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避免优树的重复是毛白杨选优的重要原则，可通过以下措施基本实现：①将现实毛白杨群体分为老树、自然类型、普通毛白杨和野生资源，然后在各类中分别选优；②以物候、形态等性状鉴别优树是否属同一基因型；③用同工酶等生理指标进行鉴定。对于老树，不评定生长量，作为基因资源全部入选；对于自然类型、普通毛白杨和野生资源，可进一步分为散生木、行进树和片林，然后分别评定生长量。散生木用绝对值评选法；行道树用小标准段法或绝对值评选法；片林用小标准地法，当通过形态和物候等性状的观察，确信片林中候选树周围为不同无性系时，也可用优势木对比法。通过１０４７株毛白杨优树生长量的分析，得出了选优的绝对值标准如下：１０年生左右时，年均胸径生长量２．５ｃｍ以上，年均树高１．３ｍ左右，年龄每增加１０ａ，年均胸径生长量约降低０．３ｃｍ，但年均树高都为１．０ｍ左右。
To avoid the duplication of superior trees is an important principle of the selection of Populus tomentosa, which can be basically achieved through the following measures: ①The Populus tomentosa group is divided into old trees, natural types, Populus tomentosa and wild resources, ; ② to phenological, morphological and other characteristics of superior trees are the same genotype; ③ isozymes and other physiological indicators were identified. For old trees, no growth was assessed, and all the selected genetic resources were selected. For natural types, common poplar and wild resources could be further divided into scattered trees, traveling trees and patch forests, and then the growth rates were respectively assessed. The method of absolute value selection for scattered wood was adopted. The standard section method or absolute value method of street tree was used. When the small forest was used as a small standard method, the morphological and phenological traits were used to confirm that the surrounding trees were different clones When, but also can use the dominant wood contrast method. Based on the analysis of the growth of superior tree of 1047 Populus tomentosa, the absolute value of the optimal selection was obtained as follows: When the growth rate was about 10 years, the average annual DBH growth was more than 2.5cm, and the average annual tree height was about 1.3m. 10a, average annual DBH growth decreased about 0.3cm, but the average annual tree height is about 1.0m.