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Regeneration and tanoak mortality in coast redwood stands affected by sudden oak death

Informally Refereed

Abstract

Sudden oak death, an emerging disease caused by the exotic pathogen Phytophthora ramorum, is impacting coast redwood (Sequoia sempervirens) forests throughout coastal California. The most severely affected species, tanoak (Notholithocarpus densiflorus), is currently widespread and abundant in the redwood ecosystem, but diseased areas have begun to experience considerable mortality. Tanoak, which is extremely valuable as food source to numerous wildlife species, is unlikely to successfully regenerate in these areas, and thus affected redwood forests are transitioning to a novel state. In this study, to predict which species might replace tanoak, we investigated regeneration patterns in heavily impacted stands in Marin County, California. Our main findings were: (1) despite reductions in canopy cover, there is no evidence that any species other than tanoak has exhibited a regenerative response to tanoak mortality, (2) the regeneration stratum was dominated by redwood and tanoak (other tree species were patchy and/or scarce), and (3) some severely affected areas lacked sufficient regeneration to fully re-occupy available growing space. Our results indicate that redwood is likely to initially re-occupy the majority of the ground relinquished by tanoak, but also provide evidence that longer-term trajectories have yet to be determined and may be highly responsive to management interventions.

Parent Publication

Keywords

Lithocarpus densiflorus, Notholithocarpus densiflorus, Phytophthora ramorum, regeneration, redwood, Sequoia sempervirens, sudden oak death, tanoak

Citation

Ramage, Benjamin S.; OHara, Kevin L.; Forreste, Alison B. 2012. Regeneration and tanoak mortality in coast redwood stands affected by sudden oak death. In: Standiford, Richard B.; Weller, Theodore J.; Piirto, Douglas D.; Stuart, John D., tech. coords. 2012. Proceedings of coast redwood forests in a changing California: A symposium for scientists and managers. Gen. Tech. Rep. PSW-GTR-238. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture. pp. 377-386.
Citations
https://www.fs.usda.gov/research/treesearch/41170