Efficacy of Herbicide Application Methods Used to Control Tanoak (Lithocarpus densiflorus) in an Uneven-Aged Coast Redwood Management Context1

Three methods of tanoak (Lithocarpus densiflorus [Hook. & Arn.] Rehd.) control involving the application of the amine or ester form of triclopyr were evaluated in this coast redwood uneven-aged forest management study of herbicides. A cut-stump application with the amine form of triclopyr (Garlon 3A), frill cut with the amine form of triclopyr, basal-bark (outer surface) with the ester form of triclopyr (Garlon 4), and an untreated control were replicated three times. The tanoak control results in Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) and/ or coast redwood (Sequoia sempervirens [D. Don] Endl.) predominated stands obtained in earlier studies in northern California and Oregon appear to be similar to the results of this study obtained in Santa Cruz County coast redwood stands. The need for tanoak control in an unevenaged forest management context is discussed. Tanoak (Lithocarpus densiflorus [Hook. & Arn.] Rehd.)6 is a prolific sprouter and aggressive competitor with coast redwood (Sequoia sempervirens [D. Don] Endl.) and Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) in mixed coniferous forests (Barrett 1995, Burns 1983, Burns and Honkala 1990a, 1990b, Little 1979, Tappeiner and others 1990). The coniferous species are commercially more valuable than tanoak (although tanoak is presently useful for fuelwood in the Santa Cruz area). Finding an effective means to control the competing populations of tanoak is often desirable. Whereas significant research information is available on controlling tanoak competition under management of even-aged forests, little information is available about controlling tanoak under management of uneven-aged coast redwood. Although tanoak has many ecosystem values, as a source of food and cover for various species of wildlife, in cut areas following timber harvest operations, tanoak sprouting can often interfere with the natural regeneration and growth of coast redwood and Douglas-fir. In such instances, the selective use of herbicides accompanied with planting of coast redwood and Douglas-fir could help maintain the site for commercial purposes and ensure that tanoak will not be an undesirable competitor. The goal of this research was to find an effective means to reduce a wide range of tanoak diameter classes (fig. 1). The specific objectives of this research project were to: •Evaluate the efficacy of herbicide application techniques for control of tanoak, and •Identify tanoak research priorities in the context of uneven-aged management of coast redwood and Douglas fir stands.