Study on Vertical Distribution of Branch Volume, Surface Area and Number of Larix kaempferi

Developed mixed-effects models for vertical distributions of branch volume, surface area, and number in Larix kaempferi (Lamb.) Carr. plantations across three climatic regions (Hubei, Liaoning, Gansu) using 1770 standard branches from 234 sample trees in 78 plots. The final models of branch volume, surface area and number were respectively Weibull, Hossfeld, and zero-truncated negative binomial models. Incorporating crown width (CW), Gini coefficient of DBH (DGC), and annual heat-moisture index (AHM) into branch volume and surface area models, CW, stand age (AGE), and mean warmest month temperature (MWMT) into branch number model greatly improved accuracy. Mixed-effects models further enhanced fit, yielding final R_a^2 and RMSE of 0.8243, 105.76 (branch volume); 0.8263, 194.06 (branch surface area); and 0.6412, 6.20 (branch number). Branch volume and surface area increased in S-shaped patterns with depth into crown (DINC), while branch number decreased. DGC negatively affected branch volume and surface area, mainly in middle and lower crown. AHM showed weak negative effects, mainly observed in the middle crown. MWMT positively affected branch number, but this effect weakened with increasing DINC; AGE reduced branch number and flattened its vertical gradient. This study provides a basis for crown regulation and climate-adaptive management of L. kaempferi.