粤北石漠化过程土壤与植被变化及其相关性研究   总被引：6，自引：1，他引：5  

魏兴琥  李森  罗红波  聂磊  李辉霞  何巧如 《地理科学》2008,28(5):662-666

粤北英德市岩背镇典型石漠化区在石漠化从轻度向极重度发展的过程中,土层厚度、土壤覆盖度和土壤有机碳含量均呈显著下降的趋势,土壤有机碳含量在石漠化初期下降幅度更大,而土层厚度、土壤覆盖度在石漠化发展的后期阶段下降程度更为明显;石灰岩植被随石漠化程度加重,向旱生和岩生方向演替,群落结构渐趋简单,植被盖度和现存生物量显著降低;除岩石裸露率与土层厚度、土被覆盖度、土壤有机碳、植被盖度和生物量都呈极显著的负相关关系外,其它各因子之间都呈显著性的正相关关系。  相似文献   

Benthic foraminiferal assemblages of the South Brazil: Relationship to water masses and nutrient distributions     

P.P.B. Eichler  B.K. Sen Gupta  B.B. Eichler  E.S. Braga  E.J. Campos 《Continental Shelf Research》2008

Using distributions of benthic Foraminifera and bottom-water variables (depth, salinity, temperature, oxygen, suspended matter, organic matter, phosphate, silicate, nitrite, and nitrate), we investigated movements of water masses on the South Brazilian Shelf (27–30°S) and assessed the seasonality of continental runoff on the distribution of shelf water masses. The data were obtained from water and sediment samples collected in the austral winter of 2003 and austral summer of 2004 in three transects. The terrestrial nutrient input was significantly reduced at stations away from the coast, but high values of nutrients were maintained in subsurface waters due the presence of South Atlantic Central Water (SACW) at greater depths. At shallow sampling stations the influence of freshwater runoff was related to (1) the dominance of calcareous benthic Foraminifera, such as lagoon-related Pseudononion atlanticum, Hanzawaia boueana, Bulimina marginata, Bolivina striatula, Elphidium poeyanum, together with several agglutinated species, including Arenoparrella mexicana, Gaudryina exilis, and Trochammina spp., common in coastal environments subject to wide salinity fluctuations. In contrast, smaller forms and higher species diversity characterized the assemblage at offshore stations. In winter, the presence of Buccella peruviana and Uvigerina peregrina at Santa Marta Cape suggest the possible transport of those species of Subantarctic Shelf Waters (SASW) origin. Foraminifera associated to Subtropical Shelf Water (STSW) were dominated by Globocassidulina subglobosa in both seasons. In summer, the occurrence of U. peregrina in the shallower stations suggested the influence of SACW nutrients brought up by upwelling of deeper waters.  相似文献   

云南金平长安金矿大倾角钻孔绳索取心施工技术          下载免费PDF全文

易强忠  郎学伟  周兴华  王晓松  王森 《探矿工程》2019,46(4):48-55

金平长安金矿区矿体以硫化矿形式赋存于砂岩中,属于埋藏较深、倾角较陡、勘查难度较大的金矿。矿区的勘查钻孔设计范围为：方位70°～250°、倾角30°～75°、孔深100～800 m。针对该矿区地层呈现硬、碎、漏复杂情况,钻孔设计倾角大、孔斜要求高等特点,采用了新型设备（XDJ4型全液压岩心钻机）钻孔及低粘、低密度、润滑性好的冲洗液护壁方法,采取“控制钻机安装”、“减速法”或“小径导向增压纠斜法”等措施进行控斜及纠斜。有效地解决了易斜、易漏等斜孔施工问题,保质保量按期完成了施工任务,取得了很好的经济和社会效益。本文总结了该矿区大倾角钻孔施工中的部分经验和存在问题,为同类工程施工提供了较好的参考。  相似文献   

内蒙古科右前旗一带梅勒图组火山岩U-Pb测年及地球化学特征     

吴昊  陈满  龚全德  曹元宝  张力强  刘学元  杜士澍  秦越强  陈彪  张钧贵  孙浩  郝森 《地质通报》2019,38(11):1836-1845

通过对科右前旗一带梅勒图组火山岩LA-ICP-MS锆石U-Pb定年和元素地球化学分析,获得梅勒图组安山质晶屑熔结凝灰岩及安山岩的喷发年龄分别为125.6±1.6Ma和120.2±2.2Ma,指示梅勒图组火山岩的形成时代介于120～126Ma之间,形成于早白垩世中期。岩石具有高的SiO_2(60.4%～65.3%)和全碱(7.0%～9.5%)含量,铝饱和指数A/CNK为0.89～0.98,属于钾玄岩及高钾钙碱性系列;稀土元素总量为124×10~(-6)～169×10~(-6),(La/Yb)N值为5.83～13.4,负Eu异常微弱(δEu=0.84～1.05);在原始地幔标准化微量元素蛛网图上,样品富集Rb、Ba、Th、U、K、La、Nd,亏损Nb、Ta、P和Ti,Sr/Y值介于19.4～29.7之间。其岩石源区为富集地幔,岩浆上升过程中受到地壳物质的混染,岩石形成于板内伸展环境,其地球动力学背景可能与古太平洋板块的俯冲有关。  相似文献   

38 ka以来海南岛东海岸风成沙的粒度特征及其反映的沉积环境演变过程   总被引：4，自引：2，他引：2  

廖肖霞  李森  王贵勇  黎志伦 《中国沙漠》2009,29(6):1086-1092

 木堆地层剖面是海南岛东海岸沙丘与丘间地沉积过程的典型记录。在对该剖面地层高密度采样和光释光定年的基础上,对风成沙及相关沉积物的粒度组成、粒度参数和概率累积曲线及粒度敏感指标（SC/D值）的分析表明,风成沙、弱沙质古土壤、风水两相沉积物和泻湖相沉积物的粒度特征各异,反映38 ka BP来海南岛东海岸沉积环境经历了阶段Ⅰ（38～22 ka BP）、阶段Ⅱ（22～17 ka BP）、阶段Ⅲ（17～10 ka BP）、阶段Ⅳ（10 ka BP至今）等4个演变阶段,气候环境经历了暖湿-暖干-暖湿-暖干-暖湿-干凉-温湿-波动-暖湿的演变,沉积环境也经历了泻湖沉积-沙丘与丘间地沉积-沙丘固定成壤-流沙沉积的演变过程。  相似文献   

基于道路和城镇的区位优势度分析   总被引：1，自引：0，他引：1  

徐明德  王森 《世界地理研究》2009,18(4):91-99

区位优势度是反映区域经济、社会发展现状和潜力的重要指标。从影响区域经济与社会发展的主要因素道路与城镇出发,进行区位优势度理论与方法研究。确定交通网络密度、交通干线影响度、城镇影响度为区位优势度研究的基本指标;根据交通和城镇对区域社会经济影响的方式,基于网格的思想,建立了交通网络密度、交通干线影响度、城镇影响度模型及平方根法的区位优势度模型;利用GIS和网格技术实现了区位优势度各模型的计算。以泽州县全域为研究对象,应用所建立的模型与采用的技术方法进行验证性分析,其结果与泽州当地实际情况吻合较好,表明所建立的模型与技术方法是合理性可行的。  相似文献   

Changes in plant species composition and diversity of alpine Kobresia (Kobresia pygmaea) steppe meadow at different stages of desertification in the North Tibetan plateau     

XingHu Wei  Ping Yang  Sen Li  YuXiang Dong  ChunLai Zhang 《寒旱区科学》2009,1(1):0071-0079

The impacts of desertification on the vegetation composition, structure, and species diversity of alpine Kobresia steppe meadow were evaluated in an area of severe desertification in Anduo County, Tibet Autonomous Region, northern China. We investigated and analyzed the floristic features of communities at four different stages of desertification (slight desertification [SLD], moderate desertification [MD], severe desertification [SD], and very severe desertification [VSD]). The composition and structure of the alpine Kobresia steppe meadow at the SLD site differed significantly from that at the MD, SD, and VSD sites. Species that were more drought resistant and inedible by livestock were the dominant species at the SD site. No plants were found in the shifting dunes of the VSD site. Species diversity also decreased with increasing desertification. The SLD site had the largest mean number of species and individuals and the largest richness index; the MD grassland had the largest Shannon-Wiener index and evenness index, but the smallest Simpson’s index. The vegetation cover declined from 91.8% to 34.8% as desertification increased from SLD to SD, and reached 0% in VSD areas with shifting dunes.  相似文献   

Numerical modeling of wave equation by a truncated high-order finite-difference method   总被引：1，自引：0，他引：1  

Mrinal K.Sen 《地震学报(英文版)》2009,(2):205-213

Finite-difference methods with high-order accuracy have been utilized to improve the precision of numerical solution for partial differential equations.However, the computation cost generally increases linearly with increased order of accuracy.Upon examination of the finite-difference formulas for the first-order and second-order derivatives, and the staggered finite-difference formulas for the first-order derivative, we examine the variation of finite-difference coefficients with accuracy order and note th...  相似文献   

青年地震工作者在2008年汶川8.0级地震后科技支撑工作中的作用——对青年科技人员教育和培训的评估和讨论     

乔森  张东宁  陈瑶  肖春艳  封长华  刘爱文  陈学良 《国际地震动态》2009,(12):1-6

2008年5月12日汶川8.0级地震发生后,地震科技工作者立即投入到震后应急救援、现场余震监测、灾害评估、地震机理研究、震情趋势判定和现场科学考察中。其中,中国地震局地球物理研究所青年专家在地震精定位、震源机制及数字化地震参数计算、震源破裂过程、地震灾区区划图编制、余震破坏影响范围确定、地震社会学分析与应用等方面发挥了重要作用。截止到2008年12月,研究所40岁以下科技人员在各种科研刊物上发表了SCI、EI文章就有10余篇,参加现场工作人员41人次。青年科技人员能够迅速投入到震后科技支撑工作中,得益于研究所平时对青年科技人员教育和培训工作的重视,本文对此进行了评估和讨论。  相似文献   

Back Trajectory Analysis of Precipitation Chemistry in the Urban and Forest Areas of Istanbul,Turkey     

Levent Saylan  Hüseyin Toros  Orhan Sen 《洁净——土壤、空气、水》2009,37(2):132-135

There are many influences on precipitation chemistry and its variation. The transport paths of air masses before rainfall provide useful knowledge for evaluating and understanding the results of the analysis of the chemical compositions of precipitation. As a consequence, it is important to determine the variation of the chemical composition of rainwater by back trajectory analysis for estimating the source of the emissions. In this study, the rainwater samples were collected using specially designed collectors between November 1997 and June 1998 in the urban and forest areas of Istanbul. The rainwater samples were analyzed for major ion concentrations and pH. The volume‐weighed mean pH values were 5.8. The rainwater samples were classified to determine the source region of pollutants in rainwater using synoptic maps. In general, the results of the analysis on the chemical concentrations of precipitation during the measurement period showed that most of ions reached Istanbul from the directions of W‐SW, NW‐W, and NE‐N, respectively.  相似文献