UCCE Humboldt - Del Norte Counties
University of California
UCCE Humboldt - Del Norte Counties

Sudden oak death

For background information and additional context, please see our Tree Mortality and Fire page.



Sudden oak death is a major killer of tanoak and coast live oak trees. Valachovic et al. (2011) found that the waves of disease related to mortality can cause significant increases in surface fuel loading. The disease can also greatly reduce the foliar moisture content of tanoak leaves, increasing risk of active crown fire in the period where leaves remain on the dead trees (Kuljian and Varner 2010). These fuels patterns result in shifting fire hazards and severities with time since infestation (Metz. et al. 2011). Of great concern is the mix of disease-generated surface fuels with understory vegetation, which can respond positively to increased light availability as a result of tree mortality. The graphic below illustrates the fire hazard and risk to firefighters and suppression response. The additional challenge with sudden oak death is the chronic, unpredictable nature of the disease, which challenges long-term fire risk mitigation planning efforts.


Valachovic figure


Valachovic, Y.S., Lee, C.A., Scanlon, H., Varner, J.M., Glebocki, R., Graham, B.D. and Rizzo, D.M., 2011. Sudden oak death-caused changes to surface fuel loading and potential fire behavior in Douglas-fir-tanoak forests. Forest Ecology and Management, 261(11), pp.1973-1986.
Research brief: CFSC Brief_Valachovic et al. 2011
Full paper: http://www.fs.fed.us/psw/publications/uesd/psw.2011.valachovic.SODcausedchanges.FEM.pdf

Kuljian, H. and Varner, J.M., 2010. The effects of sudden oak death on foliar moisture content and crown fire potential in tanoak. Forest Ecology and Management, 259(10), pp.2103-2110. http://www.fs.fed.us/psw/publications/sod/kuljian.2010.forestecologymanagement.SODeffectTanoak.pdf

Metz, M.R., Frangioso, K.M., Meentemeyer, R.K. and Rizzo, D.M., 2011. Interacting disturbances: wildfire severity affected by stage of forest disease invasion. Ecological Applications, 21(2), pp.313-320. http://onlinelibrary.wiley.com/doi/10.1890/10-0419.1/full

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