热带地区几个珍贵树种干形曲线研究

Equations describing stem profiles for several precious tropical tree species

准确描述热带珍贵树种的林木干形变化,可为预估各材种数量、蓄积量及合理造材提供支撑。以热带格木、红锥和柚木3个珍贵树种,共120株解析木为研究对象,利用简单削度方程、分段削度方程和可变指数削度方程分别构建格木、红锥和柚木3个热带树种的干形曲线方程,通过相关指数、剩余残差平方和、平均残差、残差方差和均方误差统计量比较分析,找出最佳削度模型作为3个树种最终的干形曲线方程,并对各曲线变化趋势进行了初步的定量分析。结果表明,所选的3类典型基础模型对每个树种的预估效果都很好,其中基于双因素自动优选法拟合且以分段削度方程构建的干形曲线预估效果最好。3个树种的干形曲线变化趋势表明：相对高在（0-0.8）时,柚木干形变化最大,红锥干形变化最小,格木干形介于二者之间;当相对高〉0.8时,红锥干形变化最大,格木和柚木干形变化几乎相同。因此,基于双因素自动优选法拟合的分段削度方程可作为3种热带树种的干形曲线方程,用于3种珍贵树种活立木蓄积量和材种数量的估计,以及指导合理造材。

An accurate description of stem profile curve of the precious tree species in tropical region can help to estimate the tree number and volume of certain species, and thus provides technical support for reasonable bucking. With a total of 120 trees （40 for each species）, three species induding Erythrophleum fordii, Castanopsis hystrix and Tectona grandis, were investigated in this research. The tape equations for the three species were developed using the simple taper equation, segmented taper equations and the variable form taper equations respectively. The optimal taper equations for the three tree species were determined through the comparison and analysis of statistical quantities of the index of correlation, the residual sum of squares, the mean prediction error, the variance of prediction errors and the root mean square error. With the optimal taper equation, a preliminary quantitative analysis was carried out on the stem profile variations of the three precious tree species. The results showed that the prediction precision of the taper equations for each species was high. Especially, the segmented taper equations with optimization algorithms were the best. With the optimal equation, the variation tendency of the stem profile of the trees were found as following ： the variation of stem profile of T. grandisin in the relative height range of 0 to 0.8 was the largest, followed by E. fordii, and the variation of C. hystrix was the smallest. But in the relative height range of 0.8 to 1, the variation of stem profile of C. hystrix was the largest, while the variation of E. fordii and T. grandis were comparable. Therefore, the segmented taper equations with optimization algorithms is recommended to describe the stem profile of these three tree species in tropical regions, which can be used to estimate the stumpage and timber quantity and to guide reasonable bucking for precious tree species.