上海盐沼植被的多季相地面光谱测量与分析

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.研究选择上海崇明东滩候鸟自然保护区的盐沼植被为研究对象,使用ASD便携式地物光谱仪测定芦苇、互花米草、海三棱藨草和糙叶苔草4类主要群落的春、夏、秋各季冠层反射光谱,并计算生成350～1000nm的反射率曲线的一阶导数曲线,在此基础上分析反射率与一阶导数曲线在可见光与近红外波段以及物候特征的“绿峰”和“红边”等波段的差异.分析显示,不同盐沼群落在各生长季都有较独特的光谱特征,四类盐沼群落的光谱特征在季相上表现各异.上海地区盐沼植被各类群落的遥感识别和分类的适宜季相不尽相同,应用多季相影像进行综合分类可取得较好的效果.研究结果可为遥感监测外来种互花米草的空间分布与动态提供技术支撑,为高光谱遥感的影像判读和解译分类以及盐沼植被制图提供科学依据.

AMeasuring and analyzing of the multi-seasonal spectral characteristics for saltmarsh vegetation in Shanghai

Remote sensing technology has become the primary tool for ecological research at large scales,but there is a major problem in differentiating between different spectra for the same vegetation and the same spectra for different vegetation,when classifying saltmarsh vegetation in remotely sensed images in Shanghai.The spectral characteristics of the saltmarsh vegetation canopy,including four main communities: Phragmites australis community,Spartina alterniflora community,Scirpus mariqueter community and Carex scabrifolia community,were measured by a ground FieldSpec~(TM) Pro JR spectroradiometer,in the Chongming Dongtan Natural Reserve.The spectral data were converted to the reflectance curves,and their first derivative curves between 350nm and 1000nm were calculated.The differences in the reflectance and first derivative curves were then analyzed, with particular attention paid to the characteristics in the bands of visible,near infrared,"green peak" and "red edge".The results from this study showed that the different saltmarsh communities had different and rather unique spectral characteristics during the three seasons studied(spring,summer and autumn).As well,the differences among the spectral characteristics during the three seasons for these four communities were not the same.It is proposed that the optimal strategy for classifying the saltmarsh vegetation may be through the integration and analysis of multi-seasonal images.The results from this study can serve as a tool for monitoring the distribution pattern and dynamics of the exotic plant Spartina alterniflora,as well as to provide a basis for the judgment and interpretation of the hyper-spectral image,and for the mapping of saltmarsh vegetation.