Feasibility of alternatives to herbicides in young conifer plantations in California

Abstract
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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