陕西省水蚀土壤因子指标插值方法比较研究

基于地统计学原理和半变异理论,采用地理信息系统技术定量研究了陕西省水蚀土壤因子指标的空间变异特征。分析比较了反距离权重法、样条函数法与普通克吕格法对陕西省土壤因子指标空间插值的精度。结果表明,研究区土壤抗冲系数具有中等强度的空间相关性,块金系数为32.29%,而稳渗速率、崩解速率、抗剪强度均表现为强烈的空间相关性,块金系数分别为13.19%,11.61%和12.98%。综合考虑平均相对误差、均方差及插值效果,认为普通克吕格法最好,更能反映土壤参数的空间特征并符合区域水土流失模型对数据的要求。对于普通克吕格法,稳渗速率的Lag步长为30 000 m,半方差理论模型为指数模型;抗冲系数、崩解速率、抗剪强度的Lag步长为55 000,半方差理论模型均为高斯模型。在空间分布上,各指标随土壤类型由北到南呈现明显的地带性规律。

两种土壤水分特征曲线间接推求方法对黄土的适应性评价

土壤水分特征曲线(SWCC)是模拟土壤水分运动和溶质运移的一个重要参数,利用土壤的基本物理性质来间接推求SWCC的方法已经成为当今土壤物理学领域的研究热点。为了比较两种SWCC间接推求方法——Arya-Paris物理经验方法(简称AP方法)和Tyler-Wheatcraft分形几何方法(简称TW方法)对黄土的适应性,该文分析了黄土高原296组土壤颗粒分布、容重和水分特征曲线等资料,利用简化的Fredlund(Fred3P)模型模拟得到连续的土壤颗粒分布曲线,然后应用AP和TW方法预测出相应吸力下的土壤含水量。研究结果表明,对于黄土性土壤,AP和TW两种方法的预测结果均达到了一定的精度,相比较而言AP方法的预测效果明显优于TW方法,且受质地影响小。

Numerical Study on the Spatial and Temporal Characteristics of Water Quality in the Taihu Lake of China

Taihu Lake is the third largest fresh water lake in China. With the fast economic development, abundant industrial and agricultural waste water has been discharged into Taihu Lake, causing the eutrophication of the water quality, which greatly affected the water utility. In the past decades, the treatment of Taihu Lake has witnessed limited success. Therefore, it is practically and theoretically significant to study the eutrophication of Taihu Lake. This research has focused on the issue of water quality including the characteristics of spatial and temporal distributions, and the rules of nutrient diffusion in the Taihu lake area. Based on the monitoring data, the basis distribution characteristics of water quality in Taihu Lake are analyzed. Comparing Taihu Lake with other Lakes shows that one important reason for Taihu eutrophication is the long period of water retention. A transporting and diffusing model of Taihu nutrient is developed by combining with the hydrodynamics model. Using the model, the concentration field of the total phosphorus (TP) and the influence of wind-driven current are numerically investigated, which leads to the conclusion that the flow field has a great influence on the spatial and temporal distributions of TP in Taihu Lake. Furthermore, the effect for improving the water quality by the project of water diversion from the Yangtze River to Taihu Lake was analyzed by simulation. The results demonstrate that short-term water diversion cannot improve the water quality of the heavily-polluted Meiliang Bay and the western bank areas of Taihu Lake.

Investigation on the influence of methanol on adsorption and leaching of pesticides with soil column liquid chromatography

The effect of methanol of low concentration on adsorption and leaching of atrazine and tebuconazole was studied in this paper. The adsorption coefficients and the retardation factors (R-m) of pesticides on EUROSOIL 3# log-linearly decreased as volumetric fraction of methanol (f(c)) was increased in the binary solvent mixtures of methanol and water. These data are consistent with solvophobic theory formerly outlined for describing the adsorption and transport of hydrophobic organic chemicals from mixed solvents. Nevertheless, the adsorption of these pesticides in soil-water system slightly increased when the soil was pre-washed with methanol in comparison with that pre-washed with water (pure water system). Furthermore, their adsorption coefficients were still higher in binary solvent systems with methanol of very low concentrations, i.e. f(c) < 0.03 for atrazine and f(c) < 0.01 for tebuconazole, than those in pure water system. The adsorption coefficients (logK(w)) of atrazine and tebuconazole predicted by solvophobic theory were 0.5792 and 1.6525, respectively, and their experimental logK(w) were 0.3701 and 1.6275 in pure water system. Obviously, the predicted log K-w of the two pesticides was higher than the experimental log K-w in pure water system. The predicted K-w and the retardation factor (R-w) in pure water system by solvophobic theory are thus possibly inaccurate. (C) 2004 Elsevier Ltd. All rights reserved.

冬小麦田秸秆覆盖的小气候效应

The winter wheat field straw mulching was conducted. Compared with the unmulched field, the straw mulching could alter turbulent heat exchange, evaporative heat loss and soil heat fluxes, and improve the temperature and humidity of air close to the ground as well as play a active role in water-saving and soil moisture retention, thus provided better microclimatic conditions for the growth and development of winter wheat.

Soil microbial community analysis using terminal restriction fragment length polymorphisms

Terminal restriction fragment length polymorphism (T-RFLP) analysis is a polymerase chain reaction (PCR)-fingerprinting method that is commonly used for comparative microbial community analysis. The method can be used to analyze communities of bacteria, archaea, fungi, other phylogenetic groups or subgroups, as well as functional genes. The method is rapid, highly reproducible, and often yields a higher number of operational taxonomic units than other, commonly used PCR-fingerprinting methods. Sizing of terminal restriction fragments (T-RFs) can now be done using capillary sequencing technology allowing samples contained in 96- or 384-well plates to be sized in an overnight run. Many multivariate statistical approaches have been used to interpret and compare T-RFLP fingerprints derived from different communities. Detrended correspondence analysis and the additive main effects with multiplicative interaction model are particularly useful for revealing trends in T-RFLP data. Due to biases inherent in the method, linking the size of T-RFs derived from complex communities to existing sequence databases to infer their taxonomic position is not very robust. This approach has been used successfully, however, to identify and follow the dynamics of members within very simple or model communities. The T-RFLP approach has been used successfully to analyze the composition of microbial communities in soil, water, marine, and lacustrine sediments, biofilms, feces, in and on plant tissues, and in the digestive tracts of insects and mammals. The T-RFLP method is a user-friendly molecular approach to microbial community analysis that is adding significant information to studies of microbial populations in many environments.

2种高分子保水材料对土壤持水能力的影响

采用离心机法,研究聚丙烯酸钠与聚丙烯酰胺2种高分子化合物在5种使用浓度(占干土质量0、0.01%、0.08%、0.2%与1%)的条件下对3种土壤(砂土、壤土、黏土)持水能力的影响。结果表明:3种土壤在0.01~1.5MPa水吸力时,持水能力随着2种高分子材料用量的增加而增加,砂土的作用效果较壤土、黏土更显著;2种高分子材料与土壤质量比控制在8/10000~2/1000范围内其作用效果较好,该用量条件下高分子吸持水分平均可释放83.7%供植物吸收利用。2种高分子材料对土壤持水能力的作用效果基本相同。

黄土高原水蚀风蚀交错区土壤剖面水分动态的数值模拟研究

利用SWAP(Soil-Water-Atmosphere-Plant)模型对黄土高原水蚀风蚀交错区坡地土壤-植被-大气系统中的水循环进行数值模拟。结果显示,SWAP模型很好的模拟了不同土地利用方式条件下的土壤水循环过程。根据模拟结果,水蚀风蚀交错区的丰水年份,农地和种植第一年的紫花苜蓿地季末土壤水分稍有盈余,谷子和紫花苜蓿的日蒸散量分别为1.2~2.6 mm和1.2~2.5 mm。

土壤结构改良剂影响下的土壤水分有效性研究

以聚丙烯酰胺(PAM)与磷石膏(PG)为土壤结构改良剂,利用离心机法,测定土壤水分特征曲线,从分析土壤的吸水能力和持水能力的角度出发,研究土壤结构改良剂对土壤水分有效性的影响。研究结果表明,土壤的吸水能力、持水能力与释水能力均表现出与用量密切相关;在使用土壤结构改良剂的情况下,仍然可用van Genuchten方程很准确的模拟土壤吸力与含水率之间的关系,即可作为使用土壤结构改良剂后的土壤水分特征曲线的模拟表达式;在试验的用量范围内,土壤结构改良剂的使用不会影响植物对水分的吸收和利用。

Drivers of soil net nitrogen mineralization in the temperate grasslands in Inner Mongolia, China

Soil net nitrogen mineralization (NNM) of four grasslands across the elevation and precipitation gradients was studied in situ in the upper 0-10 cm soil layer using the resin-core technique in Xilin River basin, Inner Mongolia, China during the growing season of 2006. The primary objectives were to examine variations of NNM among grassland types and the main influencing factors. These grasslands included Stipa baicalensis (SB), Aneulolepidum Chinense (AC), Stipa grandis (SG), and Stipa krylovii (SK) grassland. The results showed that the seasonal variation patterns of NNM were similar among the four grasslands, the rates of NNM and nitrification were highest from June to August, and lowest in September and October during the growing season. The rates of NNM and nitrification were affected significantly by the incubation time, and they were positively correlated with soil organic carbon content, total soil nitrogen (TN) content, soil temperature, and soil water content, but the rates of NNM and nitrification were negatively correlated with available N, and weakly correlated with soil pH and C:N ratio. The sequences of the daily mean rates of NNM and nitrification in the four grasslands during the growing season were AC > SG > SB > SK, and TN content maybe the main affecting factors which can be attributed to the land use type.

Probabilistic modelling of soil moisture dynamics of irrigated cropland in the North China Plain

A probabilistic soil moisture dynamic model is used to estimate the soil moisture probability distribution and plant water stress of irrigated cropland in the North China Plain. Soil moisture and meteorological data during the period of 1998 to 2003 were obtained from an irrigated cropland ecosystem with winter wheat and maize in the North China Plain to test the probabilistic soil moisture dynamic model. Results showed that the model was able to capture the soil moisture dynamics and estimate long-term water balance reasonably well when little soil water deficit existed. The prediction of mean plant water stress during winter wheat and maize growing season quantified the suitability of the wheat-maize rotation to the soil and climate environmental conditions in North China Plain under the impact of irrigation. Under the impact of precipitation fluctuations, there is no significant bimodality of the average soil moisture probability density function.

Seasonal and interannual variation in water vapor and energy exchange over a typical steppe in Inner Mongolia, China

In this study, we conducted eddy covariance (EC) measurements of water vapor exchange over a typical steppe in a semi-arid area of the Inner Mongolia Plateau, China. Measurement sites were located within a 25-year-old enclosure with a relatively low leaf area index (similar to 1. 5 m(2) m(-2)) and dominated by Leymus chinensis. Energy balance closure was (H + LE) = 17.09 + 0.69 x (Rn - G) (W/m(2); r(2) = 0.95, n = 6596). Precipitation during the two growing seasons of the study period was similar to the long-term average. The peak evapotranspiration in 2004 was 4 mm d(-1), and 3.5 mm d(-1) in 2003. The maximum latent heat flux was higher than the sensible heat flux, and the sensible heat flux dominated the energy budget at midday during the entire growing season in 2003; latent heat flux was the main consumption component for net radiation during the 2004 growing season. During periods of frozen soil in 2003 and 2004, the sensible heat flux was the primary consumption component for net radiation. The soil heat flux component was similar in 2003 and 2004. The decoupling coefficient (between 0.5 and 0.1) indicates that evapotranspiration was strongly controlled by saturation water vapor pressure deficit (VPD) in this grassland. The results of this research suggest that energy exchange and evapotranspiration were controlled by the phenology of the vegetation and soil water content. In addition, the amount and frequency of rainfall significantly affect energy exchange and evapotranspiration upon the Inner Mongolia plateau. (c) 2007 Published by Elsevier B.V.

Prediction of soil organic partition coefficients by a soil leaching column chromatographic method

The soil organic partition coefficient (K-oc) is one of the most important parameters to depict the transfer and fate of a chemical in the soil-water system. Predicting K-oc by using a chromatographic technique has been developing into a convenient and low-cost method. In this paper, a soil leaching column chromatograpy (SLCC) method employing the soil column packed with reference soil GSE 17201 (obtained from Bayer Landwirtschaftszentrum, Monheim, Germany) and methanol-water eluents was developed to predict the K-oc of hydrophobic organic chemicals (HOCs), over a log K-oc range of 4.8 orders of magnitude, from their capacity factors. The capacity factor with water as an eluent (k(w)') could be obtained by linearly extrapolating capacity factors in methanol-water eluents (k') with various volume fractions of methanol (phi). The important effects of solute activity coefficients in water on k(w)' and K-oc were illustrated. Hence, the correlation between log K-oc and log k(w)' (and log k') exists in the soil. The correlation coefficient (r) of the log K-oc vs. log k(w)' correlation for 58 apolar and polar compounds could reach 0.987, while the correlation coefficients of the log K-oc-log k' correlations were no less than 0.968, with phi ranging from 0 to 0.50. The smaller the phi, the higher the r. Therefore, it is recommended that the eluent of smaller phi, such as water, be used for accurately estimating K-oc. Correspondingly, the r value of the log K-oc-log k(w)' correlation on a reversed-phase Hypersil ODS (Thermo Hypersil, Kleinostheim, Germany) column was less than 0.940 for the same solutes. The SLCC method could provide a more reliable route to predict K-oc indirectly from a correlation with k(w)' than the reversed-phase liquid chromatographic (RPLC) one.

基于土壤水分平衡原理的毛乌素沙地草地种植咨询系统

本研究初步建立了基于土壤水分平衡原理的毛乌素沙地草地种植咨询系统“ASSG”，该系统用于进行毛乌素地区沙地草地利用和种植管理咨询，并可进行更新知识库和存储有关咨询结果的操作。该系统适用于田间工作者、农场管理者、有关科研人员以及任何对生态科学和自然资源管理感兴趣者。 在文中描述了该咨询系统的开发过程，即系统的需求分析、设计、实现和运行，该系统实现了专家系统和仿真模型的结合，该模型即基于水分平衡的最佳植被覆盖率模型，有如下初步结论产生：土壤水分的平衡随植被覆盖率变化的情况（上升或下降）取决于立地条件的差异，笼统地讲“植被覆盖率越高越好”或“植被覆盖率一概不宜太高”未免失之偏颇。 在解决复杂的生态学问题时人工智能／专家系统技术的应用以及在定性模型和方法（如专家系统）的应用中使用定量模型（如仿真模型）正处于发展之中，本系统的实现是应用专家系统与仿真模型结合的方法解决实际生态学问题的又一个例子。