ORIGINAL RESEARCH article
Front. For. Glob. Change
Sec. Forest Management
Volume 8 - 2025 | doi: 10.3389/ffgc.2025.1635431
Nonlinear mixed effects height to crown base model for Larix kaempferi plantation in China by considering initial planting density and thinning intensity
Provisionally accepted
- 1Shenyang Agricultural University, Shenyang, China
- 2Research Institute of Forestry, Chinese Academy of Forestry, Beijing, China
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Height to crown base is a main component of crown structure to understand the growth of tree. It is essentially important to construct a comprehensive height to crown base model to facilitate the application in the forest management practice decision making. Measurements for a total of 13822 trees from 159 sample plots developed in the forest stands of Larix kaempferi plantation from Liaoning province and Hubei province were used to fit the model. Variables of tree size, competition, climate and thinning practice were considered in the model development. Dummy variable approach was used to analyse the effect of initial planting density and study area on the height to crown base and the interaction of initial planting density and competition was also considered in the height to crown base model. Nonlinear mixed effects model was developed to eliminate the heteroscedasticity at the sample plot level. The results showed that Logistic model had the best performance and was thus selected as the base model. Total tree height and height-diameter ratio from tree level variables, stand basal area of competition variables, spring degree-days below 0℃ (DD_0_sp) of climate variables, and thinning variables showed significant contributions to height to crown base and were finally included into the finial model. Height to crown base increased with the increasing of total tree height, competition, height-diameter ratio, thinning intensity, and decreased with the increasing of DD_0_sp and logarithmic transformation of altitude. Large initial planting density resulted in the rising of height to crown base. The effect of competition on the height to crown base was reduced with the increasing of thinning intensity especially for the trees from Hubei province. The relative contributions of each group of variables to height to crown base were tree size (41.7%) > competition (27.3%) > thinning (24.5%) > interaction of competition and thinning (3.2%) > climate (2.4%) > site quality (0.9%). The developed height to crown base model of Larix kaempferi will lay a foundation to conduct forest management strategies decision.
Keywords: Height to crown base, Nonlinear mixed effects model, Initial planting density, Thinning intensity, Larix kaempferi
Received: 26 May 2025; Accepted: 27 Jun 2025.
Copyright: © 2025 Liu, Liu, Gao, Chen and Lyu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Huilin Gao, Shenyang Agricultural University, Shenyang, China
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