Development of post-fire crown damage mortality thresholds in ponderosa pine

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Contents Vol 19(5)

doi:10.1071/WF08193

Development of post-fire crown damage mortality thresholds in ponderosa pine

James F. Fowler ^A ^G, Carolyn Hull Sieg ^A, Joel McMillin ^B, Kurt K. Allen ^C, Jose F. Negrón ^D, Linda L. Wadleigh ^E, John A. Anhold ^B, Ken E. Gibson ^F

^A USDA Forest Service, Rocky Mountain Research Station, 2500 S Pine Knoll Drive, Flagstaff, AZ 86001, USA. Email: csieg@fs.fed.us
^B USDA Forest Service, Region 3 Forest Health Protection, 2500 S Pine Knoll Drive, Flagstaff, AZ 86001, USA. Email: jmcmillin@fs.fed.us; janhold@fs.fed.us
^C USDA Forest Service, Region 2 Forest Health Management, 8221 S Highway 16, Rapid City, SD 57702, USA. Email: kallen@fs.fed.us
^D USDA Forest Service, Rocky Mountain Research Station, 240 W Prospect Street, Fort Collins, CO 80526, USA. Email: jnegron@fs.fed.us
^E USDA Forest Service, Region 3 Fire Management, 1824 S Thompson Street, Flagstaff, AZ 86001, USA. Email: lwadleigh@fs.fed.us
^F USDA Forest Service, Region 1 Forest Health Protection, PO Box 7669, Missoula, MT 59807, USA. Email: kgibson@fs.fed.us
^G Corresponding author. Email: jffowler@fs.fed.us





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International Journal of Wildland Fire 19(5) 583–588 http://dx.doi.org/10.1071/WF08193
Submitted: 26 November 2008 Accepted: 17 November 2009 Published online: 9 August 2010

Abstract

Previous research has shown that crown scorch volume and crown consumption volume are the major predictors of post-fire mortality in ponderosa pine. In this study, we use piecewise logistic regression models of crown scorch data from 6633 trees in five wildfires from the Intermountain West to locate a mortality threshold at 88% scorch by volume for trees with no crown consumption. For trees with >40% crown consumption volume, linear regression indicates >85% mortality, but for trees with crown consumption volume <40%, there is a statistically significant, linear relationship between increasing crown scorch and increasing probability of mortality. Analysis of an independent 600+ tree dataset from Colorado produced similar results and supports the analysis approach. Crown scorch volume (>85%), crown consumption volume (>40%), and crown consumption between 5 and 40% combined with crown scorch volume >50% mortality thresholds could be incorporated into post-fire marking guidelines for forest management goals.

Keywords: crown consumption, crown scorch, logistic regression, marking guidelines, piecewise regression, Pinus ponderosa, statistical models, wildfire.