荒漠-绿洲交错地带典型植被光谱特征研究

Research on the Spectral Characteristic of Typical Vegetation in Desert-Oasis Crisscross Zone

植被对区域生态环境保护具有重要意义,尤其是在荒漠-绿洲交错地带,植被对土壤保持、提高土地的抗剪切性能有重要意义,对土壤风蚀和荒漠化防治的影响作用较大,利用高光谱技术测定并分析荒漠-绿洲交错带典型植被的光谱特性,不仅能够指导区域的植被遥感分类,还能够对植被实行远程监控提供依据。研究借助美国Field Spec 4高分辨率地物光谱仪,在研究区采集棉花、柽柳、梭梭和盐穗木等四种典型植被不同条件下的光谱数据,在对数据进行归类、筛选及综合处理后,分别对原始数据进行FDR（一阶导数反射率）和RLR（倒数取对数反射率）变换。利用原始数据、FDR和RLR分别分析不同植物的光谱敏感波段和表达方式。结果表明：植物的光谱曲线具有类似的变化特征,植被种类不同在＂红边＂区和近红外780~1 260nm波段的表达方式区别较大;植物对可见光的吸收非常强烈,对不同波长的光吸收强弱变化会形成波峰和波谷;植物红边特征具有特殊性,蕴含植物自身的特有信息,三种方式的处理结果显示,光谱特征在经FDR计算后,植物光谱红边特征区差异性非常明显;利用三种不同方式处理后的光谱数据,分别来计算改进的植物NDVI值,经RLR变换后重新计算得到的NDVI值在植物不同种之间表现出较大差别,用于植物种类区分的效果明显。

Vegetations in desert play key a role in protecting eco-environment,especially in desert-oasis crisscross zone.Vegetations are of great significance in soil conservation and improving the shear resistance of land.Therefore,they can help to prevent soil from wind erosion and keep land from desertification.Analyzing the spectral data of typical vegetation in desert-oasis crisscross zone by using the hyper spectral technology can be a guidance for remote sensing vegetation classification and serve as the basis for remote vegetation monitoring.In our research,four kinds of typical vegetations have been selected：cotton,tamarix chinensis,Haloxylon ammodendronand Halostachys caspica.The researcher collected series of spectral data of different typical vegetations under different conditions with the help of Field Spec 4high resolution spectrometer.The collected data was classified,flitted and synthesized with two kinds of transform methods：FDR（First Order Derivative Reflectance）and RLR（Reciprocal Logarithmic Reflectance）transformation.And then three kinds of data were used in further research to analyze the sensitive spectrum band and expression of different vegetation.The result shows that the spectral curve of different vegetations show the same changing trend;different vegetation show different expression in＂red edge＂with the near infrared band of 780~1 260 nm.The visible light absorption of vegetation is very strong,and the difference of absorption extent causes peaks and troughs.The＂red edge＂characteristic is unique,which will carry the proper information of certain vegetation,and the result of different kinds of transformation show that FDR can express the red edge characteristic much better than other ways.At last,three ways were used to calculate NDVI,using the original spectral data,transforming spectral data with FDR and transforming spectral data with RLR.Result shows that the NDVI,which calculated by RLR can help to distinguish the type of vegetation with higher accuracy is.