DOI: 10.1016/j.foreco.2017.04.044
Scopus记录号: 2-s2.0-85019150374
论文题名: Modelling conifer crown profiles as nonlinear conditional quantiles: An example with planted Korean pine in northeast China
作者: Gao H. ; Bi H. ; Li F.
刊名: Forest Ecology and Management
ISSN: 0378-1127
出版年: 2017
卷: 398 起始页码: 101
结束页码: 115
语种: 英语
英文关键词: Jackknife model averaging
; Nonlinear quantile regression
; Outer crown profile
; Pinus koraiensis
; Quantile selection
Scopus关键词: Iterative methods
; Crown profile
; Model averaging
; Pinus koraiensis
; Quantile regression
; Quantile selection
; Forestry
; Coniferales
; Coniferophyta
; Pinus koraiensis
英文摘要: With few exceptions crown profile models for coniferous trees have conventionally been estimated within the least squares framework that is confined to describing the central trend of whorl radius along the stem. This article introduces a new approach of modelling the outer profiles of conifer tree crowns as nonlinear conditional quantiles using plantation grown Korean pine in northeast China as an example. The approach was demonstrated with two nonlinear model forms using data from detailed measurements of 83 sample trees with a total number of 1415 whorls and 5123 live branches. One model was based on a segmented polynomial function and the other was a modified variable-exponent function. For each model form, 11 nonlinear quantile curves were estimated using the branch radius data by taking 11 values of q, representing the qth quantile, from 0.5 to 0.95 with an even interval of 0.05 plus one extreme value of 0.99. Parameter estimates for a given value of q were obtained through repeated fitting by leaving one tree out each time in a simple form of jackknife model averaging. To select the best q values for delineating the outer or outmost contours of the exterior edges of tree crowns, three fix-effects (marginal) models of the same nonlinear form was fitted iteratively to the entire, about one-half and one-quarter of the whorl radius data after removing non-positive residuals at each iteration. Based on graphical evaluations and comparisons of benchmarking statistics, the 0.90th and 0.95th nonlinear quantiles were chosen for depicting the outer and outmost crown profiles of Korean pine trees for both model forms. The variable-exponent model appeared to be superior to the segmented polynomial model not only in delineating the outer crown profiles but also in estimating the largest crown radius of individual trees. In comparison to the marginal models or to the more traditional least squares regression, the new approach enables more accurate depictions of the outer or outmost crown profiles without subjective data selection and thus any loss of information. It also has the potential to profile the inner part of individual tree crowns through a family of nonlinear conditional quantial curves, therefore providing a greater insight into the crown structure than the conventional methods. © 2017 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/64291
Appears in Collections: 影响、适应和脆弱性
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作者单位: School of Forestry, Northeast Forestry University, No. 26 Hexing Road, Harbin, China; Forest Science, NSW Department of Industry – Lands, Level 12, 10 Valentine Ave, ParramattaNSW, Australia; School of Ecosystem and Forest Sciences, The University of Melbourne, Australia
Recommended Citation:
Gao H.,Bi H.,Li F.. Modelling conifer crown profiles as nonlinear conditional quantiles: An example with planted Korean pine in northeast China[J]. Forest Ecology and Management,2017-01-01,398