| Current research indicates that projected climate change may influence the growth of individual trees. Therefore, it has become necessary to develop growth and yield models that can respond to potential changes in climate. TREE-BGC, a variant of the ecosystem process model FOREST-BGC, calculates the cycling of carbon, water and nitrogen in and through forested ecosystems. TREE-BGC allocates stand level estimates of photosynthesis (PSN) to each tree using a competition algorithm that incorporates tree height, radiation-use efficiency, and absorbed photosynthetically active radiation. This model was used to simulate the growth of trees grown in a dense and an open stand near Kamloops, B.C. Stand variables were aggregated from a tree list. Trees were grown using allometric equations. Sapwood and phloem volume were used to calculate maintenance respiration. Mortality occurred when the maintenance respiration demands of the tree exceeded the carbon allocated to the tree. The competition algorithm dynamically allocated stand estimates of PSN to individual trees such that the predicted reductions in diameter growth with stand density were similar to the observed reductions in diameter growth.;Model results were tested statistically, using goodness-of-fit procedures to compare the cumulative diameter distributions, and the stand basal area and volume growth after a 20-year period. Model behavior was tested by simulating the growth, over a 100 year period, of individual trees initially grown at different stand densities. Plot level estimates of basal area growth and volume growth were highly correlated with actual measurements (r;Model behavior was tested qualitatively using long-term simulations. Individual tree diameter and height growth rates reflected the influences of competition, as did stand basal area and volume growth, and stand density. |
