Effects of Sudden Oak Death on the crown fire ignition potential of tanoak (Lithocarpus densiflorus)

Abstract

In the face of the sudden oak death (SOD) epidemic, decreasing foliar moisture content (FMC) of tanoak (Lithocarpus densiflorus) has land managers, fire managers, and property owners concerned with the increased possibility of crown fire in affected areas. A need exists to link local SOD-affected foliar moisture content (FMC) values and current FMC data to decision support tools, allowing managers to better predict crown fire in areas where SOD-affected tanoaks are prevalent. We tracked FMC of live (uninfected) tanoaks, Phytophthora ramorum-infected tanoaks, dead tanoaks, and surface litter for 12 months. We found that FMC values differed significantly among the three categories of uninfected, P. ramorum-infected and dead leaves. FMC of live tanoaks averaged 82.3 percent for the year whereas FMC of infected tanoaks had a lower average of 77.8 percent (ANOVA, P = 0.04). Dead trees had a significantly lower FMC, averaging 12.3 percent (ANOVA, P < 0.01) for the year. During fire season (June to September), dead tanoak FMC reached a low of 5.8 percent, with no significant difference between dead canopy fuels and surface litter (ANOVA, P = 0.44). Application of low FMC values to a crown ignition model results in extremely high crown base height (CBH) values to escape crown ignition. Remote estimation of dead leaf moisture using 10-hour fuel moisture shows promise. Preliminary results indicate a strong relationship between remote automated weather station (RAWS) 10-hour fuel moisture data and the FMC of dead leaves (R² = 0.78, P < 0.01). Results from this on-going study will aid the decision support process for fire managers in SOD-affected areas and may also be applicable to conditions in other ecosystems where diseases and insect epidemics have altered forest canopy fuels.

Parent Publication

• Proceedings of the Sudden Oak Death Fourth Science Symposium

Citation

Kuljian, Howard; Varner, J. Morgan. 2010. Effects of Sudden Oak Death on the crown fire ignition potential of tanoak (Lithocarpus densiflorus). 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. 251-257