DENSITY, AGES, AND GROWTH-RATES IN OLD-GROWTH AND YOUNG-GROWTH FORESTS IN COASTAL OREGON

We studied the ages and diameter growth rates of trees in former Dougl as-fir (Pseudotsuga menziesii (Mirb.) Franco) old-growth stands on 10 sites and compared them with young-growth stands (50-70 years old, reg enerated after timber harvest) in the Coast Range of western Oregon. T he diameters and diameter growth rates for the first 100 years of tree s in the old-gowth stands were significantly greater than those in the young-growth stands. Growth rates in the old stands were comparable w ith those from long-term studies of young stands in which density is a bout 100-120 trees/ha; often young-growth stand density is well over 5 00 trees/ha. Ages of targe trees in the old stands ranged from 100 to 420 years; ages in young stands varied by only about 5 to 10 years. Ap parently, regeneration of old-growth stands on these sites occurred ov er a prolonged period, and trees grew at low density with little self- thinning; in contrast, after timber han est, young stands may develop with high density of trees with similar ages and considerable self-thi nning. The results suggest that thinning may be needed in dense young stands where the management objective is to speed development of old-g rowth characteristics.