt that soil database is an important mnemonic and analytic tool for soil studies.This paper deals with spatial heterogeneity of soil properties with the aid of a 1:50 000 soil database of Wuxi and Changzhou cities, which is built up with the ArcGIS and Visual FoxPro technology and consists of 8 830 mapping polygons and data of 269 soil profiles.A map is compiled in the accordance to the criteria for grading of soil fertility fixed up in Research Project "973" on Principles of Soil Quality Changes and Sustainable Land Use (for pH, available phosphorus and potassium) and in the National Soil Nutrient Grades (for total nitrogen) to show the spatial heterogeneity of pH, total nitrogen, rapidly available phosphorus and potassium in the surface soils (0～15 cm) of the study area.The map shows that soils of grade 1～2 in pH value constitute about 90% of the total study area, and that the most part of the soils on the flat Tai Lake-Ge Lake Plain are commonly in grade 1 in total nitrogen, rapidly available phosphorus and potassium.Moreover, variance analysis is conducted of the data of physico-chemical properties of the soils of various parent materials and of various types (soil subgroups).Result shows that all determined soil properties, except for total nitrogen, are quite heterogeneous.It is concluded that, at the scale of 1:50 000, parent material is the dominant factor for the spatial heterogeneity of pH, bulk density, total phosphorus, organic matter and rapidly available potassium,while soils type for the spatial heterogeneity of pH.That is to say, the impacts of parent materials have stronger impacts on spatial heterogeneity of soil properties than soil types do.

Abstract:Based on the land surface temperature data figured out of the composite data of channel 4 and channel 5 light temperature of NOAA-AVHRR, together with spectrum vegetation indices, water deficit index (WDI) was estimated as the indicator of drought.The spatio-temporal characteristics of droughts and drought occurrence frequency of each month in China in the past two decades (1982~2001) were analyzed.Results showed that in spring, Northwest China, North China and South China had a higher drought occurrence frequency; from May to August, Northwest China and North China had; and from September to December, Northwest China, North China, Central China and Sichuan basin had.The analysis of relationship between average annul precipitation and average WDI, drought occurrence frequency in the 20 years demonstrated that they were closely related in a linear pattern when the average annul precipitat ion was less than 500 mm but when the average yearly precipitation was more than 500 micro-metal, WDI was not distinctly related to precipitation and drought level.

Abstract:Geochemical characteristics of rare earth elements (REE) in the soils were deemed to relate to the endemics of a region.In order to determine soil geochemical characteristics of the REE in Hong Kong, 46 soil samples typical in Hong Kong were collected and analyzed for contents of rare earth elements with an Inductively Coupled Plasma (ICP) and an Atomic Emission Spectrometer (AES).The results indicate that the average content of REE in Hong Kong soils is relat ively lower than in thesoils of the Mainland and increases gradually with the depth in soil profile due to downward leaching of the elements.The fractionation between LREE and HREE is apparent in the whole soil profile.The positive anomaly of cerium in the soils developed from pyrogenet ic rocks and negat ive anomaly of europium in the soil from granite are quite distinct.Parent material, major mineral elements in the soils, soil basic characteristics, topography and vegetation are all supposed to make important contribution to the enrichment and fractionation of soil REE.

Abstract:Based on the lab data of concentrat ions of total Cu, Zn, Cr, Cd, Hg, and As obtained through determination of 54 topsoil samples, continuous classification of heavy metal concentrations of the sampled soils was conducted with fuzzy c-mean algorithm (FCM).And, membership values of the sampled soils in each class were interpolated using ordinary kriging to predict spat ial distribution of soil heavy metal concentrations and pattern of soil heavy metal pollut ion of the investigated area.The obtained results show that the concentrations of Cu, Zn, Cr, As and Cd in soils in the area were below the national criteria for soil environment and even their background values, and that no accident of soil heavy metal pollution had ever occur.The concentrations of Cu, Zn, Cr and As, however, in the soils of the west and south parts of the investigated area were higher than that in the rest, and in a fewer plots enrichment of Zn and Cr was found, perhaps demonstrating influences of industrial activities and traffic on the soil environment.It was revealed that Hg was the dominant heavy metal pollutant, and soil Hg pollution occurred mainly in vegetable production bases and land on either side of Chuhe River, especially the vegetable production bases in the central part of the investigated area.Compared to the interpolation method, spatial predict ion based on the fuzzy set theory could achieve a continuous output with significantly higher accuracy.

Abstract:Situated at Yangtze Rive Delta (YRD), Zhangjiagang City has been undergoing a very rapid economic development since the adoption of the reform and opening policy in the 1980s.Based on intensive soil sampling from large fields and fields near the factories, (ⅰ) status of soil heavy metal (Cd, Hg, and Pb) pollution, (ⅱ) effect of sampling methods, i.e.sampling in large fields (A) and in combination of large fields and fields near factories (B) on the assessment of soil heavy metal pollution, and (ⅲ) effect of industrial types on soil heavy metal accumulation with the aid of ratios of soil heavy metal content in top-soil and sub-soil (element ratio) were discussed in the paper.In general, the soil heavy metal pollution in Zhangjiagang City were not serious with the average content of the elements close to their respective background value or lower than criteria of the second grade of the national standard for soil environmental quality (GB15618-1995) and the limitation values for soil environment pollution of green-food production bases (NY/T391-2000).However, heavy metal contents in some samples were over the standard, resulting in a distribution of small area of soils with high element contents.The sampling methods had a significant effect on assessment of soil pollution.For Cd and Pb, the soils had a lower contents of the elements (p<0.05) from method A than B.However, it is contrary for Hg.The area of soils with high element content was larger for three metals from methods B than A.Most of the samples from the soils near factories were higher in element ratio than those from large fields.Metallurgical industry caused a significant accumulation of Pb, whereas the chemical industry and electrical industry could cause accumulation of more metals.All these results provide valuable basic data and a decision-making basis for planning of investigation, assessment and management of soil environmental quality in Zhangjiagang City or other similar regions in China.

Abstract:Nitrate content of groundwater was surveyed in rural areas of the Beijing Plain from 1999 to 2000.The wells covered in the survey were grouped into four types according to depth and use, i.e.drinking wells (DW) about 120 to 200 m in depth, irrigation wells (IW) about 70 to 100 m in depth, hand-pumping wells (HW) about 6 to 20 m in depth and shallow groundwater (SG) about 3 to 6 m in depth.Findings of the survey show that nitrate content of groundwater is inversely related to depth of the wells.The deeper the well, the lower the nitrate content of the groundwater.NO₃^--N contents of the groundwaters from 145 DWs, 336 IWs, 41 HWs and 77 SGs averaged out at 5.16 mg L^-1, 5.98 mg L^-1, 14.01 mg L^-1 and 47.53 mg L^-1, respectively, and 13.8%, 24.1%, 46.3% and 80.5% of the four types of waters exceeded 10 mg L^-1 NO₃^--N, the international maximum permissible limit for drinking water.Nitrate contamination of groundwater from deep wells was somewhat acceptable, while that of shallow groundwater was terrible.The situation in the suburbs of Beijing, such as Haidian, Fengtai and Chaoyang Districts, was much worse than in the exurbs of Beijing, such as Shunyi, Tongzhou, Changping, Daxing Districts.In the suburbs, 38.7% of the DWs and 52.6% of the IWs had NO₃^--N content above 10 mg L^-1, but in the exburbs, only 3.0% of DWs and 15.3% of IWs did.Nitrate content of Groundwater from wells was remarkably affected by surrounding conditions of the wells.In wells located in vegetable fields, especially old vegetable fields it was more serious than in cereal fields or farmyard.The mean value of 140 IWs located in cereal fields was 2.45 mg L^-1, and only 8.5% of the wells exceeded the limit in NO₃^--N content, while that of 189 IWs in vegetable fields was as high as 8.66 mg L^-1,and 36.0% of the wells did, And also the mean value of 26 SGs located in fields of winter wheat in rotation with summer maize was 18.02 mg L^-1, and 55.4% of the SGs went above the limit, while that of 43 SGs under greenhouses reached as high as 72.42 mg L^-1, and 100% did.Nitrate leaching as a result of overfertilization in vegetable production is the major cause of nitrate contamination of groundwater in rural areas of the Beijing Plain.

Abstract:Humic acid (HA) was extracted from the surface soil of an evergreen broadleaf forest in the Jingyun Mountain in China.Characteristics of humic acid adsorbing and desorbing Fe³⁺ ions under conditions varying in pH, ion strength and temperature were studied with the C-25 glucosan gelchromatography method.The results show that the max adsorption S_max and adsorption equilibrium constant k increased with pH, and the thermodynamic standard molar free energy change ΔG_m^o decreased, when ion strength and temperature remained the same.With pH and temperature unchanged, S_max and k increased and ΔG_m^o decreased when ion strength rose from zero to 0.10 mol L^-1, but things all went in reverse when ion strength continued to rise to 0.15 mol L^-1.When temperature increased, S_max, k, and ΔG_m^o all decreased significantly, indicating that higher temperature was disadvantageous to adsorption reaction.The thermodynamic standard enthalpy change ΔH_m^o and entropy change ΔS_m^o of adsorption reaction were both below zero, suggesting that adsorption reaction was an exothermic one and tended to be more in ordered state.When the other factors remained the same, the higher the pH, the higher the absolute values of ΔH_m^o and ΔS_m^o, suggesting that higher pH was advantageous to the process of adsorption reaction.The percent reduction of Fe³⁺ ions decreased with increasing pH, which fit the power function equation for description, showing a correlation coefficient reached the level of significance.The desorption rate of HA-Fe³⁺ increased when pH decreased, showing a curve that fit the linear equation, with a correlation coefficient also reaching the level of significance.Obviously, the Fe³⁺ adsorption reaction was a "two-phases" reaction, encompassing interior and exterior reactions of humic acid.

Abstract:A long-term field experiment was carried out in Jinxian County, Jiangxi Province, China.One of the aims of the experiment was to study soil organic carbon (SOC) distribution in different size groups of aggregates in four horizons (A, P, W₁, W₂) of red paddy soil impacted by different fertilization patterns.The experiment was designed to have four treatments : (1) Zero fertilization (CK), (2) chemical fertilizers alone (NPK), (3) organic manure alone (OM) and (4) combination of chemical fertilizers and organic manure (NPKM).Results show that the percentage of soil aggregates in the size group of >3 mm increased in all horizons, which were in the following order : A > P > W₁ > W₂, but the percentages of the other groups decreased, following the same order.The treatments of NPK, OM and NPKM were in favor of increasing the percentage of aggregates in the size groups of 1～3 mm and 0.25～1 mm.Results also show that the content of SOC in aggregates of the same horizon in all the fertilization treatments decreased in all horizons, showing a sequence of A>P>W₁, W₂.The contents of SOC in different size groups were significantly different and showed an increasing sequence of >3 mm>1～3 mm>0.25～1 mm>0.05～0.25 mm except for the size group of <0.05 mm being the lowest in content.The total content of SOC showed a positively linear relationship with the content of aggregates of the size groups of 1～3 mm and 0.25～1 mm.The storage of total SOC varied between the treatments, showing an increasing sequence of CK>NPK>OM>NPKM.The storages of total SOC in different 2 sized aggregates of the same horizon in the same treatment were also significantly different, showing a decreasing sequence of >3 mm<1～3 mm<0.25～1 mm<0.05～0.25 mm<0.05 mm.The newly enriched organic carbon mostly appeared in the size groups of 1～3 mm and 0.25～1 mm.

Abstract:Denitrification occurring mostly in flooded soil is considered as an important process which reduces use efficiency of soil nitrogen and affects environmental quality.In this study, 3 strains of denitrifiers were isolated from soil.Of the 3 strains, one is obligate aerobic bacteria coded as AD26, the other two strains are facultative bacteria coded as AD7 and AD60.Based on the morphological, physiological, and biochemical features of the three isolated strains, they were identified as Pseudomonas sp.In an aerobic incubation trial, N denitrification loss in the liquid culture medium inoculated with AD26 and AD7 reached to 21% and 18%, respectively, in 24 hours.In an aerobic soil incubation trial, about 56% of the soil nitrate2N was lost in the first three days due to denitrification in the presence of AD26 or AD7.Moreover, soil nitrate was eventually transformed into nitrogen oxide or N₂, leaving no nitrite left in accumulation.Therefore, the bio2denitrification in the farmland should not be overlooked.

Abstract:In order to clarify nitrogen uptake and metabolism of rice roots on a molecular basis, studies by means of quantitative real-time PCR were carried out on expression of nitrogen absorbing and metabolizing genes in relation to different ammonium/nitrate ratio in treatment.The results show that (1) in terms of expression level, OsAMT1.1 among N absorbing genes, OsGln1.1 among GS genes and OsGlu among GOGAT genes was the highest; (2) Significant up-regulation by ammonium and down-regulation by nitrate were found in the expression of OsAMT4 1, in any treatment whereas significant nitrate-depressed expression for OsAMT1.1, OsAMT1.2, OsAMT1.3 and OsNRT2 was observed when the ratio of ammonium to nitrate varied from 100:0 to 50: 50, and significant nitrate-induced expression for OsAMT1.2 and OsAMT1.3 when the ratio of ammonium to nitrate varied from 50:50 to 0:100; (3) Among the genes coded as GS, OsGln1.1 were significantly up-regulated by nitrate and down-regulated by ammonium, significant nitrate-induced expression for OsGln2 and nitrate-depressed expression for OsGln1.2 when the ration of ammonium to nitrate varied from 100:0 to 50:50; (4) Among the genes coded as GOGAT, OsGlt1 and OsGlu showed no significant variation in the process of the ratio of ammonium to nitrate varying from 100:0 to 50:50, but were significantly down-regulated with the ratio of ammonium to nitrate further varying from 50:50 to 0:100; significant up-regulation by ammonium and down-regulation by nitrate were found in the expression of OsGlt2; (5) In general, the regulation of expression of these genes by ammonium and nitrate depends on the ratio of ammonium to nitrate in the primary solution where the rice grew.

Abstract:Chemical composition and structure of humic acids extracted from composted corn stalk residue(CSR) were studied with the aid of Fourier transform infrared (FTIR) spectroscopy, ¹H and ¹³C nuclear magnetic resonance(¹H-NMR, ¹³C-NMR) spectroscopy and chemical analysis.The carbons in Humic acid from composted CSR (CCSR HA) can be mainly divided into three groups: aliphatic-C, aromatic-C and carbonyl-C, accounting for 59.62%, 26.94% and 13.44% of the total C, respectively.The major functional groups in the CCSR HA include hydroxyl, alkyl, carboxyl, amide, benzene ring, methoxyl, carbonyl and carbohydrate, with residual lignins being their skeleton and carbohydrates, and long-chain aliphat ic structural groups their basic composition units.CCSA HA is of the Rp type of humic acids.In uncomposted corn stalks per se humic acids (OCSR HA) can be found and it is somewhat different from CCSR HA in composition of funct ional groups.The latter is relatively lower in methyl, methylene, ether and phenol hydroxyl but higher in amide, free carboxyl, methoxyl and carbohydrate.Aromaticity of CCSR HA is 29 97, and significantly lower than that, 42.19, of OCSR, but the capacity of CCSR HA combining with inorganic matters becomes stronger.As far as variation of the elemental composition is concerned, the contents of C and H are lower and the contents of N and O are higher in CCSR HA as compared to what is in OCSR HA.Compared with soil HA, CCSR HA is significantly lower in aromat icity, but much higher in content of sugar-like components, which are not present as free carbohydrate, and instead are incorporated into structures such as hydrolyzable lignins.CCSR HA is also comparatively lower in content of carboxyl groups, which exist in different forms.

Abstract:Since 1998, many paddy fields related to Majiabang Culture have been discovered at Chuodun site (31°24'12"N, 120°50'31.5"E), Jiangsu Province.Studies of the ancient paddy fields at the Chuodun site are of great importance for unraveling the history of rice domestication in East Asia.To further validate this site as paddy fields, phytolith and pollen analyses were conducted for P01 and P03 profiles, which are located in the northeastern part of Unit.Pollen assemblages of ancient paddy soil also were compared with those of modern paddy soil to validate the method of pollen analysis as a possible approach to-ward the ident ification of ancient paddy fields.Results of phytolith analysis show that rice cultivation activities can be traced back to middle and late Majiabang Culture, Maqiao Culture and Song Dynasty at Chuodun site.Pollen data indicate that low aquatic herb pollen corresponding to more phytoliths in ancient paddy field.Low aquatic herb pollen value is also found in modern fields.This suggests that weeds might have been removed by human during rice cultivation in the Neolithic periods.Gramineae and aquatic herbs, together with phytolith analysis, can be used as an indicator of ancient paddy fields at archaeological sites on the Yangtze River Delta.

Abstract:Crude oil is a kind of organic matter, relatively insoluble in water, which seriously affects its bioavailability.Some bacteria are found to be able to produce biosurfacant, which can emulsify the crude oil and enable the bacteria to adhere to the hydrophobic surface of the oil very strongly, thus enhancing bioavailability of the crude oil in the environment.It is reported that bacteria with hemolytic circle in the blood plate show emulsifying activity.Therefore strains of the bacteria were isolated from the petroleum contaminated soil through enrichment culture in BH medium with crude oil from Jianghan as the sole carbon source and hemolytic activity assay on blood agar plates.Nine strains with high degrading and emulsifying ability were isolated.Strain X13-1 was found at the top of the list of the bacteria with emulsifying ability reaching 80% and 75% at 1h and 24 h respectively.OD_600nm of the culture fluid with paraffin as the sole carbon source was used to indirectly measure petroleum-degrading abilities of bacteria.The OD_600nm of strain X13-1 was up to 0.566.Besides its emulsifying ability and petroleum-degrading ability, strain X13-1 was chosen for ulterior research.Cell wall composition, morphology, metabolism Biolog Microstation Identification System and the sequence analysis of 16S rDNA fragment amplified from total DNA of bacterium X13-1 were used to identify the strain of bacterium.The results show that the bacterium is G^- and bacilliform.SIM (Similarity) in Biolog to typical Acinetobacter calcoaceticus is 0.826 and 16S rDNA sequence homology with typical A.calcoaceticus in the genebank is 97%.To sum up the above-described characters, it can be concluded that strain X13-1 is likely to be an A.calcoaceticus.

Abstract:To overcome limitations of the traditional enrichment culturing method for degrading bacteria isolation, two strains of bacteria, AG1 and ADG1, capable of degrading atrazine efficiently, were isolated by diluting and plating atrazine-contaminated soils directly onto plates coated with soil extracts and atrazine.They grew in medium with atrazine as the sole sources of nitrogen, carbon and energy, degrading 1 000 mgL^-1 of atrazine within 44 h and 48 h, respectively, and could also grew with some other s-triazine herbicides as sole nitrogen sources.Based on their 16S rDNA sequences analysis and their physiologic and biochemical characteristics, AG1 and ADG1 were identified as Arthrobacter spp..Results of amplifying their degrading genes with PCR, showed that atrazine metabolic genotype of AG1 and ADG1 were both combination of trzN and atzBC.It is the first report in the country about atrazine-degrading bacteria with such metabolic genotypes.

Abstract:In a pot experiment, it was found that host infection rates, and activities of hyphal SDH (succinate dehydrogenase) and ALP (alkaline phosphatase) enzymes of Glomus intraradices (G.i), Acaulospora laevis (A.l) and G.i + A.l were significantly enhanced by hesperitin.After treatment with 15 nmol L^-1, 150 nmol L^-1, and 1.5μ mol L^-1 hesperitin, respectively, samples of maize and cotton roots were collected for test at the 6th week.Results of the tests showed that with the maize roots, the G.i infection rates were 76.2%, 84.5% and 75.8% (the control was 45.9%), hyphal SDH activity of G.i were 68.4%, 75.9% and 67.4% (the control was 40.7%), and hyphal ALP activity of G.i were 45.8%, 51.4% and 45.1% (the control was 27.1%), respectively.And with the cotton roots, the G.i infection rates were 85.2%, 88.9% and 83.8% (the control was 59.8%), hyphal SDH activity were 76.8%, 81.2% and 75.0% (the control was 53.1%), hyphal ALP activity were 51.2%, 53.7% and 49.4% (the control was 35.2%), respectively.And hesperitin could increase significantly total amount of hyphae of AM fungus in the soil.The biomass of maize and cotton could also be affected by hesperitin.

Abstract:Aloe, a typical xerophyte, is of important value in medicine and therapeutics, cosmetics, food industry, land-scape and ornamental hort iculture.According to biological characteristics, aloe belongs to a glycophyte rather than a halophyte.So far, available information on response of aloe to salt stress is little.In this study several aspects embodying salt resistant ability were studied with seven-leaf old Aloe vera cultured in sand for 120 days.Experimental results show that growth of aloe was closely correlated with salt concentration in irrigated nutrient solution.The treatment of 200 mmol L^-1 NaCl significantly retarded growth of aloe, reducing elongation dynamics, length, width, thickness, weight, water content, and chlorophyll content of its leaves, perimeter of the root system, dense radicel zone, biomass of different organs and a single plant, but increasing the number of withered leaves, which were even more remarkable when sodium chloride concentration reached to 400 mmol L^-1.However, the negative effects of salt stress on aloe growth were not very marked when sodium chloride concentration was less than 100 mmol L^-1 as was compared with C the control K, no NaCl added into irrigated solution, especially when the concentration of NaCl was 50 mmol L^-1.The effects of salt stresses between 50 and 100 mmol L^-1 NaCl treatments on physica-l chemical properties of aloe leaf juice, such as rate of leaf juice, soluble solids content, rotation viscosity, relat ive density, absorbance, electrical conductivity, pH value, ash percentage, total carbohydrate content and polysac-charide content were not significant.Both of the treatments produced active effects on physical-chemical properties.Based on these results, considering absorption of salt by soils, washing of rain and snow, and effect of ground water, Aloe vera is suitable to be irrigated with brine or weakly brine water.

Abstract:Non-pressure Subsurface Drip Irrigation at Crop Root Zone (shortened as Non-pressure Irrigation), is a method of local water control irrigat ion, having pipes with fine apertures buried at the crop root zones.Water oozing out through the apertures under the suction of soil irrigates the crop and satisfies its need during growth.Optimal parameters of the system are-4 to 8 cm in pressure, 10 to 30 cm in depth of buried pipe, and 3 to 8 mm in diameter of the aperture.Comparison between non-pressure irrigat ion and furrow irrigation was carried out to study their effects on movement and variation of soil water, evapotranspiration, relationship between crop yield and water productivity and mechanism of effect of irrigat ion pattern on quality of tomato and cucumber in greenhouse in 2004 and 2005.The results show that non-pressure irrigation improved living conditions of the crops, and left enough oxygen in the root zone so that quality of the crops was raised due to improved distribution of photosynthetic assimilates to different organs.Compared with furrow irrigation, non-pressure irrigat ion did not decrease crop yield, but improved water availability and productivity, and in turn significantly raised contents of vitamin C, soluble sugar, total sugar and inorganic phosphorus, demonstrating its funct ion of adjusting quality with water.

Abstract:Wetland is a transitional zone between the water and the land.Changing redox is the most common process which is brought about by alternation of wetting and drying in the wetland.Oxygen diffusion occurring in the roots of wetland plants further strengthens the process.Fe is one of main elements involving in reduction and oxidation soils.Its change can indicate wetland environment.This review introduced the distribution and transformation of Fe and influencing factors Fe cycling, analyzed its effect on wetland soil formation, physiological ecology of wetland plants, material cycling in wetland and environment indicators.Finally, further researches on Fe cycling in wetland were proposed.

Abstract:土壤盐渍化是松嫩平原农业发展和生态环境安全面临的主要问题之一。据统计,目前松嫩平原土壤盐渍化面积约327万hm²,占平原总面积的21%左右^[1]。研究表明:盐渍土的盐分含量和化学特征常具有高度的空间变异性^[2~6]。盐渍土的这种空间变异性是由土壤的非均质性和各种随时空变化的外在因素引起的。这些外在因素包括浅埋深地下水、微地貌、季节性渍涝、人类活动等。定量描述苏打盐渍土盐分空间变异特征不仅有助于理解各种外在因素在土壤盐渍化过程中的作用,深化对土壤发生盐渍化机制的认识,而且将为苏打盐渍土的改良和治理提供必要的基础数据。

Abstract:土壤水分特征曲线是描述土壤含水量与吸力(基质势)之间的关系曲线,它反映了土壤水能量与土壤水含量的函数关系,因此它是表示土壤基本水力特性的重要指标,对研究土壤水滞留与运移有十分重要的作用。几十年来,人们投入大量的精力发展确定水分特征曲线的方法,这些方法归纳起来分为两大类:一类是直接测定法,如张力计法、离心机法、压力膜法等;另一类是间接推求法。这些方法中多数缺乏精度、耗时、需昂贵的专用设备、需特殊操作技能,或者仅能提供很有限范围内的导水特性资料。

Abstract:土壤孔隙是土壤中水分与空气存在的场所,是植物根系与微生物的生活空间。土壤的孔隙特征是土壤的一项重要的物理性质,它对土壤肥力有多方面的影响^[1]。孔隙性质良好的土壤能够满足作物对水分和空气的需求,有利于养分的调节、合理供给以及作物的正常生长。但土壤是一个复杂的多相体系,其内部存在着形态各异、大小不同的孔隙。

Abstract:从土壤中提取土壤总DNA,切割成一定长度的DNA片段并连接到载体上,然后转化宿主菌,形成一个重组DNA文库即宏基因组(metagenome)文库。目前对宏基因组的研究在国际上是土壤微生物学研究的前沿领域和热点。文库构建后可以根据宿主细菌获得的功能筛选相应的克隆;也可以用已知的探针分离目的基因片段,加上表达调控元件后获取活性产物,所以通过宏基因组文库可以规避微生物培养的限制而寻找新的功能基因或者直接筛选活性物质^[1,2];在早期宏基因组还被用来研究土壤微生物的遗传多样性^[3,4]。

Abstract:红树植物群落(或红树林)是生长在热带、亚热带海岸潮滩盐渍土的特有的木本植物群落,具有防浪护岸固沙,保护和改善当地生态系统,促进滩涂养殖业发展等重要作用。国内外对红树植物群落土壤理化性质和酶活性等已进行了一系列研究^[1~7],而有关红树植物群落土壤腐殖质组成和特性的研究国内未见报道。本文在对广西英罗港不同红树植物群落的土壤理化性质与酶活性以及红树植物中元素分布特征的研究基础上^[8~10],进一步对各红树植物群落的土壤腐殖质组成、特性及结合形态进行分析比较,为红树植物群落的保护、恢复和发展提供科学依据。

Abstract:20世纪70年代以来,有机农业在全球兴起,目前在发达国家已经成为农业生产方式的主流^[1]。有机肥料是有机农业生产的主体,含有多种作物可吸收利用的微量元素和有机物,以及有益微生物和各种活性酶,在保持、改善和提高土壤肥力;活化土壤养分;增强微生物活性;促进农作物高产、优质、降低农产品成本有着不可替代的作用^[2]。因此在今后一定时期内,研究有机肥对土壤生物活性的影响十分重要^[3]。近年来,国内外有关施肥对大田耕作土壤酶活性及土壤养分变化的影响研究较多,但对菜田土壤酶活性的影响报道较少^[4,5]。

Abstract:随着城市化进程的加快、城市人口的增加,工业废水与生活污水的排放量日益增多,污泥的产出量迅速增加。据有关资料统计,目前美国所积累的干污泥总量已达1000万t,欧洲各国总计达660万t,日本为240万t左右。