Transforming climate-competition interactions into adaptive pruning decisions via crown dynamics modeling in Pinus koraiensis plantations

Abstract

Optimizing the trade-off between wood quality and tree vigor is a central challenge in silviculture, particularly for Pinus koraiensis plantations where weak natural pruning leads to severe knot defects. While artificial pruning is essential, current guidelines rely on static morphological ratios that ignore the complex interplay between crown physiology and environmental variability. To address this, we integrated retrospective knot analysis with a nonlinear seemingly unrelated regression (NSUR) system to reconstruct and model the dynamic trajectories of three hierarchical metrics: total height (

\mathit{HT}

\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$HT$$\end{document}

, representing vertical growth potential), height to crown base (

\mathit{HCB}

\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$HCB$$\end{document}

, defining the upper limit of knot-free timber), and height to effective crown (

\mathit{HEC}

\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$HEC$$\end{document}

, a physiological threshold for functional vigor). We then employed a nonlinear seemingly unrelated regression (NSUR) system to integrate these parameters with environmental variables. Hierarchical partitioning revealed that crown recession dynamics are driven by distinct, size-mediated mechanisms. Large trees were predominantly governed by ontogeny and site quality, whereas small trees exhibited high sensitivity to direct climate stress. Crucially, medium-sized trees displayed strong competition-climate interactions, where competitive dominance (larger relative diameter) amplified the benefits of spring warming on height growth while buffering the adverse effects of drought on crown recession. The NSUR system captured these interdependent dynamics with high precision (

R^2

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: 0.84–0.90;

\mathit{RMSE}

\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$RMSE$$\end{document}

: 1.10–1.23 m). Translating these ecological insights into practice, we developed a climate-responsive pruning decision framework covering nine site-climate scenarios. By identifying

\mathit{HEC}

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as the critical biological boundary, this tool enables forest managers to transition from fixed schedules to adaptive interventions, ensuring premium timber production under an uncertain future climate.

Keywords

Korean pine / Artificial pruning / Crown dynamics / Nonlinear seemingly unrelated regression

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Funding

the Fundamental Research Funds for the Central Universities(2572025AW01)

the Young Scientists Fund of the National Key R&D Program of China(2022YFD2201800)

RIGHTS & PERMISSIONS

Northeast Forestry University