REPEATED MANUAL RELEASE IN A YOUNG PLANTATION - EFFECT ON DOUGLAS-FIRSEEDLINGS, HARDWOODS, SHRUBS, FORBS, AND GRASSES

Douglas-fir seedlings on the Arcata Resource Area, Bureau of Land Mana gement, U.S. Department of the Interior, in central coastal California , were released by chain sawing and grubbing competing vegetation arou nd them at different frequencies (0, 2, and 3 grubbings) over a 5-year period. After 5 years, average Douglas-fir stem diameter (measured at 12 inches above mean groundline) of seedlings grubbed at ages 1, 2, a nd 5 was 0.91 inches, and of seedlings grubbed after the first and fif th growing season was 0.95 inches. Both were significantly larger than counterparts in the control (0.57 inches). Tanoak, the most competiti ve species, constituted 84 percent of total plant cover in the control after 5 years, but only 25 percent on treated plots. Combined shrubs varied little between the untreated control and treated plots and aver aged about 7 percent of total foliar cover. Grasses were not present i n the control and only for the fifth year in treated plots. The most a bundant forb, a hedge nettle, increased greatly in density in both con trol and treated plots. These relationships and others denoted in the paper yield valuable ecological information on species and community d ynamics in both a natural and treated environment. Crew time (no overh ead or travel costs) for the three grubbings was 52 hours and for the two grubbings was 44 hours.