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本文以８年生的２４个白榆（ＵｌｍｕｓｐｕｍｉｌａＬｉｎｎ．）杂交无性系为试验材料，进行了白榆生长早期选择的研究。结果表明：不同无性系之间在生长量（胸径、树高、材积）上存在着极显著的差异。通过对白榆历年生长的分析，计算出生长性状间的年一年秩次相关，表明表型相关和遗传相关是极显著的。以胸径、树高、材积等性状的早晚期相关系数建立的回归方程算出的年选择效率表明，从造林后第３年的胸径估计造林后１５年的胸径，造林后３年的胸径和材积估计造林后１２年的材积，均具有极显著的相关性（ｒ＝０．５４９９～０．６６０１）和最高的选择效率（１．２７～２．２７），说明当白榆无性系造林后３年，即４年生时即可根据胸径和材积进行早期选择。
In this study, 24 elm Ulmus pumila Linn. Clonal clones of 8-year-old were used as experimental materials to study the early selection of elm growth. The results showed that there were extremely significant differences in growth (DBH, tree height, volume) between different clones. Through the analysis of the growth of the white elm over the years, the year-to-year rank correlations between the growth traits were calculated, indicating that phenotypic and genetic correlations are extremely significant. The annual selection efficiency calculated from the regression equation established by the early and late correlation coefficient of DBH, tree height and volume showed that the DBH at 15 years after afforestation and the DBH at 3 years after afforestation were estimated from the DBH at the third year after afforestation The volume of 12 years after afforestation had extremely significant correlation (r = 0.5499 ~ 0.6601) and the highest selection efficiency (1.27 ~ 2.27), indicating that when P. elm clonal afforestation 3 years , That is, 4-year-old can be based on DBH and volume early selection.