岷江上游毛榛、辽东栎灌丛及3种人工幼林土壤种子库的比较   总被引：7，自引：0，他引：7  

刘文胜  曹敏  唐勇 《山地学报》2003,21(2):162-168

本文采用野外调查与萌发实验相结合的方法对岷江上游地区自然恢复的灌丛以及 3种人工林的土壤种子库状况进行了比较研究。结果显示 ,各样地土壤种子库的储量为 192 5 0～ 3 13 60粒 /(m2 × 10cm)之间 ,人工林的土壤种子库储量和物种数量都大于自然恢复的灌丛 ,其顺序为连香树Cercidiphyllum japonicum、油松Pinustabulaeformis混交林 >连香树林 >油松林 >毛榛Corylusmandshurica、辽东栎Quercusliaotungensis灌丛 ,各样地土壤种子库密度的垂直分布均为上层 >中层 >下层。在各样地土壤种子库的生活型组成中 ,乔木种类所占比例极少 ,而草本种类的数量较多。在灌丛的土壤种子库中 ,灌木的物种数量及其在种子库中所占的比例均大于人工林。大序醉鱼草Buddlejamacrostachya、喜阴悬钩子Rubusmesogaeus、华西绣线菊Spiraealaeta在种子库中的大量存在明显提高了灌木在各样地土壤种子库中所占的比例  相似文献   

滇西北亚高山针叶林、硬叶栎类林的树种多样性   总被引：2，自引：0，他引：2  

于洋  曹敏  刘文胜 《山地学报》2003,21(5):568-575

在滇西北香格里拉地区,以长苞冷杉(Abiesgeorgei)林、丽江云杉(Picealikiangensis)林作为亚高山针叶林的代表,以川滇高山栎(Quercusaquifolioides)林作为硬叶栎类林的代表,分别选择了6块样地,采用Shannon-Wiener多样性指数(H)、Simpson多样性指数的倒数(D')、Pielou均匀度指数(JH、JD)分别测定其树种多样性,并进行了比较研究。结果表明,三个森林类型的Shannon Wiener指数、Simpson指数的倒数、物种丰富度的顺序均为:长苞冷杉林>川滇高山栎林>丽江云杉林;而前两类森林的Pielou均匀度指数差异不大,但都高于丽江云杉林的均匀度指数值。滇西北的川滇高山栎具有很强的萌生能力。人工种植的亚高山针叶林的树种多样性较原始林低,需要较长时间的恢复过程。亚高山针叶林的存在极大地丰富了云南省的树种多样性,使云南植被的垂直地带性得到了充分体现。  相似文献   

叶碲铋矿研究中存在问题分析   总被引：1，自引：0，他引：1       下载免费PDF全文

刘玉琳胡旻  苗国均 《岩石矿物学杂志》2003,22(1):103-104

叶碲铋矿最初定名为wehrlite，结构式为Bi2 xTe3-x，后于1982年改名为pilsenite，结构式相应改为Bi4Te3。楚碲铋矿(BiTe)的成分介于原叶碲铋矿的成分范围之内。有些研究者仍用原成分确定叶碲铋矿或把楚碲铋矿当作叶碲铋矿，本文旨在提醒研究者注意，避免误用。  相似文献   

河道沿岸芦苇带对氨氮的削减特性研究   总被引：32，自引：0，他引：32       下载免费PDF全文

王超  王沛芳  唐劲松  杨敏 《水科学进展》2003,14(3):311-317

氨氮污染已成为我国江河湖库水质下降和水生态系统退化的重要因素之一.借助现场对比观测试验和理论分析的方法,研究不同季节氨氮对河流水质的影响规律,得到了雨洪初期汇流河流水质污染最为严重的结论.系统地研究了沿河岸芦苇带对氨氮的削减净化效应,得到了芦苇带吸附氨氮的主要影响因素为:芦苇生长期、水体污染物浓度、河道流速及气象条件.运用数值模拟和参数优化估算技术,确定氨氮在河道两岸有、无芦苇等植物条件下的衰减系数和削减量,分析了衰减系数的变化规律和削减量大小的影响因素,为河流水生态系统修复和水质预测预报提供科学依据.  相似文献   

Contemporary crustal deformation of the Chinese continent and tectonic block model   总被引：1，自引：0，他引：1  

Min Wang  Zhengkang Shen  Zhijun Niu  Zusheng Zhang  Hanrong Sun  Weijun Gan  Qi Wang  Qun Ren 《中国科学D辑(英文版)》2003,46(2):25-40

We obtain the preliminary result of crustal deformation velocity field for the Chinese continent by analyzing GPS data from the Crustal Motion Observation Network of China (CMONOC), particularly the data from the regional networks of CMONOC observed in 1999 and 2001. We delineate 9 technically active blocks and 2 broadly distributed deformation zones out of a dense GPS velocity field, and derive block motion Euler poles for the blocks and their relative motion rates. Our result reveals that there are 3 categories of deformation patterns in the Chinese continent. The first category, associated with the interior of the Tibetan Plateau and the Tianshan orogenic belt, shows broadly distributed deformation within the regions. The third category, associated with the Tarim Basin and the region east of the north-south seismic belt of China, shows block-like motion, with deformation accommodated along the block boundaries only. The second category, mainly associated with the borderland of the Tibetan Plateau, such as the Qaidam, Qilian, Xining (in eastern Qinghai), and the Diamond-shaped (in western Sichuan and Yunnan) blocks, has the deformation pattern between the first and the third, i.e. these regions appear to deform block-like, but with smaller sizes and less strength for the blocks. Based on the analysis of the lithospheric structures and the deformation patterns of the regions above, we come to the inference that the deformation modes of the Chinese continental crust are mainly controlled by the crustal structure. The crust of the eastern China and the Tarim Basin is mechanically strong, and its deformation takes the form of relative motion between rigid blocks. On the other hand, the northward indentation of the Indian plate into the Asia continent has created the uplift of the Tibetan Plateau and the Tianshan Mountains, thickened their crust, and raised the temperature in the crust. The lower crust thus has become ductile, evidenced in low seismic velocity and high electric conductivity observed. The brittle part of the crust, driven by the visco-plastic flow of the lower crust, deforms extensively at all scales. The regions of the second category located at the borderland of the Tibetan Plateau are at the transition zone between the regions of the first and the third categories in terms of the crustal structure. Driven by the lateral boundary forces, their deformation style is also between the two, in the form of block motion and deformation with smaller blocks and less internal strength.  相似文献   

Absence of Archean basement in the South Kunlun Block: Nd-Sr-O isotopic evidence from granitoids   总被引：3，自引：0，他引：3  

Chao Yuan  Min Sun  Mei-Fu Zhou  Hui Zhou  Wenjiao Xiao  Jiliang Li 《Island Arc》2003,12(1):13-21

Abstract   The West Kunlun mountain range along the northwestern margin of the Tibetan Plateau is crucial in understanding the early tectonic history of the region. It can be divided into the North and South Kunlun Blocks, of which the former is considered to be part of the Tarim Craton, whereas consensus was not reached on the nature and origin of the South Kunlun Block. Samples were collected from the 471 Ma Yirba Pluton, the 405 Ma North Kudi Pluton and the 214 Ma Arkarz Shan Intrusive Complex. These granitoids cover approximately 60% of the Kudi area in the South Kunlun Block. Sr, Nd, and O isotope compositions preclude significant involvement of mantle-derived magma in the genesis of these granitoids; therefore, they can be used to decipher the nature of lower–mid crust in the area. All samples give Mesoproterozoic Nd model ages (1.1–1.5 Ga) similar to those of the exposed metamorphic complex of this block but significantly different from those of the basement of the North Kunlun Block (2.8 Ga). This indicates that the South Kunlun Block does not have an Archean basement, and, thus, does not support the microcontinent model that suggests the South Kunlun Block was a microcontinent once separated from and later collided back with the North Kunlun Block.  相似文献   

Dinosaur tracks from the Cretaceous of South Korea: Distribution, occurrences and paleobiological significance   总被引：2，自引：0，他引：2  

Min Huh  Koo Geun Hwang  In Sung Paik  Chull Hwan Chung  Bo Seong Kim 《Island Arc》2003,12(2):132-144

Abstract   Abundant dinosaur fossils including dinosaur footprints, eggs and nests, teeth and bones have been found from the Cretaceous non-marine deposits of Korea. Among them, dinosaur tracks are the most distinctive, and some track sites are among the most famous in the world. Until now, 27 dinosaur track localities have been discovered from the Cretaceous strata in the Gyeongsang Basin and several small basins. Ornithopod tracks are most abundant at most Korean track sites, and most of them are identified as Caririchnium ; that is, large ornithopod footprints with wide hoof impressions. Most theropod tracks are found in Neungju Basin and they consist of various types of small or medium-sized bird-like footprints, and other large footprints. Sauropod tracks are also abundant in the Gyeongsang Basin. The sauropod tracks vary in size, shape, and pattern of trackway, and suggest that diverse sauropods existed in this area. These diverse tracks in South Korea suggest that various dinosaurs flourished at the margins of lakes distributed in the southern part of the Korean Peninsula during the Cretaceous.  相似文献   

Landslide susceptibility analysis using GIS and artificial neural network     

Saro Lee  Joo‐Hyung Ryu  Kyungduck Min  Joong‐Sun Won 《地球表面变化过程与地形》2003,28(12):1361-1376

The purpose of this study is to develop landslide susceptibility analysis techniques using an arti?cial neural network and to apply the newly developed techniques to the study area of Yongin in Korea. Landslide locations were identi?ed in the study area from interpretation of aerial photographs, ?eld survey data, and a spatial database of the topography, soil type and timber cover. The landslide‐related factors (slope, curvature, soil texture, soil drainage, soil effective thickness, timber age, and timber diameter) were extracted from the spatial database. Using those factors, landslide susceptibility was analysed by arti?cial neural network methods. The landslide susceptibility index was calculated by the back‐propagation method, which is a type of arti?cial neural network method, and the susceptibility map was made with a geographic information system (GIS) program. The results of the landslide susceptibility analysis were veri?ed using landslide location data. The validation results showed satisfactory agreement between the susceptibility map and the existing data on landslide location. A GIS was used to ef?ciently analyse the vast amount of data, and an arti?cial neural network to be an effective tool to maintain precision and accuracy. The results can be used to reduce hazards associated with landslides and to plan land use and construction. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

基于虚拟监控技术的机器人系统   总被引：2，自引：0，他引：2  

赵晓光  徐德  谭民 《武汉大学学报(信息科学版)》2003,28(2):233-237

介绍了一种虚拟现实技术(VR)与智能机器人监控技术协同作业的机器人系统，该系统使用虚拟现实技术建造具有良好交互性的人机界面，并且结合智能机器人监控技术，实现了虚拟监控操作。通过机器人系统，将虚拟操作结果作为一个整体对象投射到工作现场，完成了实际作业，并以水下机器人检查钻井平台水下部分的焊缝工作为背景，说明了本系统各种功能的实现过程。  相似文献   

基于先验知识的GIS路径寻优算法   总被引：2，自引：0，他引：2  

张连蓬  刘国林  江涛  李云岭  季民 《测绘科学》2003,28(3):27-29

针对地理信息系统中特定的两点路径寻优问题,提出了一种基于先验知识的快速搜索算法。该算法模拟人脑寻找路径的思维过程,首先针对实际问题建立先验知识库,在路径搜索过程中,利用知识库中的信息剪去不可能的搜索路径,构造出简化的查询树,从而大大提高最优路径的搜索速度。  相似文献