Spatial Patterns of Canopy Mortality in Riparian Areas and Uplands Following a Large Wildfire in Oregon
Event Website
http://www.nafew2009.org/
Start Date
6-22-2009 1:30 PM
End Date
6-22-2009 1:50 PM
Description
Some of the ecological characteristics of streamside ecosystems, such as mesic vegetation, cooler, moister micro climate, and low topographic position, might lead one to assume that wildfires would burn less severely in riparian areas than adjacent uplands. Other characteristics, such as multi-storied vegetation and higher fuel accumulations, might promote relatively higher levels of fire damage. The limited empirical studies of this phenomenon in the coastal Douglas-fir region suggests few differences in fire effects, at least at the canopy level. We examined canopy mortality patterns immediately following the 2002 Biscuit Fire, which burned under extreme weather conditions in southwestern Oregon. Canopy damage was estimated using the differenced Normalized Burn Ratio (dNBR) calculated from 2001 and 2002 Landsat TM satellite imagery. Levels of canopy vegetation mortality were then predicted for the fire area by regressing canopy damage from aerial photo plots on dNBR (R2 = 0.93). Analysis of model performance suggested little difference in the predictive power of the model in riparian zones and uplands. Areas within 50 meters of streams experienced lower canopy damage from the fire than areas that were more than 100 meters away from streams. The degree of difference between uplands and streamsides varied with stream order, with the largest differences occurring in 3rd to 6th order streams and no differences occurring in low order streams (1st to 2nd) that occur higher in the drainages. Random Forest and classification regression tree analysis revealed how weather and other physical characteristics affected fire severity near streams relative to uplands. Our work suggests that fire severity patterns can still differ between riparian areas and uplands even in high intensity fires, and that comparisons of fire behavior in riparian zones across fires will need to take stream size and weather into account.
Spatial Patterns of Canopy Mortality in Riparian Areas and Uplands Following a Large Wildfire in Oregon
Some of the ecological characteristics of streamside ecosystems, such as mesic vegetation, cooler, moister micro climate, and low topographic position, might lead one to assume that wildfires would burn less severely in riparian areas than adjacent uplands. Other characteristics, such as multi-storied vegetation and higher fuel accumulations, might promote relatively higher levels of fire damage. The limited empirical studies of this phenomenon in the coastal Douglas-fir region suggests few differences in fire effects, at least at the canopy level. We examined canopy mortality patterns immediately following the 2002 Biscuit Fire, which burned under extreme weather conditions in southwestern Oregon. Canopy damage was estimated using the differenced Normalized Burn Ratio (dNBR) calculated from 2001 and 2002 Landsat TM satellite imagery. Levels of canopy vegetation mortality were then predicted for the fire area by regressing canopy damage from aerial photo plots on dNBR (R2 = 0.93). Analysis of model performance suggested little difference in the predictive power of the model in riparian zones and uplands. Areas within 50 meters of streams experienced lower canopy damage from the fire than areas that were more than 100 meters away from streams. The degree of difference between uplands and streamsides varied with stream order, with the largest differences occurring in 3rd to 6th order streams and no differences occurring in low order streams (1st to 2nd) that occur higher in the drainages. Random Forest and classification regression tree analysis revealed how weather and other physical characteristics affected fire severity near streams relative to uplands. Our work suggests that fire severity patterns can still differ between riparian areas and uplands even in high intensity fires, and that comparisons of fire behavior in riparian zones across fires will need to take stream size and weather into account.
https://digitalcommons.usu.edu/nafecology/sessions/fire_effects/1