以北京地区的公益林为例 ,调查了一些公园、学校、绿化地块和两种类型的五条公路路段的行道树。发现这些公益林存在着 :群落结构简单、乔木空缺率高 (单位乔木空缺率平均 2 3 6% ,一般公路的行道树空缺率 33 3% )、过龄树常存、劣势木较多等问题。对以上问题 ,文中提供了调查数表和有关照片 ,并对群落结构和过龄树更新换代作了较深入的分析 Take the public welfare forest in Beijing as an example, we surveyed some street trees of parks, schools, green land plots and two types of five road sections. It is found that these public welfare forests have the following problems: simple community structure, high vacancy rate of trees (average tree vacancy rate of 236% and 33.3% of the general public’s roadway tree vacancy), persistent old trees and more inferior woods. The above questions, the paper provides a survey of the number of tables and related photos, and community structure and aging tree replacement made a more in-depth analysis