Five years of monitoring infection and mortality in redwood tanoak forests

Abstract

Rates of disease incidence and tree mortality in redwood-tanoak forests were determined by repeated sampling across a system of 120 plots at five long-term research sites from 2001 through 2006. Plots were located within the known geographic area of Phytophthora ramorum in California, ranging from Monterey to Sonoma counties. All overstory species were monitored, but analysis was restricted to three important host species: California bay laurel (Umbellularia californica), tanoak (Lithocarpus densiflorus), and redwood (Sequoia sempervirens). Infection in bay laurel and tanoak varied among years and plots suggesting weather patterns and abundance of susceptible species are important determinants of disease dynamics. Disease incidence was greatest in bay laurel followed by tanoak and redwood. Tanoak stems greater than 10 cm diameter at breast height were killed more frequently than smaller trees. Further analysis will use statistical modeling and validation to evaluate the role of vegetation structure and climate variation on rates of infection and mortality of tanoak. By proving baseline rates of infection and mortality across structurally heterogeneous stands, this effort will help in the design of stand-level management strategies and identification of local areas where control strategies will be most effective.

Parent Publication

• Proceedings of the sudden oak death third science symposium

Citation

Cobb, Richard C.; Lynch, Shannon C.; Meentemeyer, Ross K.; Rizzo, David M. 2008. Five years of monitoring infection and mortality in redwood tanoak forests. In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M., tech. coords. 2008. Proceedings of the sudden oak death third science symposium. Gen. Tech. Rep. PSW-GTR-214. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. pp. 215-217