Efforts to mitigate hazardous fuel conditions have expanded in response to the severe wildfire events of recent years. But scant information exists on the efficacy of fuel treatments for mitigating wildfire severity, much less the influence of fuel treatments on second-order fire effects, such as exotic plant invasions. We are investigating the relationships among fuels, wildfire severity, and exotic plants in three montane forests of the eastern Rocky Mountains. We seek to address the following questions: To what extent is fire severity related to stand conditions? Is fire severity a predictor of exotic abundance? Do disturbances created by pre-fire treatments provide a source for post-fire exotic invasions? Does post-fire seeding mitigate invasion risk? And do invaded areas represent greater post-fire fuel hazard? Answers to these questions will improve our understanding of some of the ecological risks and benefits associated with pre- and post-fire management activities.

Field data collection has been completed in two fires over the past two summers (the 2000 Cerro Grande in NM and the 2000 Hi Meadow in CO) and a third fire (2002 Hayman in CO) has been selected for sampling in summer 2003. Multiple regression models developed from the Cerro Grande landscape to predict fire severity (percent scorch and consumption), exotic abundance (relative cover), and fuelbed flammability (predicted flame length) have fair explanatory power (adjusted R²=0.34, 0.51, and 0.64, respectively).

Significant (p<0.05) predictors of Cerro Grande fire severity were mean tree diameter and fuel treatments involving prescribed fire: both had a moderating influence. Thin-only fuel treatments were associated with higher fire severity, but not significantly. Fire severity was a significant predictor of exotic abundance, along with aspect and an interaction between slope steepness and soil nitrogen. Pre- and post-fire treatments were not significant as predictors of exotic abundance, but were included in the set of most informative models: the association was negative with prescribed burning and post-fire seeding, but positive with thinning. Post-fire flammability increased significantly with sample date (i.e., seasonal curing) and fuelbed depth, and decreased significantly with fire severity and cover of native plant species. Cover of seeded and exotic species were associated with greater flammability, but not significantly. We will compare and contrast these trends with those found in the Hi Meadow fire.