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Title: Timing and Duration of Release Treatments Affect Vegetation Development in a Young California White Fir Plantation
Author: McDonald, Philip M.; Fiddler, Gary O.
Source: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; 14 p
Station ID: RP-PSW-246
Description: The density and development of snowbrush, greenleaf manzanita, goldenbush (rabbitbrush), and graminoids were evaluated in a young California white fir plantation in northern California from 1986 through 1995. Manual grubbing and an herbicide created treatment regimes that lasted for 3 to 6 years and vegetation recovery times of 4 to 10 years. The timing and duration of the grubbing and spraying operations constituted the treatments. In terms of foliar cover and height, snowbrush was the most vigorous shrub species. By the end of the study it had more foliar cover (16,350 ft2 per acre) in the control than all the other species combined and had the greatest height (2.9 feet). It also was significantly wider and taller in the control than in any other treatment. California white fir survival and height, diameter, and foliar cover growth were all enhanced by early release. Releasing every year for the first 3 years and for the first 6 years after planting were significantly effective treatments. However, treating for the first 6 years had no significant advantage over treating for the first 3 years. Delaying treatment for 3 years and then treating each year for years 4 through 6 gave no significant growth advantage over seedlings in the control. For white fir seedlings in the control, their foliar cover was less than that of the shrubs and graminoids, and their average height was less than that of snowbrush. Increased mortality and lower growth for these seedlings are likely. Early release was effective because it kept the competing shrubs and graminoids from recovering from the effects of site preparation, providing needed site resources to the white fir seedlings.
Key Words: competing vegetation, northern California, plant succession, white fir seedlings, timing of release
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McDonald, Philip M.; Fiddler, Gary O. 2001. Timing and Duration of Release Treatments Affect Vegetation Development in a Young California White Fir Plantation Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; 14 p.
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