科尔沁沙地典型沙丘植被光谱特性

摘要

采用Field Spec4(美国ASD)的便携式光谱仪对科尔沁5种典型沙丘植被的光谱曲线进行测量,并对其特征进行提取分析.结果表明,1)5种典型沙丘植被黄柳(Salix gordejevii)、冷蒿(Artemisia frigida)、麻黄(Herbal ephedrae)、差巴嘎蒿(Artemisia halodendron)和小叶锦鸡儿(Caragana microphylla)的光谱形态大致相同.根据原始光谱差异和多个光谱特征参数可以区分植被类型."红边斜率"由高到低依次为冷蒿(0.99%)>小叶锦鸡儿(0.68%)>黄柳(0.59%)>麻黄(0.58%)>差巴嘎蒿(0.56%).2)对差巴嘎蒿不同季节光谱反射率特性进行比较分析得知,随植被生长期推移,差巴嘎蒿呈现出"双峰"和"红移"现象,但该现象并不明显.由于研究区在7月份出现持续干旱,植被缺水严重,导致差巴嘎蒿的"红边位置"在7月6日出现微小浮动,显现两个"红边平台".3)分析不同覆盖度下差巴嘎蒿的光谱特性,差巴嘎蒿的导数光谱呈现"双峰"特性,且当覆盖度大于40%时,"红边位置"与覆盖度并无直接联系,但"红边斜率"与覆盖度呈正比关系.对不同覆盖度下差巴嘎蒿光谱可见光波段的连续统去除,得到吸收深度随覆盖度的增加而增大,吸收峰面积随覆盖度的增加而减小,对覆盖度敏感性参数比较可知,研究该地区差巴嘎蒿覆盖度变化优先考虑吸收峰面积.因此,基于植被高光谱特性的分析,对于今后利用遥感监测沙丘植被长势、植被分类识别及反演植被覆盖度等的应用提供重要的参考价值.%Field Spec4 portable spectrometer (ASD Company) was used to measure the spectral curves of typical vegetation on the sand dunes of Horqin Desert.The spectrum was extracted and analysed.The results revealed that: 1) spectral morphologies of five typical species (Salix gordejevii, Artemisia frigida, Herbal ephedrae, Artemisia halodendron, Caragana microphylla) were similar.The descending order of seeking "red-edge slope" was A.frigida (0.99%) > C.microphylla (0.68%) > S.gordejevii (0.59%) > H.ephedrae (0.58%) > A.halodendron (0.56%).However, the vegetation types can be distinguished according to the spectral differences and the parameters of the multiple spectral features.2) Spectral reflectance characteristics of A.halodendron in different seasons changed with vegetation growth stages.Although this species showed "twin peaks" and "red shift", these phenomena were not clearly observed.Because the study area appeared to be persistently exposed to drought in July, water shortage in vegetation was severe, which led to the reduction of 'red edge position' of A.halodendron to tiny dots on July 6 that appeared as two 'red edge platforms'.3) The analysis of spectral characteristics of A.halodendron at different coverage revealed that the derivative spectra represented 'twin peaks'.Moreover, when the coverage was more than 40%, the 'red-edge position' and the coverage were not directly linked, but the canopy coverage was proportional to the 'red-edge slope'.Removal of the visible band revealed an increase in absorption depth and decrease in absorption peak area of A.halodendron with increasing coverage.A comparison of coverage-sensitive parameters indicated that the area of the absorption peak was the preferred parameter for studying coverage variation of A.halodendron in this region.Therefore, analysis of vegetation hyperspectral characteristics provide an important reference value for the application of remote sensing-based monitoring of vegetation characteristics, such as growth, vegetation classification, and vegetation cover.