Land degradation in the source region of the Yellow River, northeast Qinghai-Xizang Plateau: classification and evaluation   总被引：6，自引：0，他引：6  

Jianmin Feng  Tao Wang  Shanzhong Qi  Changwei Xie 《Environmental Geology》2005,47(4):459-466

Land degradation imposes a great threat to the world. It is not merely an environmental issue, but also a social and economic problem. Land desertification is among the main aspects of environment changes in the source region of the Yellow River. Previous studies focused on water resource utilization and soil erosion, but land degradation in the source region of the Yellow River even the whole Qinghai-Xizang Plateau received little attention. Based on the data obtained by field investigation and TM satellite images of 2000, this study provides the classification and evaluation information of the land degradation in the source region of the Yellow River. There are six types of land degradation in this region: water erosion in the northern mountains around the Gonghe Basin, sandy desertification in the Gonghe Basin and Upland Plain Area, aridization in the lower reaches, salinization in the Gonghe Basin, vegetation degradation in the intramontance basin and freezing and thawing erosion in the high mountains. The total degraded area is 34,429.6 km², making up 37.5% of the land in the study area. Finally, land degradation in the source region of the Yellow River was evaluated according to changes in the physical structure and chemical component of soils, land productivity, secondary soil salt and water conditions.  相似文献   

Electromagnetic Radiation from Rock During Uniaxial Compression Testing: The Effects of Rock Characteristics and Test Conditions   总被引：3，自引：0，他引：3  

K. Fukui  S. Okubo  T. Terashima 《Rock Mechanics and Rock Engineering》2005,38(5):411-423

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相山火山-侵入杂岩的反方向岩浆演化系列研究   总被引：12，自引：0，他引：12       下载免费PDF全文

张万良 《中国地质》2005,32(4):548-556

相山因是中国最大火山岩型铀矿产地而倍受关注,相山火山-侵入杂岩从喷发-侵出-侵入,SiO2含量、Rb/Sr、Rb/Ba比值降低,而TFe（Fe2O3＋FeO）、CaO、MgO、TiO2、P2O5含量、SI（固结指数）、δEu则呈增高趋势,岩浆演化与正常岩浆房酸度逐渐增高的岩浆分异趋势相反,称反方向岩浆演化系列.不相容元素的比值如Th/U、Rb/Ba、Th/Nb、Th/Ta、La/Nb、Nb/Ta变化幅度较大,与SiO2组分没有明显的正消长或反消长关系,稀土配分曲线也不尽一致,火山喷发相、侵出相和侵入相岩石具有不同的源区性质.  相似文献   

川西邛崃县白马庙气田上侏罗统蓬莱镇组高分辨率层序地层分析          下载免费PDF全文

赵永刚陈景山  雷卞军蒋裕强王身建  徐丹舟 《中国地质》2005,32(4):674-681

以高分辨率层序地层学理论及其技术方法为指导,通过地表露头、岩心、测井和地震资料的综合分析,在白马庙气田上侏罗统蓬莱镇组识别出3类不同成因类型和发育规模的层序界面、3个级别的湖泛面,划分出2个长期、6个中期、38～40个短期基准面旋回层序,并对不同级次旋回层序的特征进行了详细讨论.同时,发现中期基准面旋回层序近顶部的薄层灰岩和钙质泥岩也是识别中期基准面旋回的重要标志之一.在此基础上,运用旋回等时对比法则对各级次旋回层序进行对比,建立了3个不同时间尺度的等时地层格架,认为开展高分辨率层序地层分析对深化白马庙气田蓬莱镇组气藏的勘探开发工作具有重要意义.  相似文献   

Environmental variables related to wheat yields in the semiarid pampa region of Argentina   总被引：1，自引：0，他引：1  

B.V. Scian  M.E. Bouza 《Journal of Arid Environments》2005,61(4):669-679

The current paper analyses various environmental parameters in relation to wheat yields in Bordenave, Province of Buenos Aires, Argentina. The variables used are: precipitation (ppt), maximum (Tx) and minimum temperature (Tmi) as well as those obtained by applying the Palmer model. Decadic and phenological scales are used for data corresponding to the period 1977–2000. The stepwise method is used to obtain a multi-variate equation to calculate yield taking into account environmental variables only. For a five variates model the coefficient of determination, R² equals 95.79% and the standard error of estimation is 129.0 kg ha⁻¹. In the sample yields, the incidence of total variability for thermal variables is 42.7% and for hydrological variables, 53%. The value and sign of the correlation coefficients were analysed throughout the cultivation cycle. The α coefficient is mainly responsible for yield variance during tillering and stem elongation. There is good correlation with the values of Palmer's Drought Severity Index (PDSI) for the flowering and grain filling stages.  相似文献   

Climatic response of thick leaf spruce (Picea crassifolia) tree-ring width at different elevations over Qilian Mountains, northwestern China   总被引：3，自引：0，他引：3  

X. Gou  F. Chen  M. Yang  J. Li  J. Peng  L. Jin 《Journal of Arid Environments》2005,61(4):513-524

Tree-ring cores of thick leaf spruce (Picea crassifolia) taken from four sites at different elevations, in the middle of the Qilian Mountains, in the arid and semi-arid region of northwestern China, were used to develop four tree-ring width chronologies using standard dendrochronological methods. Results indicate that with increasing altitude the chronologies’ year-to-year variations decreased. Hence, the sensitivity of the tree-ring chronologies to climate decreases with altitude. Further analysis showed that the significant limiting factor on tree growth is spring precipitation. Measurements of stomata density and leaf dry weight suggest the species’ ecological adaptation strategy changes with elevation. At high elevation the metabolic rate of thick leaf spruce decreases, thus showing the effect of the climate.  相似文献   

三峡水库区巫山新县城库岸综合治理设计回顾     

刘加龙  张纯根 《中国地质灾害与防治学报》2005,16(3):24-27

三峡水库区巫山新县域库岸综合治理工程范围内涉及到滑坡、泥石流、塌岸等多种地质灾害。治理工程综合运用了多种技术与结构措拖，工程的复杂性和典型性在整个三峡库区具有极强的代表意义。笔者对整个治理方案的布置情况进行了归纳总结，并以翔实的第一手资料对治理工程设计过程中出现的几种典型问题一一进行了分析与论述．提出了相应的解决方案与合理化建议。结论认为，库岸综合治理工作，必须根据不同的地形特征，结合城区总体布局及沿线市政工程建设，综合考虑，有机结合，做到治理和利用相结合，最大限度地改善新城建设用地环境和城市生态环境。设计人员必须依照现场实际条件进行动态设计，确保工程方案合理、可靠、经济。文中讨论的问题和实践经检对同类工程具有一定的借鉴意义。  相似文献   

长江口沉积物210Pb分布及沉积环境解释   总被引：19，自引：0，他引：19  

段凌云  王张华  李茂田  潘建明  陈中原  Yishiki Saito  Yutaka kanai 《沉积学报》2005,23(3):514-522

在长江河口潮滩、分流河道和水下三角洲共获得18个柱样,进行沉积学分析和210Pb测定,并对其中6根柱样进行137Cs测定。经研究发现,长江口外在水深25～30m,122°30′N,31°00′E附近存在一个泥质沉积中心,沉积速率达2.0～6.3cm/yr。另外,在潮滩和涨潮槽也获得较高沉积速率,其中南汇和横沙岛潮滩沉积速率(1.03～1.94cm/yr)高于崇明东滩(0.51～0.76cm/yr),涨潮槽沉积速率也达0.86cm/yr。此外,在石洞口、南汇、九段沙潮滩和三角洲前缘有部分柱样未获沉积速率,推测为沉积环境不稳定或沉积速率过快所致。  相似文献   

长江口沉积物~(210)Pb分布及沉积环境解释     

段凌云  王张华  李茂田  潘建明  陈中原  Yishiki Saito  Yutaka kanai 《沉积学报》2005,(3)

在长江河口潮滩、分流河道和水下三角洲共获得18个柱样,进行沉积学分析和210Pb测定,并对其中6根柱样进行137Cs测定。经研究发现,长江口外在水深25～30m,122°30′N,31°00′E附近存在一个泥质沉积中心,沉积速率达2.0～6.3cm/yr。另外,在潮滩和涨潮槽也获得较高沉积速率,其中南汇和横沙岛潮滩沉积速率(1.03～1.94cm/yr)高于崇明东滩(0.51～0.76cm/yr),涨潮槽沉积速率也达0.86cm/yr。此外,在石洞口、南汇、九段沙潮滩和三角洲前缘有部分柱样未获沉积速率,推测为沉积环境不稳定或沉积速率过快所致。  相似文献   

Correlation Fractal and Multifractal Characteristics of Seismic Activity in the Taiwan Area, China   总被引：2，自引：0，他引：2  

XU Jiandong  HUANG Jianf  WEI Fuquan  YAN Yunpeng  LI Yaping  LIN Chien-te Institute of Geology  China Earthquake Administration  Beijing  Chin  Earthquake Administration of Fujian Province  Fuzhou  Fujian  China China Aero Geophysical Survey  Remote Sensing for Land  Resources  Beijing  China Leader University  Tainan  Taiwan  China 《《地质学报》英文版》2005,79(2):225-232

Based on the analysis of newly collected data of plate tectonics, distribution of active faults and crustal deformation, the Taiwan area is divided into two seismic regions and six seismic belts. Then, correlation fractal dimensions of all the regions and belts are calculated, and the fractal characteristics of hypocenteral distribution can be quantitatively analyzed. Finally, multifractal dimensions Dq and f(α) are calculated by using the earthquake catalog of the past 11 years in the Taiwan area. This study indicates that (1) there exists a favorable corresponding relationship between spatial images of seismic activity described with correlation fractal dimension analysis and tectonic settings; (2) the temporal structure of earthquakes is not single but multifractal fractal, and the pattern of Dq variation with time is a good indicator for predicting strong earthquake events.  相似文献