Succession
“Pioneer” trees such as aspen or White Birch often establish themselves on treeless land such as from a field, or from a complete harvest (devoid of young trees), or fire. These trees, while intolerant of growing in shade, out-compete other species when establishing a new forest. Balsam fir, while tolerant of growing in shade, is often found in these pioneer forests. As they become mature, spruce and / or tolerant hardwoods grow up from the shaded understory, overtaking these primarily intolerant stands to become the climax forest. Depending on the site, this will be either a hardwood, softwood, or mixedwood stand.
Management of climax forest types to promote natural regeneration of the tolerant trees will prevent intolerants from overtaking the site. This will maximize production of the site by “quality” trees.
Site disturbance will also affect what trees will regenerate, with spruce, Yellow Birch, cedar, and pine regenerating better when mineral soil is exposed. Site disturbance should not be carried out in sites prone to erosion.
Dominance of a site by intolerant hardwoods will delay production of higher value wood, with the exception of Red Maple, which while intermediate in tolerance, often accompanies White Birch and Poplar in pioneer forests. Red Maple provide much higher fuel value than these other species, so short management can be carried out to favor the maples.
There are reasons to maintain pioneer species such as aspen for wildlife habitat (ex. Ruffed Grouse, beaver) in specific locations by periodic clearcutting or other means in specific locations.