PS 72-138
Crash and burn: The influence of wind damage and landscape pattern on forest fuels and fire behavior
Natural disturbances such as tornados and fire are major drivers of forest dynamics. Both the extent and pattern of damage from a single disturbance or the interaction between concurrent disturbances can influence forest recovery. Here, we report findings from two ongoing studies of forest disturbance, which lead to new insights of how wind damage and fire interact at the landscape-scale. In the first study, we simulated tornado damage by winching over trees in forested plots to create 80% damage severity. Half of these plots received a controlled burn after one year, and we measured how wind damage affected fuel characteristics and subsequent fire behavior. Given the effects of an 80% wind severity on fire behavior in our field experiment, we then conducted a landscape-scale study of two 2011 tornado tracks to evaluate the extent to which the plot-scale patterns from the winching study apply at the landscape-scale.
Results/Conclusions
Overall, we found that simulated wind damage increased fuel loading and altered fuel composition and aggregation. Furthermore, the heterogeneous arrangement of fuels in damaged plots led to intense fire behavior—especially in downed tree crowns—where fire had a longer residence time and higher fire radiant energy released compared to areas outside of crowns. In the landscape-scale study, by evaluating damage severity along two tornado tracks, we found that the severe level of wind damage from our field experiment only affected about 20% of the damaged areas. The remaining areas received wind damage at lower severity. Thus, the next step in this research is to determine how wind damage affects fuel and fire behavior at a larger range of damage severities. We propose that as damage severity increases, downed tree crowns may begin to coalesce potentially leading to sudden, non-linear, increases in fire intensity and spread as wind damage severity increases.