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

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.