Abstract:Oxidation, reduction and methylation of arsenic in paddy soil are the key factors regulating transportation, transformation, and crop uptake of the element. Flooding is a common farming practice in rice cultivation, forming an anaerobic environment in the paddy soil, which not only affects the biochemical behavior of arsenic significantly, but also is often associated with enhanced uptake of arsenic by rice, thus further posing a health risk to those who consume rice as staple food. Studies in the previous focused mainly on those behaviors of soil arsenic in flooded anaerobic paddy soil and their relevant mechanisms, but a comprehensive review of the studies is yet to be prepared. In this study, the biochemical behaviors of arsenic in paddy soil is summarized, and their relevant mechanisms and influential factors, including iron oxides, organic matter, redox potential (Eh) and pH are discussed. Besides, the paper also elaborates discussed how the anaerobic condition in the flooded paddy field during the paddy rice growing season affects those biochemical behaviors. Generally speaking, the iron and arsenic reducing microbes in the soil are mainly anaerobic microbes, e.g. Geobacter, Shewanella and Myxobacter, while the iron and arsenic oxidizing microbes are predominantly aerobic microbes. Therefore, the development of an anaerobic reducing condition in flooded paddy fields favors microbial iron and arsenic reduction, and what is more, as iron oxides are the most effective scavenger of arsenic in paddy soil, the flooded anaerobic environment also favors release of arsenic. It is noteworthy that arsenic desorbed from iron oxides is more prone to bioreduction. Studies in the past indicate that adsorption of arsenic by iron oxides like ferrihydrite, goethite and hematite, especially ferrihydrite, the most abundant amorphous iron oxide in paddy soil, retards bioreduction of arsenic. Another contributor to enhanced bioreduction and release of arsenic is organic matter, which serves as nutritional substance and electron donor for microbes in metabolism. In flooded anaerobic paddy soil, the addition of extraneous organic matter facilitates formation of a reducing environment, stimulates reductive iron dissolution, arsenic reduction and arsenic release in rate and extent. Besides, flooded anaerobic paddy soil is also favorable to arsenic methylation, which uses arsenite as potenital inorganic substrate. Although flooded anaerobic paddy soil is not good to microbial arsenic oxidation, anaerobic arsenic oxidation processes mediated by microbes harboring arxA gene in paddy soil was reported in studies in the past. In terms of genes in microbes responsible for arsenic metabolism, current researches focus mainly on the following ones: arxA, arsenic respiratory reduction gene; arsC, arsenic detoxification reduction gene; arxA, arsenic oxidation gene; arxA, anaerobic arsenic oxidation gene; and arsM, arsenic methylation gene. In the past studies, gene arsC was found in close relationship with arsM, which is related to the response of the microbes harboring these genes to the stress of arsenic toxicity. By studying changes in abundance, diversity and gene expression of the microbial community in flooded paddy soil, a clearer picture can then be plotted of the biochemical behavior of soil arsenic in paddy soil as affected changes in environment. At the end, the paper describes prospects of the research and holds that the researches may serve as references for prevention of arsenic contamination in paddy soil and for alleviation of uptake and accumulation of arsenic by rice. For future researches the following aspects should be covered: (1) effects of organic matter, relative to type, on diversity of arsenic metabolising microbes that are capable of mediating dissimilatory iron reduction, arsenic reduction and methylation, direct physciochemical interaction between organic matter and arsenic, and ternary interaction of organic matter-iron mineral-arsenic as affected by chelation, competition and coupling; (2) Response of arsenic metabolism related enzymes to variation of micro-environment and its relationship with arsenic transportation and transformation, and relationship between organic matter and arsenic methyltransferase in the microbes; (3) Influence of carbon and nitrogen recycling, particularly Feammox, on biochemical behaviors of iron and arsenic, and influences of nitrogen-iron recycling and carbon-iron recycling on arsenic redox, e.g. influences of the competition between dissimilatory iron reduction and Feammox on arsenic dynamics; (4) Systems research on dynamics of the microbial community involved in arsenic metabolism in rhizospheric soil and bulk soil and biochemical behaviors of arsenic at the soil interface and soil-solution interface in paddy fields subjected flooding and draining, long term flooding or sprinkler irrigation.

Abstract:【Objective】Nitrous oxide (N₂O) is an important kind of greenhouse gas, and forest soil is the main source of atmospheric N₂O, posing a great uncertainty in budgeting of atmospheric N₂O. Forest management, like fertilization, felling, litter burning, understory management and land-use change in forests would affect soil properties and soil micrometeorology, and hence production and emission of N₂O from forest soils significantly.This paper discussed responses of forest soil to different management practices in N₂O emission, explored major mechanisms of forest management affecting soil N₂O emission, and highlighted shortages of the current researches and focal points of future studies.【Method】Withreference to the databases of Scopus,Web of Science,SDOS and China National Knowledge Infrastructure (CNKI), current studies on N₂Oemission from forest soil were reviewed, and findings of the researches on influences of forest management on soil N₂O emission in recent 20 years were systematically summarized, mechanisms of forest management affecting soil N₂O emission discussed, and shortages of the current studies and prospects of the researches in this field in future described.【Result】Reclamation of forests into agricultural land or grass land would increase soil N₂O emission, whereas the reverse course would did the other way around. How replacement of natural forest with artificial or secondary forest to soil N₂O emission is still unclear. The response of N₂O emission from forest soils to fertilization exhibited a nonlinear curve, consisting of no significant response at the early stage,linear increase at the middle stage, and exponential increase at the late stage, depending on degree of “N saturation” of the forest ecosystems. It was generally held that burning stimulated soil N₂O emission; felling affected soil temperature, water content, organic matter decomposition and utilization, thus enhancing soils N₂O emission capacity; and removing understory increased soil temperature, sped up decomposition and mineralization of organic carbon in the surface soil layer, thus promoting soil N₂O emission. Planting N-fixing plants also increased soil N₂O emission. 【Conclusion】Therefore,future researches should focus on the following four aspects 1) to define sources of soil N₂Oin the forests of North China and of South China by means of the ¹⁵N-¹⁸O labeling technique in combination of molecular biology,and workout non-linear curves of the responses of N₂O emission to increased N fertilizer application, through multi-dosage multi-form (ammonium nitrogen fertilizer, nitrate nitrogen fertilizer and amide nitrogen fertilizer) N fertilizer application experiments at different latitudes and under climate conditions; 2) to use molecular biological and matagenomic methods and techniques to determine effects of forest management on abundance and composition of N₂O producing bacterial communities,and quantify the coupling relationships between soil N₂O emission and major soil microbial functional groups,such as nitrifiers,denitrifiers ammonia-oxidizing bacteria, etc.; 3) to extend the observation in period and frequency of soil N₂O emissions after different forest fire chronosequence; and 4) to unfold research about response of soil N₂O emissions to select-cutting, especially in North and South China, rich in coniferous forest and rainforest, respectively.

Abstract:【Objective】Soil spectrum, as a comprehensive reflection of soil physical and chemical properties, is of important significance to soil quality management, digital soil mapping, analysis of soil properties and soil classification in the red soil regions. 【Method】 In this paper, a total of 443 surface soil samples were collected in the typical red soil regions, e.g. Ji’an County, Yujiang County, Xingguo County and Wanli District of Jiang Province, and visible and near infrared reflectance hyper-spectra (350～2500 nm) of the samples were measured with an ASD spectrometer in laboratory. After the treatment of the spectra with the continuum-removal and second order derivative methods, the spectra of the four major soil subgroups and their subordinate soil families in this region were characterized. Then, 19 characteristic variables, such as spectral reflection and absorption of parent materials, iron oxide (goethite and hematite) minerals, organic matter and clay minerals and hyper-spectral reflectance, were cited as indices for Fastclus cluster analysis of the spectra. 【Result】Results show that the soils in the region varied sharply in spectral reflectance from sub-group to subgroup. In terms of spectral characteristic absorption area, in the 620～740 nm spectral bands, the four subgroups exhibited an order of yellow red soil > red soil > brown red soil > weakly red soil, but in terms of the difference between second order derivatives at 420 nm and at 447 nm, they followed an order of yellow red soil > brown red soil > red soil > weakly red soil. The brown red soil was higher in reflectance in the Vis-NIR spectral range, but lower and wider in spectral absorption intensity in the range of 1 900 nm than all the other subgroups. The weakly red soil was the steepest in spectral curve and the highest in reflectance in the near infrared region, showing two relatively strong absorption peaks at 1 400 nm and in 1 900 nm, separately, and a super strong peak at 2 200 nm. In terms of the peak at 2 200 nm, the sub-group of red soil was similar to the sub-group of reddish soil in spectral curve variation tendency, but lower in absorption intensity at 900 nm, 1 400 nm, 1 900 nm and in 2 200 nm and higher in position of the curve. As a result of variation of the duration of flooding, paddy soils of the four sub-groups of red soils varied greatly in spectral characteristics, and they followed an order of gleyed paddy soil > waterlogged paddy soil > submergic paddy soil in terms of spectral reflectance; an order of submergic paddy soil > waterlogged paddy soil > gleyed paddy soil in terms of spectral absorption area in the range of 620 nm～740 nm; and an order of gleyed paddy soil > submergic paddy soil > waterlogged paddy soil in terms of difference between second order derivatives at 420 nm and at 447 nm. Classification, based on the 19 indices, of red soils in the region by soil subgroup reached 86.23% in accuracy and by soil family 66.37%. 【Conclusion】Obviously soil Vis-NIR spectral characteristics can be used as quantitative indices for reference in classification by sub-group of the red soils in Jiangxi Province.

Abstract:【Objective】Before the digital soil mapping technology emerged, the soil category linkage method (SCLM),linking means or median values of properties of the soils of the same soil category with their corresponding polygons in the soil map, or linking soil properties with polygons based on pedological expertise (including type of the soil and its location), was the major method used in mapping of soil organic carbon density (SOCD). Even nowadays, it is still of quite high practical value, because it is quite hard to build up a DSM model for relationships of external environmental covariates with SOCD in deep soil layers and/or on large scale, e.g. Provincial, continental and global. To understand in-depth relative efficiency of the two linking methods, it is necessary to perform some comparative studies. In terms of the DSM technology, most of the comparative studies have come to the conclusions that sophisticated machine learning models are superior to simple ones and that mixed models (regression Kriging) are of high superiority in most cases. However, there are a few papers reported some contradictory results. All the conclusions suggest that SOCD mapping quality could not be explained merely by method and also affected by the effectiveness and accuracy of the parameters used in the method. To elaborate in-depth the contradictory conclusions and to analyze the essence of the problems, in this paper a comparison was performed of SCLM with weighted least squares regression(WLS), geographically weighted regression(GWR), random forest (RF),ordinary kriging (OK) and regression kriging (RK) in SOCD mapping, and establishment of relationships between abilities of the methods to explain SOCD variability and effects of their mapping was discussed. 【Method】A tract of land, 26600 km2 in area, in Nanyang of Henan Province, was selected as a study area, of which soil categories, elevation, slope, aspect, and normalized difference vegetation index (NDVI), and wetness (TCW) of tasseled cap transformation (TC) were worked out as parameters of the SOCD prediction model, based on a 1:50 000 soil map, Digital Elevatation Model, 30m in resolution and a 1990 thematic mapper(TM) image. A total of 439 soil profiles were cited as training dataset for SOCD mapping using SCLM, WLS, GWR, RF, OK and RK, separately, and another 49 soil profiles were used to verify accuracy of the maps. 【Result】Results show that soil genus and soil organic matter content of the topsoil layer is the most important and the second most important parameter, explaining jointly 57.5% of the SOCD variance, while terrain and remote sensing parameters jointly explain just less than 2%, and hence are very limited in contribution to SOCD mapping. However, SCLM makes use only of variables in soil category, like soil group, soil subgroup, soil genus, etc., while regression methods, like WLS and GWR, can only use numerical variables, like SOM and TCW, so none of these can achieve satisfactory prediction result. RF is based on both variables in soil category and numerical variables (SOM and TCW) and hence much better in SOCD prediction. The use of RK in prediction may end up in the following two situations. 1) The residues of WLS regression, GWR regression, and soil OM-and-TCW-based RF vary spatially and structurally to a varying extent, then regression kriging (RK) could improve the SOCD predictions of these models. 2) The residues of the predictions using SCLM, SOM+soil genus-based RF, SOM+soil genus+TCW based RF and all-variables-based RF vary spatially and randomly, for which the use of RK is meaningless. The cross-verified accuracy of WLS, GWL and soil OM-and-TCW-based RF increased in turn, however their RK ability predicting test data are reversed. And all prediction ability of RKs do not reach as high as the SOM+soil genus-based RF.【Conclusion】All the findings demonstrate that the ability of method to explain SOCD variability is the causa essentiae deciding the effect of SOCD mapping, and RK is not necessarily the fittest model because of the interactions in explanation ability between covariates and the spatial correlation.

Abstract:【Objective】Digital soil mapping is based on Jenny's classic theory, of which the core is that soil is the yield of the interactions among numerous soil forming factors. To establish relationships between environmental variables and soil attributes, a soil-landscape model is built up and used to predict soil types or attributes. Although this model has been extensively used in digital soil mapping, investigations are still on the way on what the relationships between environmental variables varying with the region and soil attributes are. Therefore, how to extract rapidly and accurately knowledge of soil environment has become the key to the current researches in this field. Knowledge acquisition based on sampling points is often affected by the number of sampling points, errors in sampling processes and representativeness of sampling points. Traditionally, soil mapping iis based on manual soil surveys and tends to have errors in the following two fields, i.e. enclosure and displacements of boundaries. The knowledge acquired from soil maps can not be used to predict local soil conditions, and especially lacks details specific to soil grade and issues the users are interested in. To solve these problems and attain soil environment information high in accuracy, a method based on knowledge intercomplementation and fusion is set forth.【Method】This paper uses decision tree coupled with a uncertainty model to extract soil environment information. Through limiting threshold values, the decision tree model can be used to predict soil type rapidly and efficiently. With the soil lowering in type level, the prediction lowers steadily in accuracy. Therefore, ignored uncertainty and exaggerated uncertainty can be used to judge truly and efficiently accuracy of the inferred map to a certain extend and hence to realize accurate quantitative evaluation of the inferred map. So coupling of the two models can not only save money and time, but also raise efficiency and realize scientific re-extraction and fusion of soil information. .The Nieshui River Basin in Huajiahe Town，Hongan County，Huanggang City of Hubei Province was selected as a case for study. The proposed method proceeded in three steps. 1) By means of the standard See5 algorithm, decision trees were constructed and used to extract soil -environment information and hence spatial distribution for soil mapping; 2) With the aid of the SoLIM software, a spatial distribution map of exaggerated and ignored uncertainties was plotted. The two kinds of uncertainties appeared in the processes of classifying a geographic entity, i.e. ignored uncertainty, which is attributed to the similarity of the studied soil to all the soil types, and exaggerated uncertainty, which is associated with the deviation of the studied soil from the prototype specified in the processes of soil hardening. A similarity model can be used to estimate the two uncertainties; and 3) Soil samples were collected again based on the spatial distribution map of the uncertainties.The higher the values of exaggerated and ignored uncertainties, the higher the probability of a soil beingmis-classified.So resampling should be performed in location low in uncertainty value. The soil environment information acquired from the resampled soil sample set combined and updated or optimized the original knowledge. In the end, soil mapping by inferring was performed with the aid of the SoLIM software and based on the eventually obtained soil-environment knowledge, and validated with the validation set of 253 sampling sites in the field for accuracy.【Result】Results show that the soil map plotted through inferring contains more specific spatial distribution information and reaches up to 86.9% in accuracy as validated with the field validation sites. Obviously it is 13% higher than the soil maps so far available.. Moreover, its Kappa coefficient is 0.842, higher than 0.8, indicating its high degree of consistency, and conformity with the attributes and spatial distribution of the soils in the study area. 【Conclusion】It is, therefore, concluded that the proposed method which acquire the knowledge of soil-environment relationship using the uncertainty modelis feasible and effective.This method not only increases spatial detailedness of the soil map, but also improves its accuracy.

Abstract:【Objective】Multi-resolution DEM (digital elevation model)resample plays the important role in multi-scale DEM conversion, this paper was aiming to investigate influences of the use of difference resampling methods to calculate LS of gullies different in development stage. 【Method】Based on the vector data in the 1:5000 scale contour map of the Ganre River Valley inYuanmou County, DEMs, 2m in resolution, of six typical gullies were established on the ArcGIS platform, using three different resampling methods, known as Near (Nearest neighbor), Bil (Bilinear interpolation) and Cubic(Cubic convolution), and LS(Slope Length and Slope Steepness, LS) calculated for comparison quantitatively. Differences between the three methods in LS calculation were analyzed by comparison of the methods in relative difference coefficient, area percentage of LS factor grades, and XY scatter plot.【Result】Results of the paper are summarized as follows: (1) Near is significantly different from Bil and Cub in LS value, while Bil and Cub methods have no significant difference between each other;(2)Bil, rather than Near and Cub, is the most appropriate choice for gullies at their young stage; Near is better than Bil and Cub for gullies at their erosion stage; Cub is more suitable than Near and Bil for gullies at their stable stage.【Conclusion】In conclusion, the research described in this paper has shown that the choice of resampling methods has potentially important consequences for the calculation of LS value of gullies different in development stage.

Abstract:【Objective】In order to explore genetic characteristics and ascription in the Chinese Soil Taxonomy of sierozem,a zonal soil typical of Central Ningxia, 8 representative soil profiles were dug for examination and analysis in the study area.【Method】Firstly, sites for the eight soil profiles were defined with the aid of Arcgis 9.3 and GPS; profiles dug out for examination, description and characterization; and then soil samples collected from each soil layer of the profiles for analysis of physicochemical properties.【Result】From morphological characterization of the soil profiles and analyses of the soil samples, it was learnt that the main soil forming processes of the typical sierozem involved weak humus accumulation process, and weak calcium carbonateeluviation-illuviation processes. By referring to and identification in line with“the Keys to the Chinese Soil Taxonomy (third Edition)”, it was found that the eight profiles had the following diagnostic horizons and characteristics, ochric epipedon, aridic epipedon, calcipan, loess and loess-like deposits, ustic/aridicsoil moisture regime, mesictemperature regime, sodic feature and calcaric property, and calcic accumulation. In the Chinese Soil Taxonomy, the 8 soil profiles could tentatively be sorted into the soil order of Cambosols and Aridosols, the soil group of Hapli-Ustic Cambosols and Hapli-Orthic Aridosolss, and the subgroup of Typic Hapli-Ustic Cambosols and Sodic Hapli- Orthic Aridosols. According to the standard for classification of soil families and soil series in the Chinese Soil Taxonomy, the 8 soil profiles could tentatively be sorted into five soil families, i.e. Sandysilica mixture calcareous mesic-TypicHapli-Ustic Cambosols, Loamysilica mixture calcareous mesic-TypicHapli-Ustic Cambosols, Loamyfeldspar mixture calcareous mesic- Sodic Hapli- OrthicAridosols, Loamysilica mixture calcareous mesic-Sodic Hapli- OrthicAridosols and Loamyfeldspar mixture calcareous mesic-TypicHapli-Ustic Cambosols, and five soil series, i.e. Qingshan series,Majiatan series, Dazhanchang series,Haochuan series and Xiamaguan series.【Conclusion】The reference studies of the eight soil profiles in different soil classification systems show that between the two soil classification systems, the Chinese Soil Genetic Classification and the Chinese Soil Taxonomy, does not exist any simple one to one relationship.While the sametypes of soil in the Genetic Classification System may correspond with several type in the Chinese Soil Taxonmy. The quantitative norms in the Chinese Soil Taxonomy make soil classification more quantified, thus improving the accuracy of soil classification and eliminating the phenomena of different soils having the same soil name.

Abstract:【Objective】 Aeolian sand movement is very frequent in the Cele oasis-desert ecotone in Xinjiang of China. So it is of great importance to explore rules of the near-surface aeolian sand movements, in expectation of providing certain theoretical basis for prevention and control of sandstorms in the southern fringe of the Taklimakan Desert. 【Method】 In-lab measurements and assays, linear regression analysis and correlational statistical analysis were adopted to explore particle size and fractal characteristics of grain size of the sand and dust materials in sand movements on land surface and near surface over different terrains of the Cele oasis-desert ecotone. 【Result】 Results show that the sand and dust materials in various sand movements consist of five kinds of sand and dust materials, from very coarse silts to very fine sands, and coarse silts are the major component of the atmospheric dustfall, with fractal dimension varying in the range of 0.25 ~ 2.25 and the five kinds of aeolian sand and dust vary in mean fractal dimension of particle size, exhibiting an decreasing order of sand materials on the surfaces of nebkhas > those in dustfall > those on bare flat sandy land > those transported near ground surface > those shifting with sandy, averaging 1.03 ~ 1.67 in fractal dimension of particle size, while standard deviations of their fractal dimension values are in an opposite trend. Along the prevailing wind direction from shifting sandy land to oasis, with growing vegetation coverage, fractal dimension of aeolian sand and dust materials increases, while wind speed declines. The very coarse silt and very fine sand particles in the air higher above the ground surface tend to get deposited around shrubs in the oasis-desert ecotone, so the fractal dimension of the sand and dust materials in nebkhas are the highest in value, while the surface wind speed on shifting sand dunes sparse in vegetation is high, more coarser sand particles get deposited on the surfaces of the shifting sand dunes, being the lowest in fractal dimension. Fractal dimension of the sand materials on the surfaces of nebkhas is linearly related to mean particle size, sorting coefficient and some others. But no such correlation is found with the sand materials on the surfaces of shifting sand dunes. Fractal dimension of the sand materials in nebkhas, shifting sand dunes and sand transported near ground surface is positively related to their clay content at the 0.01 significance level, but negatively related to their content of sand grade of material in nebkhas and sand transported near ground surface; positively related to content of silt grade materials in sand dunes on bare flat land and sand transported near ground surface; negatively related to silt content at the 0.05 significance level in dustfall; but it has nothing to do with silt and sand contents on the surfaces of shifting sand dunes. 【Conclusion】 Particle size fractionation, movement mode, vegetation coverage, wind forces and terrain are the main causes responsible for the differentiation of characteristics of particle size and fractal dimension of the aeolian sand and dust materials in the oasis-desert ecotone.

Abstract:【Objective】Facilitated vegetable cultivation is a general term, encompassing glass greenhouse, sunlight greenhouse and plastic greenhouse, and characterized by high yield and high economic efficiency. However, as facilitated vegetable cultivation is going on in a confined space where temperature, humidity, ventilation and water/fertilizer management, all are different from those in the open field, high fertilizer input, consecutive years of cultivation and improper management make the soils therein liable to have secondary salinization. Shandong Province is an important base of facilitated vegetable production, enjoying great advantages, in China. By studying the soils under greenhouse in Shandong Province and analyze distribution, degree and major causes of secondary salinization in the soils is expected to be able to provide certain data, support and reference for management of secondary salinization in the soils under greenhouse all over the country. 【Method】From May to June 2014, soil samples were collected from facilitated vegetable fields in 17 cities of Shandong Province for analysis of total salt and salt content, while a survey was conducted on the farmers. For soil sampling, sampling points were laid out, one every 133~333 hm², and samples collected evenly from the 0~20 cm soil layer of each sampling point. Soil samples from 8~10 points were blended into one sample. Total soluble salt was determined with the mass method, using water bath, electric ovens, dryer, and 1000mL porcelain evaporating dish; CO₃^2- and HCO₃^- was with the double indicator neutralization method; Cl^- was with the silver nitrate titration method; SO₄^2- was with the Barium Sulfate Turbidimetry; Ca²⁺ and Mg was with the EDTA complexometric titration; and Na⁺ and K⁺ was with the flame photometry. For the survey, a questionnaire titled as "Questionnaire on Basic Situation of Facilitated Vegetable Cultivation" was distributed for farmers to fill out. It contained the following items: planting type, cropping system, position in land relief, parent soil, soil type, soil texture, irrigation water source, irrigation mode, tillage pattern, restraining factors, etc. The criteria for grading sulfate-type salinized fluvo-aquic soils for the Second National Soil Survey was cited as reference, that is, soils 2~4 g kg^-1 in total water-soluble salt are sorted as slightly salinized soil, soils 4~6 g kg^-1 as moderately salinized soil, soils 6~10 g kg^-1 as severely salinized soil, and soils >10g kg^-1 as saline soil. 【Result】Secondary salinization of greenhouse vegetable soils in Shandong was investigated and analyzed. In 2014, the greenhouse vegetable (including melons) land totaled 64.98×10⁴ hm² in area, accounting for 35.45% of the total vegetable land of the province. Of the greenhouse vegetable land in Shandong, 25.06×10⁴ hm² was under sunlight greenhouses; 20.94×10⁴ hm² under large arched plastic huts; and 18.98×10⁴ hm² under medium and small arched plastic sheds. The salt ions in the greenhouse vegetable soils, consisted mainly of SO₄^2- dominated anions and Ca²⁺ dominated cations About 39.73% of the greenhouse vegetable soils in the province suffered salinization varying in degree, and among them, 0.43% was slightly salinized, 2.29% moderately salinized, 8.37% severely salinized and 28.64% saline soils. In terms of salinization degree, the three types of greenhouses displayed an order of, sunlight greenhouse > large arched hut > small arched shed. In the 17 cities investigated of Shandong Province, Liaocheng, Laiwu, and Dongying was relatively high in secondary salinization degree. The province applied 1 624 kg hm^-2 (on nutrient element basis) of chemical fertilizers on average, consisting of 559.5 kg hm^-2 N, 465.2 kg hm^-2 P₂O₅ and 599.3 kg hm^-2 K₂O. Analysis shows that among the factors affecting secondary salinization, high chemical fertilizer input ranked first, although in the actual production practice affected by a huge variety of factors, no apparent linear relationship was observed, Instead, accumulation of soluble salts was found closely related to cropping history. Canonical correspondence analysis shows that both input of fertilizers and cropping history would affect salinization degree, though varying in impact. Input of NPK fertilizers was the major factor affecting contents of K⁺, Na⁺ and Mg²⁺ in the soi, while cropping history was the one affecting contents of Ca²⁺, Mg²⁺ and SO₄^2-, rather than contents of K⁺, Na⁺, HCO₃^- and Cl^-. Content of Mg²⁺ was significantly affected by both factors.【Conclusion】About 39.73% of the facilitated vegetable land in Shandong Province exhibits a varying degree of secondary salinization. High input of chemical fertilizers is an important cause of the increase in soluble salt, and cropping history is another. It is, therefore, recommended that management of the cultivation under greenhouse should be intensified case-specifically in response to differences in type of greenhouse input of fertilizers and cropping history so as to mitigate the risk or reduce the degree of secondary salinization.

Abstract:【Objective】To find a water efficient technique using underground drainage pipes to wash off soil salt is an issue that has aroused attention from scientists all over the world, because such a technique would make great valuable contribution to agricultural production and economic returns, especially in regions that have large areas of saline alkali soils. 【Method】 In this paper, a field experiment was conducted with drainage pipes, 50 mm or 90 mm in diameters,buried 0.6 m, 1.0 m or 1.4 m deep in the field under drip irrigation to explore effect of the usage of drainage pipes on soil salinity, relative to diameter and burial depth of the pipe. 【Result】 The experiment shows that desalinization effect of two rounds of drip irrigation varied from soil layer to soil layer. The effect was the highest in the 0~60cm soil layer, lowering the soil salt content down below 12g kg^-1 or to the moderate salinization level, but the effect was not significant in the soil layers below 100 cm. Drainage pipes buried at 0.6m in depth were higher than those 1.0 and 1-4m in depth in desalination effect, reducing soil salt content by 14.34 g kg^-1 in total, or by13.32 g kg^-1 as compared with CK, field without using drainage pipes Pipes buried at 1.4 mhad no significant effect on soil desalinization.The pipes different in diameter varied in desalinization effect. Pipes 90mm in diameter were much higher than those 50mm. The effect of pipes 50 and 90mm in diameter varied with burial depth, being in the range of 20.69%~30.20% and 34.59%~57.04%, respectively. 【Conclusion】In the fields with drainage pipes90mm in diameter buried 0.6m in depth, two rounds of drip irrigation reduced soil salinization in the 0~60cm soil layer to the mild salinization level (3~6 g kg^-1), indicating that the technique is high in desalinization efficiency and applicable to the regions of salt-affected soils in Xinjiang. And the findings in this paper may serve as scientific basis for choice of diameter and burial depth of drainage pipes in application of the technique.

Abstract:【Objective】Soil thermal characteristics, including thermal diffusivity, thermal capacity and thermal conductivity, are basic physical parameters reflecting changes in soil temperature, and maintenance and transport of heat in the research on soil physical processes. Heat pulse probing method is the most common one used nowadays to determine soil thermal properties. However in using the method, spacing between probes is a major factor affecting accuracy of the results. In measuring, especially in the field, when probes are inserted into the soil, spacing between probes may vary with penetration resistance of the soil. In addition, alternation of soil freezing and thawing, movement of soil organisms, and growth of plant roots may all cause expansion and contraction of the soil, thus forcing the tips of the probes to deviate or squint and hence change in spacing. It is therefore, essential to perform in situ calibration of probe spacing. 【Method】To that end, Liu et al. proposed a method to calibrate probe spacing. They found that once the heating probe or temperature probe squinted by 1o, the thermal conductivity and thermal capacity measured would deviate by more than 10%. So Liu et al. put two thermistors on to the temperature probe in different positions, and figured out a theoretical formula to calibrate the spacing. The formula was very sensitive to the maximum temperature difference (ΔT_m) and the time when the maximum temperature difference appeared (t_m). In this study, the calibration method was applied to field measurement and monitoring of changes in probe spacing. Temperature probes were installed at 3 cm, 8 cm and 13 cm deep in the soil, separately, to record heat pulses from the heat pulse probe during summer from May 19^th to July 3^rd, 2015 and the winter from February 11^th to March 28^th. 2016. 【Result】Results show that firstly, probe spacing did not have any impact on the measurement of thermal conductivity, which suggests that the soil is homogeneous in texture, and when comparison was made of the measurements of thermal capacity, it was found that the differences between the two thermistors was determined by accuracy of the probe spacing; and secondly, the measurements of soil thermal properties with the probe spacing calibrated method were more accurate and reliable than those without any spacing calibration. However in the winter, when soil temperature was under 0℃, the soil would freeze and thaw alternately, causing the probe tips to deviate. Besides when the heating probe heated, the heat would be divided into two portions: one to melt the ice and the other to warm up the soil. Consequently, the measurements were not so accurate and could be corrected with the spacing calibration method. Besides, the freezing and thawing processes of the soil in winter also made it hard to use heat pulse probes to determine soil thermal properties. It was also found that the measurement with the probes embedded in the surface soil layer was more sensitive to variation of probe spacing. So far as of yet, it is still very hard to explain why, because of various unknown causes. Nevertheless soil thermal properties in the surface layer mean extremely significant to soil water movement, measurement of ground heat flux and so on. Therefore, more efforts should be done in studying accuracy of the heat pulse probe method and practicability of the spacing calibration method. 【Conclusion】To sum up, in using the modified dual heat pulse probe method to monitor soil thermal properties in the field in summer and winter, it is found that probe spacing varies more in the surface soil layer than in the others, and the use of the probe spacing calibration method can significantly minimize deviation of the measurements of volumetric heat capacity, and the spacing calibration method is applicable to field measurement. However, due to the presence of frozen soil in the surface soil layer in winter, it is hard to determine accurately soil thermal properties with the heat pulse probe method and to use the probe spacing calibration method, too.

Abstract:【Objective】The purpose of this article is to study mineral composition and cation exchange capacity (CEC) of the colloids and non-colloids in the two red soils collected from Hunan and Hainan provinces, separately, and adsorption behavior of Cu(II), Cd(II) and Pb(II)on thecolloids and non-colloids, too.【Method】 Soil colloidal and non-colloidal fractions were separated from bulk soils using sedimentation method, where particles in the upper portion of the suspension are collected as colloids at fixed time intervals after stirring. X-ray diffraction analysis was performed to determine mineral compositions of the colloids and non-colloids in the red soils. Free Fe and Al oxides were extracted with the DCB method and determined using ICP-AES. The batch method was used to investigate adsorption and desorption of Cu(II), Cd(II) and Pb(II) on and from soil colloids and non-colloids. Un-buffered salt of 1.0 mol L^-1 NaNO₃ was used to desorb pre-adsorbed heavy metals from soil colloids and non-colloids. 【Result】X-ray diffraction analysis shows that the colloids in the two red soils were composed mainly of secondary minerals with 1:1-typed kaolinite in dominancy and little of primary minerals.The contents of 2:1 typed minerals, such as vermiculite and hydro-mica in the soil colloids decreased with increasing soil development degree, while the content of kaolinite changed oppositely. The non-colloids in the two red soils contained mainly quartz and some other primary minerals.Soil Fe and Al oxides accumulated mainly in the soil colloids. The contents of free Fe and Al oxides were much higher in the soil colloids than in the soil non-colloids. For example, the content of free Fe oxide was as high as 78.03 g kg^-1 in the colloids and only 9.93 g kg^-1 in the non-colloids of the red soil from Hunan. The colloids in the two red soils were also much higher than, or 12 times as high as the non-colloids of the soils in CEC. The isothermal adsorption experiment indicates that the colloids were significantly higher than the non-colloids in adsorption capacity and affinity for Cu(II), Cd(II) and Pb(II), and the colloids of the red soil from Hunan was higher than those of the red soil from Hainan in adsorption capacity, which was consistent with mineral composition and CEC of the colloids of the two red soils. Cd(II) was adsorbed by soil colloids and non-colloids mainly through electrostatic attraction, however both electrostatic and non-electrostatic adsorptions were important mechanisms contributing significantly to adsorption of Cu(II) and Pb(II) on soil colloids and non-colloids. 【Conclusion】The secondary minerals and Fe/Al oxides are mainly distributed in the colloids of the two red soils. The colloids are much higher than the non-colloids in the two red soils in CEC, and hence in adsorption capacity and affinity for these heavy metals.

Abstract:【Objective】Grain production in China is now subjected to the stresses of climate warming and soil contamination. Therefore, it is vital to understand effects of the dual pressures on growth and production of crops. Climate warming exhibits the characteristic of asymmetric warming that highly increases the temperature at night and in the spring and winter seasons. The asymmetric warming basically overlaps with the growth period of wheat (Triticum aestivum), a grain crop widely planted in China and the world, to feed around one fifth of the world's population. Obviously, asymmetric climate warming has a great potential impact on wheat production. As one of the main heavy metal pollution elements in soil, lead (Pb) has some detrimental effects on growth, development, yield formation and quality of the corp. With the rapid development of industries and increasing human activities, the risk of Pb pollution in some agriculture regions has become more and more prominent, which is deleterious to sustainable development of agriculture and safety production of grains. Since asymmetric climate warming and soil Pb accumulation potentially affects the production of wheat in China, it is very important to analyze the effects of night warming on uptake and distribution of Pb in wheat under the stress of Pb pollution, so as to provide some scientific information essential to ensure safety production of wheat grain in the future harassed by climate change and heavy metal pollution.【Method】 A pot experiment was carried out during the wheat growth season of 2013—2014 in the Zhoushan Experimental Farm of the Henan University of Science and Technology (34°38′N, 112°22′E), which is rainfed and hilly agriculture area with annual average temperature of 13.7 ℃ and annual average rainfall of 650.2 mm. The experiment was designed to have two treatments for temperature, CK and night warming under a passive night warming system, and three levels of Pb pollution (36.8 mg kg^-1, 153.4 mg kg^-1 and 415.7 mg kg^-1). The Pb polluted soils in the pots were collected from the topsoil (0~20 cm) layer of farmlands near the Pb mining and smeltery and the same in physic-chemical and al properties and fertilization (moderate level) but different in Pb content. Responses of the crop (vs. Zhongmai 175) in yield, biomass of different aboveground tissues, and content, accumulation, bioaccumulation coefficient and translocation coefficient of Pb in aboveground tissues to night warming and Pb contamination were investigated. 【Result】Results show that night warming significantly increased yield of the crop by 8.3% and significantly decreased biomass of its aboveground tissues, stem and leaf. Negative effects of Pb pollution on yield and biomass of the crop intensified with increasing level of the pollution. Night warming significantly decreased Pb contents in shoot, grain and glumes, but not in stem and leaf. Night warming significantly decreased Pb accumulation by 7.6% and 6.8 % in grain in the treatments low and high in Pb pollution level, respectively, by 12.0% and 13.9% in glume in CK (no pollution) and the treatments high in Pb pollution level, and by 14.0%~ 23.3%, 22.5%~24.9% and 17.9%~31.8% in shoot, stems and leaves in CK and the treatments high and low in Problem pollution, respectively. Night warming significantly decreased Pb bioaccumulation coefficient in stem, leaves, grain and glumes in CK and in stem, grain and glumes in the treatments low in Pb pollution level, but not in the treatments high in Pb pollution level. Night warming significantly decreased Pb translocation coefficient of Pb from stem to grain and glumes in all the treatments. 【Conclusion】All the findings in this experiment highlight the effects of night warming improving wheat production and lowering the potential detrimental effects of Pb pollution on grain quality of the crop.

Abstract:【Objective】Adsorption-desorption is a key factor governing translocation, transformation, fate and bioavailability of organic pollutants, such as atrazine (AT), in the soil. The adsorption-desorption behaviors of organic pollutants in the soil are not only related to physico-chemical properties of the organic pollutants per se, but also affected by soil organic matter (SOM), inorganic minerals and some other important soil components. There have been large volumes of studies demonstrating that SOM is the major factor governing adsorption-desorption of AT in the soil, but some others indicating that soil inorganic minerals may be almost equal to or higher than SOM in such effect in the case that SOM is relatively low in content in the soil. Current researches about soil inorganic minerals affecting AT adsorption-desorption behavior in the soil focus mainly on crystal silicate clay mineral (e.g. montmorillonite and kaolinite), but researches focusing on soil metal oxides, such as iron oxide, were , much less in number. Amorphous Fe oxides (AHOs Fe) is a kind of highly active iron oxide For its relatively high specific surface area and relatively big number of proton donating functional groups, AHOs Fe plays an important role in controlling the fate of organic pesticides. However, AHOs Fe is extremely unstable and ready to transform into crystalline iron oxide (e.g. goethite and hematite) under natural conditions, which makes it difficult to study characteristics of organic pollutants adsorption to AHOs Fe. In addition, what we had done in the past indicate that AHOs Fe in the soil was apt to form complex with SOM into organic-inorganic complexes, so soil adsorption capacity of butachlor was extremely and positively related to AHOs Fe content in the soil. Therefore, mere correlation analysis could not accurately determine contributions of SOM and AHOs Fe to adsorption of organic pollutants, and what is more, the mechanism of AHOs Fe adsorbing organic pollutants is still not clear. 【Method】In this study, artificially synthesized AHOs Fe and two typical types of soils, black soil from Heilongjiang and latosol from Guangdong were used, and half of the soil samples were surface coated with AHOs Fe. AT sorption behaviors were studied using the batch equilibrium method and its desorption behaviors were through one cycle of adsorption-desorption in various sorbents. At the meantime, in order to learn the extent of delay of AT desorption in the sorbents, delays of the initial desorptions in various adsorbents were quantified with Hysteresis index (HI ). 【Result】 Results show that the isotherms of AT sorption in all the tested sorbents could well be described with the Frundlich equation (r≥ 0.996, p< 0.01). Compared with the soils, AHOs Fe exhibited a relatively high sorption capacity and high nonlinearity in sorption, Once coated with AHOs Fe, the AT sorption capacities of the two soils, black soil and latosol increased, significantly or by 56.3 % and 43.8 %, respectively. AT desorption delayed in all the sorbents and coating of AHOs Fe, decreased hysteresis coefficient (HI ) of the AT desorption with increasing AT concentration in the case that the initial AT concentration was low, and acted reversely in the case that the initial AT concentration was high, indicating that the mechanism for delaying desorption in the sorbents varied with the initial AT concentration. Compared with the soils, AHOs Fe exhibited high hysteresis effect on AT desorption. But once it was used to coat the soils, it lowered the hysteresis effects of the soils. 【Conclusion】AHOs Fe has a relatively high sorption capacity and affinity for AT. However, in natural soils, complexing with soil organic matter (SOM) inhibits AHOs Fe capacity of directly adsorbing AT, because AHOs Fe has more SOM adsorbed or bonded on its surface, which indirectly affects AT adsorption by soil. Obviously, coating with AHOs Fe improves soil AT adsorption capacity, but also increases reversibility of AT sorption in the soil. All the findings in this study may help further understand roles of metal oxides, like AHOs Fe, in soil adsorbing AT-like organic pollutants and hence provide certain scientific basis for avoiding environmental risks of pollution with organic pollutants.

Abstract:【Objective】 Freezing and thawing alternation is a natural phenomenon, especially in high latitude areas, like the northeast and northwest parts of China, The oasis in the arid regions where the winter is long with plenty of snowfall are naturally subjected to frequent freeze-thaw alternations in spring. A large number of researches have demonstrated that freeze-thaw alternation could lead to emission of high volumes of greenhouse gas. So, it is supposed that the croplands in the area studied may emit high volumes of greenhouse gases in winter and spring, but dynamics of the emission and fluxes of greenhouse gases emitted during this period are not well documented.【Method】Along-term field experiment was initiated in April 1990 at the National Grey Desert Soil Station of Xinjiang Academy of Agricultural Sciences, and designed to have a total of 12 treatments, among which 5 fertilization treatments, i.e. CK (No fertilization), NPK (nitrogen, phosphorus and potassium), NPKS (0.9NPK + 0.1 Straw nitrogen), NPKM (1/3NPK + 2/3 sheep manure- nitrogen) and NPKM+ (1.5NPKM), were laid out for this study in a cropland of grey desert soil, and emissions of greenhouse gases during the freezing and thawing alternation periods of 2013 and 2014 monitored with the static box method and gas chromatography.【Result】Results show that Treatments NPKM and NPKM+ reached C 113 and 85 mg m^-2 h^-1 on average in CO₂ emission, respectively, relatively higher than the other three Treatments NPKS, NPK and CK, being 72 mg m^-2 h^-1, 75 mg m^-2 h^-1 and 35 mg m^-2 h^-1, respectively. Similarly, Treatments NPKM+ and NPKM was relatively higher in N₂O flux, too, reaching N 73 and 42 µg m^-2 h^-1 on average, respectively, which were obviously much higher than 22 µg m^-2 h^-1 in Treatment NPKS and 17 µg m^-2 h^-1 in Treatment NPK (p<0.05). However, the treatments were all relatively low and did not differ much in CH₄ emission from each other. N₂O emission displayed a significant rising trend in flux during the early freeze-thaw period, but a declining one in the late period. CO₂ emission exhibited a similarly trend, too, but not so strong. The N₂O emission during the freezing and thawing alternation period (27 days) reached N 0.1~0.5 kg hm^-2 a^-1,accounting for 9%~18% of the total of a year, while the CH4 emission during the period accounted for 6%~14% of the total and did not vary much with the treatment. 【Conclusion】The freezing and thawing period in spring is a time period of high frequency in greenhouse gas emission in the oasis of gray desert soil. Especially during the early and mid phases of the alternation period, both CO₂ and N₂O emissions were apparently on a rising trend, but during the late phase they dropped significantly along with the decline of soil moisture content. Among all the treatments, Treatments NPKM and NPKM+ had significantly longer emission periods and higher emission fluxes, while Treatments NPK and NPKS had higher peak values, but short emission periods. In addition, snowfall in winter was found to be a key factor affecting emissions of greenhouse gases. High snowfall could increase the soil water content and sustain the content for a longer period of time, which could in turn prolong the greenhouse gas emission period, while low snowfall could hardly sustain high soil water content for long, thus shortening the emission period. To sum up, all the findings in this experiment demonstrate that the emission of greenhouse gases from farmland of gray desert soil in the oases is high during the freezing and thawing alternation period. So it is necessary to take into account the greenhouse gas emission during this time period, when estimating volume of greenhouse gas emission and its warming potential in this area.

Abstract:【Objective】Tea (Camellia sinensis L. Kuntze) is a perennial plant widely cultivated in South China. As a high N-demanding cash crop, tea has been applied widely with synthetic N fertilizers to increase its yield. However, application of excessive synthetic N fertilizers in tea gardens might affect chemical properties of the soils and their nutrient supply to tea plants; in addition, it may have some negative impacts on growth of the tea plants and the environment. Although researchers in China have been doing some experiments simulating application of synthetic N fertilizers in tea gardens, so far none of them has been doing to systematically or quantitatively evaluate responses of tea soils to application of synthetic N fertilizer. Through meta-analysis, this paper tries to evaluate quantitatively how application of synthetic N fertilizers affect basic chemical properties and nutrient supply of the soil, and loss of reactive N to the environment. 【Method】In this paper, meta-analysis was done of the 17 papers published in the literature during 2004-2016 involving 15 indicesin 246items of data and records. 【Result】Results indicated that application of synthetic N fertilizers lowered soil pH significantly by 0.20 units on average. In soils of tea gardens different in tea tree species, application of synthetic N fertilizers significantly decreased soil pH and no significant difference was found between subgroups. Soil acidification in the tea gardens was expedited because the application accelerated nitrification process, triggered loss of base cations, and damaged the soil buffering system, thus resulting H+ release. As a whole, application of synthetic N fertilizers had on significant impact on soil organic carbon (SOC). However, it did increase SOC by 15% (7%~24%) in tea gardens of green tea and by nil in tea gardens of oolong tea. Application of synthetic N fertilizers increased soil total N by 18% (10%~27%), and soil dissolved inorganic N availability by 172% (127%~236%). The responses of soil DIN, NH₄⁺-N and NO₃⁻-N concentrations to application of synthetic N fertilizers varied between soils with different tea trees. DIN and NH₄⁺-N concentrations were significantly higher in tea gardens of oolong tea than in those of green tea. NO₃⁻-Nconcentration was significantly higher in tea garden of black tea and oolong tea, but remained almost unchanged in those of green tea. Soil phosphorus and potassium was not much affected in the tea gardens of China. In addition, the application lowered soil calcium and magnesium content by 23% (-30%~-16%) and 37%(-48%~-24%), respectively, but raised soil aluminum accumulated by 54% (38%~69%) in the soils. Besides accelerating microbial nitrification processes, the application also stimulated losses of soil reactive N from the soil to the environment as a result of its increasing N₂O emission and inorganic N leaching by 292% (140%~575%) and 127% (55%~206%), respectively, or more specifically leaching loss of soil NH₄⁺-N and NO₃⁻-N by 422% (280%~617%) and 92% (31%~161%). The stimulated loss of reactive N might pose a great threat to the environmental and ecological safety of the tea planted areas, even the whole country. 【Conclusion】To sum up, application of synthetic N fertilizers significantly enhance the supply of total N and available N in the tea garden soils in China. However, it also causes serious environmental problems in the areas and the whole country by accelerating soil acidification, leaching loss of massive base cations, accumulation of toxic aluminum and loss of reactive N through emission of N₂O and leaching, thus affecting sustainable development of tea gardens. Most of the studies so far done have been conducted on a small scale (greenhouse or pots) both in area and time. It is advisable to have some long-term field studies so as to evaluate accurately responses of the tea garden ecosystems in key processes and provide some theoretical and practical bases for understanding N recycling processes in the tea garden ecosystem and scientific N management for sustainable development of tea cultivation in China.

Abstract:【Objective】 Change in land-use is a crucial aspect of anthropogenic disturbance of terrestrial ecosystems. To assess its impacts on the ecosystems is of vital significance to maintenance of ecosystem functions and promotion of soil sustainability. Soil microbial properties, deemed as important bio-indicators of soil health and quality, can be influenced by changes in land-use. Reclamation of paddy into orchard was very common in South China during the last two decades. 【Method】 In order to further the knowledge about the effects on soil microbial properties, a total of soil samples were collected from surface soil layers of paddy fields and orchards along a chronosequence of cultivation in Shaoxing City, Zhejiang Province, for analysis of soil physicochemical and microbial properties, using the denaturing gradient gel electrophoresis (DGGE) method, the phospholipid fatty acid (PLFA) method analyses and some others. The DGGE gel was scanned, for analysis of fingerprints of soil microbes with the aid of the software of QUANTITY ONE 4.6.2, and relationships of soil microbial community with soil physicochemical properties were analyzed using the redundancy analysis (RDA) method. 【Result】 Results show that the soils under the two types of land use differed significantly in soil physicochemical and microbial properties. The orchard soils were significantly higher in total phosphorus (TP), available phosphorus (AP), total potassium (TK) and available potassium (AK), but relatively lower in water-stable aggregate (>0.25 mm), organic matter (OM), total nitrogen (TN) and alkali-hydrolysable nitrogen (AN). Besides, the orchards soils were 44.1%, 59.9% and 34.0% lower, respectively, in soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) and microbial biomass carbon (MBC)/total organic carbon (TOC), showing a significant and negative relationship with age of the orchards (p < 0.01). Moreover, the orchards soils were 58.1% lower in soil total microbial phospholipid fatty acids, and significantly (p < 0.01) lower in ratio of Gram negative bacteria (Gm^-) to Gram positive bacteria (Gm⁺), and in contrast, much higher in ratio of aerobic bacteria to anaerobic bacteria (p < 0.01), and in ratio of Iso/Anteiso and ratio of Cy/Pre fatty acids (p < 0.01), which indicate that nutrient stress in the orchards aggravates with the cultivation going on after the reclamation (p < 0.01). Cluster analysis of the DGGE banding patterns of the eighteen soil samples showed a clear separation between paddy and orchard soil samples, and a noticeable separation between orchard soils under short and long orchard cultivation, which indicated that both the change in land-use and cultivation history have important effects on soil microbial community. Moreover, Shannon-Wiener indexes of soil total bacteria declined in the orchard soils. Redundancy analysis of PLFA in the soils and environmental factors demonstrates that soil moisture, organic matter, total nitrogen, alkali-hydrolysable nitrogen and available phosphorus are the most important environmental factors affecting soil microbial community compositions in the paddy and orchard ecosystems (p < 0.01). In general, soil aeration and staple nutrients are the most important factors affecting soil bacterial diversity. DGGE and PLFA analyses both demonstrate that change in land-use has a greater impact on soil microbial diversity than the history of cultivation does. 【Conclusion】 This study concludes that both change in land use and history of cultivation have some important effects on soil physicochemical properties, while soil microbial community diversity can also affect soil physicochemical properties and vise versa. Being a vital carbon sink in the earth ecosystem, paddy is rich in soil microbial community diversity and hence a land use pattern, capable of promoting sustainable development of the soil resources. Furthermore, long-term cultivation of orchards is apt to cause a series of problems, such as imbalance of soil nutrients and micro-flora, which eventually negatively affects soil sustainability.

Abstract:【Objective】Nitrogen recycle is an important process in soil ecosystem, and soil microorganisms play a key role in the processes of nitrogen transformation. Nitrification is the process of soil microbe oxidizing ammonia into nitrate，involvingammonia-oxidizing bacteria (AOB)and nitrite-oxidizing bacteria (NOB), sequentially. But now,discovery of the microorganisms(Comammox)that can complete ammonia oxidization raised a number of fundamental questions. Purple soils is mainly distributed in the subtropical areas of China, particularlyin Sichuan Basin, playing a very important role in agricultural productionof the country. By pH and carbonate content,they can be divided into acidic, neutral and calcareous purple soils. Soil pH is an important factor not only affecting soil nitrification, but also influencing nitrification microorganisms in population and community structure. So what are the differences betweenpurple soils different in pH in nitrification and nitrifying microbial community? These scientific questions need to be answered.【Method】Samples of purple soils different in pH, i.e. acidic purple soil (pH=5.3) and neutral purple soil(pH=7.2) in Yongchuan of Chongqing and calcareous purple soil(pH=8.5) inYanting of Sichuan were collected for in-lab incubation to explore nitrification, soil microoganisms andcommunity structures of nitrifying microorganismsin the soils, using the stable isotope probing technique and Miseq sequencing.The incubation experiment was designed to have three treatmentsfor each soil sample, including ¹³CO₂ labeling, ¹²CO₂ control and ¹³CO₂+C₂H₂ control.Soil samples were cultured in aincubatorat 28℃ for 56 days, during which 100 mg kg^-1 urea-N and corresponding volume of gas was applied every week.Samples at D0 and D56 were analyzed with the Miseq sequencing technique. 【Result】Intense nitrification, dominantly autotrophic nitrification, was observed in both neutral purple soil (pH=7.2) and calcareous purple soil (pH=8.5),but not in acid purple soil (pH=5.3).In all the three types of purple soils, bacteria ofProteobacteria,Acidobacteria,Firmicutes,Chloroflexi,Actinobacteria,Bacteroidetes and Gemmatimonadetes were detected, but varied in proportion. Bacteria ofProteobacteria accounted for about 20% of the total in all thethree purple soils.In addition, Planctomycetes was detected in acidic purple soil. In the neutral purple soil and calcareous purple soil, Armatimonadetes and Verrucomicrobia were detected. NOB/AOB ratio reachedas high as 13 in all the three purple soils,which means that the Comammox may play an important role in the process of nitrification in purple soils. 【Conclusion】 In a word, the nitrification in the purple soils was mainly of the autotrophic type. Bacteria of Proteobacteria,Acidobacteria,Firmicutes,Chloroflexi,Actinobacteria,Bacteroidetesand Gemmatimonadeteswere detected in all the three types of purple soils.Distribution of the soil microbial community varied with the soil. Nitrosospira and Nitrospira was the numerically dominant genus of ammonia-oxidizing bacteria(AOB) and nitrite-oxidizing bacteria(NOB), respectively, in the three purple soils. NOB was higher than AOB in relative abundance.All these findings may serve as scientific basis for further study of nitrification in purple soils.

Abstract:【Objective】 Soil microorganisms are important active components in the soil. To understand impacts of farming practices on agro-ecosystems, it is of utmost importance to unfold researches on soil microbial metabolic activity in the farmland. The technique of BIOLOG Eco micro-plate assay is a conventional tool to evaluate soil microorganisms’ ability of utilizing carbon of one sole source, and though having some limitations, could provide clues to source of the carbon utilized by soil microbes relative to farming practice, while microcalorimetric technique is another means to characterize soil microbial activity by measuring heat dissipation and one of high precision. However, being a non-specific technique, it could, only with the support of specific techniques like BIOLOG, provide more explicit information about functions of soil microbe. Previous studies done by this group of researchers reported that BIOLOG could be used in couple with microcalorimetry to detect the factors of carbon source influencing metabolic activity of the soil microbes in the acid and neutral soils. However, little information has so far been reported about this issue in acidic soils. 【Method】 In this study, samples of red soil, a typical type of acid soil, were collected for exploration of ability of the soil microbes to utilize carbon substrates and microcalorimetric dynamics with the technique of BIOLOG coupled with microcalorimetric means in soils applied with chemical fertilizers and organic manure in combination (Treatment OM). Based on the information of carbon source preference of the soil microbes in the red soil obtained via principle component analysis (PCA) of the BIOLOG assay, evaluation was further performed of effects of those carbon substrates on thermometabolism of the soil microbes in Treatment OM and Treatment CK (no fertilization). 【Result】 Results show that Treatment OM significantly increased AWCD (average well color development) on the BIOLOG microplate as compared to Treatment CK. PCA indicates that Treatment OM sat far apart from the other treatments along the first principle component axis. Carbon substrates, like L-arginine, L-threonine, D-mannitol, glycogen and D-cellobiose, were positively related to the first principle component with high correlation coefficient (r>0.5). Microcalorimetric analysis demonstrates that soil microbes in Treatment OM were quite high in thermometabolic activity, which peaked pretty soon, suggesting that Treatment OM stimulated the soil microbes in activity in the red soil. When the carbon substrates found significant in correlation in Treatment OM were spiked into other corresponding Treatments OM and CK, some of them, like D-cellobiose and D-mannitol, did not show any of the effect and instead possibly delayed the appearance of peaks and suppressed metabolic activity of the soil microbes. All these findings suggest that the technique of BIOLOG has its own limitations. However, it was also found that some other carbon substrates, like L-arginine and glycogen did promote metabolism of the soil microbe in Treatments, which might be explained as that these substrates play important roles in stimulating N and P recycling in the soil. 【Conclusion】 Although both the BIOLOG technique and the microcalorimetric technique have their own limitations, coupling of the two makes it feasible to determine key carbon substrates responsible for stimulating the soil microbes in activity in acid soil. This study also demonstrates that L-arginine and glycogen might be the carbon sources of preference to microorganisms in red soil, which further implies that the application of organic manure rich in such kinds of carbon substrates is of great significance to building up soil fertility in the red soil regions.

Abstract:【Objective】Biofumigation has been broadly used to describe the action of fumigants releasing volatile compounds during biodegradation of green manure, organic amendments and compost suppressing soilborne pests and diseases and controlling weeds. It could be considered as a ‘natural’ alternative to chemical fumigation and control of a variety of soilborne diseases and hence has been suggested as a means to mitigate certain adverse effects, like infestation of soil diseases of continuous cropping on the soils. Researches in the past already demonstrated that biofumigation of soils under continuous cropping (SUCC) with Brassica juncea could effectively control soilborne pests and pathogens, change soil microbial community composition, and provide some additional nutrients. In order to explore feasibility of using marigold (Tateges erecta) as biofumigant to alleviate the hazard left by continuous cropping of apple trees in orchards, in an attempt to provide a theoretical basis for extrapolating such an environment friendly fumigation measure to control soil-borne diseases in apple orchards, a pot experiment was carried out【Method】The pot experiment was designed to have 5 treatments, i.e. Treatment CK (untreated old orchard soil), Treatment F (mulched with film), Treatment 1.5T+F (1.5 g kg^-1 Tateges erecta powder incorporated and mulched with film), Treatment 6.0T+F (6.0 g kg^-1 Tateges erecta powder plus mulching), Treatment 15.0T+F (15.0 g kg^-1 Tateges erecta powder plus mulching). All the pots in the experiment were filled up with the same soil from a 25 years old apple orchard in Wangzhuang Village, Manzhuang Town, Tai'an of Shandong, China, divided into five groups and treated separately in line with the designing. Tateges erecta powder was prepared after the plant was washed in tap water, air-dried, and pulverized with a high speed grinder, and then stored in a sealing bag ready for use. All the pots were mulched with film after watering except for Treatment CK. Then 15 days later, all the mulched pots had the film removed and remained exposed to sunlight for 7 days, before Malus hupehensis Rehd. seedlings were planted. At the end of the experiment, samples of the soils and plants in the pots were collected, separately, for analysis of biomass and root morphological indices, activities of soil enzymes (urease, phosphatase, invertase and catalase), soil microbial population and fungal community structure. Soil microbial population was determined with the dilution plating method; fungi community structure with the technique of terminal-restriction fragment length polymorphism (T-RFLP); and copy number of Fusarium proliferatum with the real-time quantitative PCR detecting system (QPCR). 【Result】 Compared with Treatment CK, the biofumigation significantly increase the biomass of apple seedlings, promoted root growth and improved activities of the soil enzymes. And Treatment 6.0T+F was the most significant in effect and was 8.1 and 13.1 times as high as Treatment CK in dry weight of shoot and root, 333.0% and 548.4% higher than Treatment CK in root surface area and root volume, 103.6% and 77.6% higher in activities of urease and phosphatase, respectively, 200.4% higher in invertase activity and 64.6% higher in catalase activity. Besides, the treatment was higher in bacterial population, but lower in fungal population, with the ratio of bacteria to fungi reaching up to 219.9, or about 5.6 times that of Treatment CK, and consequently lower in Shannon diversity index, evenness index and richness index but higher in Simpson's index of the fungi community. And gene copies of Fusarium proliferatum decreased by 57.9% in the treatment. Principal component analysis (PCA) showed that the fungal communities in the soils varying in Tateges erecta powder treatment rate were completely separated from that in the control. 【Conclusion】To sum up, Biofumigation using Tateges erecta powder at a proper rate (6.0 g kg^-1) of old orchard soils may increase the number of beneficial bacteria, inhibit propagation of soil pathogenic fungi, and preserve the diversity of the soil microbial community structure, and then effectively alleviate the hazard continuous cropping poses to replanting and improve growth of the replants.

Abstract:【Objective】As a basic biochemistral process in the terrestrial ecosystem, mineralization of soil organic carbon (SOC) is closely related to release of soil nutrients, maintenance of soil quality, and formation of greenhouse gases. Fertilization is one of the most important factors influencing of SOC mineralization. The objective of this study is to explore dynamics of SOC mineralization in paddy soil from yellow earth as affected long-term fertilization, illuminate characteristics of organic carbon mineralization in paddy fields of yellow soil different in fertilization and provide guidance for formulating reasonable nutrient management programs.【Method】Analysis of the data of the 22-year long-term stationary fertilization experiment in paddy soil from yellow earth in the Guizhou Academy of Agricultural Sciences, was done for effect of long-term fertilization on SOC mineralization in the paddy soil, and meanwhile an in-lab incubation experiment was conducted. The field experiment was designed to have five fertilization treatments: CK (no fertilizer), Treatment NPK (application of chemical fertilizer), Treatment 0.5MNPK (application of chemical fertilizer, half the rate, plus organic manure), Treatment M (application of cow dung) and Treatment MNPK (application of NPK, normal in rate, plus organic manure ).【Result】After 22 years of fertilization the SOC content was 22.8 g kg^-1 in CK and 21.6 g kg^-1 in Treatment NPK, and increased by 30.6%, 72.9% and 62.2%, in Treatments 0.5MNPK, M and MNPK, respectively. Obviously the increase was particularly remarkable in Treatments M and MNPK (p < 0.05). In the in-lab incubation experiment, it was found that CO₂ production rate reached a peak on D2, fell rapidly till D4, declined gradually until D24, and leveled off D30. In terms of SOC mineralization rate the five treatments exhibited an order of M > MNPK > 0.5MNPK > CK > NPK. The relationships between mineralization rates of SOC and duration of incubation in all the treatments fit the logarithmic function equation (p < 0.01). The cumulative SOC mineralization on D30 varied in the range of 1.23 g kg^-1 to 2.37 g kg^-1. Compared with CK treatment (1.46 g kg^-1), Treatment M and MNPK increased significantly or by 62.6% and 44.2%, respectively in cumulative SOC mineralization (p < 0.05). But all the treatments were lower than CK (6.4%) in ratio of cumulative SOC mineralization to total SOC after 30 days of incubation, especially Treatments M and MNPK treatments decreasing by 1.2% and 0.9%. The dynamic variation of the cumulative SOC mineralization with incubation time fit the first-order kinetics equation (p < 0.01). The simulation results show that soil potential mineralizable organic carbon was 1.15 g kg^-1 CK decreased insignificantly or by 11.6% in Treatment NPK, but increased in Treatments 0.5MNPK, M and MNPK by 21.3% ~ 73.6%. The increase was the most significantly in Treatments M and MNPK (p < 0.05). At the same time, Treatment MNPK increased SOC turnover rate and reduced turnover time. 【Conclusion】In conclusion, long-term application of organic manures, like in Treatments 0.5MNPK, M and MNPK, can improve SOC mineralization rate, promote SOC accumulation, reduce SOC cumulative mineralization ratio (mineralization level per unit organic carbon), and enhance soil C sequestration capacity.

Abstract:【Objective】 Sequestration of carbon (CO₂) from the atmosphere into forest soils is considered to have great potential to mitigate the momentum of global climate change. However, soil carbon saturation has been observed in some soils. When the soil is saturated with stable soil organic carbon (SSOC), any new input soil organic carbon (SOC), which would accumulate in labile pools, would easily be decomposed by microorganisms, contributing little to the soil carbon storage. The potential of soils to sequestrate SSOC is limited by SOC stabilization. SOC is stabilized mainly through inherent biochemical recalcitrance, protection through interaction with minerals, and occlusion in aggregates. Black carbon (BC) is an example of the first mechanism, gaining stability from condensed aromatic structure, while mineral-bonded organic carbon (MOC) is one of the second. SSOC plays a vital role in soil sequestration; however, researches on SSOC in natural forests are still inadequate. In this paper, MOC and BC, two representatives of SSOC, were studied and their carbon sequestration potentials (CSP) in three types of forest soils in the Great Xing'an Mountains, Northeast China were estimated. 【Method】 MOC was analyzed with a physical method and a chemical one, too. In physical analysis, soil was divided into particulate organic matter (POM, >53 μm) and mineral-bonded organic matter (MOM, ≤53 μm), and organic carbon (OC) was detected in MOM (MOC_p), whereas in chemical analysis, soil was acidified with hydrofluoric acid, and OC loss (MOC_c) was measured. BC was determined with the oxidation method using potassium dichromate. CSP was calculated based on the carbon saturation capacities of silt and clay particles according to Hassink. 【Result】 Results show that MOC and SOC was remarkably correlated to each other, however, comparative analysis shows that the particle size fractionation method overestimated MOC, because it was found that not all the OCs in MOM are bonded with minerals into MOC. Actually, only 60.6 % of the OCs in MOM are. BC in the soils was 8.46±3.85 g kg^-1 in content and declined with soil depth, however, the proportion of BC to SOC displayed a rising trend. Most of the BC (78.8%) was enclosed in MOM, and the proportion of BC in MOM increased with soil depth, meanwhile the relevances of BC with silt and clay were also reinforced, which illustrated that soil mineral plays an important role in chemical protection of BC. BC/SOC ratio in the soils was 25.4%, which was reasonable since the forests had not been affected directly by industrial activities. Thereinto, the BC/OC ratio was 26.3% and 24.9% in POM and MOM, respectively. MOC and BC contributed to SOC by around 67.2%, which demonstrates that the soil has a high disturbance resisting capacity in the study area. The surface soils were highly carbon saturated, reaching up around 97.8% in saturation, while carbon saturation declined with soil depth, down to 21.2% in bottom soil, which illustrated that the soil deep in profile could store a considerable amount of SOC. Based on calculation, CSP of the soil deep in profile could be1.86 times the current SOC storage, while the CSP of surface soil accounted only for about 1% of current SOC stock. 【Conclusion】 The SOC storage in forest soils is huge, with SSOC taking an crucial place, and what is more, the potential of forest soils for carbon sequestration is also enormous, especially in the soil deep in profile. The current carbon saturation theories are all based on the conception of SSOC, however, the existence of BC in POM manifests that the role of POC in soil carbon sequestration needs to be reconsidered, because POC is not invariably labile as is commonly understood.

Abstract:【Objective】Being the main by-product of crops, crop straw is rich in organic matter, nitrogen, phosphorus, potassium and some other nutrients. The practice of returning or incorporating straw into the field can improve soil physical and chemical properties, soil fertility quality and nutrient recycling, and hence crop yield. However, the practice has quite a number of problems waiting for solution. For example, crop straw is hard to decompose and low in utilization efficiency; produces reducing toxic substances and competes with crops for nitrogen, when decomposing; and induces incidence of crop pests and diseases. Therefore, how to optimize crop straw utilization is of great significance to guaranteeing food safety of the country and improving soil quality. Currently, straw incorporation often goes in combination with tillage, which can not only improve the soil water, fertilizer, gas and heat regimes, but also increase crop yield. It is a good effective and important measure to ensure sustainable development of the agriculture. Although a large volume of researches have recently been reported in China on effects of the combination of straw incorporation with tillage on soil fertility and crop yield of the field, most of them, except a few, focus mainly on effects of the practice in upland fields and fields under rice-wheat rotation system. The double rice-cropping system in South China is a rich resource of rice straw, but it is still unclear how to optimize the combination of straw incorporation with tillage.【Methods】A 3-year stationary field experiment was conducted from 2013 to 2015 to study effects of tillage on crop yield and soil fertility quality in combination with straw incorporation. The field experiment was designed to have four treatments, that is, conventional tillage without straw incorporation (CT), conventional tillage and straw incorporation (CTS), rotary tillage and straw incorporation (RTS) and non-tillage and straw incorporation (NTS). The straw of early rice was crushed into short sections about 5 cm in length simultaneously by the Kubota semi feeding combine harvesting the crop, and spread into the field as basal manure for late rice, and so was the straw of late rice and spread into the field as basal manure for the early rice next year. 【Results】Results show that Treatment CTS was 3.5% and 5.2% higher than Treatment CT and Treatment NTS, respectively, in mean yield of the three cropping of early rice from 2013 to 2015 and 3.6% and 6.4% higher, respectively, in mean yield of the three cropping of late rice. Especially Treatment NTS was markedly lower than Treatment CTS in late rice yield（p<0.05). But Treatment RTS was by 6.1% and 3.1% higher than Treatment CTS, respectively, in early rice yield and late rice yield. The experiment also shows that straw incorporation increased soil organic carbon (SOC), total nitrogen (TN), available phosphorus (AP) and readily available potassium (AK). In 2015, Treatments CTS, RTS and NTS were distinctly higher than Treatment CT in SOC, TN, AP and AK. Treatment NTS was 4.9% higher than Treatment CT in soil bulk density (BD) (p<0.05), while Treatment CTS and RTS was 4.1% and 5.2%, respectively, lower than Treatment CT. The declining trend was especially apparent in Treatment RTS. Straw incorporation reduced soil pH by 1.9%, 1.5% and 2.5% in Treatments CTS, RTS and NTS, respectively as compared with Treatment CT, and especially in Treatments CTS and NTS. During the three years of cultivation, Treatment CT exhibited a declining trend in soil fertility, however, in treatments with straw incorporation, soil fertility was on a rising trend. In 2015, Treatment RTS was 16.4% and 80.4% higher, respectively, than Treatment CTS and NTS.【Conclusion】 Obviously, in double rice cropping regions of South China, long-term rotary tillage is better than conventional tillage and zero-tillage in building up soil fertility and improving rice yield, when straw is returned into the field.

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