Introduction Page 9C


Watershed 5


4. Watershed 5. This watershed manipulation was designed to look at the effects of a commercial (how forests are often cut by real loggers) whole-tree harvest on nutrient cycles.

Watershed 5 was whole-tree clear-cut during the autumn of 1983 through the spring of 1984. All trees larger than 10 cm in diameter were harvested by removal of whole trees (bole and tops) using a feller-buncher machine (see below) on accessible slopes and chain saws on steep inaccessible slopes. With limbs removed, trees were removed using skidders.

In this experiment a buffer was not left surrounding the stream (as was done in Watershed 4). A total of 180 tons per hectare of biomass was removed from the watershed.

 
A feller-buncher used in the Watershed 5 clear-cut

Clearcutting northern hardwood forests like Watershed 5 results in:

  • An increase in temperature (as much as 6 degrees C) at the soil surface and in streams - unless streamside buffers of trees are left around the streams. Many fish, insects, algae, and other aquatic organisms are sensitive to temperature.

  • An increase in the moisture content of the soil. Decomposers that live in the soil can be affected by soil moisture content.

  • Watershed 5
    A maximum increase in streamflow of approximately 40 percent, and an increase in summer peak flows averaging 20 percent.
  • An earlier snowmelt runoff.
  • An increase of nutrients, especially nitrate, in the soil solution - subject to loss by leaching or uptake by plants and microorganisms. Forest nutrient loss may have negative effects on plants and trees.


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