, Volume 144, Issue 1, pp 106–114 | Cite as

Examining the strength and possible causes of the relationship between fire history and Sudden Oak Death

  • Max A. MoritzEmail author
  • Dennis C. Odion
Ecosystem Ecology


Fire can be a dominant process in the ecology of forest vegetation and can also affect forest disease dynamics. Little is known about the relationship between fire and an emerging disease epidemic called Sudden Oak Death, which is caused by a new pathogen, Phytophthora ramorum. This disease has spread across a large, fire-prone portion of California, killing great numbers of oaks and tanoaks and infecting most associated woody plants. Suitable hosts cover a much broader geographic range, raising concern over where the disease may spread. To understand the strength and potential sensitivities of a fire–disease relationship, we examined geographic patterns of confirmed P. ramorum infections in relation to past fire history. We found these infections to be extremely rare within the perimeter of any area burned since 1950. This finding is not caused by spatial bias in sampling for the disease, and is robust to variation in host abundance scenarios and to aggregation of closely spaced sampling locations. We therefore investigated known fire-related factors that could result in significantly lower incidence of the disease in relatively recently burned landscapes. Chemical trends in post-fire environments can influence the success of pathogens like P. ramorum, either by increasing plant nutrient stress or by reducing the occurrence of chemicals antagonistic to Phytophthoras. Succession in the absence of fire leads to greater abundance of host species, which will provide increased habitat for P. ramorum; this will also increase intraspecific competition where these trees are abundant, and other density-dependent effects (e.g. shading) can reduce resource allocation to defenses. Despite these findings about a fire–disease relationship, a much deeper understanding is necessary before fire can be actively used as a tool in slowing the epidemic.


Epidemiology Fire history Landscape pattern Plant disease ecology Phytophthora ramorum Spatial analysis 



We gratefully acknowledge financial support from the National Science Foundation (Award#EF-0341729); MAM was also partially supported by a grant from the James S. McDonnell Foundation during preparation of this manuscript. The input of K. Fischer, E. Sanderson, and others at WCS was helpful in formulating the research questions addressed here. We thank A. Schaffner for statistical advice, and C. Blomquist, T. Bruns, S. Cole, S. Frankel, M. Garbelotto, J. Keeley, A. McDonald, and D. Rizzo for reviewing drafts of the manuscript. The work performed here complies with the current laws of the United States of America.


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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Ecosystem Sciences Division, Department of Environmental Science, Policy, and ManagementUniversity of CaliforniaBerkeleyUSA
  2. 2.Institute for Computational Earth Systems ScienceUniversity of CaliforniaSanta BarbaraUSA

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