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Forest and Grassland Resources Research ›› 2025›› Issue (2): 141-150.doi: 10.13466/j.cnki.lczyyj.2025.02.015

• Technical Application • Previous Articles    

Modeling the relationships between tree crown and DBH and tree height for eight pine species in China

ZOU Wentao1(), ZENG Weisheng2(), WEN Xuexiang2   

  1. 1. Research Institute of Forestry Policy and Information,Chinese Academy of Forestry,Beijing 100091,China
    2. Academy of Inventory and Planning,National Forestry and Grassland Administration,Beijing 100714,China
  • Received:2025-02-16 Revised:2025-03-26 Online:2025-04-28 Published:2025-12-04

Abstract:

Crown condition may be viewed as the determinant of the growth vigor of trees,and the two key characteristic factors are crown width and crown length.There is a close relationship between crown width(CW)or crown length(CL)and diameter at breast height(DBH)and/or height of trees,but most of the studies in this area were based on local data,and few studies were carried out based on large-scale data.Using the measurement data of 1 354 representative sample trees of eight pine species collected throughout the whole country of China,the relationships between CW or CL and DBH and/or tree height were studied by using nonlinear regression estimation,mixed model and dummy variable model methods.The results showed:1)CW was positively correlated with DBH and negatively correlated with ratio of tree height to DBH;the linear model based on DBH alone can explain 80% of the variation of CW,but adding tree height or ratio of tree height to DBH has little effect on the prediction accuracy of CW.2)The ratio of CW to DBH of young trees was relatively high,but it decreased rapidly with the increase of DBH,and began to stabilize when the DBH reached 10 cm or more.3)CL had a nonlinear correlation with DBH and height,with R2 of ≥0.75;and the ratio of CL to height was positively related to DBH and negatively related to tree height.4)The average ratios of CL to height in all diameter classes had little variation,and decreased with the increase of DBH below 10 cm,but increased slowly when the DBH exceeded 10 cm;and in the same diameter class,the ratio of CL to height decreased with the increase of tree height.There are some differences among the eight pine species in the above relationships.The correlation between CW,CL,DBH and tree height is of practical significance to further study forest competition and guide scientific forest management.

Key words: crown width, ratio of crown width to stem diameter, crown length, ratio of crown length to tree height, mixed model, dummy variable model

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