January 17, 2018 at 4:13 pm
By Lands Management Biologist Eric Hoar
Forest succession is the process where vegetation establishes and progresses over a time. It frequently occurs following a disturbance whether it be natural such as a wind or fire event, or caused by people, such as a timber harvest. Regardless of cause, forest succession typically begins a period of renewal and progresses through a series of stages.
Following a significant event where large openings occur, grasses may initially populate the site, followed by shrub species and, over a period of time, trees will begin to establish. Tree species that initially occupy the site are generally referred to as early successional species and in a forested setting in Maine frequently include, among others, aspen and paper birch. Old fields on the other hand will frequently be populated by white pine after the establishment of shrubs. Sometimes aspen, paper birch, white pine, as well as a mix of other softwood and hardwood tree species, will occupy the site together.
Tree species such as aspen and paper birch are intolerant of shade (they prefer abundant sunlight) and, as trees go, relatively short lived – “relatively” in their instance would be approximately 100 years. The photo shows an old aspen doing what old aspen do – rotting, dying and falling down! This particular tree collapsed following a minor wind storm in the late summer of 2017. Beneath it are small trees, more tolerant of shade, that represent another stage of succession. The smaller, younger trees established beneath the canopy of aspen, paper birch, white spruce and white pine. They include red maple, sugar maple, American beech, eastern hophornbeam and balsam fir and, apart from the balsam fir and possibly red maple, are all tree species associated with later stages of succession. The time line image below provides a basic diagram of successional stages.
Tree species such as aspen and paper birch are intolerant of shade (they prefer abundant sunlight) and, as trees go, relatively short lived – “relatively” in their instance would be approximately 100 years. The photo shows an old aspen doing what old aspen do – rotting, dying and falling down! This particular tree collapsed following a minor wind storm in the late summer of 2017. Beneath it are small trees, more tolerant of shade, that represent another stage of succession. The smaller, younger trees established beneath the canopy of aspen, paper birch, white spruce and white pine. They include red maple, sugar maple, American beech, eastern hophornbeam and balsam fir and, apart from the balsam fir and possibly red maple, are all tree species associated with later stages of succession. The time line image below provides a basic diagram of successional stages.
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