Introduction Page 9B


Watersheds 4 and 101

2. Watershed 4: This watershed manipulation was conducted to examine the effects of strip-cutting on forest water yield (how much water leaves the forest) and nutrient input-output budgets. Strip-cutting is expected to cause less damage and disturbance than other types of forest logging such as the whole-tree harvest conducted in Watershed 5 (see next page).

Watershed 4 is in the background - this is after the 1st cut

Watershed 4 was divided into 49 east-west strips (almost following topographic contours) 25 m wide. In the autumn of 1970, every third strip was cut. The second series of strips was cut in 1972, leaving one series of strips uncut. Finally in 1974, the last set of strips was cut.

Click here to see one of these strips at ground level.

Except for a buffer of trees that was left along the main stream channel, the entire watershed was clear-cut in these three phases. All trees to a minimum of 5 cm were felled, and all products of value to the logging contractor were removed by rubber-tired skidder. Dense natural regrowth is now occurring.

Results:
  • Strip-cutting did not result in significant increases in erosion. Erosion causes soil to wash into streams and leave the forest. This can harm both the forest (plants need nutrients in the soil to grow) and streams (most aquatic organisms in the HBEF need clear water in which to live).

  • Streamwater nutrient concentrations and water yield increased during and immediately after strip-cutting, but in very small amounts. Compare this to Watershed 2, on the previous page.

  • At year 10, the strip cut had a more desirable mix of commercial species than the block cut on Watershed 101 (below), with higher densities of yellow birch and sugar maple and lower densities of pin cherry.

3. Watershed 101: In the autumn of 1970, Watershed 101 was block clear-cut (the entire watershed was cut at one time) as a comparison to the strip-cut experiment being conducted in Watershed 4. All trees to a minimum of 5 cm were cut and all merchantable products were removed by the same operator who cut Watershed 4. Rubber-tire skidders were used to remove the stems. Click here to see a winter photo of Watershed 101.

Results:
  • Simulated streamflow (no weir was present to measure actual streamflow) increased 36 percent the first year after cutting and declined steadily until it returned to precutting levels by year 6.

  • Streamwater nutrient loss increased after cutting before returning to precutting levels by year three.


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