Predicting Models Of Branch Growth And Knot Properties For Larch Plantation

This research was on the data of stem analysis, branch analysis, and knot characteristics from 95 sample trees in 19 sample plots for Larch plantations with different age, different stand density, and different site. The total number, spatial distribution and development process of branches in crown under different forest conditions were discussed in this paper. Dead branches or knots in different sizes of tree was studied and analyzed to evaluate the effect that knot size and distribution impact on timber quality. Predicting models for branch growth and knot size were developed with tree and stand variables using linear and non-linear regression models. The result indicated that:1. The total number of branches within a living crown in larch plantation was related with the crown length only. As the fierce competition among the branches, in the vertical distribution the relative frequency of branches in different DINC was basically showing staggered state. The horizontal distribution along the stem was effect on stand density for the stand with same age. However, the horizontal distribution of branches was similar for the same stand density with different age. The branching patterns of the primary branches around the bole follow a uniform or rectangle distribution.2. Based on the theory growth equation, the static branching structure models, including branch diameter, branch length, angle of origin and branch chord length of primary branches, were developed from branch attributes and tree variables by using linear and nonlinear regression models. The results showed that these models were suitable for predicting crown branching structure of Larch plantation.3. The diameter of knot increased with the height of it, Mitscherlich equation were suitable for predicting the diameter of knot for larch plantation. The angle of knot could be predicted by multiple regression model, and it was related to tree diameter at breast height, knot diameter and height of knot. The predicting model for the length of sound knot indicated that the length of sound knot increased with knot diameter and tree diameter at breast height increasing, the length of loose knot could be described by multiple linear model, it was related to tree diameter at breast height, knot diameter and height of knot.4. A knot has four development phases:from the birth of a branch to its growth cessation, from growth cessation to death and from death to occlusion. The knots of larch plantation produce perceptible rings during normal growth. The number of perceptible rings ranges from 1 to 36, with an average of 10.9. The relationship between perceptible rings and long of knots was positive linear. It is common that the knots of larch plantation have missing rings, the number of missing rings is from 0 to 19 (mean value is 3.44). The missing rings increased with knots' long increasing. During this period the branches made no contribution to the growth of trees, so this is the right time for artificial pruning. The time of knots between death and been occlusion is 12 years on average, which is about 51% of their total growth time. The loose knots produced during this period would be a great impact for the quality of wood.This research provides a theoretical basis to determine artificial pruning height reasonably, control the size of knots (dead branches) and improve the quality of wood for larch plantation.