Nonlinear mixed-effects modeling of variable-exponent taper equations for lodgepole pine in Alberta, Canada

Four variable-exponent taper equations and their modified forms were evaluated for lodgepole pine (Pinus contorta var. latifolia Engelm.) trees in Alberta, Canada. A nonlinear mixed-effects modeling approach was applied to account for within- and between-tree variations in stem form. Even though a d...

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Bibliographic Details
Published in:European journal of forest research 2009-07, Vol.128 (4), p.415-429
Main Authors: Yang, Yuqing, Huang, Shongming, Trincado, Guillermo, Meng, Shawn X
Format: Article
Language:English
Subjects:
Bark
Biomedical and Life Sciences
Evergreen trees
Forest management
Forestry
Life Sciences
Original Paper
Pine trees
Pinus contorta
Plant Ecology
Plant Sciences
Trees
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Summary:Four variable-exponent taper equations and their modified forms were evaluated for lodgepole pine (Pinus contorta var. latifolia Engelm.) trees in Alberta, Canada. A nonlinear mixed-effects modeling approach was applied to account for within- and between-tree variations in stem form. Even though a direct modeling of within-tree autocorrelation by a variance-covariance structure failed to achieve convergence, most of the autocorrelation was accounted for when random-effects parameters were included in the models. Using an independent data set, the best taper equation with two random-effects parameters was chosen based on its ability to predict diameter inside bark, whole tree volume, and sectioned log volume. Diameter measurements from various stem locations were evaluated for tree-specific calibrations by predicting random-effects parameters using an approximate Bayesian estimator. It was found that an upper stem diameter at 5.3 m above ground was best suited for calibrating tree-specific predictions of diameter inside bark, whole tree volume, and sectioned log volume.
ISSN:1612-4669
1612-4677
DOI:10.1007/s10342-009-0286-2