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Abstract
Processes operating across different spatial scales (for example, individual, community, landscape) influence disease dynamics. Understanding these processes and their interactions can yield general insights into disease control, disease dynamics within communities, and community response to disease. For
Phytophthora ramorum, pathogen establishment and disease intensity are key drivers of deleterious impacts on ecosystems such as changes in fuel loads, tree mortality, and transformation of native plant communities. We studied infection rates of
P.
ramorum for major overstory species together with mortality rates caused by sudden oak death in tanoak (
Lithocarpus densiflorus) in central coast redwood forests of California. Our analyses used a combination of individual and population-level estimates for these processes. Approximately 5800 trees were surveyed in 2002 and 2007 across 120 plots located at 14 sites from Sonoma to Monterey Counties (Maloney and others 2005). Our objectives were to examine rates of pathogen establishment amongst species and to identify key drivers of tanoak mortality. We used hierarchical path analysis to quantify community disease drivers (overstory species densities, prevalence of
P.
ramorum in infectious hosts) and survival analysis to examine characteristics that influence infection and mortality rates at the individual level (tree size, canopy position, species, post mortality sprouting). A simple theoretical model was constructed to examine the potential for tanoak persistence across redwood communities where
P. ramorum has been naturalized. The model was parameterized from the path and survival analyses.
Parent Publication
Citation
Cobb, Richard C.; Filipe, Joao A. N.; Meentemeyer, Ross K.; Gilligan, Chris A.; Lynch, Shannon C.; Rizzo, David M. 2010. Community and individual effects on SOD intensification in California redwood forests: implications for tanoak persistence. In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M. 2010. Proceedings of the Sudden Oak Death Fourth Science Symposium. Gen. Tech. Rep. PSW-GTR-229. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. pp. 217-222
