Abstract:Humic substances (HS) is the main part of natural organic matter (NOM), which have very complicated composition and structure, the reason called a kind of substances, is based on the common structural characteristics or the "distinctiveness" of their structure, formed in the humification process. But after nearly 200 years of exploration, the "distinctiveness" is still not clear. Faced with this dilemma, in recent years, some research results are deduced unreasonably, and there seems to question "distinctiveness" of HS. This relates to the foundation of HS chemistry and must be extensively studied and answered. In this paper, the existing researches, including the structural "distinctiveness" of humic substances，comparison of biological molecules monomer to the feature of the HS structure, HS formation with natural biological material based on biological diversity (evolution), formation mechanism of HS and formation sequence of humic acid (HA) and fulvic acid (FA), mineral clay catalyst for HS formation, modern techniques application such as heteronuclear single quantum coherence (HSQC), total correlation spectroscopy (TOCSY), Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and synchrotron radiation soft near-edge X-ray adsorption fine-structure spectroscopy (NEXAFS) are waiting for carrying on review, and the direction for further HS research are put forward. The "distinctiveness" of HS will be studied in future in two ways: (1) Representative HS which come from different sources is compared with the recognized precursor monomers of biological molecules and bio-based (evolution) diversity of natural biomaterials. According to the differences, we can answer the question of the HS presence of "distinctiveness" and what is the "distinctiveness". (2) Choosing universal and controllable incubation conditions, the natural biological material is incubated by microbial inoculated incubation as the HS precursors. The differences of structural characteristics before and after incubation between products and precursors, the changes in the incubation process will be investigated by the same test method, to reply the HS "distinctiveness" is whether produced by the humification or not. The research idea should be that: No matter what the research results were, at least we could make the scientific mystery about whether the HS holding the "distinctiveness" or not and what was the "distinctiveness" seeming closer to the level of known. No matter which aspect was made breakthrough, it could provide the basic data for the HS biochemistry such as the formation, nature, chemical composition and structural characteristics, stability mechanism of HS and its relationship with the environment; It also could solve how to adjust the composition of HS through pre-setting the environmental conditions, which could provide the new theoretical basis for the regulation of soil fertility and carbon sequestration. In a word, based on the mention above, It could play a promoting role in the HS research and solve the scientific problems gradually associating with the HS from the different fields, such as the soil science, biogeochemistry, agronomy and environmental science.

Abstract:With the development of microbiology, Quorum sensing (QS), closely related to many physiological characteristics and activities, is getting more and more attention. QS in bacteria is a kind of mechanism for intracellular or intercellular communication in response to variation of the community in density, aiming at coordinating their population behavior and controlling gene expression. QS of Gram-negative bacteria is generally controlled by the Luxl/R-type information system, using N-acyl-homoserine lactones (AHLs) as signal molecules to regulate diverse physiological processes such as generation of exoenzyme and toxin by pathogenic bacteria, formation of biomembrane, bioluminescence, biosynthesis of antibiotic, bacteria motility and even degradation of organic pollutants. How to rapidly and accurately detect and monitor variation of AHLs in environment and cells is an important basis for the study on quorum sensing. Therefore, an overall review is presented here on AHLs as representative signal molecules, summarizing their characteristics, structures, derivatives and different analyzing methods as well. As the concentration of AHLs in the cell and the environment is usually very low, pre-concentration is necessary for its determination. For pre-treatment of liquid samples, Liquid-liquid extraction and solid-phase extraction are two common methods used to isolate AHLs from liquid matrix. The former is the most widely used one, while the latter has dual functions, concentration and purification, simultaneously. The identification of unknown signal molecules plays a vital role in understanding the information communication between microfloras. To identify structures of AHLs, the techniques of chromatograph-mass spectrometer, capillary zone electrophoresis/mass spectrometry (CZE/MS), Fourier transform ion cyclotron resonance mass spectrometry (FTICR/MS) and nuclear magnetic resonance spectroscopy (NMR) are commonly used. To quantitatively analyze AHLs compounds, the techniques of biosensors, thin layer chromatography, high performance liquid chromatography (HPLC), radioactive isotope tracer and enzyme-linked immunosorbent assay (ELISA) are used. Each technique has its own advantages and disadvantages. Biosensors are very sensitive, however the analysis of each type of AHLs needs specific strain and plasmid. Thin layer chromatography, with a lower sensitivity, is only used to detect high concentration of AHLs. Radioactive isotope tracer is immune to interference of the external environment and hence makes the pretreatment of samples simple, however, this method can only be used to determine the total, rather than specific components of AHLs. HPLC is the most widely used to measure the content and structure of AHLs, but the samples for determination need to be pretreated for purification. Being low in cost, easy to operate and high in accuracy, ELISA has turned out to be a promising method, nevertheless, it could not be used to determine molecular structure of AHLs. The determination and characterization of AHLs are very important to understand inter-microbial signal communication, however it is still a big challenge to determine AHLs qualitatively and quantitatively because they do not vary much in molecular structure and are often very low in concentration. Although the above mentioned analytic methods are quite high in sensitivity and selectivity, each has its own disadvantage. Therefore, it is advisable to combine some of these methods to bring their advantages into full play and complement each other in determining AHLs. At the same time, how to combine these methods into one that is capable of determining a variety of AHLs efficiently and rapidly shall be the focus of the researches in future. On the other hand, the current methods are mainly focused on aqueous solution. In complex natural environments, such as soil and sediment, the existence of organic and inorganic compounds simultaneously presents a great challenge to extraction, purification and determination of N-acy-homoserine lactones. It is necessary to develop some efficient methods for qualitatively and quantitatively measuring AHLs in complex matrices. The determination will play an important role in unveiling the mechanism and action of microbial quorum sensing in the natural environment, especially the soil ecosystem.

Abstract:About ten years ago, the long-have-been neglected region in carbon cycle study, the desert region, started to get attentions, as several studies indicated that this was a huge potential carbon sink. The sparse vegetation and poor humus in desert soil made the inorganic carbon in desert soil the first candidate for seeking carbon sink. The following studies revealed that the dissolved inorganic carbon (DIC) is of atmospheric origin, and is an active participant in modern carbon cycle. Diurnal temperature variation changes the solubility of CO₂in soil water, which in turn created an “inorganic respiration” in the soil with CO₂ pumped day-in/night-out. Extra irrigation, aimed at washing salt out of the soil in the largely saline/alkaline arid region, also washed the DIC out of the soil and forms a carbon sink in the groundwater. Studies thus far still can not prove that carbonates in the soil is an active player in modern carbon cycle, but can prove that in the desert soil with weak biotic processes, abiotic process may not only dominate CO₂ exchange between soil and atmosphere, but also create carbon sink of inorganic nature.

Abstract:【Objective】In recent years, the issue of influences of human activities on soil development has been drawing more and more attention, however, present researches are main focused on impacts of modern cultivation and urban activities on soil, with little attention to those of ancient human activities on soil. As a matter of fact, ancient human activities have left so many traces in the soil that it is feasible to expose the influence of ancient human activities on soil genesis and development, and intensity and range of the activities through pedological researches and hence to provide archaeologists with certain scientific basis in their work. 【Method】In this paper, two soil profiles in the Yangshao Village cultural relic site of Henan Province, one containing obvious evidence of ancient human activities (cultural profile in short) and the other free of any ancient human disturbance (natural profile in short), were chosen for comparison. By referring to the method for studying genetic features of paleosol and the means of explore for charcoal grains that may indicate intensity of ancient human activities this paper focused on analysis of the two profiles for comparison in content of various oxides and soil weathering and development indices, Sa, Saf and ba, and hence for influences of ancient human activities on soil formation and development. 【Result】Results show that ancient human activities varied in influence on migration and accumulation of various oxides. In the ash layer formed by ancient human using fire, the number of charcoal grains was the highest, reaching 238,153 pcs g^-1，which was about 12.35 times the maximum in the natural profile, thus leading to relatively lower SiO₂, Al₂O₃, Fe₂O₃, K₂O, MgO and Na₂O contents, or down to the minimum, while bringing the contents of CaO and MnO up to the maximum, which indicates that the use of fire by the ancient human beings generated a great deal of materials abundant in Ca and Mn. In the cultural layer formed by living of ancient humans, all oxides expect SiO₂, came to the maximum or peak, which indicates that the living of ancient humans facilitated accumulation of various oxides. As the ash and cultural layers were formed with foreign objects that were brought in by ancient human activities, they were no long ordinary soils, so in comparing the two profiles in soil weathering and development indices, it is necessary to rule out the two layers. 【Conclusion】It was found that the cultural profile was on the whole higher than the natural profile in soil weathering and development indices, which indicates that the use of fire and living activities of ancient human beings inhibited soil weathering processes. Besides, the two profiles were more or less the same in content of oxides, which indicates that ancient human activities did not affect much contents of various oxides in the soil. However, the comparison of the two profiles in variation of the contents of oxides reveals that in the cultural profile, except for the ash and cultural layers, the fluctuation of the content of various oxides in all the other layers was less in frequency and magnitude than that in the natural profile, particularly in the subsoil layer, which indicates that the use of fire by ancient human beings inhibited downward transportation and accumulation of various elements, thus keeping the subsoil in a relatively enclosed environment. Meanwhile, the fluctuation of the soil weathering and development indices in value was also less in frequency and magnitude in all the other layers of the cultural profile than that of the natural profile, especially the index of ba. The assumption that the use of fire and living activities of ancient human beings impeded weathering of the subsoil further confirms the above conclusion.

Abstract:【Objective】Soil aggregate is the basic unit of soil structure. Soil aggregates in runoff cause severe abrasion of soil surface, thus significantly affecting water infiltration rate of the soil surface, sediment transport and deposition, and development of soil erosion. With the aggregates breaking into numerous small particles, soil erosion starts. Researches have been reported illustrating that changes in roughness of the surface of a slope directly affect hydraulic characteristics of overland runoffs on the slope, like friction factor,flow depth and so on, which are the best hydraulic parameters to characterize aggregate erosion in the process of aggregate transport with runoff on the slope. Therefore, roughness of the surface of a slope may also affect disintegration of soil aggregates in runoff to a varying extent relative to degree of roughness. 【Method】In order to study erosive effect of soil aggregates in runoff on slopes different in surface roughness, an experiment was conducted in the artificial rainfall simulation lab of the Huazhong Agricultural University. The soil used in the experiment was Ultisols, collected from Xianning of Huibei Province, China. The soil sample was air-dried and oven-dried at 40℃ for 24 h to ensure that the soil sample was constant in moisture content. Before the experiment, portions of soil aggregates 20 g each were weighed out, 0.0001g in diversion, and were put separately in flasks containing ethanol (95%) for 10 min to expel air from the aggregates so as to eliminate the risk of breaking up the aggregates in the process of fast-wetting. Stainless steel flumes, adjustable in slope gradient, were set up. The pretreated soil samples were spread out in the flumes and prepared into 5 degrees of roughness (d=0, 0.25~1, 1~3, 3~5 and 5~7 mm) separately. The flumes were adjusted to 10 ° in gradient and the water flow controlled at 0.4 L s^-1.The experiment was designed to explore abrasion effects of soil aggregates in runoff as affected by particle size of the aggregates (7~5, 5~3 and 3~1 mm), roughness of the surface (d=0, 0.25~1, 1~3, 3~5 and 5~7 mm) and transport distance (9, 18, 36, 54, 72 and 108 m) and effects of particle size, surface roughness, transport distance and some related hydraulic parameters (flow depth, friction factor, flow shear stress) on aggregate abrasion. 【Result】Results show that (1) aggregate abrasion aggravated with rising particle size of the aggregates, and with rising surface roughness, too, when transport distance remained the same. Yet, the effect of the latter was more obvious than that of the former. The effects of roughness and interaction of roughness and particle size all reached the significance level p<0.05, regardless of transport distance, however, the effect of particle size was not significant when the transport distance reached 54 m or 72 m. (2) On slopes the same in roughness, abrasion rate followed a paracurve, rising and then falling with increasing transport distance. Regardless of transport distance, the abrasion rate of the aggregates, 7~5 mm in particle size, increased with increasing roughness; but that of the aggregates, 5~3 mm or 3~1 mm in particle size, varied irregularily with increasing roughness. (3) When the transport distance was fixed to be 36m, W_r/W _iof aggregates declined as a power function of increasing depth of the runoff, regardless of roughness, which may be attributed to the joint effect of roughness and runoff depth, and the effect of roughness was more obvious in the case of the flow rate and slope gradient set in the experiment. Aggregate abrasion rate decreased as a power function of increasing friction factor and/or flow shear stress, declining first and then leveling off. However, in the case of varying roughness, the effect of runoff depth on abrasion rate of aggregates as affected by slope gradient and flow rate needs to be studied further. 【Conclusion】All the findings in this experiment may serve as reference for researchers in studying mechanisms of red soil aggregates breaking down in runoff and have some great theoretical significance to the development of proper soil erosion models.

Abstract:【Objective】Rill erosion is particularly serious on slope croplands of purple soil, where maize is the main crop. Therefore, it is a great significance to study how rill erosion occurs on the slope land during the maize growing season to evaluation and effective control of soil rill erosion. 【Method】To that end, a field artificial rainfall experiment was carried out for determination of characteristics of rill erosion on such slope croplands during different maize growing stages, and for analysis of effects of leaf area index and rainfall intensity on rill erosion process. 【Result】Results show that with maize growing in the field, runoff generation, drop-pit occurrence and rill formation varied temporally showing a rising-and-falling trend. Rills appeared earlier at the seedling stage (27′28″) than at the tasseling stage (48′03″). The average interval between drop-pit occurrence and rill formation was 10′59″, 15′30″, 20′16″ and 18′58″, respectively, at the seedling, jointing, tasseling and maturing stage, which indicates that rills formed much more easily during the seedling. When the rainfall was 2.0 mm min^-1 in intensity, the rills developed best in morphology during the seedling stage, with the longest rill reaching 77.62，6.25 and 4.04 cm, respectively, in length, mean width and mean depth, and with the crop growing on, the volume of rill runoff at various growing stages displayed an order of seedling stage > jointing stage > maturing stage > tasseling stage. The volume of rill runoff during the tasseling stage and tasseling stage accounted for 30.97% and 19.01%, respectively, of the total of the entire maize season, and the runoff yield rate during the two stages was 751.48 ml m^-2 min^-1 and 461.23 ml m^-2min^-1, respectively. However, the runoff yield rate, regardless of growing stage, displayed a generally rising trend, though fluctuating in the process with rainfall going on, and it fluctuated more obviously during the initial period of rainfall and gradually turned stable later on. Such fluctuation was higher in magnitude during the seedling stage than during the tasseling stage. The seedling stage was the highest among the four stages in rill sediment yield rate, reaching 6.96 g m^-2 min^-1 and followed by jointing stage, mature stage and tasseling stage. Rill sediment yield rate fluctuated with rainfall going on in all the stages and the fluctuation at the seedling stage was the highest in magnitude. Under rainfalls 1.5 or 2.0 mm min^-1 in intensity, rill sediment yield varied sharply between maize growth stages while surface runoff did not much in volume, which indicates that the effect of maize plants conserving soil was realized through reducing sediment carrying capacity of the runoff. A significantly positive relationship was observed between volume of runoff and rainfall intensity during the rill erosion stage (r=0.93**) in slope maize fields, but negative ones were between rill sediment yield and maize leaf area index (r=-0.63*). The regression equations of runoff rate and sediment yield rate with leaf area index and rainfall intensity were rated at an extremely significant level (R ²=0.95，R ²=0.65). 【Conclusion】The findings in the study demonstrate that it is feasible to effectively control rill erosion on slope lands cultivated with maize at all its growing stages.

Abstract:【Objective】Soil enzymes catalyze nutrient recycling in forms available for plants and other organisms and are actively involved in soil energy transfer processes. Therefore, soil enzyme is an important driving factor in soil organic carbon dynamic and plays an extremely important role in the global carbon cycle. Knowledge of the mechanism of soil enzymes responding to soil erosion and deposition contributes to further understanding of the role of soil erosion in the global carbon cycle. Therefore, the purposes of this study were to elucidate the response of soil enzyme activities to long-term water erosion and quantify the relationships between soil basic physico-chemical parameters and enzyme activities. 【Method】In this research, soil samples were collected separately from the soil layers (0 ~ 5, 5 ~ 10, 10 ~ 20, 20 ~ 30, 30 ~ 40, 40 ~ 60, 60 ~ 80, 80 ~ 100 cm) of the erosional and depositional sites along a slope covered with pine trees in the hilly red soil region of South Hunan for the analysis of basic physico-chemical properties and enzyme activities in the soil. Soil organic carbon (SOC), total nitrogen (TN), dissolved organic carbon (DOC) and activities of -four kinds of soil enzymes (i.e. urease, catalase, acid phosphatase and sucrase) were measured. Pearson correlation analysis and partial redundancy analysis were performed to analyze relationships between the soil enzyme activities and the soil physico-chemical properties and explore the most important physico-chemical factors influencing the soil enzyme activities. The findings in this study may provide some fundamental theoretical bases for exploration of the roles of the soil enzymes in soil carbon dynamic as affected by soil erosion. 【Result】Results show that the depositional soils were higher than the erosional soils in content of SOC, TN, DOC. Soil deposition significantly improved soil fertility. Furthermore, the content of SOC, TN and DOC in the surface soils at the erosional and depositional sites was significantly greater than that of their respective one in the deep soils. In the soil profiles, the contents of SOC, TN and DOC all displayed a downward trend with increasing soil depth. Water erosion had not only a significant effect on soil nutrition distribution in the eroded slope, but also a great impact on soil enzyme activities in soils different in slope position. All the four enzymes, except for sucrase, were much higher in activity in the depositional soils than in most erosional soils. Soil deposition apparently improved soil enzyme activities. The same as the content of SOC, TN and DOC, activities of the four soil enzymes declined with soil depth in the profile. In addition, correlation analysis reveals that positive correlations existed between urease, acid phosphatase and catalase. Furthermore, significant positive correlations (p< 0.05) between soil nutrition parameters (SOC, TN, DOC) and enzyme activities (urease, acid phosphatase and catalase) were observed. All these findings prove that under the influence of long-term water erosion, soil enzyme activities and nutrition level presented a similar curve in dynamic. Partial redundancy analysis shows that SOC, TN and DOC together were responsible for 39.7% of the variation of the enzyme activity and SOC explained up to 7.5% of the variation of the enzyme activity, whereas, TN and DOC did 0.1% and 3.5%, respectively, which demonstrates that SOC is a factor more influencing on soil enzyme activities than all the other measured physicochemical parameters. Erosion-induced SOC redistribution in the soil on a slope is one of the major routes via which soil erosion affects soil enzyme activities. 【Conclusion】 This study is quite limited to the soil on the slope covered by pine trees in a hilly red soil region. Therefore, more efforts should be devoted in future studies to further elucidate mechanisms of soil enzymes responding in activity to long-term water erosion in soils different in type and land use.

Abstract:【Objective】The knowledge about characteristics of the temporal variation of soil organic carbon (SOC) over a region and a rational sample size needed for expositing the temporal variation is of important significance to the study to reveal tendency of the temporal variation of SOC in a region efficiently and evaluate regional agricultural management practices. So far much has been done on spatial variability of SOC in a region and its rational sample size, while little has been reported on temporal variability of SOC and rational sample size needed to reveal SOC variability in a given time period. 【Method】To make up the shortage, Yujiang County of Jiangxi Province was selected as study area, and the data of soil sample size in 1982 and 2007 as basis, and then spatial distribution maps of SOC in 1982 and 2007 were plotted by means of Kriging. Through raster overlay operation of the two SOC content maps, characteristics of the temporal variation of SOC content during the period of 1982-2007 were worked out and then used as basis to estimate the number of sampling sites needed to exposit that variation. 【Result】Results show that the mean SOC content in 1982-2007 increased by from 14.18 to 16.27 g kg kg^-1 with a growth rate of 14.74%, while its coefficient of variation (CV) rose from 0.22 to 0.44, both demonstrating a large growth. However, SOC content varied with land-use. Among the three main patterns of land-use, paddy fields and forest lands experienced rising in SOC from 15.10 to 18.02 and from 12.63 to 15.75 g kg^-1 or by 19.34% and 24.70%, respectively, during the period of 1982-2007, whereas uplands did oppositely in SOC content, decreasing from 11.62 to 9.07, or by 21.94%. However, in the meantime, the three patterns all had a drastic increase in CV of SOC content. In the light of spatial distribution of the variation of SOC content, the northern and southwestern parts of Yujiang County were on a substantially increasing trend, while the central-eastern part was on a declining trend, which was closely related to spatial distribution of the land use patterns. Based on the data of sample size of the periods, 1982 and 2007, with confidential intervals being 95% and 90%, the rational number of sampling sites required to reveal temporal variability of SOC content in the whole county was calculated to be 186 and 147 for the two years, respectively. And based on the SOC variation in lands different in land use, the rational number of sampling sites for paddy field, dry land, and forest land was figured out to be 68, 44, and 144, respectively, with confidence interval being 95% and 54, 34, and 112, respectively, with confidence interval being 60%. Generally, the sample size for upland should be 60% or over of that for paddy field, while that for forest land should be 2 times or over that for paddy field. By reviewing distributions of the sampling sites in the county and in fields of three different land use, separately, it was found that the distribution of the sampling sites was not so reasonable in 1982 and 2007, that is to say, a bit too many in paddy field and too few in upland and forestland, which no doubt had some adverse effects on efficient revelation of spatial distribution and temporal variation of SOC in the county in the two time periods. 【Conclusion】The findings of the study indicate that in estimating the number of sampling sites needed for revealing temporal variation of SOC in a region on the whole, it is essential to take into account amplitude and coefficient of the variation of SOC at various sampling sites. In understanding differences between patterns of landuse, it is essential to take into account amplitude and coefficient of the variation of SOC relative to landuse pattern and work out how big a sample size is needed for each landuse pattern and what the ratio should be for the three landuse patterns in sample size. The study is expected to be able to provide some references in exploring temporal variability of SOC and consequently arranging sampling sites for the survey in hilly red soil regions.

Abstract:【Objective】So far little has been reported on accumulation and transformation processes of soil organic matter in ancient paddy soil which has been buried or covered under paddy conditions as a result of environmental evolution, geological alteration or natural disasters. The organic matter in ancient paddy soils that have long been under obturation has already altered in nature and composition. Infrared spectrum is an important means that can be used to characterize chemical structure and physical properties of polymers. As organic matter in the soil absorbs the different wavelength spectra selectively, a large amount of information about the nature, reaction characteristics and structure of oxygen-containing functional groups can be extracted from infrared spectrograms for identification. Since the organic matter in the buried ancient paddy soil is very complex in structure, how to analyze various functional groups in organic matter is a significant problem that needs to be solved in the present study. 【Method】The soil organic matter in the ancient paddy soil profiles at Sanlonggang of the Liyang Plain, demonstrated clean traits of accumulation and transformation as affected by cultivation age, environmental condition, and burial depth. So soil samples, were collected from the ancient paddy soil layers and the modern paddy soil layer of the profiles for infrared spectral analysis using the potassium bromide pressed disc method, to identify functional groups in the organic matter therein and characterize structures of the groups separately, in an attempt to provide some theoretical and practical bases for revealing structural characteristics and evolution processes of the organic matter in the buried ancient paddy soil. 【Result】Results show that the organic matter in the ancient paddy soil has become an inherent component of the soil under long-term burial and carbonization and hard to get leached, thus leading to accumulation of the matter relative to the modern paddy soil. The vibrations in the infrared spectrum of the ancient paddy soil are mainly composed of those of halogen and inorganic compounds, and some others of functional groups like olefins, aromatics and hydroxyl compounds. The wave at Band 1 882 cm^-1 (carbon olefin) of the infrared spectrum of the ancient paddy soil weakens obviously after organic matter is removed from the soil and the vibration of functional groups is mainly the stretching vibration of unsaturated C-H. In the infrared spectrum of the original red soil, the absorbance is lower with the ancient paddy soil than with the modern paddy soil at the wave band 3 620～1 631 cm^-1, but higher with the former than with the latter at the wave band of 1 631～470 cm^-1, which suggests that the benzene rings are gradually forming with alkenes gradually aromatized and halogen and inorganic ions bound more intensely. First-ordered reciprocal (FD value) of the infrared spectrum shows that the ancient paddy soil does not vary much from the modern paddy soil; After organic matter is removed from the ancient paddy soil, peaks in its infrared spectrum are all weakened, especially FD peaks, which all drop below their respective ones in the infrared spectrum of the soil without removing organic matter, which demonstrates that the functional groups bound with organic matter are weakened in the soil after organic matter is removed, and the presence of organic matter can highlight the infrared spectral features of the structural functional groups of organic matter. 【Conclusion】In the infrared spectrum of the soil with organic matter removed, the ancient paddy soil is lower than the modern paddy soil in absorbance at all wave bands, which suggesting that organic matter has a greater influence on functional groups in the ancient paddy soil.

Abstract:【Objective】Soil salinization is an issue related to the strategy of sustainable development and improvement of environment quality in arid regions. Soil salinization and irrigation-triggered soil secondary salinization are problems that severely restrict further development of the agriculture in Xinjiang and also the major factors that affect stability of the oasis ecological environment. Therefore, it is of profound significance to sustainable development of the agriculture in Xinjiang and in China as well to manage and ameliorate salinized arable lands and readjust and optimize planting structure in the region, moreover, the information of soil salinization is the fundamental basis for formulation and implementation of these policies. How to acquire the dynamic information of large areas of salinized soil quickly, accurately and inexpensively and thereby formulate rational policies and strategies for management and amelioration of salinized soils are new themes of the study of agricultural science. 【Method】Hyperspectral remote sensing is a relatively ideal means of monitoring soil. A series of tests and experiments of monitoring soil salinization with near-ground hyperspectra were performed, thus providing a theoretical basis and technical support for application of the technique of hyperspectral remote sensing to monitoring soil salinization. Based on similar soil components generating similar spectral characteristics, soil spectra is to be classified and at the same time effective information to be fully mined by making use of the data and curve characteristics of soil spectral reflectance, which is one of the importance fields for application of spectral analysis. To that end a total of three hundred and thirty-nine topsoil samples (0~20cm) were collected in Wensu, Baicheng, Awati, Xinhe and Hetian counties of Xinjiang, covering anthropogenic-alluvial soil, saline soil, fluvo-aquic soil, paddy soil. The soil samples were then air dried and ground to pass a 2 nm sieve for determination of salt content with the residue drying method. Hyperspectral reflectivities of the samples were measured separately using the American FieldSpec Pro FR spectrograph (American Analytical Spectral Devices Company), and spectral curves obtained of the samples were pre-treated by erasing the edge bands, i.e. 350～399 and 2 401～2 500 nm on the two ends of a curve and keeping the reflection spectral data of the band 400～2 400 nm for successive research. Clustering of fuzzy K-means is a commonly used unsupervised clustering method, of which the basic idea is to sort a data set into k categories so as to minimize the iteration of target functions and the advantage is the capability of yielding an analysis index for setting an optimal number of categories. 【Result】By the means of clustering fuzzy K-means, 3 indices, i.e. fuzziness performance index (FPI), modified partition entropy (MPE) and clustering independence index (S) (all being the lower the best) were obtained, and the spectral data of the soil samples were sorted into four categories (before sorting, the original spectral range was normalized as pretreatment). Hyperspectral characteristics of the soils different in soil type before and after the sorting were compared and analyzed, and then the soil samples of each category were divided into modeling dataset and prediction dataset at a ratio of 2:1 using the Kennard-Stone algorithm. The preprocessed spectral data of the modeling dataset were used as input, and then a global and category-based salinity prediction models were built up with the PLSR method. The prediction dataset was used to validate the models and evaluate the models in terms of accuracy and stability. Results demonstrate that after the spectral data were classified with the fuzzy K-means clustering method, the Kennard-Stone algorithm was used to further classify the data for modeling, which was significantly higher than the global and category-based models in precision. The overall prediction model determination coefficient (R_p²), root mean squares error (RMSE_p), relative percent deviation (RPD) and ratio of performance to IQ (RPIQ) of the prediction model was increased from 0.664, 1.219, 1.733 and 1.461 to 0.818, 1.132, 2.356 and 2.422, respectively, among which RPD was increased by up to 23.13% and the PRDs of the all the four category-based models were higher than 2.0. 【Conclusion】 The findings demonstrate that it is feasible to predict soil salt contents quantitatively and quite accurately, and that the study has opened up a new way of thought a new method for using large sample spectral data to establish soil attribute prediction models including that for sail salt content, over a large scale area.

Abstract:【Objective】Arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) are important members in the soil microbial community, capable of remediating soils polluted with toxic organics, and China has large tracts of soils contaminated with pesticides and some other toxic organic substances, waiting to be remediated. It has been proved that AMF and PGPR can degrade toxic organic matters, however, little has been reported so far about AMF or/and PGPR degrading residues of organophosphorus pesticides in soil. The purpose of the present study was to evaluate efficiency of AMF and PGPR degrading residues of organophosphorus pesticides in soil and to remedy organic pesticide polluted soils with the two groups of soil microbes. 【Method】A pot experiment, designed to have a total of 48 treatments with concentration of methamidophos (0, 50, 100 and 150 µg g^-1) and inoculation pattern of AMF and PGPR (inoculating tomato seeds with AMF Glomus mosseae (Gm), Glomus etunicatum (Ge), and tomato seedlings with PGPR Bacillus subtilis (Bs), Bacillus sp. B697 (Bsp), Pseudomonas fluorescens (Pf), Gm+Bs, Gm+Bsp, Gm+Pf, Ge+Bs, Ge+Bsp, or Ge+Pf), was conducted on tomato (Lycospersicon esculentum, Jinguan in variety) under greenhouse. Colonization of AMF and/or PGPR, and biomass of plant growth (such as plant height, dry weight of shoots per plant, and dry weight of roots per plant) was measured, and methamidophos concentrations in the pots and in the shoots of the plants were determined with gas chromatography. 【Result】Results show that Gm significantly promoted PGPR colonization in the root zone soil and roots, while Pf did significantly AMF colonization, suggesting that Gm and Pf are mutually promoted in colonization. In the pots 100 µg g^-1 in methamidophos concentration, the plants in the pots inoculated with Gm+Pf were much higher than those in the other pots in plant height and in dry weight of shoots as well (except for those inoculated with Ge+Pf), and significantly higher, too, than those in control and those inoculated with PGPR and Ge in dry weight of roots. The plants in the pots inoculated with Gm+Pf were much lower than those in all the other pots in methamidophos concentration in roots and in methamidophos concentration in shoots as well (except those in the pots inoculated with Gm+Bs, Gm+Bsp and Ge+Pf). Inoculation of AMF, PGPR, or AMF+PGPR significantly reduced methamidophos concentration in the tomato plants as compared with those in the control. AMF and/or PGPR could degrade methamidophos residue and the effects of dual inoculations were higher than those of single inoculations. Inoculation with Gm+Pf significantly reduced methamidophos concentration in the root zone soil, through mineralizing the substance by 52%~60.6%, when the concentration of methamidophos in the pots was in the range of 50~100 µg g^-1. Analysis of the dynamics of methylamine dehydrogenase activity in the root zone soil, reveals that inoculation with AMF, PGPR or AMF+PGPR could enhance enzyme activity, and inoculation with Gm+Pf demonstrated the highest enzyme activity. 【Conclusion】It is, therefore, suggested that both AMF and PGPR could promote degradation of methamidophos residue in the soil, and the inoculation of Gm+Pf is the optimal combination under the conditions of this experiment.

Abstract:【Objective】Land use and fertilization are the two important types of human activities that can influence agricultural production and soil carbon (C) stock, especially in farming-grazing interlacing zone, like Wuchuan County, Inner Mongolia of China. 【Method】In this study soil samples were collected from a long-term field experiment on land-use and fertilization located in Wuchuan County for analysis of soil organic carbon (SOC), soil inorganic carbon (SIC), total nitrogen (TN), δ¹³C_SOC, δ¹³C_SIC and δ¹⁵N to investigate impacts of land-use (land planted with Horqin peashrub (Caragana korshinskii), land planted with ryegrass and deserted land) and fertilization (chemical fertilizer, organic manure and no fertilization) on C and nitrogen (N) transformations and C stock in the soil. 【Result】Results show that SOC stock in the land under Horqin peashrub (Caragana korshinskii) or ryegrass was 0.60~0.98 Mg hm^-2 a^-1 higher than that in the crop land, and similarly, SIC was slightly higher than or on the same level, except in the land under Horqin peashrub. Compared with the deserted land, the lands under “grain for green”(planted with Horqin peashrub or ryegrass) were lower in content of primary carbonate and almost unchanged in soil TN level. Compared with CK (no fertilization), application of organic manure significantly increased SOC stock (1.08~1.19 Mg hm^-2 a^-1), while application of chemical fertilizer decreased SIC stock, mainly of secondary carbonate, at the rate of 0.06~0.16 Mg hm^-2 a^-1. Compared with application of chemical fertilizer alone, application of organic manure and application of organic manure in combination with chemical fertilizer increased SOC and SIC stock at the rate of 0.6 and 0.1 Mg hm^-2 a^-1, respectively. Changes in land-use did not have much impact on δ¹³C of SOC and SIC, but the crop land was significantly higher than the deserted land or the lands under “grain for green” in soil δ¹⁵N, due to application of chemical fertilizer. Application of organic manure significantly decreased δ¹³C value of SOC, but application of chemical fertilizer had a reverse effect, which was further enhanced by soil acidification caused by chemical fertilization. The discrepancies between fertilization treatments in SIC loss maybe attributed to leaching of SIC into deeper soil layers, which indicates that it is necessary to do in-depth study on SOC and SIC in deeper soil layers. 【Conclusion】The impact of fertilization on soil C and N transformation is much higher than that of changes in land-use in this farming-grazing interlacing zone. As regards the soil in the arid and semi-arid Inner Mongolia, the effects of land use and fertilization on SOC and SIC should be taken into full consideration in the management of regional C sequestration.

Abstract:【Objective】Carbon (C) is a major component of soil organic matter, and crop residues are the main source of soil organic C (SOC). A large volume of studies have demonstrated that straw incorporation into the field is conducive to accumulation of soil organic matter and build-up of soil fertility. However, it is still not yet very clear how incorporation of corn stalk and stubble affects distribution and fixation of SOC in soils different in fertility, and how much extraneous new C contribute relatively to SOC. Once extraneous new carbon is amended into soil, it is very hard for researchers to distinguish new carbon from native organic carbon in the soil with traditional techniques. Therefore the stable isotope labeling technique is applied to an in-lab incubation experiment to explore for differences between soils different in fertility in distribution and fixation of extraneous new carbon after incorporation of corn stalk and stubble. 【Method】Soil samples were collected from the topsoil layers (0~20 cm) of two fields different in soil fertility, LF and HF in the long-term experimental station of the Shenyang Agricultural University, Liaoning Province, China, in November 2014. The field LF had never been applied with any fertilizer for 27 years, while the field HF had been applied annually with fertilizer equaling to N 270 kg hm^-2. The soil samples were crushed gently into bits to pass through a 2 mm sieve and then air-dried to get ready for the incubation experiment. The ¹³C labeled maize leaf, stalk and root were cut into 2 cm sections, crushed to pass a 40 mesh sieve and mixed at a rate of 1% of the dried soil sample in weight separately with the prepared soil samples that had already been incubated for 7 days as pre-treatment. The mixtures were regulated in moisture content till 60% of field water holding capacity and then put into an incubator for incubation under a constant temperature (25℃) for 180 days. Each treatment had three replicates. During the period of incubation, the mixtures were sampled destructively on D1, D7, D28, D56 and D180 for analysis.【Result】Results show that (1) SOC content was found higher in the LF soils amended with maize leaf than in those amended with maize root and stalk after 28 days of incubation, while it was found higher too in the HF soils amended with maize throughout the whole incubation period; and after 180 days of incubation, the two groups of soils were quite similar in SOC content regardless of type of amendment; (2) the effects of the amendments of maize root, stalk and leaf on content of extraneous new C and residual rate of the substances varied sharply. The content of extraneous new C was found higher during the initial period of the incubation (before D28) in the low fertility soil than in the high fertility soil, while during the later half, an opposite trend was found. The residual rate of root residue was found lower than that of stalk or leaf residue in the low fertility soil during the later half period, while the residual rate of leaf was found lower than that of root or stalk residue in the high fertility soil. 【Conclusion】All the above-described findings indicate that the sequestration of extraneous new C was governed by its source and soil fertility level.

Abstract:【Objective】Being the kernel of the traditional agriculture of China, and one of the major practices in developing ecological agriculture, intercropping still occupies an important position in modern agriculture in China as well as other parts of the world. One of the advantages of intercropping is overyielding relative to monocultures, which consequently removes more soil nutrients from the soils. However, in respect of high nutrient removal, few researches have been done on intercropping as on monocultures on a long-term scale. 【Method】To find a solution to this issue, a long-term field experiment was therefore established in 2009 at Baiyun, Wuwei City, Gansu Province, Northwest China, and carried out to investigate changes in soil chemical properties in response to P application and cropping system. The experiment was laid out in a two factorial design with three replicates, where the main factor was P application rate, designed to have three rates (0, 40 and 80 kg hm^-2 of triple superphosphate) and the second factor was cropping system, including maize/faba bean, maize/soybean, maize/chickpea, maize/rapeseed and their corresponding monocultures, maize, faba bean, soybean, chickpea and rapeseed. In 2013 (the 5th year) and 2014 (the 6th year) yields were measured and some soil chemical properties (soil organic matter, soil total N, Olsen P, available K, and pH were examined after the crops were harvested to explore changes in soil fertility as affected by cropping system. To estimate yields, two rows of maize and three rows, each of the other 4 crops, regardless of cropping pattern, were selected at random and harvested at their respective harvest seasons. To collect soil samples, 0 ~ 20 cm in length, for analysis, an auger was used to minimize disturbance of the soil structure after harvest. Eight cores and four cores were collected from intercropping plot (4 for each crop species) and monocultures, separately. And then the soil samples from the same plot under the same crop were blended separately together as one for analysis. 【Result】Results show that by averaging the yields of the plots the same in cropping system regardless of P application rates, 1) The grain yield of treatment, chickpea/maize, faba bean/maize, soybean/maize, and rapeseed/maize was 38.2%, 32.6%, 34.0% and 38.4% higher than their respective monocultures treatment; 2) Intercropping significantly increased the content of soil organic matter; 3) Neither P application nor cropping pattern had any effect on soil total nitrogen concentration; 4) In 2013, intercropping decreased soil Olsen P by 5.2% in treatment chickpea/maize, by 6.9% in treatment faba bean/maize, by 15.9% in treatment soybean/maize and by 11.3% in treatment rapeseed/maize, while in 2014, it did not affect much; 5) Intercropping significantly depleted available K, by 10.3% in treatment chickpea/maize, by 14.1% in treatment faba bean/maize, by 8.5% in treatment soybean/maize and by 13.2% in treatment rapeseed/maize over the two years; 6) There was no significant differences in soil pH between P applications and cropping systems in 2013 and 2014. To sum up, intercropping enhances productivity for at least five to six years. No matter P application or not, it could increase grain yield, and the effect intensified with P application rate rising till 80 kg hm^-2. Moreover, intercropping tended to increase soil organic matter and reduce soil Olsen P and available K. But neither P application nor intercropping had much effect on soil total nitrogen or pH in 2013 and 2014. 【Conclusion】In conclusion, intercropping enhances not only crop productivity over time, but also improves stability and sustainablility of soil fertility if coupled with proper applications of organic manure, P and K fertilizers.

Abstract:【Objective】With increasing concerns about sustainability of agroecosystems, the practice of no-tillage in combination with crop straw/stalk mulching is getting widely used in China. In this scenario, large amounts of maize stalk were therefore left as mulch in the fields under a no-tillage cropping system. However, little is known about fate of the nitrogen (N) contained in the mulch of crop stalks in spite of the fact that they generally contain significant amounts of N. 【Method】Therefore, a four-year field-plot experiment was conducted to explore effects of mulching of maize stalk in fields in the agroecosystem of Northeast China on accumulative plant uptake, recovery and loss rate of the N contained in the maize stalk mulch over four experimental years. The experiment was designed to have two treatments. In Treatment T_S1, the plots were mulched with ¹⁵N-labelled maize stalk in the first year, and not with any in the following three years, while in Treatment T_S2the plots were mulched with ¹⁵N-labelled maize stalk in the first year, and with ordinary maize stalk in the following three years. 【Result】Results show that over the four experimental years, the two treatments did not vary much in accumulative yield of maize grain or stalk and total N uptake. However, in Treatment T_S1 about 14.2% and 6.7% of the N in the mulch was recovered by maize grain and stalk, respectively, and significantly higher than that (12.4% and 5.8%, respectively) in Treatment T_S2. Compared to the accumulative amount of N recovered from the mulch by crop, more of the N in the mulch was retained in the soil, especially in the top soil layer in both treatments. About 40.9% and 73.8% of the N in the mulch was retained in the soil (0 ~ 60 cm) in residue form and about 38.6% and 8.1% lost in Treatments T_S1and T_S2, respectively. Compared to Treatment TS1, Treatment TS2 was relatively higher in soil microbial biomass C and N, but lower in mineral N derived from the mulch, which indicates that continuously mulching the fields with crop stalk significantly increased the microbial retention rate of the N in the mulch, while decreasing the leaching risk of the N in the mulch in the soil-crop system. 【Conclusion】All the findings listed above suggest that long-term practice of no-tillage in combination with crop straw/stalk mulching can effectively enhance accumulation in the soil of the N brought in with mulching, which may have some significant implications for raising and maintaining the content and stability of soil N in crop fields.

Abstract:【Objective】Differences in Rare earth element (REE) content between different particle-size fractions of sediments make it more complex for geochemical tracing, thus affecting the reliability of using REE characteristics of a whole-rock sample as an indicator in provenance study. Moreover, by far the knowledge about geochemical characteristics of REE in loess relative to particle size fraction is very limited, and so is that about restraining factors of the particle-size effects, and influences and significance of the effects on and in tracing of the parent materials of loess in provenance. In this paper, systematic fractionation of the northern loess and the Xiashu loess samples collected separately in particle size was performed and REE contents of the samples were measured, so as to better understand REE distribution among different particle-size fractions of the loess and its affecting factors. 【Method】Samples of Xiashu Loess (XL) collected from Nanjing and Zhenjiang and loess from the Loess Plateau (LP) in Lingtai of Gansu Province were pretreated with the quiescent sedimentation method for fractionation in particle size, separately, into six fractions, i.e. <4 μm, 4~8 μm, 8~16 μm, 16~32 μm, 32~64 μm and >64 μm, and then REE contents in the six fractions of loess soil and the whole-rock samples were measured. 【Result】Results show: 1) significant differences in ∑REE existed between the two types of loess soils and in REE content between fractions of the soils, which indicates that obvious particle-size effect does exist on REE distribution. In practical terms, the effect is the most obvious in the fractions <4 μm and > 64 μm. In LP, REE accumulates in fraction <4 μm, but not in fraction >64 μm, while in XL, it does in both fractions and particularly in Fraction >64 μm; REE content does not vary much between the fractions in the middle, i.e. 4~8 μm，8~16 μm，16~32 μm and 32~64 μm and so the particle-size effect therein is not obvious; 2) the accumulation of REE in the fractions of <4 μm of both of the soils is characterized mainly by that of heavy REE (HREE), which is possibly governed by weathering-based soil formation and attributed to specific adsorption of HREE by Fe-Mn oxides in fine particles; and 3) in Fraction >64 μm of Xiashu Loess accumulates mainly LREE (light REE), which may be possibly related to the high content of titanite and some other minerals typical of nearby regions in the parent material of XL and suggests that the materials coarse in particle size in XL may come mainly from nearby regions through short distance transportation. 【Conclusion】All the findings in this study suggest that fraction＞64 μm may be the most sensitive one that can be used to distinguishes XL from LP in REE content. Whether or not fraction＞64 μm has an apparent accumulation of LREE is an effective indicator of the distinction. This study also demonstrates that the researches in the past used to analyze whole rock samples for REE, thus possibly glossing over the important tracing information, whereas REE analysis by fraction has a greater potential as indicator in provenance study of loess and therefore can be used to exposit in depth internal differences between particle size fractions and between heavy and light REE and to provide more accurate evidence for provenance study.

Abstract:【Objective】Zinc (Zn) is an element essential for plants and animals, but becomes a pollutant of heavy metal element when it is too much in the soil. It is, therefore, of great significance for researchers to study forms and availability of Zn in black soil to protection of the agro-eco-environment of the black soil region, a major agricultural producing one of China. 【Method】Based on the data of a 13-year field experiment, designed to have 5 treatments, i.e. no fertilizer (CK), chemical fertilizer (NPK) and chemical fertilizer plus different amounts of organic manure (NPK+OM₁, NPK+OM₂and NPK+OM₃), in the black soil region, transformation and availability of Zn in the soil were analyzed with physical-chemical methods. 【Result】Results show that CK was as high as 1.96 mg kg^-1in DTPA-Zn content, Treatment NPK, increased Ex-Zn and AFeo-Zn contents, and decreased Min-Zn content, thus improving the availability of soil Zn up to 3.3 mg kg^-1, but did not have much effect on total Zn. Treatments NPK+OM₁, NPK+OM₂ and NPK+OM₃ all significantly increased all forms of Zn in content, except for Min-Zn. About 37.5%～55.5% of the input of Zn with organic manure was stored in the soil as AFeo-Zn, and the content of available Zn in the soil increased with increasing organic manure application rate and peaked up to 14.5 mg kg^-1 in the field experiment In terms of Zn²⁺ adsorption strength and capacity, the 5 treatments displayed an order of NPK+OM₂ ＞ CK ＞ NPK+OM₃ ＞ NPK ＞ NPK+OM₁, with Zn²⁺ adsorption rate and desorption rate varying in the range of 25.9%～72.1% and 4%～25.3%, respectively. Treatment NPK caused soil acidification, thus reducing the Zn²⁺ adsorption strength and capacity of the soil and making adsorbed Zn²⁺ more desorbable, while the addition of organic manure in fertilization, though unable to inhibit soil acidification, did retard the declining trend of the Zn²⁺ adsorption strength and capacity to some extent, and made absorbed Zn²⁺ harder to desorb from the soil with increasing organic manure application rate. On the whole, black soil is relatively high in available Zn content, and in Zn²⁺ adsorption strength and capacity, too. Long-term application of chemical fertilizers acidifies the black soil, thus transforming Min-Zn into Ex-Zn and AFeo-Zn in the soil; Zn in the applied organic manure is stored in the soil as AFeo-Zn. 【Conclusion】Long term application of chemical fertilizer decreases Zn²⁺ adsorption strength and capacity of black soil, while addition of a certain amount of organic manure in fertilization may retard the trend.

Abstract:【Objective】Salicylic acid (SA), a kind of phenolic hormone, could regulate the growth and development of plants, and affect stress resistance of plants. This investigation is to explore effect of extraneous salicylic acid mitigating salt stress on Lolium perenne seedlings.【Method】A pot experiment was carried out, using vermiculite as medium in the pots (20 cm × 15 cm × 9 cm each) for cultivation of Lolium perenne, in greenhouse. The experiment was designed to have two levels of salt stress (0 and 150 mmol L^-1 NaCl) and 5 levels of extraneous SA (0, 0.2, 0.4, 0.6 and 0.8 mmol L^-1) to form 6 treatments, that is treatments CK, S, SSA1, SSA2, SSA3 and SSA4. After germination, Lolium perenne seedlings began to get watered with 50% Hoagland nutrient solution (6.5 ± 0.1 in pH). NaCl solution and salicylic acid were added with the solution on D0 (the 10th day after sowing) when the seedlings was approximately 5 cm in height and then watered once every other day. So the seedlings were watered a total of four times. The seedlings in the treatments were sampled four times on D0, D3, D6 and D9 for systematic analysis of physiological and biochemical indices. 【Result】Results show that application of extraneous salicylic acid, regardless of concentration, significantly mitigated salt stress on Lolium perenne seedlings; relatively improved the seedlings in plant height, and fresh and dry weights of shoot and root; significantly increased the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), thus strengthening the antioxidant enzyme system of the plants; reduced membrane lipid peroxidation and hence damage of the membrane, which was manifested in reduction of cell membrane permeability and malondialdehyde (MDA) content. Compared with Treatment S (150 mmol L^-1 NaCl), Treatment SSA3 was the most prominent in the effect of mitigating salt stress. It increased the plant height of the Lolium perenne seedlings by 43.38%, the fresh and dry weight of the shoot by 37.92% and 31.36%, respectively and the fresh and dry weight of the root by 25.46% and 15.32%, respectively. On D3, SOD activity in the seedlings increased by 17.20%, and on D9, MDA content decreased by 27.60%. 【Conclusion】To sum up, 0.6 mmol L^-1 salicylic acid is the optimal rate among all the concentrations designed to mitigate salt stress of 150 mmol L^-1 NaCl on Lolium perenne seedlings.

Abstract:【Objective】Carbon, nitrogen, phosphorus and potassium, being elements essential to plant growth, play important roles in the growth and development of plants and functioning of the individuals. Ecological stoichiometry is a discipline integrating the principles of ecology and stoichiometry and studying energy balance and mass balance of multiple chemical elements in living systems, and can be used to analyze constraints and consequences of these mass balances during ecological interactions. 【Method】This paper was to characterize contents and eco-stoichiometric proportions of carbon (C), nitrogen (N), phosphorus (P) and potassium (K) in leaves and litter of eight dominant species of plants, i.e. Pinus tabuliformis, Populus L., Robinia pseudoacacia L., Hippophae rhamnoides, Amorpha fruticosa Linn, Stipa bungeana Trin, Medicago sativa Linn, Agropyron cristatum (Linn.) Gaertn, in three different types of vegetation (forest, shrub, and grass) in the revegetated area of the Heidaigou opencast coal mining, Zhungeer, Inner Mongolia by means of field surveying and sampling and in-lab analysis, and further to explore relationships of plant homeostasis of degraded ecosystems with vegetation type and NP limiting rate, in an attempt to provide some proposals for rational combination of plant species in restoring and/or reestablishing vegetation on the Loess Plateau and some evidence for perfecting the theory of eco-stoichiometry. 【Result】Results show that the content of C, N, P and K varied in the range of 418.2 ~ 564.1, 7.19 ~ 33.21, 0.82 ~ 2.37 and 4.98 ~ 32.77 g kg^-1, respectively in leaves of the plants, and in the range of 368.9 ~562.3, 3.98 ~22.65, 0.58 ~ 0.97 and 1.18 ~20.98 g kg^-1, respectively in litter of the plants. Among the eight species of plants, a decreasing order of non-nitrogen-fixing plant Hippophae rhamnoides > nitrogen-fixing plants > the other non-nitrogen-fixing plants was observed. The leaves were higher than the litter in content of total carbon, nitrogen, phosphorus and potassium, especially N content in the leaves, which was even slightly higher than the average of the country. But the P content in the leaves was lower than the average of the country. Among the three types of vegetations, a decreasing order of shrubbery > forest plants > grass was found in content of organic carbon in leaves; an order of shrubbery > grass > forest in TN and TP and an order of grass > shrubury > forest in TK. Eco-stoichiometric characteristics of C, N, P and K in leaves and litter varied with species of the plant and the ratio of N:P, P:K, N:K, C:N, C:P and C:K varied in the range of 7.16 ~ 22.45, 0.036 ~ 0.23, 0.70 ~ 4.55, 14.92 ~ 64.44, 218.54 ~ 557.36 and 12.78 ~ 121.14, respectively in leaves and in the range of 6.97 ~ 23.78, 0.076 ~ 0.64, 0.92 ~ 6.71, 16.09 ~ 160.28, 292.89 ~ 1096.02 and 20.24 ~ 795.31, respectively, in litter. In terms of N:P ratio in leaves, the three types of vegetations followed an order of shrubbery (18.86) > grass (15.44) > forest (14.68), indicating that P is the major limiting factor for growth of shrub plants, while N and P the two factors limiting development of forest and grass vegetations. 【Conclusion】It could, therefore, be concluded that for revegetation of the area, shrubs are the priority choice. All the findings in the study may provide theoretical and practical guidance for restoration and re-establishment of vegetation in the Zhungeer Heidaigou opencast coal mining area.

Abstract:【Objective】To explore for effective ways to prevent and control nematode infection in facilitated vegetable fields, and to fertilize the fields for better soil quality, a field experiment was carried out on effects of combined application of vermicompost and probiotics on population and community structure of soil nematodes in greenhouse tomato fields. 【Method】The experiment was laid out in a greenhouse of the Nanjing Institute of Agricultural Sciences, using a commonly grown crop in the region, cherry tomato, and designed to have six treatments: CF (chemical fertilizer alone), CF BM (chemical fertilizer and bacillus megaterium), CF BA (chemical fertilizer and bacillus amyloliquefaciens), VC (vermicompost alone), VC BM (vermicompost and bacillus megaterium ) and VC BA (vermicompost and bacillus amyloliquefaciens), and four replicates for each treatment, making up a total of 24 plots (2.5 m×2.5 m each) in randomized block. The treatments were applied with almost the same amount of nutrients in the form of vermicompost (15 t hm^-2, dry mass) or chemical fertilizer (N 150 kg hm^-2，P₂O₅ 398 kg hm^-2 and K₂O 334 kg hm^-2). Probiotics was prepared in fermentators, containing 1×10⁸ cfu ml^-1 of viable bacteria and inoculated with BM or BA at a rate of 1 L m^-2 and for bio-solution not inoculated was cultured using ordinary bacterial culture medium (10g peptone 5g yeast extract 10g sodium chloride, volume 1 L). For application they were both diluted 100-fold and sprayed when chemical fertilizer or vermicompost was applied. And then the plots were plowed. The subsequent management was kept consistent for all the plots, that is, on May 8, 2014 28 seedlings, similar in plant height and growth were transplanted in,4 rows and 7 lines in each plot,, and soil samples were collected from each plot at the flowering (June 18) and harvest (August 20) stage for isolation and identification of nematodes. 【Result】Results show that due to difference in fertilization pattern, the treatments varied sharply in population, community structure and trophic groups of soil nematodes. In this field experiment, a total of 25 genera of nematodes were identified, and the population of nematodes in all the six treatments varied in the range of 150 ~ 472 per 100 g dry soil. Compared with Treatment CF, Treatment VC increased the population of soil nematodes and Treatments VC BM and VC BA did more significantly, however, the effect in Treatments CF BM and the CF BA was not significant at the full bloom stage and not so significant as in Treatment VC BM or BA at the harvest stage. Treatment CF or VC increased the relative abundance of herbivorous nematodes ( Pratylenchus), but the effect was more significant in Treatment VC and in Treatment CF Compared with Treatment CF, Treatment VC significantly decreased the proportion of bacterivorous nematodes and Treatment CF BM or BA increased the proportion of fungivorous nematodes, and decreased that of bacterivorous and herbivorous nematodes, while Treatment VC BM or BA significantly increased the proportions of bacterivorous and fungivorous nematodes, and reduced those of herbivorous and omnivorous nematodes when compared with Treatment VC. Compared with either Treatment CF or VC, the addition of probiotics positively affected Wasilewska index (WI), ratio (F/B) of fungivorous to bacterivorous nematodes and plant-parasitic index (PPI) of herbivorous nematodes, and the effect was more significant in Treatment VC than in Treatment CF. It was found through overall comparison that from the flowering stage to the harvest stage, the population of herbivorous nematodes increased in all the treatments, and the effect was the most significant in Treatment VC; and the application of vermicompost plus probiotics effectively inhibited growth of herbivorous nematodes, and more effective than the application of chemical fertilizer plus probiotics in this aspect. With tomato growing on, soil environment and nametode community tended to be more healthy and stable in Treatment VC BM or BA than in the others. 【Conclusion】Therefore, it is a fertilization pattern worth extending, but in practice, it is more advisable to choose a proper probiotics in the light of variety of the crop and soil environment, and potential effect of herbivorous nematodes on the crop to follow.

Abstract:【Objective】No-tillage and straw mulching are two important techniques in soil building. It is, therefore, of great significance to understand effects of the two on diversity of the cellulose-decomposing bacteria (CDB) community in the soil. To this end, analyses were done of effects of long-term no-tillage and straw mulching on diversity of CDB, microbial community structure, and richness and dominance of CDB, so as to provide a theoretical basis for the study and demo-extrapolation of the technique of conservation tillage. 【Method】A long-term experiment, designed to have four tillage treatments, i.e. tillage with mulching (W_tS), no-tillage with mulching (W_ntS), tillage without mulching (W_t) and no-tillage without mulching (W_nt), was conducted at the State Experimental Station for Agro-Ecology in Fengqiu, Henan Province. Soil samples were collected from the plots of the four treatments, incubated in CMC-Na Congo red medium for counting of CDB and analyzed with PCR-RFLP for effects of no-tillage and straw mulching on CDB community. 【Result】The results of plate counting show that the population of CDB was 8.40×107 (W_tS ), 11.4×107 (W_ntS), 4.57×107 (W_t) and 5.27×107 (W_nt), indicating that both No-tillage and straw mulching increased the number of CDB to a varying extent. Out of the soil samples collected from the four treatment plots, a total of 425 strains of CDB were isolated, 4 CDB gene libraries built based on treatment, and a total of 33 OTUs obtained. The number of OTUs of CDB in the treatments range from 19 to 26, among which 7 were found common in all the 4 treatments. 8 particular in the treatments with straw mulching soil and 3 in the treatments of no-tillage, which indicates that the practices of straw mulching and no-tillage did have some effects on CDB community structure in the soil. The 4 clone libraries varied sharply in CDB diversity index, which was the highest in Treatment W_ntS, and higher in the two treatments with straw mulching than in the two without straw mulching, which indicates that compared with tillage, no-tillage is more conducive to diversity of the CDB in the soil. Phylogenic analysis shows that the CDB in the soils varied in the range of 80% ~ 99% in 16S rDNA homology. The 33 OTUs could be sorted into 4 phyla, 7 classes, 11 orders, 15 families and 20 genera. Proteobacteria is the dominant phylum, composed of 15 OTUs, which could be sorted into 11 genera. In Treatment W_tS, Sphingobium, Stretomycetacea, Sinorhizobium and Promicromonsporaceae are the dominant groups, accounting for 67.92%, in Treatment W_ntS, Stretomycetaceae, Promicromonsporaceae and Flavobacterium are, accounting for 48.15%, in Treatment W_t, Sinorhizobium, Promicromonsporaceae and Acinetobacter are, accounting for 54.29%, and in Treatment W_nt, Rhizobium, Phyllobacterium, Pseudomonas and Promicromonsporaceae are, accounting for 63.21%. The treatments with straw mulching are significantly higher than the treatments without straw mulching in relative abundance of Stretomycetaceae,Flavobacterium and Sphingobium, which indicates that straw mulching is conducive to growth of these bacteria, which play an important role in straw decomposition. And the treatments of no-tillage are apparently higher than the treatments of tillage in relative abundance of Pseudomonas, Phyllobacterium, Paenibacillus, Promicromonosporaceae and Sphingobacterium, which indicates that no-tillage is conductive to growth of these bacteria. Canonical correspondence analysis shows that great changes have taken place in CDB community structure in all the four treatments, that pH, TP, organic carbon and TK is significantly and positively related to no-tillage and that TN, analyzable N, readily available K, readily available P and organic carbon is significantly and positively related to straw mulching. 【Conclusion】It is quite clear that no-tillage and straw mulching can significantly raise the number and diversity of cellulose-decomposing bacteria in the soil, and alter cellulose-decomposing bacteria community structure. Conducted as key techniques for sustainable agriculture to improve soil quality by increasing the number and variety of microorganisms, no-tillage and straw mulching or incorporation do have some theoretical significance and enormous potential for extrapolation.

Abstract:【Objective】As the Qinling Mountain is the division line between the two climate zones, south and north in China, the mountain, as a result of its huge variation in climate and altitude, has a great number of unique forest stands that have never been disturbed by human activities. Therefore, the study on the soils under these forests, including soil enzymes and nutrients, can be of great reference value to the studies on other types of soils, and may lay down a foundation for revelation of soil effects relative to forest stand and selection of optimal forest stands. 【Method】In this study, soils samples were collected from five typical types of forest stands ( Quercus aliena var acuteserrata, Pinus tabuliformis, Pinus armandii, Picea asperata, and pine-oak mixture) at various altitudes, for analysis of activities of seven soil enzymes and soil nutrients, so as further to determine relationships between the two as affected by type of the forest stand. 【Result】Results show that significant differences in soil enzyme activity and soil nutrient existed between the forest stands. Properties of the soils were significantly affected by type of forest and bio-environment conditions, such as attitude. The soil under Picea asperata (one of the dominant well-grown species in the Qinling Mountain) was the highest in organic matter, total N, alkalytic N, readily available potassium and slowly available potassium, and what is more, soil organic matter, total N and alkalytic N followed similar trends; soil alkaline phosphatase, fluorescein diacetate(FDA) hydrolase and the total enzyme activity index (TEI) were in significantly positive or extremely significant and positive relationships with soil nutrient, which indicates that forest and altitude have similar influences on the three types of enzymes like soil nutrient does. Principal component analyses (PCA) of sole soil enzyme activity and combination of soil chemical properties and soil enzyme activity were quite similar in result, with integrated scores significantly and positively related to the above-listed three enzymes. 【Conclusion】So soil alkaline phosphatase, FDA hydrolase and TEI can be used as indicators of quality of forest soils, especially soil alkaline phosphatase that can be easily used as a single enzyme indicator to reflect soil nutrient condition. Other than those, no soil enzymes are found so closely related to soil chemical properties.

Abstract:【Objective】Soil detachment is the initial stage of soil erosion, providing sediments for subsequent transport and deposition. Yet, it is governed by dynamics of the flow on slope, soil properties, and growth of the vegetation root system. During the season when vegetation grows, the growing root system may cause changes in soil properties and the seasonal variation of soil properties may affect soil detachment processes, which has been reported in just a few of the researches on loess in Europe. Most of the researches in the past used to focus on soil detachment on gentle slopes, leaving mechanisms affecting soil detachment processes on steep slopes still in haze. In hilly regions of the Loess Plateau, the growth of grass roots in rehabilitated grasslands under the practice of “Grain for Green” was found to have caused changes in soil properties of the lands and consequently in soil detachment processes. However, it is still unclear how they are related to each other quantitatively. 【Method】In this study, an experiment was carried out using water flumes with adjustable bed gradient to investigate changes in soil detachment processes during the plant growing season and their potential affecting factors and especially effects of changes in soil properties and growth of grass roots on soil detachment capacity in two tracts of rehabilitated grasslands different in “Grain for Green” history. One (Tract A) had been planted with Leymus secalinus for 3 years and the other (Tract B) with Medicago sativa for 17 years. 【Result】Results show that soil detachment capacity of the two tracts of grasslands declined significantly during the whole growing season (p＜0.05). The mean soil detachment capacity was much higher in Tract A (0.076±0.036 kg m^-2 s^-1) than that (0.057±0.055 kg m^-2 s^-1) in Tract B. They varied seasonally and were mainly affected by hardening of the soil, formation of water-stable aggregates, and root growth. With increasing soil cohesion, bulk density, content of water-stable aggregates, and grass root density, soil detachment capacity in either soil declined exponentially. Seasonal variation of the soil detachment capacities of two soils could well be simulated with soil bulk density, root density, and flow shear stress (R2＞0.73，ME＞0.85). Dynamic changes of the soil properties, such as soil cohesion, bulk density and water-stable aggregates, and growth of the grass roots are the main factors that affect the seasonal variation of soil detachment capacity in the two tracts of rehabilitated grasslands in hilly regions of the Loess Plateau of China. The mean soil detachment capacity of Tract A and Tract B during the whole plant growing season was only 6.32% and 4.79% of that of the control tract, respectively, which suggests that the practice of “Grain for Green” in hilly regions of the Loess Plateau of China is conducive to soil and water conservation in that area. 【Conclusion】 The findings of this study may serve as theoretic basis and data support in elaborating hydrodynamic mechanisms of the soil detachment processes, evaluating effect of grass roots in fields of “Grain for Green” on soil and water conservation, and rationalizing arrangement of soil and water conservation practices and measures in hilly regions of the Loess Plateau of China.

Abstract:It is of great significance to use soil amendment in combination with brackish water irrigation in rationalizing the exploitation of brackish water, improving saline soil structure and promoting crop growth. Polyacrylamide(PAM), a kind of organic polymer material, is regarded as an effective soil amendment because of its strong water holding capacity. In this paper, ponding infiltration experiments on one-dimension vertical soil columns and absorbing infiltration experiments on horizontal soil columns were carried out for investigation of effect of PAM application rate (0, 0.02%, 0.04% and 0.06%) on water and salt movement in soils with brackish water. Results show that (1) PAM reduced soil infiltration rate and enhanced soil water retention capability in the soil under brackish water infiltration, and the soil amended with 0.04% PAM was the highest in soil water retention capability; (2) PAM application significantly affected the parameters of the Philip and Kostiakov infiltration models and the soil amended with 0.04% PAM was the lowest in soil sorption rate S and empirical coefficient K, but the highest in empirical index β; in the Philip model soil permeability rate fell at first and then rose again with increasing PAM amendment rate; and the infiltration rate in the soil amended with 0.04% PAM was 0.547 cm min^-0.5, which was the lowest; (3) In the soil amended with 0.04% PAM, the soil saturated volumetric water content reached the maximum; and the intake suction h_d increased by 15.30% in the Brooks-Corey model, as compared with the control, which indicates that PAM can enhance soil water-holding capability significantly in soil under brackish water infiltration, minimize soil moisture diffusion rate and make water the most evenly distributed; and (4) PAM amendment significantly improved water-holding capability of the soil and salt leaching efficiency as well. The highest soil holding water capacity and the highest salt leaching rate t was found in the soil amended with 0.04% PAM.

Abstract:An experiment was conducted to study effects of salinity, varying in level, 50, 100 or 200 mmol L^-1 NaCl, on plant growth, ion absorption and distribution of wild tomato Solanum pimpinellifolium (WT), cultivated tomato( S. esculentum) (CT) and their hybrid F1 generation. Results showed that dry weight (DW) of the three tomato varieties decreased significantly under salt stress, either 50, 100 or 200 mmol L^-1NaCl, displaying a descending order of CT>WT> F1. With rising salt stress, Na content increased, while K content decreased significantly in all the tomato plants. Besides, under salt stress, K /Na decreased significantly in all the tomato plants and the decreases in the plants, regardless of variety, were similar in extent. With rising salt stress, the roots of the plants of either variety enhanced their K or Na selectivity ratio (S_K,Na), but the enhancement varied slightly in extent with variety, showing an order of WT> F1>CT. However, salt stress decreased stem S_K,Na in all the tomato plants by a similar degree. But with rising salt stress, the drop in CT was much bigger than that in F1. Salt stress increased leaf S_K,Na of all the tomato plants, but with rising salt stress, leaf S_K,Na declined in WT, while it kept increasing gradually in CT and F1 and the rise in F1 was more significant than that in CT. To sum up, the F1 generation is similar to its wild parents in maintaining ion balance, especially in their leaves, which makes F1 generation better in growth and higher in salt tolerance than its parents.

Abstract:BTEXs (Benzene, Toluene, Ethylbenzene & Xylene) as a kind of pollutants in the hunman living environment, like soil, could cause serious harm to human health. In this study an analytical method of BTEXs in soil samples was developed to determine these pollutants in the soil in a simple, convenient and environment friendly way. Soil samples contaminated with BTEXs were determined with CP-8 ms capillary column by Static Headspace-Gas Chromatography/Mass spectrometer (HS-GC/MS) under modified conditions. The optimal procedure goes: put fresh soil samples in 20 ml flasks, 10 g each, and have them heated at 95 ℃ in the hot shakable incubator, agitated at rate of 500 r min^-1 for 20 s, kept still for 90 s subsequently, and after 15 mins incubation the whole system reaches equilibrium. The BTEXs detection limit of the method varied in the range of 0.23~1.35 μg kg^-1; and the standard curve correlation coefficient (r) of each BTEXs target ranged at 0.993 3~0.998 0. The sample recovery rate lingered in the scope of 74.2%～123% with the method precision varying in the range of 2.35%~7.27% (n=7). All demonstrate that the method meets the requirements of organic analysis.

Abstract:《中国土壤地理》是龚子同、黄荣金、张甘霖等知名学者领衔主编，包含中青年学者的参与编著，由北京科学出版社于2014年3月出版的一部专业巨著，是中国科学院主持出版的《中国自然地理系列专著》之一。 该专著是对近几十年来，国内外土壤地理及相关学科最新进展和研究成果，进行了总结和高度概括的基础上编写的。它充分反映了土壤地理学发展的方向和时代特征。这是我国土壤科学发展史上一部具有重要的里程碑意义的专著。 其主要特色如下： （一）、从理论上对土壤地理学的研究对象、内容、任务和发展方向，作了全面而精辟的论述。提出“土壤地理学是研究土壤时空变化的科学”。把“土壤整体”作为研究对象，不但需要进行土壤与环境之间的相关性研究，而且需要将其提升到“土壤圈”之层面，研究其和地球表层系统中其他圈层（大气圈、水圈、岩石圈和生物圈）之间的相关性。 土壤圈是地球表层系统中最后形成的，并最终使地表系统成为一个完整而运转的自然系统的圈层。其在地表系统中的地位及重要性不言而喻，它与当代诸多重大危机都息息相关，如全球气候变化，生态环境危机，环境污染，土地退化，粮食安全生产，食品健康。土壤圈的研究是解决这些世界难题的关键之一。美国土壤学界于21世纪初提出了有关地球地表系统“关键带”的概念，并指出土壤圈是这一关键带的核心。上述两者是遥相呼应，不谋而合。这必将大步提升土壤科学的地位，成为推动土壤科学向前沿性学科发展的动力。同时也标志着我国土壤地理学理论研究的水平，已跨入了国际土壤科学研究领域的先进行列。并凸显了土壤地理分支学科在土壤科学领域内的研究导向和基础支撑作用，其它分支学科任何研究都需要或不能离开土壤整体基础研究的支撑。 （二）、为我国土壤地理研究的实质内容，土壤时空变化规律搭建崭新的平台，即以中国土壤系统分类作为它的研究和表述单元。中国土壤分类已历经数十年的研究和应用的考验。它既汲取了国际土壤分类发展主流体系的经验，与国际接轨；又根据我国土壤分类发展的历史传统和我国土壤的具体实际情况，创新发展了具有中国特色的土壤系统分类。例如，我国独立原创研究拟订了人为土纲系列，提出干旱土纲内涵不同的新定义、盐成土纲和潜育土纲的单独划分、以及铁铝土与富铁土的命名和内涵也有所发展。它已得到国际土壤学界的充分肯定，并已产生重要的国际影响。 （三）、开拓了土壤资源开发和可持续利用研究的新视野。这是由土壤资源的多功能性所决定的，因而也突出展现了许多新亮点。例如，（1）中国土壤分区的依据、原则和划分，不再是依据单一的土壤资源的生产功能，而是着眼于土壤资源的生产、生态和环境的多功能进行划分；（2）重视土壤信息系统的建立，以及在采集、集成和融合土壤信息数据库的过程中“3S”等新技术和方法的应用；（3）对土壤资源的可持续利用，提出不少建设性对策和建议，其中特别值得提出的对土壤有机碳储量研究的重视。土壤有机碳储量是土壤生命、能源、功能和资源可持续利用之本，其重要性如何说都不为过。 此外，本著采集和引用的参考文献资源之丰富，图文并茂和精美，亦是一大特色。 土壤科学将随着时代的发展而发展，无论是理论和实践都还存在着很大的发展空间。《中国土壤地理》专著为我国土壤科学的继承和创新发展提供了一个范例，并赋予我们以民族自信心和激励，推动我国土壤学界为发展其有中国特色的土壤科学，为世界土壤科学的发展而不懈地努力向前，做出我们应有的贡献。