冬小麦冠层氮素非均匀垂直分布的遥感方法研究

The non-uniform leaf nitrogen distribution and its effects on canopy photosynthesis have been reported for many plants. However, it has not been given much attention in crop nitrogen remote diagnosis. This may be due to the current difficulties in directly capturing the spectral reflectance information of different vertical layers of crop canopy by remote sensing. The objectives of this study which will be carried out based on the field experiments of winter wheat, are as follows: (1) to investigate the vertical profiles and changing dynamics of leaf nitrogen distribution in canopies with different geometries, plant densities, nitrogen fertilization rates, and water conditions, and improve the quantitative description methods of canopy nitrogen distribution; (2) to clarify the contributions of different vertical layers to canopy hyperspectral reflectance, and the effective depths of canopy hyperspectral measurements as well as the ability of capturing canopy vertical structure information from multi-angle spectral data based on hyperspectral imaging spectrometer observations; (3) to establish an approach for estimating the non-uniform leaf nitrogen profile by coupling canopy nitrogen distribution model and hyperspectral imaging data. By this method,it can acquire the leaf nitrogen status of different vertical layers from the dataset that is relatively easy to access from satellite platforms. The expected outcomes of this study will be useful in comprehensively evaluating the effects of leaf nitrogen distribution on crop production, advancing crop modeling, and improving the accuracy and practical application values of crop nitrogen remote diagnosis, which is great significant to ensure both food and environment security in modern agriculture production.

植物冠层氮素非均匀垂直分布及其对光合生产的影响已引起许多关注，但在遥感作物氮素状况时尚未给予充分考虑，其面临的主要困境是遥感观测难以获取大面积作物冠层不同层次的光谱反射信息。本项目基于冬小麦田间处理实验，拟研究：(1) 不同株型品种、密度、施氮量、水分处理下冬小麦冠层氮素的非均匀垂直分布特征，深化完善其数学描述方法；（2）根据不同方式测得的冠层成像高光谱数据，阐明不同叶层对冠层高光谱反射信息的贡献率、冠层高光谱观测的有效深度及多角度成像高光谱对冠层垂直结构信息的获取能力；（3）建立耦合冠层氮分布数学模型与成像高光谱信息的作物冠层氮素垂直分布遥感方法，从而实现采用较易获取的常规或多角度高光谱遥感数据估算作物冠层氮素的垂直分布。研究结果有助于全面合理地评价冠层氮素垂直分布对作物生产的影响，为作物模型的改进提供依据；有助于提高作物氮素遥感精度及其实际应用价值，对维系粮食和环境安全具有重要意义。

植物冠层氮素非均匀垂直分布及其对光合生产的影响已引起许多关注，但在遥感作物氮素状况时尚未给予充分考虑。鉴于作物氮素状况的遥感监测对于现代农业生产的重要性以及作物不同层次叶片氮含量的差异分布和不同层次叶片对氮素胁迫的敏感性不同，根据研究计划，本项目基于冬小麦田间观测实验和情景模拟分析，主要开展了以下研究：（1）揭示了不同株型品种、密度、施氮量、水分处理下冬小麦冠层氮素垂直分布特征，建立了数学描述方法；（2）揭示了穗组分和不同叶层对冠层高光谱反射及其导出植被指数的影响和贡献，阐明了冬小麦高光谱和多角度光谱反射对冠层垂向信息的感知能力等；（3）结合冠层氮分布数学模型与高光谱信息，建立了冬小麦冠层氮素垂直分布遥感方法，从而可基于较易获取的常规高光谱数据估算作物不同层次叶片的氮素含量。上述研究结果不仅有助于深入理解作物吸收利用氮素的生理生态机制，而且有助于提高作物氮素状况遥感监测的精度和实际应用价值。. 在本项目的资助下，目前已发表学术论文5篇，其中SCI收录4篇，EI收录1篇；相关研究成果还在整理中，后续还会产出。本项目培养博士后1名（即本项目负责人），协助培养博士研究生1名，培养副研究员1名（即本项目负责人），培养科技部国家遥感中心遥感青年科技人才1名（即本项目负责人）。