Selection and Utilization of Seed Orchard and Superior Tree Open Pollination Families of Larix kaempferi

In the Shaoban area of Xiaolongshan, Gansu Province, a completely randomized block design was used to conduct an afforestation experiment on 25 seed orchard free-pollinated families and 30 elite tree free-pollinated families of Larix kaempferi on logging sites. The data from the 9-year-old plantations were statistically analyzed using SPSS 16.0 and ASReml v3.0. The results showed that there was rich genetic variation among the family-level traits of tree height, breast diameter, and volume in both the seed orchard free-pollinated family and elite tree free-pollinated family trial forests. There was a significant correlation between different traits of the same family. The coefficient of variation for phenotype and genetic variation for volume were the highest. The heritability and individual heritability of family traits such as tree height, breast diameter, and volume in the seed orchard free-pollinated family trial forests were 0.492, 0.680, and 0.694, and 0.093, 0.162, and 0.171, respectively. The heritability and individual heritability of family traits such as tree height, breast diameter, and volume in the elite tree free-pollinated family trial forests were 0.560, 0.544, and 0.496, and 0.128, 0.109, and 0.096, respectively. The heritability of family traits was greater than that of individual traits, and family traits were controlled by moderate to high genetic factors, indicating great potential for family selection. According to the parental breeding values of the seed orchard free-pollinated family progenitors, the initial seed orchard was pruned and replanted with the 1.5th generation seed orchard. Based on volume as the main selection criterion, with consideration given to breast diameter and tree height, the project combined single-tree selection with family selection to select 20 superior single trees from the seed orchard free-pollination family and the elite free-pollination family, respectively, to construct a high-level production group. The expected genetic gain and realized gain of the high-level production group were 25.74% and 22.85%, respectively, and 122.59% and 154.22% respectively. The 50 single trees selected from the seed orchard free-pollination family were used as the application material for constructing a genetic improvement group, while the 45 single trees selected from the elite free-pollination family were used as supplementary material for the breeding group to construct an improvement group with constantly improving genetic quality and expanding genetic foundation.