Study On Individual Tree Competition Growth Model For Cyclobalanopsis Glauca Secondary Forest

In this study,the Cyclobalanopsis glauca secondary forest of Loutu Forest Farm which belongs to Central South University of Forestry and Technology are set as research object.Based on the investigation and two-stage survey data from 12 sample plots and stem analysis data from 16 Cyclobalanopsis glauca,the study found out the most suitable methods and indicators to express the competition condition of Cyclobalanopsis glauca by analyzing a few kinds of competition wood selection methods and indicators.The growth stages are divided by using order cluster analysis method,while the main growth factor which influence Cyclobalanopsis glauca are filtered by using stepwise regression method.Based on the individual tree competition growth models of each growth stage which are built by the method of empirical equation,tending management measures will be proposed.Specific research conditions are as follows:(1)Using the data of 89 dominant tree crown,the study constructs the dominant tree crown model,and promotes it to free tree crown model by using the adjustment method of average deviation percentage:CW=0.1773+0.2799*D.(2)On the basis of the free tree crown model,dynamic radius method which determined the different sample round through different diameter class were raised.Three methods including fixed radius method,crown overlap method and dynamic radius method were used to choose the competitive tree of objective tree in the 12 sample plots.The Chapter analysisd that the number of competitive trees reduced significantly due to the dynamic radius method which eliminated the interference of invalid trees.(3)The Hegyi simple competition is improved by using tree-height adjustment coefficient:in(1+Hj/Hj).By comparing the correlation of objective tree’DBH and competition index,the comparison of three kinds of competitive indicators for the applicability of Cyclobalanopsis glauca is Hegyi-improved model>Hegyi simple competition index>Bella competition index.The competition index,including DBH,distance and height ratio is the most optimal.(4)Based on the stem analysis data of 16 dominant tree,the growth functions about DBH and volume are built.The growth stage of Cyclobalanopsis glauca is divided into unmature stage(0-16cm)and near-mature stage(>16cm)after the orderly cluster method is used to calculate the current annual increment of DBH and volume.Two competition growth models for unmature stage and near-mature stage are built by using empirical equation method that the dependent variable of model includes the current annual increment of DBH(Zg)and the independent variables of model include the DBH and competition index CI.The formula of competition growth models are as follows:The competition growth model of unmature stage:Zg=e0.002*D^2+1.186*lnD-0.164*D-0.019*CI-0.857-1(0<D<17)The competition growth model of near-mature stage:Zg=e-0.0104*lnD-0.011*Cl+0.617-1(D≥17)...