Analysis of Stand Structure Characteristics and Selection of Superior Trees of Cunninghamia lanceolata var. luotian

Taking the remaining three mature artificial Cunninghamia lanceolata var. luotian as the research object, this study investigates and analyzes its stand structure characteristics and laws, and selects superior trees using a comprehensive evaluation method of membership functions, in order to provide technical support for the resource protection and breeding of this Chinese fir variation type. The results showed that the average breast height diameter, tree height, crown length, and volume of the three forest stands were 16.9-19.8 cm, 16.2-16.5 m, 3.0-3.3 m, 0.222-0.286 m³, The coefficient of variation for traits such as crown length and individual volume ranges from 25.57% to 38.33% and 30.79% to 45.47%, There is obvious differentiation between individuals, which lays the foundation for selecting excellent individual plants. The skewness values of the diameter structure of the three forest stands are all greater than 0, and they are normally distributed to the right. The maximum frequency distribution of diameter in Xianqiling and Maliping is higher than that in Tielingao. The tree-height structure of the forest stands, except for Xianqiling, follows a normal distribution with a rightward skew. The maximum frequency distribution of tree height in Maliping and Tielingao is higher than that in Xianqiling. Meanwhile, the crown length structures of the three plots all follow a normal distribution and are mainly distributed in the 3 m crown length range. The Pearson correlation analysis showed a highly significant positive correlation among breast height diameter, tree height, crown length, and volume. Based on selection intensity and total membership letter value sorting and screening, the number of selected excellent trees for this project is 53, and the selection rate of excellent trees ranges from 3.66% to 4.84%. Among them, the selection value and rate of excellent trees in Ma Liping are the highest. The main traits of superior trees show significant gains, with breast height diameter, tree height, and volume increasing by 27.48%, 23.73%, and 90.35%, respectively, indicating a clear selection effect.