Construction And Application Of Larix Individual Tree Growth Model In Linjiang Forestry Bureau

Taking the larch plantation of Linjiang Forestry Bureau as the study’s object,the preliminary survey and retest of 60 square fixed plots with an area of 0.06 hm~2 were carried out in 2018 and 2021 respectively,and the survey data of 1845 larch trees were obtained.A simple and practical distance-independent individual tree growth model of larch was constructed by stepwise regression technique.The relationship between DBH growth and its own size,competition and site quality was analyzed,and the dominant factors affecting DBH growth of larch in this area were found.The application of the constructed model was studied,and a single tree growth prediction system was developed to dynamically predict the growth of larch.The research results can provide reference for the later management.The specific research results are as follows:(1)Through comparative analysis,it is found that the effect is better than the DBH increment when the chest height area increment is used as the dependent variable.As for the independent variables of the model,there are 13 independent variables to be selected:ln D,D~2,H,N,BAL,RD,DDM,P,SL,SL~2,SLS,SLC and HB.After collinearity test,t test and adjustment of multiple correlation coefficient R~2,the optimal number of variables in the model is 5,which are ln D,RD,P,SL and SLS.The final model is determined as:ln(BAI+1)=-0.448+1.161ln D+1.364RD+0.786SLS-1.205P-0.675SL(2)The results of single tree growth model of larch showed that the main factor affecting the DBH growth of artificial larch in Linjiang Forestry Bureau was ln D,followed by RD,P and SLS.The least influential is SL.From the three directions,competition factor(47%)>forest size factor(33%)>site factor(20%).The three variables of initial DBH logarithm(ln D),relative diameter(RD)and slope rate and aspect combination(SLS)were positively correlated with the growth of basal area,and canopy density(P)and slope rate(SL)were negatively correlated with the growth of basal area.(3)This study uses a ten-fold cross-validation method,which can use all the data to build the model and increase the accuracy of fitting.According to the test findings,the model fitting effect is good,there is little variation between the predicted value and the measured value,and the prediction accuracy is both high and very adaptable.It can well describe the growth of the basal area of larch single tree.Taking into account the principle of practicality,so on this basis,the dependent variable is inversely deduced by mathematical thinking to verify the DBH.The multiple correlation coefficient R~2 between the predicted value and the true value of the final DBH is as high as 0.988,which further shows that the model fitting effect is better.(4)When using the model,which is based on the model,the prediction system of the DBH growth of larch in this area was compiled,and the system was used to compile the prediction table of DBH growth of single tree.By combining with the one-dimensional volume table of artificial larch in this area,the volume prediction table is compiled.In summary,this study quantitatively analyzed and simulated the growth of larch in Linjiang Forestry Bureau,and obtained the growth equation of single tree that can be used locally and the growth prediction table that can be referred to.It provides a valuable reference for the future development trend of larch plantation in this area and the management and sustainable management of larch plantation in this area.