In-growth is defined as new trees that pass the 1.1 cm Dbh threshold. In-growth is included in a growth projection only if the "Allow In-growth" option, found in the Options event dialog, is checked. Allowing in-growth in a projection increases substantially the computational time for a projection since new trees may be added to the internal tree list in each year of the projection.
Except for aspen, in-growth is not allowed if the species is not already present in the stand. In-growth may lead to presence of species that were originally in the tree list. The in-growth dialog includes a setting to provide for site index defaults if needed for new species introduced into the stand.
For each of the four major species in MGM, the annual probability of in-growth is predicted based on stand characteristics. A randomization test is conducted and if successful, the number of in-growth trees is predicted and added to the tree list. The in-growth relationships are based on the work of Qin (1998) using an approach similar to that of the Prognosis regeneration model described by Ferguson et al (1986).