SOIL CONSERVATION EFFICIENCY OF DIFFERENT MODELS CONVERTING FROM STEEP FARMING SLOPE PLOTS IN YA''''AN, SICHUAN, CHINA     

Yulin DENG  Yan PENG  Yukuan WANG  Zongting YANG Institute of Mountain Hazards  Environment  Chinese Academy of Sichuan  P. R. China  College of Forestry  Horticulture of Sichuan Agricultural University  Sichuan  P. R. China. Water Resources Administration in Ya''''an  Sichuan  P. R. China. 《国际泥沙研究》2003,18(4)

Converting farming slope land into artificial forestland or grassland is a major measure of soil/water conservation. Five conversion practices, namely, 1) a control plot still tilled with a crop (maize), 2) a folder grass-growing plot seeded with Lolium perenne , 3) a young alder tree-growing plot, 4) a pear orchard plot and 5)a bamboo plot intercropped with folder grass, were monitored to compare the soil conservation efficiency of those changes in Ya'an, Sichuan for 3 years between September 1998 and August 2001. Results showed that the 5 designed converting models functioned differently in erosion control. The most effective model was bamboo groves intercropped with folder grass (Lolium perenne). The folder grass (Lolium perenne) growing model was more effective than the pure pear orchard model. The least effective model was the young alder tree-growing slope, which was even less effective than the control (a slope without converted cultivation). Meanwhile, changes in the soil's physical properties r  相似文献   

Acoustic and electromagnetic properties of soils saturated with salt water and NAPL     

Jos M. Carcione  Gza Seriani  Davide Gei 《Journal of Applied Geophysics》2003,52(4):177-191

Electrical, seismic, and electromagnetic methods can be used for noninvasive determination of subsurface physical and chemical properties. In particular, we consider the evaluation of water salinity and the detection of surface contaminants. Most of the relevant properties are represented by electric conductivity, P-wave velocity, and dielectric permittivity. Hence, it is important to obtain relationships between these measurable physical quantities and soil composition, saturation, and frequency. Conductivity in the geoelectric frequency range is obtained with Pride's model for a porous rock. (The model considers salinity and permeability.) White's model of patchy saturation is used to calculate the P-wave velocity and attenuation. Four cases are considered: light nonaqueous phase liquid (LNAPL) pockets in water, dense nonaqueous phase liquid (DNAPL) pockets in water, LNAPL pockets in air, and DNAPL pockets in air. The size of the pockets (or pools), with respect to the signal wavelength, is modeled by the theory. The electromagnetic properties in the GPR frequency range are obtained by using the Hanai–Bruggeman equation for two solids (sand and clay grains) and two fluids (LNAPL or DNAPL in water or air). The Hanai–Bruggeman exponent (1/3 for spherical particles) is used as a fitting parameter and evaluated for a sand/clay mixture saturated with water.Pride's model predicts increasing conductivity for increasing salinity and decreasing permeability. The best-fit exponent of the Hanai–Bruggeman equation for a sand/clay mixture saturated with water is 0.61, indicating that the shape of the grains has a significant influence on the electromagnetic properties. At radar frequencies, it is possible to distinguish between a water-saturated medium and a NAPL-saturated medium, but LNAPL- and DNAPL-saturated media have very similar electromagnetic properties. The type of contaminant can be better distinguished from the acoustic properties. P-wave velocity increases with frequency, and has dissimilar behaviour for wet and dry soils.  相似文献   

Neuzeitlicher Schadstofftrend: Polycylische aromatische Kohlenwasserstoffe (PAK) in aquatischen und terrestrischen Sedimenten     

Hubert Hellmann 《洁净——土壤、空气、水》2003,31(2):85-96

A Recent Contamination Trend: Polycylic Aromatic Hydrocarbons (PAHs) in Aquatic and Terrestrial Sediments Concentrations of polycylic aromatic hydrocarbons (PAHs) measured in aquatic sediments of small, medium‐sized or very large inland lakes, of estuaries as well as in terrestrial sediments from Germany, the UK, Finland, and the USA were plotted in 10 trend curves over the period from 1800 to 1990. The segments of the bore cores were dated for their deposition age. For comparability of the results, the trend is preferentially shown by the guide parameter fluoranthene. Until the 19th century, a constant background value of C_Fluo = 10…50 μg/kg was observed in all regions. Then a steep increase in concentration followed, reaching in the aquatic sediments a maximum in the period 1940 to 1965, while the individual fluoranthene values ranged widely from 90 to 2400 μg/kg. In several regions, a more or less distinct decrease superseded this maximum, although this development did not appear in terrestrial sediments, in one estuary, and in remote forest lakes in Finland. The trend curves reflect the atmospheric deposition of PAHs in airborne dust and in some cases the import through runoff via rivers. Thus, the sediment profiles depict the development of air pollution by pyrogenic contaminants over more than a century. Sediment profiles from rivers can be used only with a high degree of reservation, because of the irregularity and low representativity of the sedimentation.  相似文献   

西北地区戈壁局地陆面物理参数的研究   总被引：30，自引：4，他引：30       下载免费PDF全文

张强  王胜  卫国安 《地球物理学报》2003,46(5):616-623

采用2000年8月～2001年9月在敦煌戈壁上观测的陆面过程资料，分析了敦煌地区荒漠戈壁地表反照率与太阳高度角和土壤湿度的关系以及土壤热传导率与土壤湿度的关系，初步给出了具有试验基础的戈壁局地反照率和土壤热传导率的多因子参数化公式. 并通过与观测值的比较发现试验资料拟合的参数化公式能够比较好地反映降水等气候因子引起的动态变化.  相似文献   

热惯量法在监测土壤表层水分变化中的研究   总被引：95，自引：2，他引：95  

余涛  田国良 《遥感学报》1997,1(1):24-31,80

利用遥感方法监测一定层水深土壤水分变化，关键是建立卫星数据与地表水热变化关系，该文地遥感定量反演土壤水热变化的数值模拟系统及热惯量在其边界，初始条件确定中所起的作用进行的简述，并介绍了热惯量法求解表层水分含量的发展概况，为进一步提高定量化监测方法的地必琢计算精度，该文发展了地表能量平均方程的一种新的化简方法，经过这样的处理，可从遥感图象数据直接得到真实热惯量值，进而得到土壤水分含量分布，通过野外实  相似文献   

江苏省主要作物农田水分盈亏量的研究   总被引：5，自引：0，他引：5       下载免费PDF全文

汤志成  张旭晖 《应用气象学报》1997,8(4):503-508

利用江苏省1980～1992年土壤湿度资料，根据土壤水分平衡原理，运用运筹学中的优化技术，结合本省的自然条件和作物生长实际情况，提出有效降水量、下层水分补给量等计算方法，建立了旱地和稻田农田水分盈亏量的计算模式，以便应用实时降水和土壤湿度等资料，计算全省农田水分盈亏量，及时提供农业气象情报服务。  相似文献   

既有房屋饱和土地基极限承载力增长的探讨     

罗哲  黄院雄 《上海国土资源》1997,(4):19-23

饱和土地基在既有房屋长期荷载作用下,地基土强度参数值随着地基土的排水固结和压密而提高,地基极限承载力也同时增大,如何估算此提高值而挖掘其潜力,传统方法只是借助于统计回归讨论了设计承载力。本文从土力学基本原理出发,借助Prandtl假定,对既有房屋饱和土地基极限承载力的增长进行了探讨。  相似文献   

红壤丘陵小区域水平上不同时段土壤质量变化的评价和分析   总被引：39，自引：1，他引：39  

王效举  龚子同 《地理科学》1997,17(2):141-149

引相相对土壤质量指数的概念，应用地理信息系统技术，为小区域水平上土壤质量时空变化的评价提供了一种方法，并用于千烟洲试验站开垦利用１１ａ后土壤质量变化的评价。统计分析服农田，桔园，牧草地，人工林，天然林等多种土地利用方式下土壤质量变化的特征。  相似文献   

黄连山自然保护区的土壤及其地理分布规律   总被引：1，自引：1，他引：1  

虞光复  陈永森 《云南地理环境研究》1997,9(1):73-79

本文根据野外调查，土样室内理化分析及对前人工作成果的系统分析结果表明，黄连山自然保护区的土壤及其地理分布规律是；海拔800m以下为砖红壤；海拔800－1100m为砖红壤性红壤；海拔1100—1600m为山地红壤；海拔1600—1900m为山地黄壤；海拔1900m以上为山地黄棕壤。  相似文献   

沙地果树节水渗灌技术的试验研究   总被引：7，自引：4，他引：7  

荔克让  刘新民 《中国沙漠》1997,17(4):447-452

果树渗灌是灌溉水通过特殊的透性材料持续缓慢地渗入并浸润土壤，借助土壤毛管水运动原理向果树根系供水。干旱地区沙地渗灌能有效地减少地表蒸发、避免无效渗漏造成的水分损失，提高灌溉水利用率，从而达到节水的目的。在沙地果园采用节水渗灌技术，比传统的大水漫灌和沟灌方式分别节水８３．１％和６３．１％。  相似文献