Do mountain pine beetle outbreaks change the probability of active crown fire in lodgepole pine forests?

Abstract

An expansive mountain pine beetle (MPB) epidemic is currently impacting North American forests (Raffa et al. 2008). As beetle-attacked trees die, lose their needles, and eventually fall to the ground, there are substantial changes in stand structure. These fuel changes likely affect both surface and crown fire behavior, but there is not yet a consensus among experts regarding the nature and magnitude of these effects (Jenkins et al. 2008). Simard et al. (2011; hereafter referred to as SRGT) used linked crown fire models implemented in the NEXUS crown fire modeling system (Scott and Reinhardt 2001) to predict the occurrence of active crown fire across a chronosequence of increasing time since attack. They concluded that, under moderate fire weather conditions, recently attacked or red-stage stands had a lower occurrence of active crown fire than undisturbed stands. Here, we suggest that these conclusions are compromised because (1) the fire behavior modeling framework used has no mechanisms for considering highly heterogeneous fuels and (2) their use of this framework omitted critical aspects of how canopy and surface fuels change after an attack, particularly during the first two to three years.

Citation

Jolly, W. Matt; Parsons, Russell; Varner, J. Morgan; Butler, Bret W.; Ryan, Kevin C.; Gucker, Corey L. 2012. Do mountain pine beetle outbreaks change the probability of active crown fire in lodgepole pine forests? Ecology. 93(4): 941-946.