林龄和立地条件对冀北山地油松单木生长量和生长率的影响

Influence of age and site factors on the growth of Pinus tabulaeformis in mountain areas of northern Hebei Province

为了解林龄和立地条件对冀北山地油松单木生长的影响,以该地区油松林为研究对象,选取不同立地条件下的油松优势木进行树干解析,分析单木胸径、材积生长量和生长率随林龄的变化及其对立地条件的响应。主要结果为,随着林龄增长油松单木材积生长量呈幂指数上升趋势,但是不同立地条件下其生长量差异逐渐变大,而直径生长率和材积生长率呈现幂指数函数下降,并在林龄达到20年时逐渐收敛,分别趋于稳定在5%和6%,表现出生长率与立地条件无关。然而,不同立地条件下油松材积生长率也存在较大变异,显示材积生长率也受到立地条件影响。通过建立该地区油松林立地指数,进一步发现立地质量对直径、材积生长量和生长率均有影响,其中,海拔是影响材积生长率最重要的立地因子。本研究认为探讨油松单木生长率及建立模型时,应当同时考虑林龄和立地条件的影响。

This study took the Pinus tabulaeformis plantation in the northern mountain areas of Hebei Province to understand the influence of age and site factors on tree growth.Dominant trees of different site quality were selected and the stem analysis was carried out.The main results were as follows:The tree volume growth showed the power exponential trend with the tree-age,and the data distribution was in a horn shape,indicating that the volume growth gradually dispersed with tree growth under different site quality.While the diameter growth rate and volume growth rate showed the power exponential function decreased,and gradually stabilized when the tree-age reached about 20 years and tended to be stable at 5%and 6%respectively,showing that the growth rate had no effects with the site quality.However,we found that it had non-negligible the coefficient of variation of volume growth rate,indicating that the volume growth rate also was affected by site quality.By establishing the site index of P.tabulaeformis stand in this area,it was further discovered that site quality had a significant effect on the volume growth and growth rate,and the altitude was the most important site factor.This study suggested that the effect of age and site quality should be also considered when studying the growth rate of P.tabulaeformis.