The objective of this project is to develop species-specific models that predict the probability of mortality for an individual tree given current radial growth. The focal species are subalpine fir (Abies lasiocarpa (Hook.) Nutt.), hybrid spruce (a complex of white spruce (Picea glauca (Moench) Voss) and Engelmann spruce (Picea engelmannii Parry ex Engelm.)), lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia) and trembling aspen (Populus tremuloides Michx.). The mortality models were developed with an empirical and a 'theoretical' approach. In the theoretical approach existing information on density dependent mortality in single-species even-aged stands were utilized to develop approximate models. In the empirical approach, field sampling was performed and the mortality models were parameterized with maximum likelihood methods. We generally found that the empirical and the theoretical mortality models were very similar. The exception was lodgepole pine for which the two types of models were quite different. The general similarity of the theoretical and the empirical models improved our confidence in the empirical models. The empirical mortality models were incorporated into the simulation model SORTIE-ND. Hereafter, the mortality models predictive ability was evaluated by comparing SORTIE-ND stand level predictions to permanent sample plot data. It was found that the mortality models provided relatively good predictions of stand density.
Bruce Larson and Rasmus Astrup.
Larson, Bruce C., Astrup, Rasmus. 2006. Modeling individual tree mortality for northern mixed-species stands. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2006MR261