<正>研究了福建卫闽林场光皮桦种群的密度随径级年变化以及光皮桦种群个体平均重量与密度之间的动态关系。提出了描述光皮桦种群密度随径级年变化的分段函数表达式以及光皮桦种群个体平均重量与密度之间规律的模型。经实测资料验证，笔者提出的模型在拟合光皮桦种群自然稀疏过程中，均具有较高的可信度。同时，对其它种群的自然稀疏研究也具有普遍意义。

This paper discusses the population density of Betula Luminifera with the changes of diameter classes, the dynamic relationship between individual mean weight of Betula Luminifera population and its density. The phasic function was presented of Betula Luminifera population density with the changes of diameter classes. The model between individual mean weight of Betula Luminifera population and the density was also presented. According to the verified data, the model presented in this paper characterizes its higher credibility in the process of natural thinning of Betla Luminifera population. At the same time, it has also a magnificence for the study on self_thinning of the other population.