A comprehensive crown profile model of planted Larix kaempferi from different latitudes in China

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发表日期：

2024年6月7日

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Yiwen Tong,
Dongsheng Chen,
Xiaomei Sun,
Huilin Gao

摘要

Crown profile has been the key indicator for assessing tree vigor and has many potential applications in forest growth modelling and forest management. Based on the measurement of the branches for a total of 156 Larix kaempferi individual trees from Liaoning province, Hubei province and Gansu provinces, we developed a nonlinear mixed effects outer-and inner-crown profile model, which included tree variables, climate variables, competition indices, and site quality. The effects of dominant tree height (H_dom), competition indices and climate variables on crown modelling were analyzed. The results showed that climate, competition and H_dom all had significant effects on the outer-and inner-crown profile. Among them, the ratio of DBH of the subject tree to the DBH of the largest individual tree in the stand (DDM) is the most significant competition index. The outer-crown radius increased with the increasing of DDM, and the inner-crown radius decreased with the increasing of DDM. H_dom also showed significant effect on outer-and inner-crown radius. Mean warmest month temperature (MWMT) were selected as the best climate variable to incorporate into the outer-crown profile model, and mean coldest month temperature (MCMT) for the inner-crown profile model. The regularity for the difference of outer-crown radius among three regions was Gansu > Liaoning > Hubei and Liaoning > Hubei for the inner-crown radius. Compared with base model, mean square error reduction (MSER) of the nonlinear mixed effect outer-crown profile model was 22.3% and the nonlinear mixed effect inner-crown profile model was 37.5% compared to the base model. The relative contributions of each variable to the outer-crown profile were DBH (40.05%), site quality (31.11%), CR (16.16%), competition (5.83%), HD (5.47%), and MWMT (1.38%), and the relative contributions to the inner-crown profile were MCMT (40.79%), DBH (32.32%), site quality (25.68%), and competition (1.21%).