Note

Pine cones facilitate ignition of forest floor duff

Jesse K. Kreye,^a J. Morgan Varner,^a ^b Christopher J. Dugaw,^c Jing Cao,^c Jonathan Szecsei,^b Eamon A. Engber^b ^d

^aDepartment of Forestry, Forest and Wildlife Research Center, Mississippi State University, Box 9681, Mississippi State, MS 39762, USA.

^bWildland Fire Laboratory, Department of Forestry and Wildland Resources, Humboldt State University, One Harpst Street, Arcata, CA 95521, USA.

^cDepartment of Mathematics, Humboldt State University, One Harpst Street, Arcata, CA 95521, USA.

^dRedwood National Park, 121200 Hwy. 101, Orick, CA 95555, USA.

Corresponding author: Jesse K. Kreye (e-mail: jesse.kreye@msstate.edu).

Published on the web 21 March 2013.

Received January 14, 2013. Accepted March 19, 2013.

Canadian Journal of Forest Research, 2013, 43(5): 512-516, 10.1139/cjfr-2013-0019

Abstract

The ignition and combustion of forest floor duff are poorly understood yet have been linked to soil heating and overstory tree mortality in many temperate coniferous forests. Research to date has focused on the characteristics of duff that facilitate ignition and spread, including fuel moisture, mineral content, and depth. Field observations suggest that the presence of pine cones on and within the forest floor might facilitate ignition of intermixed forest floor fuels. We investigated the effect of cone fuel additions on the ignition of underlying forest floor from fuels collected in long-unburned longleaf pine (Pinus palustris Mill.) forests in northern Florida, USA. Fuels were wetted to threshold gravimetric moisture contents to evaluate the relative effect on ignition. In stark contrast to fuel beds without cones, in which duff ignition only occurred in 17% of samples, those with cones added ignited the underlying duff 94% of the time. Flame heights were 40% taller and flaming duration was 47% longer in fuel beds with cones. Where present, pine cones act as vectors of ignition for forest floor fuels, and their role in fires deserves more attention to enhance our understanding of forest floor combustion.

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