Growth Variation and Early Selection of Superior Tree Half-sib Families of Toona sinensis in Qinba Mountain Areas

In order to select excellent families of Toona sinensis suitable for Qinba mountain areas and provide good varieties for afforestation of fast-growing precious timber species in this area. The random block design was used to compare the afforestation of Toona sinensis families from 4 provinces and 10 regions in Wangcang county of Qinba mountain areas. Through the analysis and comparison of 3-year-old DBH, tree height and individual volume from different families, the early selection of excellent families was carried out. The results of afforestation for 3 years showed that the average DBH, tree height and individual timber score of 34 half-sib families were 4.81 cm, 4.30 m and 0.005 m3 respectively, and the coefficient of variation was 22.43%, 21.36% and 55.78% respectively, with significant differences among different families. Three early excellent families, Pengxi 22, Pengxi 25 and Hongya 9, were preliminarily selected, and the selection rate was 8.82%. The mean values of DBH, tree height and individual volume were 6.10 cm, 5.23 m and 0.0087 m³, respectively. The selection differences were 1.29 cm, 0.93 m and 0.0037 m³, respectively. The genetic gains were 22.19%, 18.30% and 58.28%, respectively. The average annual growth of DBH and height of the three excellent families were 2.03 cm and 1.74 m respectively. They had low selection rate, great selection differences, obvious growth advantage and great genetic gain. Through further observation, they are very likely to become good varieties in Qinba mountain areas.