In-growth is the process whereby previously open forests become denser and treed grasslands become more densely covered with young trees.

An activity, such as harvesting or road construction, that removes trees in an old-growth management area.

The arrival of an organism in an area where it was not formerly represented.

Plant species that were absent in undisturbed portions of the original vegetation of a specific range site and will invade following disturbance or continued heavy grazing.

Plant species, of the original vegetation, that increase in relative amount due to overgrazing.