Individual Tree Growth Model System For Mongolian Oak Forest

Individual tree growth models are of imporance for natural forest management. The dataused to develop individual model for Mongolian oak forest was collected from195re-measured permanent sample plots with10-year period from1997to2007in WangqingForest Bureau of northeast China. Growth model system was developed which inludedindividual diameter growth model, height-diameter model, mortality model, and recruitmentmodel.(1) Based on analyzing the relationship between diameter increment of individual treeswith tree size, competitive status, and site condition and the major independent variables,individual tree growth model of Mongolian oak forest was developed using stepwise regressionmethod. The model was characterized by simple form, good predicting precision, and easyapplication. Main variables which had influence on diameter increment of individual trees weretree size and competition index. The site condition was not related with diameter increment.(2) Fitting results of local and general height-diameter models were compared. R2valueswere around0.65and between0.73-0.91for local and general height-diameter models,repectively. This result indicated that the general height-diameter models had higher precision.So optimal generalized height-diameter model was developed,and the independed variblesinclude diameter, the number of trees per hectare, stand basal area per hectare, average heightof dominant trees.(3) The mortality model for Mongolian oak was developed using binary logistic model,and results indicated that the diameter, competition index and stand density had significanteffects on tree mortality. As diameter decreases, the mortality probability increases.Chisquare-Test results and ROC curve showed that the binary logistic can generate rationalprediction. (4) Two-stage estimate was used for recruitment model of Mongolian oak. Firstly, therecruitment probability model was developed using binary logistic model, and the independedvaribles include elevation,site class index,stand basal area per hectare, the number of trees perhectare. Chisquare-Test results and ROC curve show that the model has good explanatory andpredictability. Secondly, the number of recruitment trees were estimated using the ordinarylinear stepwise regression method, and results indicated that the model can generate rationalprediction.(5) The simultaneous equations of individual diameter growth model and mortality modelfor Mongolian oak were developed using seemingly unrelated regression, so the parameterestimation of the group of correlated equations was unbiased and the equations werecompatible. Results indicated that the estimated values of the diameter growth and mortalityare accurate.