Research Reveals that Crown Fires Can Kill Trees and Cause Difficulties with Tree Regeneration

A flood of ash and sediment fills the washes in the white mountains after the fire; photo by Dan Neary
A flood of ash and sediment fills the washes in the white mountains after the fire; photo by Dan Neary

This headline reminds me of the past weekend’s Research Reveals that Elk Eat All Year.

Nevertheless, thought I should post this article… I am looking for the link to the research study. Note: journalists out there- please put the links in your stories.

Here’s the link and below is an excerpt, but the whole piece is of interest.

The researchers spent years exhaustively measuring the contrasting recovery of two stretches of forest, both on Stermer Ridge at the headwaters of the Little Colorado River. They estimated the surviving trees, the amount of wood on the ground, stream flows, soil absorption, the total mass of grass and shrubs and the number of elk, deer, squirrels, rabbits and other animals.

#Watershed A suffered a high-intensity crown fire, which means the flames jumped from one treetop to the next — rather than burning along the ground. The fire killed about 55 percent of the trees immediately — and about 75 percent of the survivors within a year or two. The patch of ground ended up bereft of trees, with even the fire-adapted gambol oaks mostly dying off along with the ponderosas and junipers.

#On the adjacent Watershed B, a road served as a firebreak that halted the crown fire next door. Instead, the fire there burned along the saplings, shrubs and downed wood on the ground. It consumed 5 percent of the trees immediately, with a total of about 15 percent dying from the effects of the fire in the next two years.

#The study demonstrated the dramatic effects of such high-intensity fires.

#For instance, the searing heat of the crown fire fused the soil in Watershed A, sharply reducing the rate at which the ground could absorb water — making it “hydrophobic.” Two-thirds of Watershed A had strongly hydrophobic soil and one third has moderately water repellent soil.

#By contrast, in Watershed B only one-third of the soil was strongly and 15 percent moderately hydrophobic.

#The combination of the loss of the trees and the changes in the soil produced dramatic changes for the next three years whenever it rained.

#For instance, a storm on Watershed A produced a stream flow that was 2,230 times what would have flowed into that same stream with the same amount of rainfall before the storm, according to estimates. By contrast, the storm increased stream flows in Watershed B by about 50 percent compared to pre-fire levels.

#In the fall of 2002, the severely burned area lost about 28 tons of topsoil per acre to erosion, compared to about 17 tons per acre in the moderately burned area. In the spring of 2004, the severely burned area lost 35 tons of topsoil per acre compared to about 20 tons in the moderately burned area. A stable area in a normal year will lose almost no topsoil to erosion.

#The figures offer a sobering cautionary note for Rim Country, whose water future now depends on the Blue Ridge Reservoir, which sits in a small, wet, thickly forested watershed. Payson officials have urged the U.S. Forest Service to make thinning the watershed of the Blue Ridge Reservoir a high priority, for fear a crown fire could cause a dramatic increase in erosion — which would reduce the life of the deep, narrow reservoir.

#The study found that plants, grass and shrubs returned to both areas quickly — with the severely burned area actually producing more grass and shrubs initially than the lightly burned area. That’s probably because in the lightly burned area most of the trees survived and continued to shade the ground and compete for water with the ground cover.

#Elk actually used the severely burned area more than the lightly burned area initially, probably reflecting the initial, denser growth of grass. Mule deer returned quickly to both areas, but in smaller numbers.

#On the other hand, many of the smaller animals like rabbits remained all but absent in the severely burned area — along with pine tree dependent species like Abert’s Squirrels.

#Fewer birds also returned to the severely burned area, probably because they no longer had the diverse habitat offered by the tree canopy.

Yes, you heard some of these observations first by individuals on this blog. I would just comment that people can figure out how to plant trees and get them to grow back. About 40 years ago the Forest Service started a major effort to figure it out. The FS had reforestation experts hired, administrative studies of various cultural practices and nurseries to experiment with practices, investments in refrigerated trucks and tree coolers, etc. If we had a small amount of the bucks directed to downscaled modeling, I bet we could figure it out.

28 thoughts on “Research Reveals that Crown Fires Can Kill Trees and Cause Difficulties with Tree Regeneration”

  1. In my vast experience with salvage projects, I agree with all observed above. I’ve even seen where just the hot wind from fires have killed huge amounts of trees. The needles were frozen in the direction of the hot gases, similar to how a convection oven works. Most of those projects had some erosion problems that occurred in both logged and unlogged areas. On the Biscuit Fire, I saw one slope with 99% old growth mortality, with a 10 year old plantation just 200 yards away surviving pretty well.

    This is just another clear sign that site-specific science should be guiding our forest management activities. Our silviculturalist walks most of our units, giving us specific directions in different parts of the unit. He is extremely happy that our crew sees his vision and implements it on the ground.

  2. “This headline reminds me of the past weekend’s Research Reveals that Elk Eat All Year.”

    Exactly…..starting to sound like stories from the Onion!

  3. I reject as sort of absurd the notion that we can pay the suppression costs of having these fires or we can pay people ahead of time to “thin” the forest.

    Try and think about this logically.

    So, the 538,000 acre Wallow Fire was started by two 20-something year old cousins who left an unattended and unextinguished campfire in the Bear Wallow area, which quickly spread out of its fire ring due to high winds when the kids were out on a hike.

    But apparently, these imaginary thinning crews would have had the foresight and ability to look into the future to know this, because this thinning crew would have been working years, maybe even decades, ahead of this human-causes fire to “thin” 538,000 acres.

    Or how about the other big Arizona fire, the Rodeo-Chediski Fire.

    Are we really to believe these same thinning crews would have known the location of where an arsonist was going to start a fire near the Rodeo Fairgrounds on the Fort Apache Indian Reservation on the afternoon of June 18, 2002? Of course, again, the wind was a huge factor in the spread of the fire, something that no amount of “thinning” can prevent.

    The Chediski portion of the fire was started on June 20, 2002 by a stranded motorist who was trying to signal a news helicopter (Potential Darwin Award winner, for sure). Again, the winds were very strong and the fire spread rapidly.

    But again we are supposed to believe that a “thinning” crew would have had the foresight and ability to look into the future to thin all of that area ahead of the arson-caused and stupid-caused fires? Added together, these fires were over 1,000,000 acres. How long ago in the past would these thinning crews have had to have started thinning these forests to have finished in time to prevent these humans from burning down the forest?

    • You cannot exclude the “dumb human syndrome” from our forests. Accidental forest fires are predictable, in the sense that you know they will start close to popular areas. We simply cannot continue to preserve hazardous conditions in areas humans use. American Indians certainly knew that, and dealt with the situation as well as they could. If they had better technology, they probably would have cut more trees down, instead of relying solely on burning practices. It is pure denial that you are trying to remove human ignitions from the discussions. Do you really think such big fires would have never happened if not for such incidences?

      In 1987, we had 43 fires from three days of lightning, on our one Ranger District. It WILL happen again, and there surely are more fuels now than then. This includes unthinned plantations, overstocked understories and brushfields. Do we really want to maintain such a continuous fuel build-up, enhanced by fire suppression and climate change?

      Again, it is impossible to return our forests back to a pre-human condition, as many still lust for.

      • Larry, The first two graphs make total sense, but the third graph is just a jab at the folks who may have a different idea than you as to the definition of a “healthy forest.” We may not be able to return forests to “pre-human” conditions (I doubt anyone really wants that), but neither can we completely fireproof and tame all our forests, or turn them into tree plantations, as, perhaps, some other people lust for.

        • “Re-wilding” wants to do exactly that. Removal of all human traces. Yes, there are PLENTY of people wanting that. Of course, many continue accuse us pro-management people of wanting to treat every acre, and that surely isn’t true, Bob. There is VAST acreage that is already “protected”, in one form, or another. We haven’t done ANY clearcutting here in TWENTY years!!!

          Our forests evolved, side-by-side, with the humans who lived here before the Europeans came. I wonder if some of those humans also wanted “pre-human” forests “restored”. I doubt it. Some of the wisest were also in charge of “managing” their lands. If you do a search for “rewilding”, you get over 250,000 entries! I think it would be quite difficult to find ANYONE who wants to go back to 80’s style clearcutting.

          Once again, it is about active restoration, which would seek to restore species compositions, tree densities and soil moistures.

          Sorry, Bob, but I am not in favor of cutting timber on all slopes, everywhere. My views are based on reality.

          • Larry, Please provide evidence and documentation to support your claim here that “‘Re-wilding’ (who ever they are or what ever it is) wants to remove all human traces.” Also, please provide supporting documentation for your claim that their are supposedly “PLENTY of people wanting that.”

            Once again you seem to be fighting battles against ghosts or imaginary opponents.

              • I love it when requests here for evidence and documentation to support claims get the “thumbs down.”

                And what in the hell does “250,000 mentions via google” mean? Again, Larry, please provide provide evidence and documentation to support your claim here that “‘Re-wilding’ (who ever they are or what ever it is) wants to remove all human traces.” Thanks.

          • Larry, I don’t think it’s accurate to say forests “evolved” with humans, at least in the technical sense of evolution, which involves genetic adaptation over multiple generations. I think it’s fair to say that forests have been shaped, in the past few centuries, by human intervention.

            Forests evolved with fire, insects, changing climate … I think that’s an important distinction in the context of a discussion about desired conditions. It may seem like a point of semantics, but for the sake of accuracy, we should probably leave evolution out of the debate for now.

            • Certainly, the “genetic makeup” of pre-European forests is different than pre-human forests. Ponderosa pines could have become even more fire-resistant, due to Indian burning. The survivors of centuries of burning produced offspring that is even more fire resistant. Certainly, at least 15,000 years of burning has had a genetic effect on species in these areas, eh? Tree bark became thicker and buds became more insulated during that time.

              • I wouldn’t say “certainly” because I doubt that that the scope of human activity in forest landscapes has been significant for long enough to result in evolutionary changes, but that’s just my non-scientific opinion. I won’t ask you for scientific proof to show that what you say is true, though 🙂 But it’s an interesting question — I wonder if there has been research along those liines.

                • So here is how a geneticist thinks about it… evolutionary pressure is a function of the selection pressure on a trait and how strongly the variation you see has a genetic component. Times the number of generations… so give a generation of 75 years for forest trees, post glaciation, say 14,000 years with Native Americans around…

                  But it took them a while to get across North America and I don’t know exactly.. say 9000 years of activity that would be 120 tree generations. That’s long enough to have an influence, certainly.

                  What we don’t know is whether different genotypes would be selected for under Native American practices than would otherwise exist based on wildfires that would have occurred without intentional burning or suppression. This probably has to do with the intensity of their practices (how frequently they burned). Confusing all this is the fact that the climate was warming and drying after glaciation.

                  Native Americans and EuroAmericans have had all kinds of direct and indirect patterns on the landscape.. now I forgot how this came up…

    • Matthew, that’s not the idea; the idea is to have strategic defensible areas so that firefighters can safely and effectively protect communities or at least manage the fire to reduce the possibility of it getting to a level of intensity that is dangerous to firefighters and infrastructure.

  4. The Apache-Sitgreaves 1987 forest plan called for 20,000 acres/year of “commercial thinning.” The timber sale program was shut down in 1993. So yes, 300,000 acres of “thinning” DID NOT occur in the last 15 years. And yes, it also called for 10,000 acres/year of “overstory removal”…removing remnant old growth that had already had been logged in a shelterwood seed cut in the 60’s through 80’s. Scattered old growth that wasn’t Owl habitat in the firest place. 90% of the pre-settlement forest consisted of this low density “very open” scattered OG which wasn’t even owl habitat. 20% of the forest today(pre-fire of course) is classified as “high density Old growth”, while only 10% was in that catagory 100 years ago. Mostly on terrain to steep for logging…which…as it turns out…is where 80% of owl nest are found. It’s also interesting to note the Plan phased out “shelterwood Seed cut harvests” by 1997. This hints that the forest was already transistioning to the very type of thinning that is proposed now by the 4FRI…but never got the chance. This coiniceded with the advent of mechanical thinning…which makes harvesting small diameter trees profitable. Montana loggers have been making do with 8-12″ diameter Lodgepole for years. Too bad the media doesn’t want to tell this story…but then the era of pointing fingers is past…especially if you might have to point it at yourself too.

  5. One component of a crown fire that makes a difference in erosion rates is if the needles were consumed. Where the needles were consumed there is no needle cast which often makes a mulch like layer on the ground. No needles, no needle cast, no ground mulch. Establishing some sort of ground cover is benifical for reducing erosion. I had one hydrologist tell me salvage logging would be benificail because it would put slash (limbs and tops on the ground), a different hydrologist said no salvage since the area was severly burned, and could handle more disturbance.

    Some of our fires in central Idaho had crown fires for large areas in Ponderosa Pine and Douglas which basically removed seed sources, so natural regeneration will take a long time. I’ve seen some former ‘Old Growth” Ponderosa Pine/ Douglas fire stands effectively convert to brush, due to lack of seed sources.

  6. I hope this doesn’t sound too “retro” but a way to get trees back is to...plant them! And spray or otherwise removed brush until they get established. Just sayin’, the technology exists. Or at least it did until the people who got good at it, the last time it was popular, retired.

    • The majority of the stand replacing wildfires in central Idaho were in roadless areas and wilderness, Planting has been minimal if that. The Forest Plan calls for passive restoration in these areas, interpreted as meaning let nature take its course.

      • Michael D: Could you please provide some documentation and evidence to back up your claim that “The majority of the stand replacing wildfires in central Idaho were in roadless areas and wilderness.”

        Also, what year(s) are we talking about? As well, what forest type are we talking about? Are we talking mainly ponderosa pine stands? Or are we talking about mixed severity forests that include pine, Doug fir, sub-alpine fir, lodgepole pine, etc? Thanks.

        • Like I said, I love it when requests here on this blog for evidence and documentation to support claims get the “thumbs down.” Come on boys….show me what you got!

        • I don’t have time to chase all of the years of fire down, but we’ll use 2007 as an example, the Payette NF burned 470,218 acres that year of which approximately 50,000 acres were in the roaded areas, the remaining 420,000 were in wilderness and roadless. With these kind of acreages all timber types were involved. I believe at least 800,000 acres burned in central Idaho that year on the Boise, Sawtooth, Payette, and Nez Perce Forests. Not all was stand replacing but a lot of it was. I have a picture from space that shows smoke plumes stretching for 50 miles from Warm Lake on the Boise NF, going north along the SF Salmon river through the Payette NF to the Nez Perce NF north of the Main Salmon River, all of this area is primarily roadless or wilderness. The photo was taken Aug 13 2007. You should take an airplane flight sometime and look at the burned areas in MF Salmon, Big Creek, Elk Creek and SF Salmon River, it’s an eye opener.

          • Michael- I wonder who might fund a video taken on an overflight.. any researchers/journalists out there with ideas? I know we had trouble describing the extent of mountain pine beetle in Colorado until we had the flight videos.

  7. Bob…a cool book you should check out is titled “America’s Ancient Forests” by Tom Bonnicksen. Especially chapters 6 and 7 dealing with Indian burning in pre-settlement times. Native Americans were shaping the forests with fire for a lot longer than the last “few hundred years.” Seriously, I think you’d enjoy it. He doesn’t make any big policy endorsements, so it’s pretty apolitical.

    Oh, do you ever wonder why 60% of Colorado burned off in the late 18th century? Was it global warming then?(little Ice age got over.)Why so much Aspen.I can’t think of one “major” wildfire in the lodgepole country for the last 100 years.


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