Graduate Thesis Or Dissertation
 

An alternative to clearcutting

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/70795b64p

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  • Clearcutting is a sound silvicultural practice when exercised in the proper environmental location. Foresters have learned through bitter experience that clearcutting Douglas-fir forests, located on droughty south-facing slopes, often leaves uncorrectable regeneration problems. Thousands of acres of unproductive grass and brush throughout the Douglas-fir region are unavoidable reminders of inappropriate sites for clearcutting. Underplanting, as demonstrated in this study, is an alternative to regeneration problems commonly associated with clearcutting in arid portions of the Douglas-fir region. This technique of planting Douglas-fir seedlings under the overstory of a mature Douglas-fir forest before removal of the entire canopy, was tested in the dry, arid portion of the interior Coast Range near Corvallis, Oregon. On a typically droughty south-slope, consisting of an old growth stand, a recently thinned Douglas-fir stand, and an old unsuccessfully regenerated clearcut, 1200 seedlings were planted. An attempt was made to evaluate survival as a function of three parameters: light, moisture stress, and vegetative competition. Ozalid light integrators measured light at each seedling on the forest floor. Seedling moisture stress was evaluated with a pressure bomb, while a measure of vegetative cover surrounding each tree indicated competition. Contrary to generally recognized supposition, this study indicates that Douglas-fir seedlings can survive, become established, and grow in the shade of a mature forest. After one growing season, survival, was highest in the old growth stand with 614 percent, and lowest in the clearcut with 38 percent. In addition, Douglas-fir does not require full sunlight for survival Less than 30 percent of full sunlight provides the best survival conditions. Further experiments will be conducted to investigate survival at the end of two growing seasons and ultimately test seedling response when the overstory is removed.
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