林分结构随生长变化的动态模型

Dynamic Model of Growth Variety of Stand Structure

本文提出了一个研究林分树龄和直径结构动态变化规律的偏微分方程定解问题.在给出林木直径增长率与树龄和直径的关系的近似表达式的基础上,求出了该定解问题的解.从而得到了描述林分树龄和直径结构动态变化规律的解析表达式;并附带地给出了同龄林分,当其直径分布为Weibull分布或正态分布时,其参数随时间变化的函数关系式.作为应用实例,对一块小叶松林分直径结构的变化进行了动态模拟和预测.

Together with the initial condition (i.c.) and the boundary conditions (b.c.) a partial differential equation (PDE) is proposed to deal with stand growth relating to the structure of age and the one of diameter.Based on a formula which is given to describe,approximately,the relations between age,diameter and growth-rate of a tree,the PDE problem with i,c.and b.c.is solved.Thus an analytical expression describing changing structure of age and the one of diameter is obtained.When a stand is even-aged and its diameter distribution follows the Weibull Distribution or the Normal Distribution,the changing distribution parameters are incidently formularized.As an example of the application,the changing structure of the diameter of an even-aged Jack pine stand is simulated and forecasted.