Tree size, growth, and anatomical factors associated with bear damage in young coast redwood

Abstract

Precommercial thinning is an important tool for coast redwood (Sequoia sempervirens (D Don) Endl.) forest management but is often followed by black bear (Ursus americanus) damage in northern parts of redwood’s natural range (Fritz 1951; Giusti 1988, 1990; Hosack and Fulgham 1998). The bears scrape off bark and feed on the sugar-rich phloem of coast redwood and coast Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco) (Kimball et al. 1998). A prior study at the same study area within the Mill Creek watershed in Del Norte Coast Redwoods State Park, near Crescent City, in Del Norte County, California, showed that frequency of damage was higher among larger trees in these conifer-dominated mixed even-aged stands, and that redwood was more likely to be damaged than Douglas-fir, especially near roads. Precommercial thinning (PCT) incited damage to redwood, and PCT to lower residual densities incited more damage in Douglas-fir. Unthinned control stands were least damaged. Increment cores collected from pairs of damaged and undamaged redwood trees confirmed that damage occurred after thinning and revealed that,at the time of bear damage, trees sustaining damage had been growing faster than undamaged trees of similar size (Perry et al. 2016). These findings support mitigation strategies such as lighter thinning, leaving higher densities of redwood in anticipation of higher damage rates, and leaving unthinned buffers adjacent to roads and other paths travelled by bears.

Parent Publication

• Coast redwood science symposium—2016: Past successes and future direction

Citation

Berrill, John-Pascal; Perry, David W.; Breshears, Larry W.; Gradillas, Garrett E. 2017. Tree size, growth, and anatomical factors associated with bear damage in young coast redwood. In: Standiford, Richard B.; Valachovic, Yana, tech cords. Coast redwood science symposium—2016: Past successes and future direction. Proceedings of a workshop. Gen. Tech. Rep. PSW-GTR-258. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 326-328.