Authors: Alan Taylor*, Pennsylvania State University, Lucas B Harris, Department of Geography, The Pennsylvania State University, Stacy Drury, USDA Forest Service, Pacific Southwest Research Station
Topics: Biogeography, Environmental Science, Physical Geography
Keywords: Fire severity, Disturbance ecology, Topography, Fuels, Fire suppression, Fire Effects
Session Type: Paper
Start / End Time: 1:10 PM / 2:50 PM
Room: Regency Ballroom, Omni, West
Presentation File: No File Uploaded
The number of large, high-severity fires has increased in California mixed conifer forests during the past thirty years. A major reason for the increase in area burned and area burned at high severity in recent decades is related to an increase in fuels caused by fire exclusion, and climate warming has also contributed. Here, we use Random Forest to identify the influence of terrain, weather, and fuels on patterns of fire severity in the Klamath Mountains. We developed separate models for initial fires, or areas that burned with no record burns and re-burn fires, that burned over earlier fires. Only fires with daily fire progression maps (2002-2017 ) were analyzed with 101 fires and 55 fires in the initial, and reburn model, respectively. Variable importance suggests that weather played the strongest role in the initial fires with daily temperature, AET, y relative humidity, and the energy release component in the top five variables along with tree canopy cover. Wind direction, wind speed, and elevation were also moderately important. In the re-burn model, previous fire severity was by far the most important variable and pre-fire tree canopy cover and vegetation height were important and there was also an influence of time since last fire. Weather variables were notably less influential than in the initial model. This demonstrates the importance of ecological memory and legacy effect of initial burns on subsequent fire severity, and the long term potential for self-reinforcing fire behavior and shifts in vegetation patterns.