那曲典型草地植被光谱特征分析

遥感是大尺度生态研究的重要工具之一,而地面植物群落特征与其光谱特征之间的关系是解译遥感影像的关键。地面实测数据由于其高空间分辨率和高光谱分辨率,能够准确反映地物光谱信息,可以用来指导卫星遥感解译工作,同时为遥感监测草地退化、草地模型建立等提供数据支持。选取西藏那曲地区的优势植被类型作为研究对象,利用ASD FieldSpec 3便携式光谱仪测定优势种的冠层光谱并进行比较,并取其中一种优势种测量其在不同覆盖度和不同生长期的光谱反射特点。研究结果表明:①不同植被群落冠层光谱具有特殊的光谱曲线,可见光波段光谱反射率依次是紫花针茅、小嵩草和藏北嵩草,近红外波段光谱反射率则依次是小嵩草、藏北嵩草和紫花针茅;红边位置可以识别藏北嵩草,但是不能区分小嵩草和紫花针茅;②不同覆盖度的小嵩草红边、“绿峰”位置不随覆盖度的变化而发生变化;连续统去除后得到吸收深度随覆盖度的增加而变大,吸收峰面积随覆盖度的增加而增加;③小嵩草衰退期内,在可见光波段和红边波段,冠层光谱反射率随着叶绿素含量的减少而下降,出现“红边蓝移,绿峰下降”的现象。

Research on Spectral Reflectance Characteristics for Naqu Typical Grassland

Remote sensing is one of the important Methods for the large\|scale ecological research.The relationship between terrestrial plant community characteristics and their spectral characteristics is the key to interpret  remote sensing images.Because of its high spatial and spectral resolutions,ground experimental data would be an accurate reflection of spectral information of surface features.So as a good guide for satellite remote sensing interetation,ground experimental data can provide supporting data for remote sensing monitoring of grassland degradation and building of grassland model.This study selected the dominant vegetation types of the Naqu Prefecture in Tibet ,the canopy spectra measuring by ASD Field Spec 3.One of the dominant species ,as an example measured in different coverage of different period.The results show that:①Canopy spectra of different vegetation communities with special spectral curve,the visible bands spectral reflectance turn Stipa purpurea,Kobresia pygmaea ,K.tibetica,near\|infrared bands spectral reflectance in turn is K.pygmaea,K.tibetica,Stipa purpurea;red edge position can be identified the K.tibetica,but not be able to distinguish between K.pygmaea and Stipa purpurea;②The position of K.pygmaea's red edge,green peak does not change with the increase of coverage;Continuum removal absorption depth and area increased with degree of coverage;③In the recession period,the visible and red edge band,Canopy spectral reflectance decreases with the reduction of the chlorophyll content decreased,becoming “Red edge blue shift,the green peak decline”.