树冠形态是反映林木生长活力的关键因素,其主要特征因子为冠幅和冠长。林木冠幅、冠长与胸径、树高之间存在紧密的相关关系,但相关研究成果多基于局部地区数据,基于大范围数据的研究极少。为此,利用在全国范围内采集的8个松属树种的1 354株代表性样木调查数据,采用非线性回归估计、混合模型和哑变量模型方法,探究冠幅和冠长与林木胸径、树高之间的关系。结果表明:1)林木冠幅与胸径呈正相关,与林木的高径比呈负相关,仅基于胸径的线性模型即可解释冠幅变动的80%,如果再增加树高或高径比,对提高冠幅预测的精度作用甚微;2)幼树阶段冠径比相对较高,随着胸径的增加而快速降低,在胸径10 cm以上趋于稳定;3)林木冠长与胸径、树高呈非线性相关,其R²高于0.75,冠长率与胸径呈正相关,与树高呈负相关;4)各个径阶的平均冠长率变化不大,在胸径10 cm以下随胸径的增加而降低,但在胸径超过10 cm时又缓慢回升,在同一径阶内,冠长率随树高的增加而降低。对于上述变化规律,8个松属树种间存在一定差异。所建立的林木冠幅和冠长与胸径和树高之间的回归模型,对进一步研究林木竞争和指导森林科学经营具有现实意义。

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.