杨树林带生长阶段与林木分级的研究

Growth stage and classification of poplar shelterbelt.

依据林带的特殊性，结合树木生长发育和林带结构变化规律，将林带生长阶段划分为幼龄期、中龄期（速生期）和防护成熟期３个时期；采用径级离散度、防护成熟龄、更新龄等量化指标，以杨树林带为例，将３个生长时期定量化；同时依据林带树木对防护效益的贡献和树木的生长状况，将林带树木划分为４级；并给出各生长发育时期的相应的经营措施．

Based on the characteristics of shelterbelt and the patterns of tree growth and shelterbelt structure, the growth of poplar shelterbelt can be divided into three stages,i.e.,initial,middle(or fast growing)and protective maturing stages.Their quantitative indexes are determined by diameter discrete degree,protective maturity age and regeneration age.Corresponding management measures for each growing stage are given.