Estimation of the directional and whole apparent clumping index (ACI) from indirect optical measurements

doi:10.1016/j.isprsjprs.2018.06.022

	Estimation of the directional and whole apparent clumping index (ACI) from indirect optical measurements
	Fang, Hongliang 1; Liu, Weiwei ; Li, Wenjuan ; Wei, Shanshan
刊名	ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING
	2018-10-01
卷号	144 页码:1-13
关键词	Apparent clumping index (ACI) Directional ACI Whole ACI Leaf area index (LAI) Optical instruments Rice
ISSN号	0924-2716
DOI	10.1016/j.isprsjprs.2018.06.022
通讯作者	Fang, Hongliang(fanghl@lreis.ac.cn)
英文摘要	Canopy clumping index (CI) indicates the non-random distribution of foliage components in space, and is an important structural parameter for better understanding the radiative transfer process in a canopy. The apparent clumping index (ACI), calculated using the logarithmic gap fraction averaging method, is reported by the LAI-2200 Plant Canopy Analyzer. While LAI-2200 calculates the gap fraction and ACI from different conical rings, calculation of ACI for other geometric units (e.g., an angular cell or an azimuth sector) and instruments has been lacked. Building upon the LAI-2200 ACI, this study compares the ACIs calculated for different geometric spaces from different optical instruments. The field data obtained from seasonal continuous measurements with LAI-2200, digital hemispheric photography (DHP), and AccuPAR at a paddy rice field in northeast China were used to calculate the directional ACIs at different levels-a directional cell (Omega(A)(theta,phi)), a concentric ring (Omega(A)(theta)), an azimuth sector (Omega(A)(phi)), and over the horizontal landscape (Omega(A)(nu)). The whole ACIs were calculated from the directional ACIs with an angular integration method, a simple averaging method, a non-linear correction method, and a variance-to-mean ratio method. The directional ACIs for paddy rice generally follow the ord er of Omega(A)(theta,phi) < Omega(A)(theta) and Omega(A)(phi) < Omega(A)(nu), displaying an increase of foliage randomness with the segment size. The Omega(A)(theta,phi) estimated from DHP indicates canopy clumping at the finest level and is consistent with the CIs estimated from the logarithmic averaging method (Omega(LX)) and the ratio method (the effective leaf area index (LAI(e)) divided by the LAI). The ACI metrics expand the current CI metrics and can be obtained with different optical instruments. The expanded metrics can be applied in the canopy radiative transfer modeling and in the estimation of canopy biophysical parameters for other vegetation ecosystems.
资助项目	National Natural Science Foundation of China[41471295] ; National Natural Science Foundation of China[41171333] ; Hundred Talent Program of the Chinese Academy of Sciences
WOS关键词	LEAF-AREA INDEX ; DIGITAL HEMISPHERICAL PHOTOGRAPHY ; RADIATIVE-TRANSFER MODEL ; MODIS BRDF PRODUCT ; CANOPY STRUCTURE ; SEASONAL-VARIATION ; CORRECT ESTIMATION ; FRACTAL DIMENSION ; FOREST CANOPIES ; DIRECT SUNLIGHT
WOS研究方向	Physical Geography ; Geology ; Remote Sensing ; Imaging Science & Photographic Technology
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000447109900001
资助机构	National Natural Science Foundation of China ; Hundred Talent Program of the Chinese Academy of Sciences
内容类型	期刊论文
源URL	[http://ir.igsnrr.ac.cn/handle/311030/52813]
专题	中国科学院地理科学与资源研究所
通讯作者	Fang, Hongliang
作者单位	1.Chinese Acad Sci, Inst Geog Sci & Nat Resources Res, LREIS, Beijing 100101, Peoples R China 2.Univ Chinese Acad Sci, Beijing 100049, Peoples R China
推荐引用方式 GB/T 7714	Fang, Hongliang,Liu, Weiwei,Li, Wenjuan,et al. Estimation of the directional and whole apparent clumping index (ACI) from indirect optical measurements[J]. ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING,2018,144:1-13.
APA	Fang, Hongliang,Liu, Weiwei,Li, Wenjuan,&Wei, Shanshan.(2018).Estimation of the directional and whole apparent clumping index (ACI) from indirect optical measurements.ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING,144,1-13.
MLA	Fang, Hongliang,et al."Estimation of the directional and whole apparent clumping index (ACI) from indirect optical measurements".ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING 144(2018):1-13.