考虑冠层垂直结构的湿生芦苇氮素遥感监测研究

It is important to monitor nitrogen of phragmites quickly for control water pollution of wetland and lake, and study nitrogen cycle of wetland and lake ecosystem. However, first, traditional method of monitoring nitrogen is time-consuming. Second, canopy nitrogen of phragmites is non-uniform vertical distribution, but it is rarely reported for canopy nitrogen vertical distribution characteristics and description method. Third, the vertical distribution characteristic of canopy nitrogen was rarely considered in vegetable nitrogen inversion model using remote sensing, which limited the monitoring precision of the vegetation canopy total nitrogen content. Therefore, the goal of this project is how to build a nitrogen version model basing on canopy nitrogen vertical distribution characteristics by hyperspectral remote sensing, and finally to realize the rapid and accurate monitoring nitrogen of phragmites. Based on Manual control and field experiment, three researches were conducted, including: 1) to study the characteristics of phragmites canopy nitrogen vertical distribution and build mathematical model of phragmites canopy nitrogen; 2) to study spectral response characteristics of phragmites canopy nitrogen and effective depth of canopy; 3) to build the nitrogen version model basing on canopy nitrogen vertical distribution characteristics by hyperspectral remote sensing. The study results can offer the theoretical basis for studying nitrogen cycle of wetland and lake ecosystem and controlling water pollution of wetland and lake. Besides, they can provide theoretical support for real-time harvest phragmites in phytoremediation projects.

湿生芦苇氮素的快速监测对湿地恢复和水体富营养化治理及湖泊/湿地生态系统氮循环研究具有重要意义。目前芦苇氮素的监测方法（人工野外采样，实验室分析法）耗时费力、时效性差，而遥感技术具有快速、无损获取地物信息的特点，但现有的植被冠层氮素遥感监测方法很少考虑氮素垂直分布特征，限制了植被冠层总体氮素含量的监测精度。本项目通过设置人工控制小区实验和野外现场观测实验，研究芦苇冠层氮素垂直分布时空变化特征及LAI、光分布垂直分层规律，建立定量描述芦苇冠层氮素垂直分布的数学模型，研究氮素光谱响应特征及光谱探测的冠层有效深度，进而构建考虑芦苇冠层氮素垂直分布特性的遥感监测模型，实现芦苇地上氮素含量的快速准确监测。研究结果能为湿地/湖泊生态系统氮循环研究、湿地恢复和水体富营养化治理提供理论基础，同时也能为植物修复工程中芦苇的实时收割提供理论依据。

湿生芦苇氮素的快速监测对湿地恢复和水体富营养化治理及湖泊/湿地生态系统氮循环研究具有重要意义。现有的植被冠层氮素遥感监测方法很少考虑氮素垂直分布特征，限制了植被冠层氮素含量的监测精度。本项目通过设置人工控制小区实验和野外现场观测实验，开展的研究和取得的成果如下：（1）探明了芦苇冠层氮素垂直分布规律为先增加后减小的抛物线趋势（R2=0.91），其氮素比例分别为0.13, 0.23, 0.31, 0.22和0.11;（2）研究了冠层氮素光谱探测的有效深度和敏感光谱指数，发现前三层为氮素遥感监测的有效层，且混合植被指数PPR/NDVI与氮素的相关性最高（R2=0.62，RMSE=0.41），且对LAI的敏感性最低(R2=0.19,RMSE=1.68)，为芦苇氮素的敏感植被指数;（3）基于以上研究结果，构建了考虑氮素垂直分布和光谱有效探测深度的芦苇冠层氮素遥感监测模型，经验证，该模型具有较高的反演精度（R2=0.88，RMSE=0.37）。研究结果能为湿地/湖泊生态系统氮循环研究、湿地恢复和水体富营养化治理提供理论基础，同时也能为植物修复工程中芦苇的实时收割提供理论依据。