Previous wildfires and management treatments moderate subsequent fire severity

Burn severity distributions for areas treated then burned (i.e., “treatment-fire”) and untreated burned controls. Density plots showing the frequency distribution of the Relativized Burn Ratio (RBR), a measurement of burn severity, for untreated areas (controls; yellow) and silvicultural or fuel treatment (cases; purple) in areas that were treated before a wildfire. Vertical dashed lines show the thresholds: <2% basal area loss (dark purple), unburned-low and moderate severity (magenta), low-moderate and high severity mixes (orange), and >98% basal area mortality (i.e., stand replacing severity; yellow). Data are from wildfires that occurred between 2001 and 2019 and treatments occurring from 1982 to 2017, within the northeastern Washington State, USA study area.