Study On The Crown Structure And Aboveground Biomass Of Pinus Massoniana Plantation

The canopy is the main part of tree photosynthesis and transpiration,and its structural characteristics affect the growth of the tree and the distribution of the yield of various components,and have a huge effect on the physiological and ecological processes of the tree.In order to understand the canopy structure characteristics and growth regularity of Pinus massoniana plantation,and to solve the problem of crown branch attribute factors and the estimation of biomass of each component of forest tree.In this paper,the four-age group of P-massoniana plantations distributed in the middle of Guizhou is taken as the research object.On the basis of plot survey,branch analysis factor survey,biomass measurement and trunk analysis,the crown structure and biomass of different types of trees are analyzed.Distribution and tree growth rules,constructing the prediction models of tree crown and branch attribute factors and their biomass,the prediction models of the biomass of various organs on the forest floor and the growth models of each tree factor.It can provide a theoretical basis for improving the productivity and wood quality of P-massoniana plantation,and also lay the foundation for the sustainable management of P-massoniana plantation.The main research conclusions are summarized as follows:(1)In the trees of different age groups and dominant grades,the measurement factors of the canopy showed different degrees of difference.As the age group increases,the number of branches,branch base diameter,branch length,living branch height and crown length all increase,but the crown length rate decreases.As the dominance level increases,the number of branches and the average base diameter also increase.There are different degrees of correlation between branch measurement factors.The base diameter of branches is significantly positively correlated with branch length,zenith angle,branch height and branch depth,and branch length is related to zenith angle and branch depth And the height of shoots were significantly positively correlated.The vertical distribution of branch length and base diameter generally shows that the lower layer of the canopy is larger than the upper layer,and the change of the vertical distribution of the number of branches is opposite.(2)A variety of methods are used to construct the prediction model of the tree crown and branch attribute factors.Among them,the crown length prediction model has the best fitting effect with the binary(breast diameter,height under branches)parabola combination model.The model of the total number of branches is the quadratic function with crown length as its independent variable.The prediction model of the length and base diameter of the branches is constructed from the level of the single tree and the branch respectively.The models on the level of the single tree are the quadratic functions with the breast diameter as the independent variable.The ternary parabolic combination model with crown length ratio and live branch height as independent variables is the best,and the branch base diameter model of branch level is the ternary parabolic combination model with branch depth,breast diameter and crown length as independent variables..(3)The branch biomass diameter and branch chord length are selected as independent variables for the construction of the branch biomass model,and the breast diameter,living branch height and height-diameter ratio are selected as independent variables for the construction of the crown biomass model.The predicted effects of the shoot and crown biomass models show a parabolic combination model>power exponential allometric growth model>stepwise linear regression model.There is a difference in the vertical distribution of canopy biomass of various forest types.For trees of young age or low dominance,there is little difference in the vertical change of canopy biomass.The biomass of canopy of old or dominant trees is mainly concentrated in the middle layer of the canopy.The biomass ratio of branches and leaves of various forest types generally increases with the increase of canopy depth.(4)The organ allocation law of biomass shows differences in different age groups and different dominant grade forests,but the trunk biomass still accounts for the main part.With the increase of tree age,the proportion of aboveground biomass occupied by trunk biomass gradually increases,the proportion of biomass of branches and leaves gradually decreases,and the proportion of bark biomass increases first and then decreases.In addition to breast diameter,volume and tree height,living branch height,crown length and crown length rate are also important factors affecting the biomass of Masson pine.However,for the biomass model of most organs,only one unary power function can be used.A total control method was used to construct the compatibility models of biomass of different dominant grades of P-massoniana,and the model satisfied the condition that the total biomass of single wood was equal to the sum of the biomass of each component.