Biomass Allocation Characteristics And Its Estimation Models Of Natural Betula Platyphylla In Daxing’anling,Inner Mongolia

The Daxing,anling Mountains in Inner Mongolia is an important part of the northeastern forest region and the main distribution area of the cold-temperate forests in China,which occupies an important position in the national carbon measurement and global carbon cycle.Biomass estimation is a prerequisite for accurate quantification of forest carbon stocks and their dynamics,and the construction of a biomass model with high prediction accuracy can provide a scientific basis for forest productivity estimation and production management.Based on the reliability and accessibility of the independent variables and the practicality of the model,we established the allometric growth models and the compatibility models by the leave-one-out cross-validation method based on the analysis of the total biomass and the biomass distribution characteristics of each component(root,branch,stem and leaf)of Betula platyphylla forest.Through the analysis of evaluation indexes,the optimal natural Betula platyphylla biomass model was selected to provide methodological reference and data support for the accurate estimation of Betula platyphylla biomass in Daxing’anling.The main findings of this thesis are as follows:(1)The biomass of different components differed.The average biomass distribution of each component in young natural Betula platyphylla stands was 57.88%for the ratio of stem and total,29.38%for the ratio of root and total,9.53%for the ratio of branch and total,3.21%for the ratio of leaf and total,and 43.30%for the ratio of root and stem.The average biomass distribution of each component in the middle-aged forest was 73.53%for the ratio of stem and total,18.18%for the ratio of root and total,5.63%for the ratio of branch and total,2.66%for the ratio of leaf and total,and 24.50%for the ratio of root and stem.The biomass distribution of each component varied with the change of DBH and tree height,but the overall biomass of young and middle-aged forests showed that stem>root>branch>leaf.(2)All the four allometric growth models of Betula platyphylla developed in this thesis achieved good fitting results.Comparing the goodness-of-fit,test indexes and relative ranking values of the allometric growth models under two different function schemes,the binary biomass models based on power function and polynomial function was superior to the univariate biomass model;the allometric growth models based on binary power functions had the best fit among the four biomass models;the binary power function biomass models corresponding to the total biomass of the single plant,root,stem,branch and leaf biomass were:w1=204.815(D2H)0.905,W3=33.103(D2H)0.678,w4=162.738(D2H)1.037,w5=9.879(D2H)0.612,w6=6.268(D2H)0.887.(3)By comparing the goodness-of-fit and test indexes of the univariate and binary biomass models constructed under two different compatibility schemes,the univariate biomass model fit better than the binary biomass model,and the algebraic sum scheme was better than the proportional allocation(proportional method)scheme under total control.Among the four compatibility biomass models constructed,the univariate compatibility biomass model under the algebraic sum scheme was optimal with biomass model parameters of a1,b1,r1,k1,r2,k2,r3,and k3 were 0.046,2.814,3.600,8.600,0.300,-0.740,8.600 and-1.336,respectively.(4)During the forest management,when estimating the biomass of natural Betula platyphylla,considering the applicability of the model,the accessibility of the independent variables and the accuracy of the model,it is recommended to give priority to the univariate algebraic sum compatibility biomass model with DBH(D)as the independent variable.