Abstract:Based on the web of science and CNKI (China national knowledge infrastructure) database, bibliometrics was used to quantitatively analyze the historical advances of soil science in the past 30 years. The newly developed information visualization technology-Cite Space and Thomson Data Analyzer (TDA) conducted the research focus and fronts of soil science during three periods (1986-1995, 1996-2005, 2006-2013) using 57 495 and 350 265 references in the domestic and international studies, respectively. Similarities and differences of soil science during different periods between domestic and international studies were compared according to the cluster analysis. As for the international studies on soil topics, the soil fertility investigations were the research hotspots in the earlier stage and then transfered to the ecological environmental investigations, as well as the soil key processes driven by the soil microbes. However, the research of regional soil was the distinct characteristic of China's soil science. Most of these investigations focused on the increase of soil productivity, soil erosion and water conservation, soil contamination and remediation, which significantly demonstrated a continuously strengthened research progress and development trend of the intersection and the fusion among different subjects. The information of the bibliometric analysis will provide academic guidance for further promoting development, and highlight the challenge and opportunities for future soil science in China.

Abstract:Soil ecosystem is an important component of the global terrestrial ecosystem. Soil provides man with food, regulates the water and atmosphere, and supports the other ecosystems in cycling. Human beings have been relying on and will continue to have to rely on the services provided by soil for survival, while human activities have profoundly altered the soil ecosystems across the globe since the industrial revolution, especially urbanization, of which the effect is mostly irreversible. China is right now in the process of ongoing rapid urbanization, but little attention has been paid to losing of the soil ecosystem services. It is, therefore, critically important to understand processes and mechanism of urbanization affecting soil ecosystem services for healthy urban development. For that reason, a summary is presented in this paper of development processes of the definition, classification and assessment of soil ecosystem services. Soil ecosystem services can be defined as welfares provided to human beings by soil, a specific natural capital. Monetary value and material quantity are the two major scales for quantification of ecosystem service. As quantification of material production may be done by modeling ecological processes, it is an applicable method for quantification of soil ecosystem services. Although quite a number of eco-process-based ecosystem service evaluation models, such as GUMBO, ARIES and InVEST, are available for use to evaluate soil ecosystem services, none of them is specific to evaluation of soil ecosystem services. Urbanization processes may affect soil ecosystem services both positively and negatively, but mainly the latter. Urbanization alienates large tracts of productive land, thus leading decline of the services of supplying food, fiber, wood, etc. to the mankind. Urban pavements form an impermeable seal over the soil, blocking or hindering water exchange between the pedosphere, atmosphere and hydrosphere. Besides, it also seriously restrains the regulating service of the soil ecosystem, like water storage, carbon sequestration, pollution purification and so on. Nevertheless, urbanization is also a coin of two sides. It helps improve some local ecosystem services, like cultural services, increase in forest land area in arid regions as a result of proper urban management. Although researches were done in the past from various angles to study effects of urbanization on the supply, regulation and culture services of the ecosystem, little has been reported on comprehensive systems study on responses of soil ecosystems to rapid urbanization in service. To make up the gap, a framework is proposed for analysis of processes and mechanisms of the soil ecosystem responding to urbanization. Loss of ecological land, population convergence and pollutant discharge are held to be the main driving forces of the changes in soil ecosystems, like changes in composition, physic-chemical and biogeochemical processes of the soil. The changes, in turn, affect the soil ecosystem producing and delivering services, which will eventually be embodied as feedback in the urban ecosystem. In view of the shortages in the research on classification and modeling of soil ecosystems, focal points are recommended for researches in future, that is, to establish a soil ecosystem service classification system with standards; to build up an eco-process based model for quantification of soil ecosystem services; to unfold researches on mapping and weighing of soil ecosystem services; and to intensify researches on mechanisms and processes of the responses of soil ecosystem services to urbanization. It is hoped that more and more people will be concerned about and involved in researches on soil ecosystem services, and that the findings of the researches will be applied to decision-making of the government on management of soil resource and construction of eco-civilization.

Abstract:Soil organic matter (SOM), as an important source of various nutrient elements in soil, plays a very important role in promoting formation of soil structure, improving soil physical properties and increasing soil nutrient retention capacity. Therefore, based on the second provincial soil survey in 1982 and soil sampling in 2009, and soil classification in line with the soil taxonomy, the paper elaborated regulations of spatio-temporal variation of SOM content in various types of soils in Henan Province, one of the major grain producing provinces of China and analyzed major affecting factors of the variation, with the aid of the techniques of traditional statistics, geostatistics and GIS. Conclusioons of the paper may serve as guidance and reference in implementing rational fertilization and nutrient regulation in Henan Province. The data of 1982 were cited from the Second National Soil Survey. Soil sampling distribution maps of all the cities and counties of the province plotted in the survey were scanned and vectorized, and 1110 typical soil sampling sites were screened out. And the data of 2009 was collected from field sampling,,covering a total of 1615 soil sampling sites. The analysis shows that the mean content of SOM increased from 12.21 g kg^-1 in 1982 to 16.02 g kg^-1 in 2009, or by 31.20%, and its coefficient of variation decreased from 67.90% to 35.52%, which indicates that the SOM contents of the two periods were both at a medium level of variation. The variograms of SOM in the two years both fitted the spherical model, with nugget coefficient decreased from 56.10% to 60.18%, and codomain from 569.05 km to 547.22 km, suggesting that the effect of stochastic variability of SOM intensified and spatial autocorrelation weakened. Through referencing between Genetic Soil Classification of China (GSCC) and Chinese Soil Taxonomy (CST), the soils of Henan Province could preliminary be sorted into 6 orders, 12 suborders, 20 groups and 38 subgroups in accordance with the CST. A general trend was observed that the content of SOM was increasing from the west to the east and the increase was more significant in the plain areas, while the content of SOM of the mountainous regions in the west, north and south of the province somewhat decreased. Besides, from 1982 to 2009, the area of soils with SOM content ranging between 15.0 and 20.0 g kg^-1 increased from 37.3 thousand square kilometers to 123.5 thousand square kilometers, or by 51.60%, and SOM contents in the other areas level all decreased somewhat. The soils of Endorusti-Ustic Cambosols, Ochri-Aquic Cambosols, Irrigation-Orthic Anthrosols, Ustic-Alluvic Primosols, Ustic-Sandic Primosols, Hapli-Udic Vertosols and Hapli-Udic Cambosols in the soil taxonomy all increased by of 5.7, 6, 5.6, 5.5, 5.4, 5.0 and 3.1 g kg^-1, respectively, in SOM content While the soils of Ustic-Orthic Primosols and Hapli-Orthic Primosols declined by 2.5 and 1.9 g kg^-1. According to the conditions in Henan, the main factors that lead to sharp spatio-temporal variation of SOM between different soil groups are believed to be parent material, climate, soil texture, land use and human activity,or further in detail,,soil particle size and viscosity degree of parent material; temperature and humidity of climate; clay content in soil texture; forest cover and cropping system in land use and straw incorporation in human activity. The soil groups with increasing SOM content are mainly distributed in cultivated land of the plain, where incorporation of crop straw and application of organic manure increases SOM content in the soils.

Abstract:Clay mineral composition and illite crystallinity (IC) value of the Quaternary Red Clay (QRC) in Xuanzhou District (XZ) and Langxi County (LX) of Xuancheng City, Anhui Province, Southeast China, were studied to explore relationship between the two and potential paleo-environmental implications of IC value for formation of the QRC. Clay fraction of the QRC was extracted and then treated with citrate-bicarbonate-dithionite (CBD) to remove free Fe. Mineral composition of the clay fraction was analyzed using the X-ray diffraction (XRD) method, and the width of half maximum height of d₀₀₁ (1.0 nm) peak of illite was measured to calculate IC value. Contents of macro elements of the QRC were analyzed by the X-ray fluorescence (XRF) method, and SiO sub>2/Al sub>2O sub>3 (Sa), SiO2/(Al sub>2O sub>3+Fe sub>2O sub>3) (Saf), Ba value as well as indicators of weathering degree of the QRC, such as CaO/TiO sub>2, MgO/TiO sub>2, K sub>2O/TiO2 and Na sub>2O/TiO sub>2 were calculated. Results show that the clay minerals in different layers of Profiles XZ and LX are quite similar in composition, despite some slight differences. The layer of Yellow-brown Earth (YBE) in the upper part of the profiles is identified as Xiashu Loess formed during the Last Glacial Period, and its clay minerals consist mainly of illite, kaolinite and 2:1 type vermiculite, but in the Uniform Red Clay (URC) and Reticulate Red Clay (RRC), the clay minerals are dominated with illite and kaolinite, and nil of vermiculite. However, in the lower part of the RRC, the peak of illite has become wide and flat, and illite-montmorillonite mixed-layer minerals are formed from weathered illite. IC values of the two profiles range between 0.4 and 0.7, suggesting that crystallization degree of the illite lingers between the high and moderate levels. IC value in the profiles varies sharply between layers. It is 0.482, 0.578 and 0.735 on average, respectively, in the YBE, URC and RRC of Profile XZ and 0.454, 0.628 and 0.717 on average, respectively, in the YBE, URC and RRC of Profile LX. The QRC in this study is significantly higher than the loess (0.3-0.4), paleosols (0.35-0.5) and Tertiary Red Clay (0.4-0.5) in the Chinese Loess Plateau, suggesting that the QRC in Southern China is highly weathered, and consequently low in illite crystallinity. In Profile XZ, IC value is negatively correlated with Ba, K sub>2O/TiO sub>2, Na sub>2O/TiO sub>2 and MgO/TiO sub>2 to a significant extent (p <0.05), and in Profile LX, IC is negatively correlated with Saf, Ba, K sub>2O/TiO sub>2 and Na sub>2O/TiO sub>2to a significant extent, too (p <0.05). The correlations between K sub>2O/TiO sub>2 and IC value in Profiles XZ and LX are the most significant, with correlation coefficient (r) being -0.818 and -0.929, respectively, which may be closely related to the high volume of K existing in the interlayer of illite, and K loss from weathering illite and decomposition of illite crystallines of the QRC. This finding fully demonstrates that IC value can be used as an effective indicator of weathering degree of the QRC in Southern China. In Profiles XZ and LX, IC value increases steadily, indicating that the crystallization degree declines from the YBE to URC and to RRC. Weathering and decomposition of illite in the RRC may also be related to long-term intensive groundwater activities during the formation of vermiculate. In the QRC profiles, the rising trend of IC value with soil depth coincides with the variation of weathering degree with soil depth. So like particle size of red soil and elemental geochemical indices, IC value of QRC possesses some similar paleoclimatic implications. Therefore, IC value of the QRC can be regarded as one of the effective paleoclimatic indicators, reflecting evolution of the paleoclimate during the period when QRC was forming.

Abstract:The Lajia Ruins is a large-scale settlement of the Qijia Culture (4 200～3 950 a BP). Archaeological excavations have exposed a shocking picture of prehistorical catastrophes in the Lajia Ruins in the Guanting Basin, Minhe County, Qinghai Province. The causes of the prehistorical catastrophes in the Lajia Ruins have become a hot topic in the field of environmental change. Unfortunately, so far little has been reported on development processes and micromorphological features of the ancient plow layer of the paleosol in comparison with the plow layer of the modern soil in the Lajia Ruins. Therefore, a comparative study was carried out on micromorphologies of the two soils in an attempt to reveal their development processes and micromorphological features. Micromorphological features of different genetic layers of the soil profile in the Lajia Ruins were observed under a Leica-DMRX petrographic microscope, and their images was quantitatively measured using Leica-Qwin V3 software. The main micromorphological features of the ancient plow layer of the paleosol of the Qijia Culture (Ah₂/Ap₄) are round to sub-round coarse grains, low C/F_15µm, poorly directive permutation, abundant illuvial clay hypocoatings and concretion, abundant needle-shaped secondary-calcite at edge of pores, high porosity consisting mainly of smooth circular pores and bag holes. The ancient plow layer of the paleosol of the Xindian Culture (Ah₁/Ap₃) is quite similar to the ancient plow layer of the paleosol of the Qijia Culture (Ah₂/Ap₄) in micromorphological features, except for C/F_15µm, which is higher in the former, and proportion of illuvial clay, which is lower in the former. The main micromorphological features of the ancient plow layer of the paleosol (Ah₂/Ap₄, Ah₁/Ap₃) are different from that of the modern plow layer (Ap₁) in the Lajia Ruins. The Ap₁horizon is characterized by sub-angular to sub-round coarse grains, abundant residual clay concretion and a little amount of illuvial clay hypocoatings, abundant needle-shaped secondary-calcite, low porosity, and high C/F_15µm. Both the Ah₂/Ap₄ horizon of the Qijia Culture and Ah₁/Ap₃ horizon of the Xindian Culture are Ustic Isohumisol. They formed in the mid-Holocene Climatic Optimum under simple cultivation of the ancient people and paleoentological climate. The Ap₁ horizon is Calci-orthic Aridosol, a soil formed under the inergrated effect of long-term manure application, crop cultivation and deposition of dust storms during the past 1 500 years. Its micromorphological features are mainly controlled by the degree and manner of human activities.

Abstract:The study on soil profiles and the various soil horizons they consist of are of great significance to the studies on soil genesis and development, soil classification, and some other disciplines of soil science. Traditional soil information acquisition methods are both time-and labor-consuming, however, the proximal soil sensing technology can be used to provide soil information of various scales rapidly and periodically, and has been widely applied to researches such as soil resource survey, land quality evaluation, soil classification, soil mapping, etc.. Traditional methods for measuring soil physical and chemical properties are complicated, time-consuming and costly, and can hardly meet the demands for rapid monitoring of changes in soil property. In recent years, the spectrometric technology has extensively been used to quantitatively analyze samples in a fast, simple and non-destructive way in various fields with results. The data acquired with using the imaging technology combined with the spectroscopic technology are high in both spatial resolution and spectral resolution, and contain very rich soil remote sensing information and hence can provide a solid foundation for quantitative monitoring and mapping of soils properties in the horizontal dimension. However, in the light of the researches done by scholars both at home and abroad, it appears that the study of soil science still lacks an imaging technique high in spatial and spectral resolution, specifically for measuring soil total nitrogen (TN) contents in entire soil profiles. At present, quantitative analyses of soil properties mostly use soil samples collected in the topsoil, 0 ~ 150 mm or 0 ~ 200 mm in depth; studies on soil point samples in the profile 0 ~ 1 000 mm in depth are rarely reported, and little has been found in literature on dot samples in the 0 ~ 1 000 mm soil profile, let alone reports on mapping of vertical distribution of soil TN contents in entire soil profiles. In view of this situation, this study is oriented to explore the feasibility of using the technology of vis-NIR imaging spectroscopy in instant prediction of vertical distribution of TN contents in soil profiles. A total of 3 soil profiles (0 ~ 1 000 mm) were collected from Chongyang, Hubei Province, China. Vis-NIR hyperspectral images (753 spectral bands in 400 ~ 1 000 nm) of the profiles were taken with an imaging spectroscoper quipped with a 25 μm slit, a 35mm focus lens 13.1° in angle of field and an area array CCD of 1 004 pixels × 1 002 pixels. First, the digital photos with fixed scenical grid scale taken by a digital camera were put to undergo geometric correction with reference to the hyperspectral images of the profiles to solve the problem of image deformation caused by technological limitations of the spectrometer and the shooting platform, and then modified to 1mm in image precision. Through spatial and spectral dimensional clipping, pixels of the wooden frame and platform background were removed leaving only soil image data (160 pixels×980 pixels) and valid spectral bands (470 ~ 1 000 nm). After geometric correction and clipping, the images were processed with a variety of supervised classification methods. Results show that the minimum distance method is the best at distinguishing invalid data (e.g., shadows and cracks) from soil data. A "sampling panel" method was proposed for strip-sampling with the panel in line with the specified, averaging the samples similarly to ROI and finally solving the problem of scale inconsistency between point samples and profile spectra. Furthermore, a PLSR calibration model was built up based on the spectral data of 10 spot soil samples, and used to predict TN contents in three complete soil profiles based on their spectral images. Results show that the technology of vis-NIR imaging spectroscopy could be used to inverse and map soil TN vertically in profiles with good prediction results. Verification with measured data demonstrates that R² and RPD was 0.56 and 1.41, respectively, for the 0 ~ 1 000 mm soil layer, which indicates that the prediction method reached the range of rough estimation. And for the 0 ~ 600 mm soil layer, the effects were better with R² and RPD being 0.87 and 1.76, respectively, which indicates that the technology of vis-NIR imaging spectroscopy might have some limitation in the vertical direction, though it can well restore the soil TN distribution patterns in the topsoil layer, especially in the 0 ~ 600mm soil layer. The above findings demonstrate that this study has preliminarily established a set of procedures for soil TN inversion and mapping using the technology of vis-NIR spectroscopy, and the method is applicable to rough estimation of soil TN contents in whole soil profiles.

Abstract:Thickness of the soil layer on a hillslope is an important factor governing hydrologic processes on the hillslope. A field survey was carried out using a ProEx ground penetrating radar (GPR), product of MALA in Sweden, to detect thickness of the soil layer on a hillslope in a karst region. The detection used two antenna frequencies, 100 and 500 MHZ, separately, Then exploratory trenchess were excavated on the slope to determine thickness of the soil layer physically and at same time to explore for factors affecting accuracy of the radar detection, like weathering degree of the bedrock at the interface between the soil layer and the bedrock. On such as basis, a linear regression model and a GEP model was established with different independent variables to verify applicability of the ground penetrating radar to soil thickness detection on karst hillslopes. Results show that as in the karst region, the soil layers on hillslopes are generally thin and contain a lot of debris, the use of a higher frequency antenna may improve detection precision; the use of the combination of the results of the radar detections with two different frequencies and weathering degree of the bedrock as input variable is higher in simulation accuracy than the use of the results of the radar detection with a frequency as input variable. When input variables are the same, the GEP model is very limitedly higher than the linear regression model in prediction accuracy because of limitations in actual detection. So, the latter is recommanded. The linear regression model combining results of the detection using 100 and 500 MHZ antennas and weathering degree of the bedrock as independent variable may reach 0.660 and 15.0 cm in coefficient of determination and root mean square error, respectively.

Abstract:Terrestrial water cycling encompasses mainly three factors, including precipitation, evapotranspiration and runoff, and dry or wet of the climate mainly depends on precipitation and evapotranspiration. Crop evapotranspiration is a major index to take into account in assessing climate drought degree, crop potential productivity, vegetation water consumption, and water resources supply and demand balance. And it may also provide a scientific basis for calculating crop water requirement, evaluating agricultural water resources, and developing reasonable irrigation schemes. It is generally believed that rising temperature will speed up surface evapotranspiration, and aggravate surface drought degree, while precipitation will increase will supplement the soil with water and relieve the surface droughtiness to a certain extent. So research and analysis on precipitation and evapotranspiration is of certain reference value to evaluating surface soil moisture conditions. The Huaihe River Basin, located between the Yangtze River basin and the Yellow River basin in the east part of China,, is a transitional zone between the north and south climates in this country, and belongs to the warm temperate semi-humid monsoon climatic region. Because of its special geographical position, the complexity and variability of its climate and frequent subjection to the impacts of convergence of cold and warm fronts from the north and south, precipitation varies frequenly and sharply, thus often leading to occurrence of droughts or flooding in this region. In the context of global warming, whether the climate in this region will change as affected by the factors mentioned above, how it will change, and what the development trend will be, are problems that call for systematic research. So analysis of changes in surface soil moisture content of the region will be of some practical significance. The precipitation data of the region monitored day by day were calculated and analyzed, and potential evapotranspiration and relative humidity at each station during that period of time were worked out using the Penman-Monteith formula. The interannual and decadal variation trends of precipitation, relative humidity index and potential evapotranspiration were analyzed through statistics. The analysis mainly used wavelet function of the Matlab software for cycle analysis and the Mann-Kendall test to analyze saltation of the variation trends. In which UF stands for clockwise standard normal distribution curve, while UB for counter-clockwise standard normal distribution curve. AcrGIS 10.1 was used to analyze spatial distributions of precipitation, potential evapotranspiration and relative humidity index The interpolation method used the inverse distance weighting(IDW) method, which set the distance between the interpolation point and the sample point as weight for calculate of weighted mean. The advantage of this method lies in being relatively intuitive and rapid in operation and applicable to dataset with sample points evenly and densely distributed. On such a basis, further study was done on characteristics of the spatio-temporal distribution and variation trend of soil moisture regime in the region, so as to provide some reference or basis for precautions to prevent flood, drought and other disasters in the Huaihe River Basin. Results show that: (1) in temporal distribution, the precipitation displayed an almost invisible slowly rising trend, and within the past 53 years, it showed 6-year primary cycles and 14-year secondary cycles, while in spatial distribution, the precipitation showed standard latitudinal difference, being relatively high in the south and low in the north; (2) the potential evaporation was on a downward trend in temporal distribution and in the past 53 years, it showed 11-year primary cycles and 4-year secondary cycles, while in spatial distribution, it displayed a trend mostly reverse to that of the precipitation; (3) in temporal distribution the relative humidity index was also on a slowly rising trend, with steady fluctuation range and frequency, while in spatial distribution. the relative humidity index in most of the region followed the same trend as the precipitation showed; and (4) the variation of the surface soil moisture regime of the region was the result of the combined effect of various meteorological factors. It is not difficult to draw the conclusion that precipitation is a positive factor and potential evapotranspiration a negative one affecting soil moistureregime.

Abstract:During the development and construction of the Shenfu coalfield, generated were large tracts of disturbed land, and large volumes of overburden and waste slag, which, unique in soil composition, complex in underlying surface layer and significantly different from deserted land, have become a major source of serious man-made soil and water loss. An artificially simulated rainfall experiment was carried out to explore characteristics of the erosion on the huge dunes of disturbed soil, overburden and/or waste slag, and methods to predict its occurrence, with a tract of deserted land as CK. Detailed field investigations found that the dunes of overburden and waste slag ranged from 33° to 40° in natural angle of repose and the tracts of disturbed soil and deserted lands ranged from 4° to 18° in slope, so in the experiment 35° and 40° were set for dunes and 5°, 10°, and 18° for slope of land. Plots in the experiment field were laid out to be 3m x 1m, each, and each had two sections set up for monitoring of water flow. Rainfall intensity in the experiment was designed to vary from 1.5 ~ 3.0 mm min ^-1, forming four levels with an interval of 0.5 mm min ^-1 between every two levels. Before the experiment, the rainfall intensity was calibrated repeatedly until uniformity coefficient of the rainfalls reached 85% or higher. Soil particle compositions of the plots were determined with the pipette method. And then fractal dimension was figured out from soil particle composition to be 2.160, 2.164, 2.256, 2.379, and 2.566, respectively, for the dune of waste slag with less sand and more stone, the dune of waste slag with more sand and less stone, the dune of overburden, the tract of disturbed soil, and the tract of deserted land. Bulk density, porosity and moisture content of the soils were measured with the oven-drying method. During every rainfall, flow velocity was measured with the dye tracing method and width and depth of the flow with a thin steel rule. For the first 3 minutes of runoff, samples of runoff and sediment were gathered once a minute, and after that once every 3 minutes. Results show that (1) on the deserted land, erosion rate followed the process of declining-fluctuating-leveling off with the rainfall going on; on the land of disturbed soil, it did the process of rising-fluctuating-leveling off; on the dune of overburden 35° in slope, it rose to peak and then declined and gradually leveled off; on the dune, 40° in slope it fluctuated all the time; and on the dunes of waste slag of either texture it fluctuated drastically in the earlier runoff generation stage with occasional mud-rock flows and then leveled off about 15 min after runoff initiation. In general, in terms of erosion fluctuation, the five types of underlying followed an order of the dune of waste slag with less sand and more stone > the dune of waste slag with more sand and less stone > the dune of overburden > the tract of deserted > soil, and the tract of disturbed land; (2) erosion rate was closely related to rainfall intensity and underlying surface (p＜0.05), but slope was not so much related (p＞0.05). Complex soil composition is the main cause, making overburden and waste slag and disturbed soil different from deserted land. The erosion rate on the dune of slag with less sand and more stone, the dune of slag with more sand and less stone, the dune of overburden and the tract of disturbed soil was 6.51~14.25, 57.91~239.15, 43.60~180.13 and 2.27~3.06 times that on the tract of deserted land, respectively under rainfalls the same in intensity; and (3) erosion rates on the dunes of slag or overburden and the tract of disturbed soil could be predicted using the equation of power function of median soil particle size, fractal dimension, rainfall intensity, and slope and runoff parameters. The study demonstrates some important scientific significance to the establishment of soil erosion models and the construction of ecological environment for mining areas.

Abstract:Sand-gravel mulch can effectively inhibit soil water evaporation, and hence promote crop growth. So far fewer researches have been reported on sand-gravel mulching than on plastic film or straw mulching, and little information is available about quantitative relationship between moisture and crop under sand-gravel mulch. To explore effects of sand-gravel mulching on soil water conservation and quantitative relationships between soil water evaporation and sand-gravel mulch, a soil water evaporation experiment, designed to have 5 mulching levels (0%, 25%, 50%, 75% and 100%), two irrigation levels (25 mm and 35 mm) and two soils (sand and lou soil), was carried out. Results show that (1) with the sand-gravel mulching increasing in coverage from 0% to 100%, the daily evaporation—time curve declined; daily evaporation was lower in plots irrigated with 25 mm of water than in the plots irrigated with 35 mm of water; and daily evaporation during the first 6 days decreased gradually with increasing sand-gravel mulching coverage, and after 7 days of evaporation, the decrease in daily evaporation tended to be lower, gradually; (2) the initial evaporation rate ( e_i ) ranged from 1.38 to 3.97 mm d^-1; it stepped down with increasing mulching coverage; e_w (steady evaporation rate) was significantly lower than e_i , varying in the range of 0.57 ~ 1.11 mm d^-1 as affected by sand-gravel mulching coverage; (3) with increasing sand-gravel mulching coverage, temporal variation curve of cumulated evaporation ( E_c ) declined and so did total evaporation ( E_t ); in the plots of bare soil, E_t accounted for 50% or so of the irrigation water (E), while E_t in the plots under 100% sand-gravel mulching did for about 35% of I only; and with increasing sand-gravel mulching coverage, evaporation to irrigation ratio decreased and evaporation difference (△E) increased; (4) The relationship between cumulative evaporation ( E_c ) and time (_t) fitted the theoretical relationship of Gardner, of which the parameter was highly related to mulching degree; thus a two parameter function was obtained for describing the relationships of cumulative evaporation and evaporation rate with mulching degree and time; and (5) at the end of the evaporation experiment, moisture contents in the soil profiles were much lower than the initial moisture content, regardless of mulching degree; but the moisture contents in the plots under mulch were generally high. To sum up, the effect of mulching on evaporation is apparent. The findings in the experiment may provide some important parameters in simulating soil water evaporation under gravel-sand mulch on a field scale.

Abstract:In agriculture production, the application of compound fertilizers and phosphate fertilizers bring into the soil large volumes of anions, dominated with phosphate, sulfate and carbonate, which in turn affect selenium availability in the soil to crops. The studies in the past on Selenium adsorption - desorption used to focus on fitting of selenium adsorption with the isotheral equation fitting and effects of single factors on selenium adsorption, and little has been reported on selenium sorption in purple soil and effects of anions on the sorption. Purple soil is the main type of soil in the Sichuan Basin, where neutral purple soil is the highest in area. The study on effects of soil pH and three competitive anions on absorption and desorption of selenium in the purple soil reveals that with increasing soil solution pH, the soil declined in Se adsorption. Selenite adsorption in purple soils varied in the range between 26% to 82% in neutral purple soils, peaked up to 130.1 mol kg^-1, when soil pH was 3, and bottomed to 26% only when soil pH was 9. This shows that soil pH may directly affect the concentration of selenite in soil solution, and hence plant uptake of selenium. With rising soil pH, purple soils reduced their adsorption of selenite, and maximized the adsorption when they were acidic. Effect of HPO₄^2- on selenite adsorption in purple soils was reflected in the finding that selenium adsorption in the soil decreased significantly or by 39.62% when 0.2 mmol L^-1of HPO₄^2- was amended. However, the effect became less significant as more HPO₄^2- was added. Addition of HPO₄^2- into the equilibrium solution significantly reduced soil absorption of selenium, while addition of SO₄^2- did not have much impact on purple soil adsorption of selenium. When 0.3 mmol L^-1 of HCO₄^- was amended, soil adsorption of selenite was significantly increased or by 20.37%, but the effect got to be less significant when more HCO₃^- was added. When 6.5 mmol L^- of HCO₃^-was added, the anion displayed slight competition with selenite. However, addition of a low concentration of HCO₃^- promoted SeO₃^2-absorption by purple soil, while the addition of a high concentration of HCO₃^- acted reversely. The impacts of HPO₄^2- and SO₄^2- on selenium absorption could be well fitted with the Langmuir and Freundlich equations, with coefficient determination R² being over 0.90 for both of them. Selenite desorption rate was significantly higher in the soil solution with HPO₄^2- in presence than in the soil solution without anions in presence, when 0.2 mmol L^-1 and 3.2 mmol L^-1 of HPO₄^2- in presence, selenite desorption rate increased by 2.72 times and 1.50 times, respectively. However, the addition of SO₄^2- did not have much effect on selenite desorption. The presence of HCO₃^-also increased selenite desorption from the soil, and compared with deionized water, it did by 1.41 times and 1.99 times. These findings indicate that desorption of selenite is related to the presence of anions in the extraction solution, and when HPO₄^2- or HCO₃^- is present in the solution selenite desorption rate is significantly increased, but SO₄^2- does not have much effect on desorption of selenite from the soil. Impacts of the three different kinds of anions on Se desorption from the soil vary. The presence of HPO₄^2- or HCO₃^- increases selenium desorption rate, while the presence of SO₄^2- does not have much impact. In the purple soil region, phosphate fertilizer and alkaline ammonium bicarbonate fertilizer are often used. These practices may increase the availability of selenium in the soil, and hence the absorption and accumulation of selenium by plants. The knowledge of the law of purple soil adsorbing and desorbing selenium at the solid-liquid interface may help improve the bioavailability of selenium in the purple soil and serve as a scientific basis for further increasing the content of selenium in agricultural produce.

Abstract:Release of non-exchangeable potassium (NEK) in soil is closely related to bioavailability of the potassium. The aim of this study was to characterize release and bioavailability of NEK in 8 soils, using pot K depletion experiments, 0.2 mol L^-1sodium tetraphenylboron(NaTPB) extraction method and kinetic models. From each soil, 3 portions, 0.5 g each as replicate, were taken out for incubation in 3 ml of extracting solution (0.01 mol L^-1 EDTA and 0.2 mol L^-1 NaTPB) separately for a period varying from 0.5 to 96h. Four kinetic models (First-order, Elovich, power function and parabolic diffusion) were used to describe NEK release characteristics. Results show that NEK release rate in soil varied sharply with the agro-ecological region, being the highest in Northwest and Northeast China, and the lowest in Central and East China. NEK release in soil could be divided into two phases, fast and slow ones. The fast phase occurred at the beginning of the release, when NEK at the edges and wedge zones of clay mineral interlattices broke up bondage of the minerals by diffusion, while the slow phase came late when NEK inside the interlattices became the major source of K release. All the four models, the first-order (R2 = 0.817~0.926, SE = 11.9~215.1), Elovich equations (R2 = 0.952~0.997, SE = 4.6~66.9), power function (R2 = 0.869~0.990, SE = 3.9~127.8) and parabolic diffusion (R2 = 0.790~0.963, SE = 7.5~211.4), were good enough to describe NEK release kinetics. However, in choosing a proper one, it is essential not only to compare them in fitting degree, but also take into account their practicality and physical significance of the information they may provide. The Elovich equation failed to describe the early period of NEK release adequately, while the parabolic diffusion model yielded more than one NEK release rates. Thus, the NEK release rate described by the power function model might be a good indicator of NEK potential of soil. By such an indicator, the 8 soils were found to be declining in NPK release potential from west to east and from north to south of the country. Ryegrass were grown for 8 harvests in a pot experiment to evaluate K supplying capacity of the 8 soils. It was found that soil K supplyingpotential consisted with soil K release capacity, and that in soils high in K release amount and rate, the ryegrass without any K fertilizer applied was still quite high in relative and cumulative biomasses, cumulative K uptake and relative K content; and vice versa. The soil NEK release rates described with the four kinetic models was significantly related to K content and K uptake of the ryegrass without K fertilizer applied. In order to judge whether K supply of a soil was adequate or not, relationships between relative biomass and K content of the ryegrass without K fertilizer applied and between K content of the ryegrass and soil NEK release rate were determined. Based on the relationships, 90% of the relative biomass of the ryegrass without K fertilizer appliedwas set as threshold of the index of soil K nutrition, equaling to 34.0 g kg-1in soil K content and 396 mg kg-1 h-1 in soil NEK release rate. It is, therefore, concluded that out of the 8 soils, only Aridosol in Xinjiang and Isohumosol in Shaanxi and Heilongjiang can ensure ryegrass a good yield without showing any potassium deficiency symptomin a short termwithout K fertilizer application.

Abstract:In this study, 4 types of red soils and a lateritic red soil collected from Anhui, Hunan, Zhejiang and Guangdong were used in an indoor incubation experiment to investigate effects of bio-ash ameliorating these soils in acidity. The bio-ash was produced by the burning of poplar skin mixed with rice and wheat straws in a power plant. Results show that application of bio-ash increased soil pH, decreased soil exchangeable Al³⁺. The ameliorating effect of 8 g kg^-1 bio-ash on soil acidity was better than that of 4 g kg^-1 bio-ash, and the effects were more pronounced when soil cation exchange capacity (CEC) was lower. Because the pHs of the five soils were in the range from 4.2 to 5.0 in which soil acidity was buffered by cation exchange reactions, therefore CECs of soils had important influences on ameliorating effect of the bio-ash on soil acidity. The soil with the higher CEC had the greater buffering capacity to acid, thus the pH of the soil was more difficult to be increased. The increase in pH for different soils due to the incorporation of the bio-ash followed the order: the red soil from crop land in Zhejiang +, Ca²⁺ and Mg²⁺ in these acid soils were also significantly increased due to the incorporation of the bio-ash. The soil exchangeable K⁺was increased by 0.40~0.63 cmol kg^-1, the exchangeable Ca²⁺ was increased by 1.93~2.57 cmol kg^-1, and the exchangeable Mg²⁺was increased by 0.30~0.36 cmol kg^-1. Therefore, the effect was the highest with soil exchangeable Ca²⁺ and then soil exchangeable K⁺. The content of available phosphorus also increased in these soils, particular in soils high in P content. Although bio-ash contains a certain amount of heavy metals, the application of bio-ash would not have much impact on contents of available heavy metals in the soil because of its low application rate. Therefore, the environmental risk of bio-ash application in acidic red soils is small. To sum up, application of bio-ash will not only effectively ameliorate red soil in acidity, but also improve red soil in fertility.

Abstract:Recently, biochar, prepared through incomplete combustion or pyrolysis of crop straws, has been a hot spot in the research of agriculture and environment. Amendment of biochar into the soil may help sequestrate C, reduce emission of greenhouse gas, improve soil fertility and hence crop yield. Besidess, biochar has a relatively high specific surface area, well-developed pore structure and abundant surface functional groups. Chlorobenzenes (CBs) are a typical kind of chlorinated hydrophobic organic pollutants and widely used in many industries, such as dye, pharmacy, pesticide and organic synthesis. China is a major producer of CBs in the world. As a result of their extensive application, CBs have been detected in soil, vegetable, water body and various environmental media, in China, posing a great potential risk to the environment. Remedying CBs contaminated environment has attracted wide concerns. Although some progresses have made in the study on biochar adsorbing hydrophobic organic contaminants, little has been reported about biochar adsorbing high chlorinated benzene. Elucidation of the process and mechanism of biochar adsorbing CBs will help readers better understand interactions between biochar and hydrophobic organic pollutants, and use biochar scientifically in environmental remediation. In this study, straw was used as raw material biochars and pyrolyzed under three different temperatures (400℃, 500℃ and 600℃) into three different kinds of biochar, which were marked as WSB400, WSB500 and WSB600, respectively. Elemental compositions of the biochars were determined using an element analyzer, their specific surface areas measured using the BET method; their surface functional groups analyzed using a Fourier transform infrared spectrometer, and their surface morphological features characterized using a scanning electron microscope. And kinetics and isotherms of biochar adsorbing pentachlorobenzene (PeCB) and hexachlorobenzene (HCB) were explored using the batch equilibration method. Results show that organic components in wheat straw were carbonized during the pyrolytic process, and their carbonization degree increased, but O/C, (O+N)/C and H/C of the biochars decreased with the temperature rising from 400℃, 500℃ to 600℃, indicating that the wheat straw based biochar decreased in hydrophilicity and polarity, but increased in aromaticity with the rising pyrolytic temperature. Higher pyrolytic temperature depleted surface polar functional groups in the biochar. The three different kinds of wheat straw biochars were all able to adsorb CBs in water quickly and efficiently. The sorption process could be divided into two phases: rapid sorption process and subsequent slow sorption and equilibrating process. It took about 48 hours for the sorption to reach equilibrium. The biochars adsorbed HCB faster than it did PeCB and the pseudo-second-order kinetic equation could be used to better describe the sorption process. CBs adsorption did not affect much FTIR spectra of the three kinds of biochars sorbing, indicating that the sorption was dominated with physical sorption. In terms of CBs saturated sorption quantity, the three kinds of biochars followed an order of WSB400 ＞ WSB500 ＞ WSB600. With the rising pyrolytic temperature, the adsorption of PeCB and HCB on the biochars became more and more nonlinear. The adsorption of PeCB and HCB displayed an apparent linear isotherm on WSB400, but concave non-linear curves on WSB500 and WSB600. A linear isotherm signifies presence of partition, while a nonlinear isotherm that of surface adsorption. The analysis of contributions of partition and surface adsorption to total sorption of CBs on wheat straw biochar reveals that higher temperature in biochar preparation turns the sorption mechanism from partition dominated into partition-surface adsorption co-dominated one.

Abstract:Biochar is a carbon-rich material produced by pyrolyzing biomass in the absence of oxygen. Due to the presence of well-developed micro-pores and high specific surface area, biochar displays an excellent sorption capacity and hence is deemed as green environmental sorbent and has been extensively used in the field of agriculture and environment. Polycyclic aromatic hydrocarbons (PAHs) are a typical kind of persistent hydrophobic organic pollutants commonly found in soil and sediments. Thanks to the high affinity of sorbents to PAHs, sorption has become a critical process governing the fate and transport of PAHs in the environment. An experiment was carried out using biochars prepared through pyrolyzing corn stalks under different temperatures, to explore kinetics of the biochar sorbing naphthalene, a volatile organic compound in the PAHs family, and effect of dosage of biochar on the kinetics. So far, reports have been available demonstrating that sorption kinetics is a useful tool to explain the mechanism of naphthalene sorption. It is, therefore, essential to have a better understanding of the mechanism of biochar sorbing naphthalene and select an optimal sorbent, through studying effects of pyrolysis temperatures and dosage of corn-stalk-derived biochar on sorption kinetics of naphthalene. The experiment was designed to use the batch processing method. Out of each of the four kinds of biochars, C300, C400 ,C500 and C600, prepared under 300°C, 400°C, 500°C and 600°C, respectively, in pyrolysis, two portions, 10 mg and 50 mg each, were taken and put into flasks separately. Into each flask, 10 mL of CaCl2 solution containing 25 mg L-1 naphthalene was added. A soil ion environment was simulated with 0.01 mol L-1CaCl2 solution as background solution. The mixture was shaken at 30±2 °C and 120 rpm for 10 min, 1, 4, 6, 12, 24 and 48 h, separately, in dark and then sampled. Fitting analysis of the kinetic data was performed with the pseudo-first-order kinetic model, the pseudo-second-order kinetic model, the intraparticle diffusion model and Boyd model to elucidate the mechanism of biochar sorbing naphthalene. Results show that Naphthalene sorption capacity at equilibrium (qe) of biochars of the same kind varied with dosage in an order of 10 mg >50 mg, but qe of biochars the same in the dosage did with pyrolysis temperature in an order of C400>C300>C600>C500 with the dosage set at 10 mg and in an order of C300≈C400≈C600> C500 with the dosage set at 50 mg. Compared with the pseudo-first-order kinetic model, the pseudo-second-order kinetic model was much better in fitting the sorption kinetic features of the biochars regardless of dosage or pyrolysis temperature, suggesting that the sorption is related to sorbing sites in biochar, rather than simplex single-layer sorption. For biochars of the same kind, both the sorption rate constant (k) and the initial sorption rate (h) varied with dosage, and were much higher when the dosage was 50 mg than when it was 10 mg, but for biochars of different kinds, both k and h were in the order of C300≈C400≈C600>C500, regardless of dosage. Fitting analyses using the intraparticle diffusion model and the Boyd model show that the sorption process was affected by both film diffusion and intraparticle diffusion. The sorption process consists three steps: (1) film diffusion of pollutant from its transport solution to external surface of the absorbent; (2) intraparticle diffusion of pollutant during its transport inside pores of the absorbent; and (3) sorption of pollutant on the interior surface of the absorbent. The sorption process consists of two steps for biochars 10 mg in dosage and three steps for biochars 50 mg in dosage. For biochars of all kinds, it took a longer time for biochars lower-in dosage to go through the steps, which is probably because biochars higher in dosage may provide more absorbing sites. Intraparticle diffusion rate constants of biochars, regardless of kind or dosage, declined with the time going on. Biochars, C300 and C400, regardless of dosage, both had a boundary layer thicker than that C500 and C600 had, indicating the boundary layer of the former had a higher impact on the sorption. The fitting analysis using the Boyd model shows that during the naphthalene sorption process of biochars, regardless of kind and dosage, film diffusion was the rate-limiting factor. Therefore, it could be concluded that the sorption of naphthalene on corn-stalk-derived biochars was mainly governed by film diffusion of the pollutant from its transport solution to the surface of the adsorbent.

Abstract:Deca-brominated diphenyl ether (BDE-209) is a new kind of persistent organic pollutant, which may have multi-physiological toxic effects on the nervous system, reproduction, development, etc. of an organism. In the present study to assess toxicity of BDE-209 at the molecular, biochemical and physiological levelsCaenorhabditis elegans (C. elegans) was chosen as a model organism. The physiological experiment performed in this study was to determine effects of the substance on spawning rate of parental generations and filial generations of C. elegans, and life span and cell apoptosis of the parental generations; the biochemical experiment was to monito r cell apoptosis of C. elegans with the acridine staining method; and the molecular-level experiment was to determine changes in antioxidation genes, such as superoxide dismutase-3 gene (sod-3) and quasi p53-1 protein gene (cep-1), and xenobiotic metabolism enzyme, such as cytochrome P450 35a2 gene (cyp35a2) and glutathione-s-transferase gene (gst-1) with the Real-Time PCR method, so as to evaluate toxicity of BDE-209 at the physiological and molecular levels. Results show that compared with control group, exposure to a low dosage (5 mg kg^-1) of BDE-209 did not have much effect on spawning rate of the parental generation, but did on that of the filial generations, particularly on that of the third filial generation, which dropped by 61.5%. Exposure to medium (20 mg kg^-1 ) and high (30 mg kg^-1) dosage of BDE-209 did inhibit their spawning rate (p < 0.05) significantly, reducing that of the third filial generation by 66.7% and 89.3%, respectively. It is clearly shown that both long-time exposure to a low dosage (5 mg kg^-1) and short-time exposure to a high dosage (30 mg kg^-1) of BDE-209 could affect brood size of C. elegans. The experiments on life span and cell apoptosis demonstrate that exposure to a low dosage (5 mg kg^-1) did not have much effect, but exposure to medium (20 mg kg^-1 ) and high (30 mg kg^-1) dosages of BDE-209 did reduce mean life span of C. elegans; and exposure to a high dosage cause apoptosis around the gential area. Real-time PCR reveals that exposure to a low dosage ( 5 mg kg^-1) of BDE-209 significantly induced the expression of stress-related genes such as sod-3, cep-1 and xenobiotic metabolism enzyme cyp35a2 genes, but inhibited the expression of xenobiotic metabolism enzyme gst-1 genes, while exposure to a high dosage (30 mg kg^-1) inhibited the expression of cep-1, cyp35a2 and gst-1, but increased the expression of sod-3 to an extent that was not so high as the former. However, it is quite obvious that the expression of gst-1 was always inhibited in either case. These findings indicate that, when exposed to a low dosage of BDE-209 (5 mg kg^-1) for a short time, C. elegans would react to oxidative stress, trying to repair the damage through regulating the expression of related anti-oxidation genes. In this case, C. elegans would be much affected in life span and spawning rate, however with the exposure going on, a low dosage (5 mg kg^-1) of BDE-209 would significantly reduce the spawning rate of C. elegansand a high dosage of BDE-209（30 mg kg^-1）would cause oxidative injury and cell apoptosis to organs of of the C. elegans, and reduce its oviposition capacity.

Abstract:Organic amendments can significantly improve soil fertility and increase the soil biota in both number and activity. However, little attention has been given to impact of composition or quality of the organic substances on soil biota communities, especially on soil microfauna. In order to explore effects of the application of different crop residues on composition of the soil microbial food web, and to harmonize the contradiction between biological mineralization and fixation of soil nitrogen and plant N uptake, investigations were conducted of responses of soil labile carbon, nitrogen and soil microfauna (nematodes and protozoan) to amendment of different crop residues through in-lab microcosm incubation. Dynamics of soil dissolved organic carbon (DOC), dissolved organic nitrogen (DON), microbial biomass carbon (MBC) and nitrogen (MBN), soil microfauna (protozoa and nematodes) were monitored in soils amended with rice straw or clove, following 14, 35 and 70 days of incubation. Results show that, compared with rice straw, clover significantly (p< 0.05) increased the contents of DOC and DON, especially the contents of DON, NO₃^--N and MBN along similar rising trends during the 70-day incubation period. However, the amendment of clover led to lower MBC and microbial C: N ratios, but higher number of amoebae and flagellates than the amendment of rice straw did (p< 0.05), particularly flagellates, of which the increase in number reached a significant level, after incubation for 14 d and 35 d (p< 0.05). In addition, quality of the residue significantly affected the number of nematodes, which was significantly higher in the soil amended with clover than in the soil amended with rice straw. The number of nematodes rose continuously with the incubation going on in the soil amended with clover, while it stayed almost unchanged in the soil amended with rice straw. Concomitantly, relative abundance of the nematode trophic groups was also significantly affected by type of the residue (p< 0.05), for example, relative abundance of bacterivorous nematodes and nematode channel ratio (NCR) were significantly higher in the soil amended with clover than with rice straw, while relative abundances, Shannon diversity, maturity index (∑MI 2-5), and structure index (SI) offungivorous nematodes, herbivorous nematodes and omnivorous nematodes were markedly lower in the former than in the latter (p< 0.05). Clover displayed a strong stimulating effect on soil bacterivores, like protozoa and nematodes, which indicates that organic amendment low in C: N ratio improves the structure of bacteria-dominated soil microbial food web. In contrast to clover, rice straw with higher C:N ratio stimulated fungivores, herbivores and omnivores in the nematode community, increasing their proportions, and diversity, maturity and structural complexity of the nematode community, which further indicates that organic substances with high C:N ratio promotes the structure of fungi-dominated microbial food web. In short, both quality and composition of the organic amendment have remarkable impacts on composition of soil carbon and nitrogen, abundance of soil microfauna, and structure and diversity of the soil microfaunal community. The use of appropriate types of crop residue may serve the purpose of manipulating size and composition of the soil microbial food web within a short period of time. Further studies should be done with more attention to research and validation of relative importance of composition of crop residue amended and some other soil abiotic factors through a longer term field experiment, so as to have a better understanding of the mechanism of type of organic amendment regulating the structure and functions of soil biota.

Abstract:In 2013, soil samples were collected in Daweijia Town of Dalian City where seawater intrusion once occurred, for analysis of soil physical and chemical properties, including soil salinity, moisture content, Na⁺ content, K⁺ content, organic matter content, nitrate content, available P and pHand for counting of soil nematodes, using the ISC process. The nematodes separated from the soil were classified and identified. Then impacts of seawater contamination and land use on soil nematodes community structure were studied using the diversity index and functional group indices. Results show that long-term irrigation with sea water polluted groundwater has caused the background soil salinity value of the region doubled or tripled, with Na⁺ content increasing, K⁺ content decreasing and the soil significantly salinized. The closer to the coast, the higher the degree of soil salinization was.Organic matter content decreased with the increasing salinity. The total of 13 308.4nematodes identified belonged to 48 genera of 30 families, including 17 genera of bacterivores nematodes and 9 genera of omnivore-predator, representing 42.81% and 25.26%, respectively, of the total. Plectus was the dominant genera, representing 13.47% of the total. Among the life history strategies of soil nematodes, c-p1~2 was the largest in proportion, and the proportion of c-p1~2 was higher in soils high in salinity than in soils low in salinity under the same land use, and higher in farmland than in soils under other forms of land use. With rising soil salinity, NCR, PPI and PPI/MI of soil nematodes and proportions of plant-parasitic nematodes, bacteria-feeding nematodes and omnivores/predatory nematodes all increased, but Shannon-Wiener, f/b, MI, and proportion of bacterivores reduced. The relationship between nematode community and soil moisture content was also quite significant. The impacts of type of land use were very significant on number and diversity of soil nematode groups (S) and extremely significant on population and PPI of soil nematodes. Among the different types of land use, orchards received large volumes of organic manure and chemical fertilizer, thus altering their soil properties and raising their soil fertility and organic matter content as well. In such soils, the higher the organic matter content, the great the population of soil nematodes, the less the number of parasite nematodes, the more favorable the soil to crop growth, and the higher the density of nematode individuals in the soil. In croplands, often short in cultivation history, but frequently disturbed by tillage, the habitat for nematodes varied sharply, thus making the density of soil nematodes lower. The findings demonstrate that soil nematode community responds to sea water contamination variably, depending on degree of the contamination. Therefore, its response can be used to indicate status of the soil environment and sea water pollution degree of the region. Beside, the impacts of land use on soil nematode communities relative to type of the land use. In orchard, soil nematodes are quite high in individual density, number of groups and diversity because orchards offer soil nematodes a better habitat than croplands do. The findings of the study provide a theoretical basis for future study on how soil nematode community respond to seawater pollution and how the soils in sea water polluted areas can be remedied.

Abstract:Nitrous oxide (N₂O) is a major greenhouse gas, which is not only an important contributor to global warming, but also a damager of the stratospheric ozone layer. Upland is an important source of N₂O, of which the emission activity has been widely reported to be related to soil structure, and denitrification is a major pathway of N₂O production in upland soil. Soil aggregates are an important component in soil structure and a factor affecting soil N₂O emission. However, little has been reported on mechanisms of soil microbes explaining differences in N₂O emission rate between different fractions of soil aggregate. In this study, soil aggregates, <1 mm, 2~4 mm, and 4~8 mm in diameter, separated from the soil of a vegetable field, over 15 years in cultivation history, were sprayed with NH₄NO₃ solution to add N 700 µg g^-1soil and regulate soil water content up to 35%. Afterwards, 50 g of aggregates on a dry weight basis was taken from each fraction and transferred into a 500 ml jar for soil incubation under 30 ℃ for a 96 h, and each had 3 replicates.Gas samples were collected once every 12 h after during the incubation and N₂O concentrations in the samples were determined with a Gas-chromatograph. Soil samples for molecular analysis were collected once every 24 h and quick-frozen in liquid nitrogen, and stored at -80 ℃. Quantitative Polymerase Chain Reaction (qPCR) and Terminal-Restricted Fragment Length Polymorphism (T-RFLP) were used to determine changes in abundance and composition of denitrifying genes, narG and nosZ. Results show that N₂O emission rate was closely related to abundance of narG- and nosZ-containing soil microbes, while the fraction of <1 mm aggregates was significantly higher in N₂O emission rate than the fractions of 2~4 mm and 4~8 mm, and the fraction of 4~8mm was the lowest. N₂O emission peaked at 12 h and 24 h of incubation. At 12 h, N₂O emission rate of <1mm aggregates reached 7.637 µg g^-1 h^-1, about 36% higher than that of 2~4 mm aggregates, while the N₂O emission rate of 2~4 mm aggregates was about 2 times higher than that of 4~8 mm aggregates, reaching 1.965 µg g^-1 h^-1. The differences between the fractions of aggregates were gradually narrowed with the incubation going on, and to the least after 96 h of incubation. Interestingly, the relationships between abundances of narG and particle size of soil aggregates were very similar to those between N₂O emission rates and particle size of soil aggregates. The fraction of <1 mm aggregates was the highest in abundance of narG-containing bacteria, much higher than the fraction of 2~4 mm aggregates, while the latter was much higher than the fraction of 4~8 mm aggregates in all the soil samples. The abundance of nosZ in soil aggregates demonstrated a similar trend that the fraction smallest in particle size was the highest in copy numbers of nosZ after 48 h of incubation, while the fraction the largest in particle size the lowest. The 2~4 mm and 4~8 mm fractions of aggregates were relatively stable in nosZ abundance, lingering around 2.5×108 g^-1 and 1.6×108 g^-1 during the whole incubation process, while the <1 mm fraction of aggregates leveled off around 3.6×108 g^-1 after 48h of incubation. N₂O emission rates of the three fractions of aggregates were significantly and positively related to narG gene abundance and to nosZ gene abundance as well at 48h, 72h and 96h of the incubation. However, T-RFLP showsthat at most of the time points during the incubation, the fractions differed in number of strips low in content of narG and nosZ,but did not in number of major strips containing narG and nosZ. When narG and nosZ were used as biomarkers characterizing structure and composition of the soil microbial community, no difference was found in structure of soil microbial community between the fractions of soil aggregates, and moreover, the main tendency won’t change with the incubation going on. To sum up, soil aggregates different in diameter vary in N₂O emission rate, displaying a negative relationship between N₂O emission rate and particle size of the aggregates, and the difference in N₂O emission rate is attributed mainly to the difference in abundance of denitrifying microorganisms, rather than in composition of their community.

Abstract:Northeast China is the main spring maize production base of China. It is of great significance to stabilize and keep on raising yield of the crop in this region in guaranteeing development of the maize-related industry and food security in China. The technique of blending controlled release N fertilizer (CRN) with common urea once for ado can be used in fertilization of maize not only to regulate the supply of available and slowly available N so as to meet the demand of the crop for N during its growing season, but also to reduce fertilizer and labor input cost to increase economic profit. However, so far little has been reported on researches on such techniques for spring maize in Northeast China, and is known of effects of the use and proper ratio of such a blend. Therefore, 3-year-long multi-site field experiments were carried out to explore effects of the blending on growth at the jointing stage, grain yield and yield composition at maturity, N use efficiency, and economic profit of spring maize relative to blending ratio and environment, so as to define effect of the use and optimal ratio of the blend by determining relationships of ratio of the blend with grain yield, partial factor productivity of N fertilizer (PFPN), and fertilization profit of spring maize. The 3-year-long (2009 to 2011) multi-site field experiments consisted of nine experiments in the major maize production area in Central Jilin province and were designed to have five fertilization treatments, i.e. Treatment I (No N fertilizer); Treatment II (100% common urea); Treatment III (15% CRN and 85% common urea); Treatment IV (30% CRN and 70% common urea), and Treatment V (45% CRN and 55% common urea). Total N fertilization rate was kept consistent for all the treatments, being 185 kg hm^-2 during the growing season. The results showed that a higher proportion of CRN in the blend improved spring maize in plant height and leaves in number and SPAD at the jointing stage, but did not affect much stem diameter. Summary of the nine experiments indicated that both grain yield and fertilization profit of spring maize increased significantly with increasing blending ratio of CRN, and reached the highest, 10.12 t hm^-2 and 5 071 yuan hm^-2, respectively, in Treatment IV, being 0.98 t hm^-2 (10.8%) and 1 639 Yuan hm^-2 (47.8%) higher than that in Treatment II, respectively. The effect of higher blending ratio of CRN increasing grain yield of spring maize was mainly attributed to the significantly increased number of kernels per ear at the maturing stage, and also to the increased ear number. A rising proportion of CRN in the blend increased significantly PFPN of spring maize, but reduced significantly contribution rate of soil N (CRSN), till it reached 30%. In all the nine sites of the experiment, significant quadratic relationships were observed of blending ratio of CRN with grain yield, PFPN, and fertilization profit of spring maize. For the above three parameters, the optimal blending ratio of CRN for spring maize was figured out to be 35.1%, 35.2%, and 33.7%, respectively. Obviously, blending of CRN with common urea in fertilization is conducive to growth of spring maize, higher yield of grains, higher N use efficiency, and higher economic benefit. Based on all the findings in the experiment, the optimal blending ratio of CRN for spring maize production in Northeast China is worked out to be 30%~35%.

Abstract:Soil family and soil series are two basic taxons of the Chinesesoil taxonomy, and will also be the focus of the study on the Chinese soil taxonomy for quite a long time in future. Based on the "Standard for Classification of Soil Family And Series" laid down and published in 2013 by the special national science and technology basic researchproject“Investigation of Soil Series of Chinaand Compilation of “Record of Chinese Soil Series” [2008FY110600]”, analysis was performed of problems in naming of soil families that have been set up in the research on taxons in Chinese soil taxonomy in this country since 1998, in the hope that the work may provide some reference for studies on soil families in China in future.

Abstract:Constructing artificial algal crusts by means of cyanobacterial inoculation could promote growth and development of biological crusts on sand dunes in desert regions and restoration of the whole desert ecosystem, and hence is considered as an effective approach to desertification control. However, in the course of constructing artificial algal crusts, the inoculated cyanobacteria or formed crusts are susceptible to various environmental stresses, mainly drought in the desert regions. An in-lab experiment was carried out to have artificial algal crusts exposed to drought and rehydration, and to explore their effects on crust biomass, exopolysaccharides and photosynthesis of the crusts. It was found that drought for one day could provisionally promote secretion of crust cyanobacterial exopolysaccharides (p<0.05). Once the crusts were completely dried, cyanobacteria of the crusts stopped all their metabolic activities, and biomass and exopolysaccharides content of the crusts remained at a certain relatively steady level. After rehydration, crust original fluorescence Fo got recovered quickly and reached the maximum within 10 min. Afterwards, Fo decreased gradually and crust photosynthetic activity (F_v /F_m) increased and leveled off steadily in line with the function y=ax/(b+x). In addition, under different water conditions, crust photosynthetic activity increased with the increasing crust water content, but crust net photosynthesis (P_n) first increased and then decreased with the increasing crust water content, showing a unimodal variation pattern. This study suggests that the regulation of crust cyanobacteria in metabolism plays an important role in the adaptation of artificial algal crusts to arid desert environmental conditions. The findings may help us further understand how cyanobacteria or cyanobacterial crusts adapt to drought stress, and provide theoretical basis and practical lessons for construction, maintenance and management of artificial algal crusts in desertification control.

Abstract:Investigation were carried out of plants and soil in shelterbelts along highways in the Taklimakan to explore effects of irrigation with saline water on plant root system and evolution of aeolian sand soil in the belts. Results show that the roots of Tamarix go much deeper, about 200 cm into the soil, while those of Haloxylon and Calligonum about 100~150 cm; Soil salts (about 8 mS cm^-1) and nutrients accumulate significantly in the topsoil layer (crust and 0~10 cm soil layers) in shelterbelts irrigated with saline water, but in the 40~60 cm soil layer, where plant roots are densely distributed, soil salinization does not exist (<1.0 mS cm^-1) . The soil in the shelterbelt is much higher than in shifting sand soil in content of soil organic C, total N and total P, and moreover, the soil is significantly higher in content of clay, silt and soil aggregates, which are relatively higher in stability than shifting sand soil. To sum up, irrigation with saline groundwater does not bring about any salt hazard or toxicity to plants growing normally in the shelterbelts, and instead it is conducive to evaluation of desert aeolian sand soil.

Abstract:An adsorption and desorption test was conducted of two variable charge soils (Ali-Haplic Acrisol from Jiangxi and Hyper-Rhodic Ferralsol from Kunmin of Yunnan) to explore distribution of desorption rates of pre-adsorbed Cu(II) from the soils in NaNO₃ solution relative to concentration of the solution and pH, at which Cu(II) was adsorbed during the pre-adsorption phase. For the test, the soil samples were first put into de-ionized water and 0.1 mol L^-1 NaNO₃, separately, for pre-adsorption of Cu(II) and then into de-ionized water and NaNO₃ solutions varying in concentration gradually from low to high, sequentially, for desorption of Cu(II). Results show that with rising pH, Cu(II) desorption rate varied sharply with NaNO₃ solution. In de-ionized water, Cu(II) desorption rate declined monotonously with the rise of pH in the Cu(II) pre-adsorption phase; while in NaNO₃ solutions, Cu(II) desorption rate followed a peak-shaped curve, but the total Cu(II) desorption rate also declined monotonously with the rise of pH in the Cu(II) pre-adsorption phase. The Cu(II) desorption rate was the highest in the solution of 0.1 mol L^-1NaNO₃. In short, desorption rates of the Cu(II) desorbable in de-ionized and in NaNO₃ solutions were distributed mainly in the high and low sections, respectively, of the range of pH studied. Desorption rate of the Cu(II) desorbable in NaNO₃ was closely related to content of ferric oxide in the soils and NaNO₃ concentration in Cu(II) pre-adsorption, so the higher the content of ferric oxide in the soil, or the higher the NaNO₃ concentration in pre-adsorption at pH > 4.0~4.5, the lower the proportion of Cu(II) desorbed by NaNO₃. The cause of such a phenomena is believed to be associated with the effect of ion-strength, specific weight of exchangeable Cu(II) relative to adsorption condition and the effect of desorption on pH of the system. Besides, comparison was also made between sequential desorption in solutions constant in NaNO₃ concentration and that in solutions varying in NaNO₃ concentration.