青海湖布哈河流域树轮宽度指数与NDVI植被指数的关系   总被引：4，自引：2，他引：2  

汪青春  时兴合  刘义花  秦宁生  邵雪梅 《冰川冻土》2012,34(6):1424-1432

利用来自青海湖流域乌兰和天峻的树轮指数和1982-2003年逐月标准化植被指数(NDVI)数据及气候数据, 在分析树轮指数及草地NDVI与气候因子关系的基础上, 探讨了树轮宽度指数序列与青海湖布哈河流域草地NDVI之间的关系.结果表明: 树轮宽度指数及草地NDVI主要受6-8月份的水热条件的影响, 温度与同期树轮宽度指数及草地NDVI具有较高的正相关, 而降水的影响存在滞后性.树木年轮指数序列与6-8月草地NDVI有显著的相关关系, 与8月份的NDVI相关性最强.树轮指数与草地NDVI间的显著相关性为研究该地区草地过去的动态变化提供了基础, 利用乌兰和天峻的两条树轮指数重建了8月份NDVI的千年变化.  相似文献   

半干旱区城镇周边防沙——以内蒙古乌审旗达布察克镇为例     

吴晓旭  邹学勇  张艺磊 《中国沙漠》2013,33(1):53-64

中国半干旱区城镇众多,风沙灾害频发,开展城镇风沙灾害防治研究势在必行。以毛乌素沙地的乌审旗达布察克镇为例,对其周边沙尘源地和植被进行实地调查;在此基础上,结合单项植物、机械沙障防风原理的风洞模拟结果,提出各种沙尘源地亚类防沙治沙措施的合理配置。根据建立半干旱区城镇防沙工程体系的原则以及城镇周边不同下垫面的防沙治沙措施配置,达布察克镇防沙治沙模式可以概括为城镇周边的“三圈模式”。第一圈是以达布察克镇为核心的绿化景观带,这一圈层大致位于达布察克镇以外600~900 m宽度范围内。第二圈层为沙丘（地）封禁与农牧业生产区,包括两个次级圈层：设施农业次级圈层的宽度约为1 km;远郊沙丘（地）封禁与农牧户独立生产次级圈层的范围较大,这一次级圈层的显著特点是大面积用于生态环境建设和保护,小面积用于农牧业生产。第三圈层是沙丘（地）封禁保护圈。该圈层位于乌审旗的西北位置,圈层内主要包括流动、半流动沙丘链以及平坦流沙地,是达布察克镇上风向主要的沙尘源地,应按照防沙治沙原理对其进行封禁与保护。  相似文献   

利用树轮宽度资料重建天山中段南坡巴仑台地区过去645年来的降水变化   总被引：1，自引：0，他引：1  

张同文  王丽丽  袁玉江  魏文寿  喻树龙  张瑞波  陈峰  尚华明  范子昂 《地理科学》2011,31(2):251-256

在分析树木生长对气候要素响应的基础上,利用采自天山中段南坡夫斯坦沟的雪岭云杉树轮宽度年表,重建了巴仑台地区1360~2004A.D.当年7月至次年6月的降水量序列,方差解释量达53%(调整自由度后为52%)。交叉检验结果表明重建方程稳定可信。过去645a以来,巴仑台地区的降水量变化存在12个偏少阶段和12个偏多阶段。巴仑台地区降水量重建序列存在10.7~11、6.7和2.1a的显著准周期及16.5~17.2和2.4~6.6a的较显著准周期,并且在1496A.D.前后发生了降水量由少向多的突变。  相似文献   

Late Holocene upper bounds of flood magnitudes and twentieth century large floods in the ungauged, hyperarid alluvial Nahal Arava, Israel   总被引：1，自引：0，他引：1  

Yael Jacoby  Tamir Grodek  Yehouda Enzel  Naomi Porat  Eric V. McDonald  Ofer Dahan   《Geomorphology》2008,95(3-4):274-294

The impact of large twentieth century floods on the riparian vegetation and channel morphology of the relatively wide anabranching and braided Nahal Arava, southern Israel, was documented as part of developing tools to (a) identify recent large floods, (b) determine these flood's respective magnitudes in alluvial ungauged streams, and (c) determine long-term upper bounds to flood stages and magnitudes. Along most of its course Nahal Paran, a major tributary that impacts the morphology, floods and sediments of Nahal Arava at the study reach, is a coarse-gravel, braided ephemeral stream. Downstream of the Arava–Paran confluence, aeolian and fluvial sand delivered from eastern Arava valley alters the channel morphology. The sand has accreted up to 2.5 m above the distinct current channels, facilitating the recording of large floods. This sand enhances the establishment of denser riparian vegetation (mainly Tamarix nilotica and Haloxylon persicum) that interacts with floods and affects stream morphology. A temporal association was found between specific floods recorded upstream and tree-ring ages of re-growth of flood-damaged tamarix trees (‘Sigafoos trees’) in the past 30 years. This association can be utilized for developing a twentieth century flood chronology in hyperarid ungauged basins in the region. The minimum magnitude of the largest flood that covered the entire channel width, estimated from flood deposits, is approximately 1700–1800 m³s^− 1. This is a larger magnitude than the largest gauged flood of 1150 m³s^− 1 that occurred in 1970 about 30 km upstream in Nahal Paran. Our estimation agrees with flood magnitude estimated from the regional envelope curve of the largest floods. Based on Holocene alluvial stratigraphy and OSL dating in the study reach we also conclude that flood stages did not reach the late Holocene ( 2.2 ka) surface and therefore we estimate a non-exceedance upper bound of  2000 m³s^− 1 flood magnitudes for Nahal Arava during that interval. This study indicates that in unfavorable areas the combination of hydrology, fluvial morphology and botanic evidence can increase our understanding of ungauged basins and give information crucial for hydrology planning.  相似文献   

一种启发式有环河系自动分级算法   总被引：2，自引：0，他引：2  

郝志伟  李成名  殷勇  武鹏达  吴伟 《测绘通报》2017,(10):68-73

在地图综合中,河流分级是对水系要素表达的重点也是技术难点,对精确性和计算速度都有较高的要求。目前对河系分级的研究中,已有分级算法的效率较低,且鲜有针对有环河系的分级。基于此,本文建立了河系分级的属性规则、几何规则、环规则,对河系中存在的不同环类型进行了分类处理,且在求取河流最长路径时,运用启发式算法迭代计算,实现了河系的自动分级。实际河系数据试验表明,该算法能在对有环河系的处理中取得良好的效果,提高了河系分级的计算效率和准确度。  相似文献   

双主卷扬配合“环形道活门机构”的快速提下钻系统          下载免费PDF全文

田炯  宋伟  刘虎  耿建璞  赵文涛  张西坤  高占听 《探矿工程》2017,44(1):61-64

为了提高快速提升钻具更换钻具的能力,研制了SPT-600D型拖车钻机。该钻机配置了SPS-600型双卷扬钻机及“环形道活门机构”。试验及应用情况表明,双卷扬配合“环形道活门机构”能够快速提升钻具更换钻具,缩短钻井施工的时间,可实现水文水井施工优质、高效、快速的要求。  相似文献   

水工环地质勘查技术的实际应用探讨     

王志强 《地质灾害与环境保护》2017,28(1)

随着社会经济的快速发展,地质勘查工作逐渐完善,其中水工环地质勘查是较为基础的工作,其重要性日益显著,但水工环地质勘查在发展过程中受诸多因素的制约,其技术不能满足地质勘查的需求,也不能满足经济发展的需要。在此基础上,本文将分析水工环地质勘查技术的概况,并阐述水工环地质勘查技术的实际应用,旨在提高水工环地质勘查技术应用的能力,促进水工环地质勘查工作的有序开展。  相似文献   

汶川地震高速远程滑坡机制实验研究   总被引：5，自引：0，他引：5       下载免费PDF全文

孙萍  汪发武  殷跃平  吴树仁 《地震地质》2010,32(1):98

汶川大地震触发了多处高速远程滑坡,导致了大量的人员伤亡及财产损失。其中,东河口滑坡是这次地震触发的最为典型的高速远程滑坡之一,同时也是目前备受关注、争论颇多的滑坡之一。野外调研结果表明,该滑坡的成因和动力特征主要包括震裂溃屈、水平抛射、碎屑流化和振动液化等4个方面。为了对该滑坡滑动过程中的振动液化这一动力特征进行模拟再现,在东河口滑坡体上采集了具有代表性的滑带土作为试验样品,并以该地震时的实测地震波作为动力输入,利用目前国际上最先进的DPRI环剪试验机,对滑坡滑动过程中的振动液化现象进行了一系列环剪试验研究。结果表明,地震作用过程中,发生在滑坡潜在滑面上的振动液化现象是导致高速远程滑坡产生的一个重要因素;伴随着振动液化过程,滑体的剪切强度迅速降低并产生逐渐增大的剪切位移,为高速远程滑坡的形成提供了条件  相似文献   

ORPOM model for optimum distribution of tree ring sampling based on the climate observation network     

Long M  TingXi Liu  YanYun Luo  HongLan Ji  ShiQiang Li  JunXiao Shi 《寒旱区科学》2010,2(6):0547-0554

Tree ring dating plays an important role in obtaining past climate information.The fundamental study of obtaining tree ring samples in typical climate regions is particularly essential.The optimum distribution of tree ring sampling sites based on climate information from the Climate Observation Network(ORPOM model) is presented in this article.In this setup,the tree rings in a typical region are used for surface representation,by applying excellent correlation with the climate information as the main principle.Taking the Horqin Sandy Land in the cold and arid region of China as an example,the optimum distribution range of the tree ring sampling sites was obtained through the application of the ORPOM model,which is considered a reasonably practical scheme.  相似文献   

Frequency and variability of missing tree rings along the stems of Pinus halepensis and Pinus pinea from a semiarid site in SE Spain     

K. Novak  M. de Luis  K. ?ufarJ. Raventós 《Journal of Arid Environments》2011,75(5):494-498

We studied the occurrence of missing rings (MR) around and along the stems of three Pinus halepensis and three Pinus pinea trees growing in a semiarid Mediterranean site in SE Spain. Tree-ring analyses were performed along 8 radii on stem discs taken at 1 m distances from the base to the top of the trees. The tree rings analysed showed that 19% were missing in P. halepensis and 10% in P. pinea. MR were recorded in 61% of P. halepensis and 24% of P. pinea in the years analysed. Dry conditions from January to May and high late winter to spring temperatures seem to be the main climatic elements promoting MR in both species. In our research into P. halepensis, the frequency of MR gradually decreased from the bottom upward, but no such pattern was observed in P. pinea. Most tree rings were missing only locally (LMR), indicating that wood formation occurred every year in at least some part of a tree, and the tree rings were often discontinuous around and along the stem. Since the frequency of LMR greatly varies around and along the stem, our results suggest that serial sectioning along the stem provides more information on wood formation and responses of trees to environment than studying the samples at breast height only. The disadvantage of the technique is that, as in our study case, research is based on a limited sample size, since it requires destructive sampling with tree felling, which is not usually possible or desirable on highly vulnerable semiarid forest ecosystems.  相似文献