|
|
|
Post-fire burn severity and vegetation response following eight large wildfires across the Western United States
Lentile, Leigh B.; Morgan, Penelope; Hudak, Andrew T.; Bobbitt, Michael J.; Lewis, Sarah A.; Smith, Alistair M. S.; Robichaud, Peter R.
2007.
Post-fire burn severity and vegetation response following eight large wildfires across the Western United States.
Fire Ecology. 3(1):91-108.
Keywords: dNBR, delta Normalized Burn Ratio, fire effects, remote sensing, species diversity, species richness
Links:
PDF [207 KB]
Abstract:
Vegetation response and burn severity were examined following eight large wildfires that burned
in 2003 and 2004: two wildfires in California chaparral, two each in dry and moist mixed-conifer
forests in Montana, and two in boreal forests in interior Alaska. Our research objectives were: 1) to
characterize one year post-fire vegetation recovery relative to initial fire effects on the soil surface
that could potentially serve as indicators of vegetation response (and thus, ultimately longerterm
post-fire ecosystem recovery), and 2) to use a remotely-sensed indicator of burn severity to
describe landscape patterns in fire effects. We correlated one-year post-fire plant species richness
and percent canopy cover to burn severity and to soil surface cover immediately after the fires.
For all eight wildfires, plant canopy cover and species richness were low and highly variable
one year post-fire. We found a greater number of forbs when compared to other plant life forms,
independent of burn severity. Plant cover was dominated by grasses in chaparral systems, by forbs
in mixed-conifer forests, and by shrubs in boreal forests, similar to the unburned vegetation. Finescale
variability in post-fire effects on soils, the diversity of pre-fire vegetation, and the resilience
of plants to fire likely explain the high variation observed in post-fire vegetation responses across
sites and burn severities. On most low and moderate burn severity sites, >30% of the soil surface
was covered with organic material immediately post-fire, and one year later, the canopy cover of
understory vegetation averaged 10% or more, suggesting low risk to post-fire erosion. In California
chaparral and the two Montana mixed conifer sites, 5% or less of the area within the fire perimeter
burned with high severity, while in Alaska, 58% was mapped as high burn severity; we think
this is characteristic in Alaska, but uncharacteristic of chaparral fires, especially given the high
proportion of non-native species post-fi re in our chaparral sites. All fi res had a mosaic of different
burn severities (as indicated by delta Normalized Burn Ratio, dNBR) with highly variable patch
size (mean 1.3 ha to 14.4 ha, range from <1 ha to over 100,000 ha).
Moscow FSL publication no. 2007l
|