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Stream Protection Zone (SPZ)

Conifer Regeneration, SPZ's

Conifer Regeneration
  • Recognize that in some soil and drainage types, clear-cutting can cause marked increases in the water table, cold-air ponding, and grass/shrub competition. All of these factors can inhibit conifer regeneration.
  • To avoid potential regeneration problems, leave some mature trees.
  • Trees act as a buffer. Except for times of extreme precipitation and runoff, trees help maintain the normal water table along streams. They are like wicks, pumping water from the soil and releasing it onto the air through leaves and needles (transpiration). Of course, some soil moisture seeps (percolates) underground, slowly reaching the stream channel.


    In the same drainage after hillside trees are harvested. The "wicks" have been removed, transpiration is reduced and percolation is increased, at least until vegetation recovers.

    In the meantime, to avoid the following consequences, always leave some mature trees in the SPZ.
    1. Removing trees can lead to cold-air ponding. This extends winter's cold temperatures into early spring and hinders conifer regeneration in the SPZ.
    2. Removing trees can raise the streamside water table, which makes soils too wet for conifer regeneration.
    3. These wet soils result in grass and shrub invasion, which chokes out conifer regeneration in the SPZ.


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