Continuous estimation of canopy leaf area index (LAI) and clumping index over broadleaf crop fields: An investigation of the PASTIS-57 instrument and smartphone applications
Continuous estimation of canopy leaf area index (LAI) and clumping index over broadleaf crop fields: An investigation of the PASTIS-57 instrument and smartphone applications
复制标题
阔叶作物田冠叶面积指数 (LAI) 和丛集指数的连续估算：对 PASTIS-57 仪器和智能手机应用的调查
DOI：
10.1016/j.agrformet.2018.02.003
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发表时间：
2018-05-01
影响因子：
6.2
通讯作者：
Ma, Li
中科院分区：
文献类型：
--
作者：
Fang, Hongliang;Ye, Yongchang;Ma, Li
自动叶面积指数(LAI)测量对于在较长时间内获得足够数量的田间数据非常重要。2016年，为了获得中国东北部玉米、大豆和高粱田的连续叶面积指数，开展了季节性田间活动。田间叶面积指数的测量是通过自动PATIS-57(PAI自主系统从57度的瞬时透过率感知)装置和两个智能手机应用程序PocketLAI和LAISmart获得的。这些测量数据与LAI-2200植物冠层分析仪、数字半球照相(DHP)和破坏性采样测量的数据进行了比较，LAI-2200和DHP的有效植物面积指数(PAI(Ef))估计在整个季节是一致的，总体相对误差(RE)小于5%。PATIS-57数据显示出对LAI-2200和DHP值的小幅低估(RE<；20%)。LAISMart数据的相对误差在-20%到-30%之间。PocketLAI严重低估了LAI-2200的值(RE>；40%)，并在PAI(Ef)=3.5左右饱和。冠层聚集指数(CI)呈S型季节变化，在营养生长期随PAI(Ef)的增加而减小，但在营养生长期后随PAI的增加而增大。Pastis-57显示出在农作物田里获得连续叶面积指数的巨大潜力，但在将智能手机应用程序用于研究目的之前，应该进一步研究它们。本研究收集的数据对遥感产品的验证具有一定的参考价值。
Automatic leaf area index (LAI) measurements are important for obtaining sufficient amounts of field data over an extended period of time. A seasonal field campaign was carried out to obtain continuous LAI measurements over maize, soybean, and sorghum fields in northeast China in 2016. Field LAI measurements were acquired with the automatic PASTIS-57 (PAI Autonomous System from Transmittance Instantaneous Sensed from 57 degrees) installment and two smartphone applications, PocketLAI and LAISmart. These measurements were compared with data obtained using the LAI-2200 Plant Canopy Analyzer, digital hemispherical photography (DHP), and destructive sampling measurements.The effective plant area index (PAI(eff)) estimates from LAI-2200 and DHP are consistent over the season, with the overall relative errors (RE) of less than 5%. The PASTIS-57 data exhibit a small underestimation of the LAI-2200 and DHP values (RE < 20%). The relative errors for the LAISmart data are between -20% and -30%. PocketLAI significantly underestimates the LAI-2200 values (RE > 40%) and saturates at around PAI(eff) = 3.5. The canopy clumping index (CI) exhibits an S-shaped seasonal variation that decreases with the increase of PAI(eff) during the vegetative growth stage but increases after this stage. PASTIS-57 shows great potential for obtaining continuous LAI measurements in agricultural crop fields, but the smartphone applications should be further examined before they can be used for research purposes. The data collected in this study are valuable for the validation of remote sensing products.