The stocking, age, and growth rates of tanoak (Lithocarpusdensiflorus [Hook and Arn.] Rehd.) were studied in the understory of 13 Douglas-fir (Pseudotsugamenziesii [Mirb] Franco) and mixed conifer stands, 53–240 years old, on a range of sites in Oregon and California. The understory was uneven in both age and size in all stands. Tanoak <2.0 cm diameter at breast height (dbh) ranged from 1 to 62 years old and from 5 to 216 cm tall. The stems of tanoak >2.0 cm dbh ranged from 18 to 98 years old and from 2 to 25 m tall. A negative exponential function describing diameter distributions generally explained more than 80% of the within-stand variation in numbers of tree stems (by 5-cm diameter classes). Seedlings have a single stem for about 5–12 years, then form a burl with dormant buds below ground, lose the original stem, and produce new stems. Because of frequent stem mortality and sprouting, tanoak age cannot be determined from stems above ground but can be estimated from xylem rings in the stem below the burl. Tanoak grows slowly in the conifer understory and at 50 years of age is only 80 to 160 cm tall. Sprouting potential also develops slowly. Three years after burning, 41- to 50-year-old tanoak averaged five sprouts only 30 to 68 cm tall. The establishment of a dense, new understory with the capacity for vigorous sprouting after disturbance may take well over 100 years. Tanoak control may be less costly and less frequently needed if accomplished in 30- to 75-year-old conifer stands.

The Forest Service of the U.S. Department of Agriculture is dedicated to the principle of multiple use management of the Nation's forest resources for sustained yields of wood, water, forage, wildlife, and recreation. Through forestry research, cooperation with the States and private forest owners, and management of the National Forests and National Grasslands, it strives-as directed by Congress-to provide increasingly greater service to a growing Nation.The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.

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Escalating controversy on clear-cutting, herbicides, burning, and grazing led to a research program with 40 studies, begun in 1980, that compared most of the vegetation management techniques used for enhancing growth of 1- to 3-year-old conifer seedlings. These include such direct techniques as manual manipulation, mulching, herbicides, and grazing for releasing conifer seedlings from undesirable vegetation, and several silvicultural practices (broadcast burning, group selection, genetically improved seedlings) that serve as indirect methods for reducing or avoiding vegetation problems. Manual release and mulching are effective but expensive. Herbicides are effective, applicable to almost all plant communities, and relatively inexpensive. Grazing is good for cattle and sheep, but does not significantly enhance conifer seedling growth. Utilizing the silvicultural practices noted above and emphasizing replacement vegetation show promise, but lack sufficient testing for us to evaluate feasibility. In most instances, forests cannot be managed economically without herbicides if the goal is to grow seedlings at the potential of the site and the plant community includes sprouting hardwoods and shrubs or rhizomatous forbs and ferns. If the goal is to create a forest with several age-classes and variable structure, but with slower seedling growth, longer time to harvest, and less species diversity in early seral stages, then it is possible to accomplish this without herbicides and other means of vegetation control.

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