用多角度光谱信息反演冬小麦叶绿素含量垂直分布

Extracting winter wheat chlorophyll concentration vertical distribution based on bidirectional canopy reflected spectrum

由于作物叶片具有一定的叶位空间垂直结构(倒一叶、倒二叶、倒三叶、倒四叶、倒五叶等),且存在不同叶位叶绿素等生化组分垂直分布的特性,该研究提出利用遥感数据反演作物养分垂直分布,尤其是作物中、下层信息的方法。运用多角度光谱信息,通过不同角度条件下,反映的作物上层、中层、下层信息的差异等通过构建基于不同观测天顶角条件下的冠层叶绿素反演指数的组合值,形成上层叶绿素反演光谱指数、中层叶绿素反演光谱指数和下层叶绿素反演光谱指数来反演作物叶绿素的垂直分布,达到了极显著的水平。表明运用基于多角度光谱信息的光谱指数组合能够较好的反演作物叶绿素含量的垂直分布。对于生产上迫切需要对作物中、下层叶片氮素或叶绿素状况的监测来指导适时和适量施肥,保证获得既定的作物产量和品质目标,提高肥料利用率有重要意义。

The objective of this study was to discuss the method of extracting dynamic growth information for foliage vertical layers by canopy spectral reflectance for improving the accuracy of quantitative remote sensing canopy chlorophyll concentration models, so as to provide a theoretic basis for monitoring the growth and development of winter wheat. The ratio of transformed chlorophyll absorption reflectance index（TCARI） to optimized soil-adjusted vegetation index （OSAVI） was named as canopy chlorophyll inversion index（CCII）, the values of CCII at nadir, ±20°,±30° view angles were selected and assembled named as bottom layer chlorophyll concentration inversion index （LBCI） for the inversion of chlorophyll concentration at vertical bottom layer; the values of CCII at nadir, ±30°, ±40° view angles were selected and assembled named as middle layer chlorophyll concentra- tion inversion index（MBCI） for the inversion of chlorophyll concentration at vertical middle layer; the values of CCII at ±50°, ±60° view angles were selected and assembled named as upper layer chlorophyll concentration inversion index（UBCi） for the inversion of chlorophyll concentration at vertical upper layer. The vertical chlorophyll concentration inversion can be used for monitoring the crop growth status and the management of fertilizer and irrigation.