This story map is an excellent resource for folks wanting to learn more about how and what wildfires burn. I plan to use it as a reference for wildland fire students.
Burn severity explained
Shovel Creek: an example of burn severity assessment and ecology in interior Alaska
The web site that you featured certainly has some excellent graphics and basic explanations, and would be great to use in a classroom, Steve. Thank you for the link.
One comment in their Shovel Creek case study surprised me, though:
First they say “Studying burned areas helps researchers determine which topographic features contributed to burn severity.” And, “Topography can then to be compared to other factors to determine the relative importance of each driver of burn severity.”
But, they then reported that “At Shovel Creek researchers did not find a relationship between burn severity and topography.”
Very interesting.
Lately, I’ve been studying from the (2021) book, “Fire Science: From Chemistry to Landscape Management,” by Rego, Morgan, Fernandes, and Hoffman (https://www.amazon.com/gp/product/3030698149/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1), and just the other day I read in that book about fire severity as a measure of fire magnitude. Some comments that especially stuck with me were:
“Fires are almost all of mixed and variable severity when enough fires are included (e.g. over enough area or enough time). Most individual fires are of mixed severity when viewed at broad scales.
All fires encompass some areas of no to very low mortality and some areas of high to complete mortality, whether viewed in terms of area burned in a day (Birch et al 2014, 2015), or full fire perimeters. Most fire regimes are a mix of severity classes, and it is important to characterize them accordingly, perhaps as mixtures of probability distributions.”
Elsewhere, under the section, Spatial Fire regime Descriptors and Matrics, they cite the following fact: “Less than one-third of the area burned in large fires had burned with high severity in the USA since 1984 (Finco et al. 2012; Picotte et al. 2016). Birch et al. (2015) found that on 42 large forest fires, the proportion burned with high severity was poorly correlated with the area burned in a day. Within most areas burned in a single day, less than 13% of the area burned with high severity except under the most extreme conditions when 49% of the area burned in a single day burned with high severity.”
“Spatial variability in fire behavior and vegetation is positively correlated with spatial variability in fire effects, critical to understanding the long-term ecological benefits or detriments from fire.”
Of course, we all know that “ecological diversity can benefit from pyrodiversity when fires burn with a mix of low, moderate, and high severity and unburned islands (refugia). Landscapes encompassing burns of different ages and severity can provide a mix of habitats (Morgan et al. 2015; Lewis et al. 2017).”
It seems to me like aspect will matter in some places and not in others. In my part of the country, different species grow on different aspects.. big water difference, big fuel difference. Then there’s how winds work in canyons and so on.
Did the authors say why it’s important to do this?
“Most fire regimes are a mix of severity classes, and it is important to characterize them accordingly, perhaps as mixtures of probability distributions.”
Part of the problem is that some trees may take up to 5 years to die from wildfire impacts, including bark beetles and cambium kill. Those post-fire facts should not be excluded.