Extensive forestry recognizes that we cannot foresee clearly enough the forest's future for the time spans required to be certain of markets, species demands, quality requirements and the human driven whims of ownership. Nor can we be certain of biological changes, either subtle or swift. Because of this, the tendency, even the objective, is to produce a mixed and therefore more flexible forest. Light partial cuts are characteristic. Even final harvest or regeneration cuts need not be total.
Partial cuts result in partial light and partial crown space.
The cost of this is increased time to reach a chosen diameter class. The reward is increased stem quality. This, the production of higher grades of lumber, dimension or veneer, is the hallmark of extensive practices. If the site quality is high enough, the inevitable intrusion of hardwoods in the regeneration can be accepted and directed in future thinnings. This method, the shelterwood, can also be successful in other timber types.