Quantitative Evaluation of Leaf Inclination Angle Distribution on Leaf Area Index Retrieval of Coniferous Canopies  

作　　者：Guangjian Yan Hailan Jiang Jinghui Luo Xihan Mu Fan Li Jianbo Qi Ronghai Hu Donghui Xie Guoqing Zhou 

机构地区：[1]State Key Laboratory of Remote Sensing Science,Faculty of Geographical Science,Beijing Normal University,Beijing 100875,China [2]Southwest China Research Institute of Electronic Equipment,Chengdu 610036,China [3]Guilin University of Technology,Guilin 532100,China

出　　处：《Journal of Remote Sensing》2021年第1期1-15,共15页国际遥感学报（英文）

基　　金：supported by the key program of the National Natural Science Foundation of China(NSFC)(Grant No.42090013);Guangxi Innovative Development Grand Grant under the grant number:Guike AA18118038;the China Scholarship Council,Grant No.201906040055.

摘　　要：Both leaf inclination angle distribution(LAD)and leaf area index(LAI)dominate optical remote sensing signals.The G-function,which is a function of LAD and remote sensing geometry,is often set to 0.5 in the LAI retrieval of coniferous canopies even though this assumption is only valid for spherical LAD.Large uncertainties are thus introduced.However,because numerous tiny leaves grow on conifers,it is nearly impossible to quantitatively evaluate such uncertainties in LAI retrieval.In this study,we proposed a method to characterize the possible change of G-function of coniferous canopies as well as its effect on LAI retrieval.Specifically,a Multi-Directional Imager(MDI)was developed to capture stereo images of the branches,and the needles were reconstructed.The accuracy of the inclination angles calculated from the reconstructed needles was high.Moreover,we analyzed whether a spherical distribution is a valid assumption for coniferous canopies by calculating the possible range of the G-function from the measured LADs of branches of Larch and Spruce and the true G-functions of other species from some existing inventory data and threedimensional(3D)tree models.Results show that the constant G assumption introduces large errors in LAI retrieval,which could be as large as 53%in the zenithal viewing direction used by spaceborne LiDAR.As a result,accurate LAD estimation is recommended.In the absence of such data,our results show that a viewing zenith angle between 45 and 65 degrees is a good choice,at which the errors of LAI retrieval caused by the spherical assumption will be less than 10%for coniferous canopies.

关 键 词：DISTRIBUTION FUNCTION viewing 

分 类 号：S71[农业科学—林学]