Simulation of annual growth is based on component relationships predicting annual in-growth , juvenile growth , height increment , diameter increment , and mortality . For juvenile trees less than 4.0 cm DBH , a separate sub-model predicts height increment, diameter increment, and survival. These relationships focus primarily on height growth and are quite preliminary since there is little data for young stands. Height increment is a predicted based on the site index for the species and the relative competition that the tree is experiencing. Diameter increment is predicted as a function of tree and stand characteristics.
Survival rate is predicted using a logistic regression model to predict probability of survival.
In addition survival is constrained based on the biological limits of size and density as well as theoretical expectations for small trees growing under the canopy of other trees.