| Thus this paper takes Larix kaempferi of Longshan County,Hunan Province,as the research subject.In the research area,the study group investigated 42 permanent sample plots and temporary sample plots,and collected the investigation data of 266 groups which were subject to the Forestry Accurate Enhancement Project carried out by Forestry Bureau of Longshan County,Hunan Province in 2018.Based on the model selection,and various fitting and testing,this paper studies the standing-tree volume and the biomass estimation model of Larix kaempferi in Longshan County,Hunan Province.What's more,it makes an exploration of the correlation between the standing-tree volume and the biomass.(1)To construct and test the estimation model of the standing-tree volume:after finishing the data reduction through Excel operation,the data of analytic trees were divided into 53 groups of modeling samples,26 groups of model testing samples,and seven mathematical models were selected to fit and test the relationship of binary standing-tree volume,the coefficient of determination R2 of each mathematical model and the mean value MSE of residual sum of squares were used as the criteria.It is concluded that the mean value of residual sum of squares based on the Binary Volume Equation Model is the lowest,MSE=0.0037,while the coefficient of determination based on the Xian-yu Meng's Volume Equation Model is the highest,R2=94.9%.After the evaluation of the fitting effect of the two models,it was found that the indexes of Binary Volume Equation Model were better than those of Xian-yu Meng's Volume Equation Model.Then the applicability test of Binary Volume Equation Model was carried out,and all the indexes in the testing index meet the specified requirements.In conclusion,it is found that the volume equations of both two models reach to the applicable conditions,detailed as follows:V=0.0003 × D2.0623 × H0.2602Based on the development of the models,the binary standing-tree volume table of Larix kaempferi in Longshan County,Hunan Province,was obtained,which is scientifically applicable for the local production.In view of the regional characteristics and tree species of Larix kaempferi in Longshan County,Hunan Province,the model being studied was compared with the standing-tree volume model of Larix kaempferi in the mountains of West Hubei and the binary standing-tree volume model of pinus massoniana in Hunan Province.Based on the dada of 26 groups of testing samples,the accurate degree P was estimated,and then after analyzing residual error(SR)and the volume comparison under the condition of same DBH and tree height,it is concluded that the standing-tree volume model being studied in this paper is more applicable to the Larix kaempferi in Longshan County,Hunan Province.Comparative results are shown in sections 4.1.3 and 4.1.4.According to the scaling data of 256 groups of each tree,the relationship betweenDBH and tree height is fitted,and the parabolic curve model is obtained:H=-1.4622+1.4752 × D-0.0372 × D2Then the model is substituted into the Binary Volume Equation Model,and theunitary standing-tree volume model is obtained:V=0.0003 × D2.0623 ×(-1.4622+1.4752 × D-0.0372 × D2)0.2602Based on the validity testing,RS value meets the requirement of-3%<RS=0.0676<3%,and then after testing the applicability of the model,it got this result:-5%<RS=-2.703%<5%;meanwhile,on the basis of the F testing(F=-131.3351?F 0.05=19.424),it is shown that the mathematical model established and selected is applicable,and then carry on the development of the unitary standing tree volume table in Longshan County,Hunan Province.(2)To construct and test the estimation model of the standing-tree biomass.basedon Larix kaempferi 85 groups of biomass data collected,59 groups of data were modeled and 26 groups of data were tested by substituting into the model.By means of model fitting and model test of biomass and DBH and tree height in each part,it is concluded as follows:to determine the coefficient R2 and the mean value of the sum of the squared residuals MSE by the fitting index;according to the testing index,to conduct the total relative error value RS,the average relative error value MRE,the absolute value of the average relative error AM RE,and estimate the accurate value P.The optimal biomass model and fitting index for each part are shown in Table 4.17 in section 4.2.1(6).On the basis of this method,the biomass model of each part(trunk,bark,branch,leaf and the parts on the ground)and DBH,the coefficient R2 and the mean value of the sum of the squared residuals MSE were determined by the fitting index;the total relative error value RS,the average relative error value MRE,and the absolute value of the average relative error AM RE were conducted by the testing index and the precision value P estimated.The fitting and the testing results are shown in Table 4.23 in section 4.2.2.(6).(3)To analyze the correlation between the standing-tree volume and biomass.After testing the dada of the collected volume and biomass of each part(trunk,bark,branch,leaf and the parts on the ground)by means of Scatterplot diagram method,the correlation model was determined based on the distribution of the scatterplot.The coefficient R2 and the mean value of the sum of the residual squares MSE are determined by the fitting index,and the biomass models of each part are selected for validity test;the results are shown in Table 4-29 in section 4.3.2.It can be seen that the correlation coefficient of biomass and volume model of each group is relatively high,the estimated accurate degree P is above 90%,the ?2 value of each model are less than the testing value ?2(0.05).On the basis of the various tests,it is found that the accuracy of the regression equation being formulated is high.The regression equation selected in this paper is proved to be feasible to calculate the biomass according to the volume being applied in the man-made forest of Larix kaempferi in Longshan County. |
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