Predicting Models Of Branch Growth And Knot Properties For Mongolian Scots Pine In Plantation

Based on the data of stem analysis, branch analysis, and knot characteristics from 123 sample trees in 23 sample plots for Mongolian scots pine 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 different branch development phases of growth, suppression, death and self-pruning was analyzed to evaluate the effect that knot size and distribution impact on timber quality. Branch and knot dynamic models were developed using stand and tree variables. Based on mixed model theory, linear and log-linear mixed model were used to predict knots length. Models of predicting height of living branches (HCB) and crown length (CL) dynamic were developed directly based on knot analysis data to reconstruct past crown recession. The models can be used to predict crown structure dynamic, determine proper pruning height, control dead branch and knot size along the stem and improve timber quality. The results are followed:1. Total number and whorl number of branches within a living crown in Mongolian scots pine plantation were related with diameter at breast height (DBH), total tree height (HT), and crown length (CL). The branch numbers in every whorl does not relate with forest conditions and they are affected by genetic factors. The Weibull distribution was used to describe the vertical distribution of primary branches and uniform distribution was appropriate to reflect branching pattern around the bole.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 the nonlinear regression model. The results showed that these models were suitable for predict crown branching structure of Mongolian scots pine plantation. Diameter increment of branches decreased gradually with increasing branch age after they were formed. The annual increment of branch length existed a peak at first 4~6 years and then decreased continuously with increasing branch age. The age factor was introduced in branch static model to establish branch dynamic growth models.3. The number of dead branches and knots in a whorl under the living crown flowed Normal distribution. The biggest knots were located in the middle of stem. The tree diameter at breast height (DBH) and lowest height of living branch (HCB) can be used to predict the size and location of mean knot diameter in a whorl. A linear mixed model expressed as function of tree and knot variables was used to predict sound knot length, and a log-linear mixed modelwas used to describe loose knot length.4. A knot has four development phases: from the birth of a branch to its growth cessation (BC) , from growth cessation to death (CD) , form death to occlusion (DO) and form birthto occlusion(BO). Branch formed visible annual rings for 8 years on the average (BC), the time period that branches remain alive without visible annual ring production(CD) was 5 yeas on average and it accounted for 38% of average lifetime of the branches. The time period from the death of a branch to its occlusion averaged 13 years and the average number of years from the birth of a branch to its occlusion was 12. The numbers of annual rings in four periods, as well as the stem width of respective zones were used as dependent variables predicted by models expressed as function of tree variables and knot attributes.5. The missing rings in the branches within the living crown ranged from 0 to 5 with a mean of 0.7 year, and 93.02 percent of the branches have no missing rings. The number of years without visible annual ring production of knots in whorls under living crown ranges from 0 to 22, and 20.9 percent of the knots lost 3 rings. The number of missing rings of knots continuously increased with increasing knot height (Hk) and branch entire lifetime (BD).6. Forest mean height of living branches can be expressed as function of forest density and forest mean tree height. It increased with the increasing stand age and density. The Schumacher and Korf equation expressed as function of tree variables can be used to predict the height of living branches and crown length dynamic of Mongolian scots pine plantation respectively.These results can provide theory base and management method for improving forest increment and timber quality which is of great significance.