A generalized logistic model of individual tree mortality for aspen, whitespruce, and lodgepole pine in Alberta mixedwood forests

A generalized logistic model of individual tree mortality was developed for trembling aspen (Populus tremuloides Michx.), white spruce (Picea glauca ( Moench) Voss), and lodgepole pine (Pinus contorta Dougl. ex Loud. var. lati folia Engelm.) in Alberta boreal mixedwood forests based on an empirical da ta base of permanent sample plots. The model is suitable for observations f rom unequal remeasurement intervals. The maximum likelihood estimation was used to fit the model, the likelihood ratio test was combined with our unde rstanding of mortality process to select the important variables, and the H osmer-Lemeshow goodness-of-fit test was conducted to evaluate the fit. The fitted model predicts the survival probability of an individual tree based on the tree diameter at breast height, annual diameter increment, stand bas al area, species composition, and site productivity.