Influence of groundwater level change on vegetation coverage and their spatial variation in arid regions   总被引：3，自引：0，他引：3  

SULTAN Danyar  SONG Yudong  MARINA Jumakeld 《地理学报》2004,14(3):323-329

Sampling and testing are conducted on groundwater depth and vegetation coverage in the 670 km2 of the Sangong River Basin and semi-variance function analysis is made afterwards on the data obtained by the application of geo-statistics. Results showed that the variance curve of the groundwater depth and vegetation coverage displays an exponential model. Analysis of sampling data in 2003 indicates that the groundwater depth and vegetation coverage change similarly in space in this area. The Sangong River Basin is composed of upper oasis, middle ecotone and lower sand dune. In oasis and ecotone, influenced by irrigation of the adjoining oasis, groundwater level has been raised and soil water content also increased compared with sand dune nearby, vegetation developed well. But in the lower reaches of the Sangong River Basin, because of descending of groundwater level, soil water content decreased and vegetation degenerated. From oasis to abandoned land and desert grassland, vegetation coverage and groundwater level changed greatly with significant difference respectively in spatial variation. Distinct but similar spatial variability exists among the groundwater depth and vegetation coverage in the study area, namely, the vegetation coverage decreasing (increasing) as the groundwater depth increases (decreases). This illustrates the great dependence of vegetation coverage on groundwater depth in arid regions and further implies that among the great number of factors affecting vegetation coverage in arid regions, groundwater depth turns out to be the most determinant one.  相似文献   

Covering Wildfires: Media Emphasis and Silence after the Carlton and Okanogan Complex Wildfires     

Alissa Cordner  Eliana Schwartz 《社会与自然资源》2019,32(5):489-507

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基于像元二分模型的地表植被覆盖度估算模块化设计与实现     

赵威成  张红华  马福义  叶欣 《北京测绘》2020,(3):285-288

地表植被覆盖度是的一种应用广泛的定量遥感产品,在水文、生态、区域变化等方面都具有重要的意义。像元二分模型是应用最多的一种遥感估算地表覆盖度的方法。目前,用遥感的方法进行地表植被覆盖度估算没有完整、系统的工具,用户只能逐步进行操作,效率低下,鉴于上述情况,本文运用IDL交互式数据语言,基于ENVI二次开发了一个植被覆盖度估算程序,取得了一定的成效,对遥感定量产品的生产、应用具有一定意义。  相似文献   

Synergetic efficiency of Lidar and WorldView-2 for 3D urban cartography in Northeast Mexico     

Fabiola D. Yépez Rincón  Diego F. Lozano García 《国际地球制图》2019,34(2):164-178

Three-dimensional urban cartography is needed for city changes’ assessment. The variety of studies using 3D calculations of urban elements grows each year. Building and vegetation volumes are necessary to assess and understand spatio-temporal urban changeable environments. However, there are technical questions as to which method can improve 3D urban cartographic accuracy. The innovative part of this current study is the creation of a six-band hybrid obtained from LIDAR and WorldView2 synergy. Two different enhancement algorithms demonstrated the most important spectral features for the urban development and vegetation classes. Results indicated an improvement in accuracy by up to 21.3%, according to the Kappa coefficient. Both infra-red band and intensity band were the most significant, according to the principal components analysis. The synergy delimited classes and polygons, as well as the direct display of information regarding heights of elements and improving the extraction of roads, buildings and vegetation classes.  相似文献   

基于时序NDVI的昭觉植被覆盖度变化研究   总被引：1，自引：0，他引：1  

陈江玲  徐京华  李国明  王渊博  武文娟 《测绘与空间地理信息》2016,(11)

归一化植被指数(NDVI)能精确地反映植被绿度、光合作用强度,在一定程度上反映着植被的演化信息,是评价生态环境状况的重要指标之一。本文利用Landsat TM数据分别对昭觉地区2009年和2014年的NDVI进行计算,并分别利用均值法、像元二分模型及NDVI差值植被指数对研究区域植被覆盖变化进行定量分析,结果表明:昭觉县NDVI均值上升了11.6%,植被覆盖度中极度改善的面积比例约占38%,昭觉县整体NDVI植被覆盖度显著提高,并对其变化原因进行简要分析,为生态环境建设提供决策依据。  相似文献   

Measuring and modeling Russian newspaper coverage of climate change     

《Global Environmental Change》2016

As a significant emitter of greenhouse gases and a country rich in fossil fuels, Russia plays a crucial role in achieving a comprehensive solution to climate-related challenges. Yet, Russia's official position on climate change has varied considerably since the beginning of global negotiations, with the country playing everything from policy leader to laggard. While there are a number factors that shape domestic policy positions, this study offers a comprehensive investigation of newspaper coverage on climate change in Russia. How have Russian newspapers discussed the issue since the Yeltsin era? We approach this question by compiling the largest data set of Russian newspaper coverage to date, which includes 11,131 climate-related articles from 65 papers over a roughly 35 year period. After introducing a “computer assisted” approach to measure the core themes running through climate change coverage, we statistically evaluate the national- and newspaper-level factors associated with how coverage is framed, focusing attention on 23 high circulation papers over the period from 2000 to 2014. We find that national-level predictors—particularly economic conditions—are highly influential in determining whether climate change is covered and how the issue is framed, while paper-level factors such as the presence of an energy interest and ownership structure also have notable effects. Overall, this study offers a rich data set and useful methods to better understand the drivers of climate communication in Russia.  相似文献   

附有物理量和气象条件约束的光学卫星国土观测有效覆盖率评估     

巫兆聪  巫远  张熠  杨帆 《测绘学报》2016,45(7):841-849

传统光学卫星国土观测覆盖评估建立在卫星对地理想覆盖的基础上,并未考虑卫星存储、星地数据传输、观测时长等物理量及观测区域气象因素对于覆盖性能的影响。本文针对光学遥感卫星的国土观测需求.建立国土观测有效覆盖能力评估指标体系,根据卫星数据存储能力、星地数据传输能力、卫星单圈最大观测时长、卫星观测太阳高度角等性能参数,提出了基于物理性能约束下的有效覆盖计算方法。根据气象台站历年气象数据,提出了气象约束因子的计算方法。综合考虑卫星物理性能约束与观测区域气象约束,计算光学遥感卫星对地观测有效覆盖能力。最后根据专家设计的光学遥感卫星国土观测有效覆盖能力评估指标权重,利用层次分析法(AHP)评估光学遥感卫星系统对于国土观测的需求满足程度。试验结果表明,本文方法对于国土观测有效覆盖的估算和评价结果更加精确,更接近于国土观测的实际应用需求,为对地观测有效覆盖能力评估提供了一种更为精确的可行方案。  相似文献   

基于 ＲS 和 GIS 的土壤侵蚀强度快速分析: 以昌都市扎玉镇为例     

陆天启  陈圣波  范宪创  郭甜甜  涂媛  李亚洲 《世界地质》2016,35(4):1145-1150

以昌都市左贡县扎玉镇为例,选用中巴地球资源二号遥感数据、数字高程模型数据和土地利用类型数据,用遥感软件提取植被指数并进行密度分割,确定植被覆盖度,并对其进行分级; 用地理信息系统软件提取坡度信息,并对坡度进行分级; 在1∶ 5 万比例尺下修正已有的土地利用类型。结果统计扎玉镇 76. 26%的土壤处于轻度及以下侵蚀状态,强烈及以上的土壤侵蚀比例达 5. 48%,土壤侵蚀剧烈的地区主要分布在耕地部分,中度侵蚀的地区主要集中在林草地部分,因此土地利用合理化以及提高植被覆盖率可以有效减小土壤侵蚀强度。  相似文献   

基于客观分析的多源卫星叶绿素a浓度产品融合方法研究     

施英妮  张亭禄  石立坚  胡晓华  南明星 《海洋学报》2016,38(3):82-87

本文基于Aqua/MODIS、Terra/MODIS和Envisat/MERIS多源卫星叶绿素a浓度产品,研究了客观分析融合方法,制作了西北太平洋海域(0°~50°N,100°~150°E)叶绿素a浓度融合产品,并从有效数据空间覆盖率和产品精度两个方面对融合方法进行了评价。与单传感器以及欧洲太空局发布的GSM模型业务化融合产品相比,客观分析融合产品空间覆盖率明显提高;与收集的2002-2012年间叶绿素a浓度实测数据比较,GSM模型业务化融合产品的匹配数据点为578个,偏差为-0.20 mg/m3,均方根误差为0.37 mg/m3,客观分析法融合产品的匹配数据点为1432个,偏差为-0.21 mg/m3,均方根误差为0.36 mg/m3。结果表明:本文研究的客观分析融合方法在保证融合产品精度的同时可显著提高产品的空间覆盖率,在海洋水色融合应用前景广阔。  相似文献   

Experimental investigation of the effects of the coverage of helical strakes on the vortex-induced vibration response of a flexible riser     

《Applied Ocean Research》2016

The effects of different helical strake coverage on the vortex-induced vibration (VIV) of a model flexible riser were studied experimentally, with the aim of further improving the understanding of VIV responses. Uniform and linearly sheared currents were simulated to study response parameters such as non-dimensional displacement, fatigue damage, suppression efficiency, and the comprehensive evaluation is further studied. Test results of the bare model for a uniform current showed that the behavior of both the standing wave and traveling wave dominated VIV displacement. However, for a linearly sheared current, traveling wave behavior dominated VIV displacement in the high-velocity range. The results of the straked model tests indicated that the response was strongly dependent upon the amount of coverage of helical strakes. The flexible riser with 75% strake coverage gave the best comprehensive evaluation in a uniform current, and 50% strake coverage gave the best comprehensive evaluation in a linearly sheared current.  相似文献