Wildfire activity in Alaskan boreal forests has been increasing in extent and frequency over the past two decades. These shifts have critical consequences for future fire and resource management since fire is a dominant driver of numerous interrelated aspects of the boreal environment, such as soil erosion, permafrost dynamics, carbon sequestration, wildlife habitat availability, the rate and nature of vegetation recovery, and the provision of subsistence resources. The potential for large-scale transformation of the forested Alaskan interior heightens the need to accurately characterize and anticipate wildfire regime trends.
To investigate how alterations in fire severity across Alaska are associated with landscape vegetation composition, USGS researchers are combining remote sensing data and derived products in Google Earth Engine, a cloud-computing platform that enables the rapid integration and processing of vast amounts of geospatial data. In this project, the key metric of analysis is fire radiative power (FRP), which is a measure of fire intensity that varies with the amount of fuel consumed. Researchers extracted all 1-kilometer (km) resolution Moderate Resolution Imaging Spectroradiometer (MODIS) pixels in Alaska from 2002 to 2016 for which the FRP value indicated the presence of active fire at the time of satellite overpass. After calculating the constituent proportions of 30-meter (m) 2001 LANDFIRE Existing Vegetation Type landcover data within every 1-km extent, ancillary information from the Bureau of Land Management Alaska Fire History database about the dates and characteristics of prior burns was associated with each pixel. Analysis of the resulting compiled datasets indicates that key landcover classes display distinctive FRP responses to the timing and frequency of repeated burns. This information may help refine models of the anticipated severity of future burns across the state.
MODIS Fire Radiative Power (FRP) 1-km pixels of the 2005 “Old Dummy” fire in Alaska showing the heterogeneity of fire intensity across the burn extent (232,000 acres).