一、前言东北的原始天然林,绝大部分是未经过任何经营措施的成熟过熟的老龄林,林木枯损现象很严重,每年都有为数不少的林木失掉工艺价值,成为枯木。森林资源这种无意义的耗损,无疑地是国民经济上的一种损失。因此,保管好现有森林资源,尽量减少林木的天然枯损,使每一株树木,每一立方米的木材,都能有效地用在社 I. Introduction The primitive natural forest in the northeast is dominated by mature and over-aged forests without any management measures. The phenomenon of forest loss is very serious. Every year, a large number of trees lose their craft value and become dead wood. This senseless depletion of forest resources is undoubtedly a national economic loss. Therefore, taking good care of the existing forest resources and minimizing the natural loss of the trees will make it possible for each tree and every cubic meter of timber to be used effectively