林木生长与养分动态模型研究 Ⅲ.生长方程的假设与前提

Study of Dynamics Models of Forest Growth and Nutrition . Basic Assumption and Precondition of Growth Equation

结合实例对吴和胡提出的杉木直径、高和蓄积生长方程的基本假设和边界条件进行了详细的说明和论证，并在直径和高生长方程的基础上给出了杉木径高比系数的动态方程．径高比系数随树龄增长而递减的规律表明杉木直径和高的生长速率递减存在不同步现象，产生这一现象的主要原因是林木生长的平面限制效应大于高度限制效应，因此，森林蓄积增长的主要限制因子是树木的直径生长速率．

Based on field observations as well as available data from literatures, explanations and arguments are given to support the basic assumptions and preconditions of the China fir forest growth equations proposed by Wu and Hu (1999). The relation of the diameter/height ratio with tree age, derived from the proposed diameter (D) and height (H) growth equations, gives a high degree of accuracy in application. The regular decrease of the D/H ratio with increasing tree age indicates the presence of nonsynchronism phenomena of decrease in diameter and height growth rates in the forest growing process, due to higher compactness of the space availability on forest growth in the horizontal direction than in the vertical direction. The tree diameter growth rate is thus the major limiting factor to forest volume growth.