1999-2007年祁连山区植被指数时空变化

基于SPOTVGT-NDVI数据,结合累积平均法、均值法、趋势线分析和影像差异法,分析了祁连山地区植被时空变化。结果表明:祁连山区植被覆盖东多西少;1999年以来植被呈增加趋势,植被指数(NDVI)增速为1.1%/10a,东段增速(1.6%/10a)大于中段(1.4%/10a)和西段(0.6%/10a);NDVI年内月和旬变化曲线均呈单峰型,7～8月达到最大。7～8月雨热达到最佳,适宜植物的生长;而从10月到翌年2月祁连山草地处于枯黄期;3～4月草地处于返青期,植物生长缓慢,NDVI都较低。祁连山NDVI增加和减少的面积分别占总面积的37.39%和10.95%。植被覆盖增加的地区主要分布在高山和亚高山森林草地,东段、中段、西段NDVI最大增加量分别为0.15,0.21和0.12。植被覆盖减少的地区主要分布在河流河谷以及青海湖周边,东段、中段、西段NDVI最大减少量分别为0.19,0.28和0.17。     

Temporal and spatial changes of chlorophyll fluorescence as a basis for early and precise detection of leaf rust and powdery mildew infections in wheat leaves

Temporal and spatial changes in parameters of fast chlorophyll fluorescence kinetics (ground fluorescence, Fo and maximal fluorescence, Fm) and red/NIR reflectance were assessed with a Pulse-Amplitude-Modulated (PAM)-Imaging system on a daily basis over a period of 2 weeks following inoculation of wheat leaves with powdery mildew and leaf rust. The early detection of these infections by means of fluorescence imaging was possible 2–3 days before visual symptoms or significant changes in normalised-differenced-vegetation index (NDVI) became apparent. The initial infection of both fungi caused an increase in Fo and decrease in photochemical efficiency (Fv/Fm, Fv/Fo). The appearance and development of fungal pustules was accompanied by reduction in Fo and Fm. This resulted mainly from lower absorption of fluorescence exciting light by the leaf mesophyll due to the shielding effect of fungal mycelium, and to lesser extent from the chlorophyll breakdown underneath pustules. Among the evaluated fluorescence parameters, Fv/Fo displayed the most pronounced response to both kinds of infection. Mildew infection influenced chlorophyll fluorescence neither in the direct vicinity of mycelium nor in the apparently healthy leaf regions. Rust infected plants, in contrast, displayed significantly reduced photochemical efficiency Fv/Fm and Fv/Fo in chlorotic tissue around pustules. The same, but less pronounced tendency was found in the apparently healthy regions of rust infected leaves in the last days of the experiment. Dark adaptation of leaves proved to be necessary for accurate detection of both pathogen infections by means of fluorescence imaging. Additional experiments are needed to estimate the potential of this technique for remote sensing under field conditions.     

偏最小二乘在遥感监测西藏草地生物量上的应用

在多年平均年最大归一化植被指数(NDVI)的基础上,结合西藏地区年降雨量、年积温等气象资料,利用偏最小二乘(partial least squares, PLS)回归方法对数据进行分析并建立西藏地区草地生物量与归一化植被指数、降雨量等解释变量的回归估测模型.并和一般最小二乘法(ordinary least squares, OLS)中的逐步回归法(Stepwise)相比较.结果表明:草地生物量与年最大NDVI值和年降雨量有很强的相关性,偏最小二乘回归在拟合及估测效果上均优于一般最小二乘的逐步回归法,回归方程的相关系数为0.89,取得了较为可靠的结果.偏最小二乘回归在解释变量多、样本个数少、变量间存在多重共线性时尤为有效,为遥感监测植被生物量时的数据处理提供了新的途径.     

基于统计算法的森林资源变化检测的研究

以汪清林业局金沟岭林场为研究区域,按照两期影像归一化植被指数（NDVI）的差值服从正态分布的规律,应用概率论中3a原则检测森林资源变化状况。结果表明：利用两期影像NDVI差值进行检测,可检测出地类发生明显变化地段的资源变化状态,并可精确定位,而对于小强度择伐、透光伐等未发生明显地类变化的地段检测不够精确。     

基于Landsat的四川盆地NDVI变化研究——以眉山市东坡区和仁寿县为例

利用Landsat遥感数据,计算归一化植被指数（NDVI）并结合空间分析技术,研究了分别代表四川盆地平原和丘陵地貌的眉山市东坡区和仁寿县的NDVI动态演变特征。结果表明,NDVI呈波动变化,总体表现为上升;除1975年外,仁寿县均高于东坡区,即丘陵区均大于平原区;NDVI变化与环境政策、农业政策和农村经济状况密切相关,而丘陵区生态最为脆弱,水是最重要的限制因子。     

基于MODIS-NDVI的水稻遥感估产——以重庆三峡库区为例

以重庆三峡库区为研究对象,利用MODIS-NDVI为遥感特征参量,分析水稻关键生育期的长势并对产量进行预测.考虑到NDVI数据饱和的局限性,选取库区各区县0.2～0.8范围内的NDVI值与作物产量建立水稻估产模型,进行相关性分析,估算出的水稻产量表明,各关键生育期的相关性系数均在0.75以上,且与实产数据对比表明,各区县预测精度均在90%以上,可见利用MODIS-NDVI能够有效的进行水稻监测和估产.     

基于遥感影像的重庆市城市热场环境效应研究

利用Landsat TM 影像定量反演了重庆市的地表温度(LST)和植被指数(NDVI),引入剖面分析方法来研究二者的相关性,并建立了不同土地利用类型和不同多样性水平上的线性回归函数.结果表明:重庆市的热场环境明显,地表温度和植被指数在总体上呈线性负相关,地表温度最高值不是分布在城市中心的商务区,而是出现在城市边缘的工业企业用地区;建设用地的热效应最明显;城市的号观多样性对热环境是反向的.     

Monitoring the effects of land use and cover changes on net primary production: A case study in China's Yongding River basin

Changing land uses and cover types influence vegetation composition and health, so understanding the effects of these changes on net primary production (NPP) provides an important tool for monitoring ecosystem responses to environmental change. Using remote-sensing images and precipitation, temperature, and total solar radiation data from 1978, 1987, 2000, and 2005, and a light utilization efficiency model, we studied the effects of changes in these parameters and land use and cover types on NPP in China's Yongding River basin. We determined the NDVI of vegetation in the basin, and used these results to estimate the NPP of vegetation in the basin and the influence of land use and cover type changes on NPP under two climate scenarios: one in which the precipitation and temperature of the previous period remain unchanged into the following period, that is, use the climate in 1978, 1987 and 2000 to analyze NPP data in 1987, 2000 and 2005 respectively, and another in which both parameters remain constant at their 1978 values throughout the study period. With the climate unchanged from the former period, NPP in 1987 decreased compared with the 1978 value by 20–50 gC/m², and then increased by more than 40 gC/m² in western and central parts of the basin from 1987 to 2000. From 2000 to 2005, NPP decreased in the northwestern, northern, and eastern parts of the basin. With climate unchanged from 1978 to 2005, NPP increased from 1987 to 2000 by from 10 to 30 gC/m² in most areas. From 2000 to 2005, some farmland in western and northwestern parts of the basin and some forest land were converted into grassland, decreasing NPP by 40–50 gC/m².     

深圳城市绿地空间分布遥感分析

选择归一化植被指数对深圳市城市绿地空间分布进行了研究,结果表明,深圳市整个市区绿地分布不均衡,而且在不同的区域植被分布差异很显著。     

基于RS与GIS的北京市植被覆盖度变化研究

选用对植被状态表征较好的归一化植被指数(NDVI),在GIS和RS工具支持下, 选用多时相北京Landsat TM遥感影像,解译和分析出NDVI的时空变化特征,利用植被指数与植被覆盖度的关系及遥感测量法测算植被覆盖度.结果显示:北京市整体植被覆盖度呈增长趋势,市区植被覆盖度变化不大,部分区县植被覆盖度则由于城镇化推进而略有减少.