I’ll be back with more content eventually, but we’ve been busy burning. There are only so many days in the spring where the wind, humidity, fuel conditions, and personnel all align just right, so we are out there when we can. So far, we are on pace to achieve our goal of increasing our number of acres burned every year.
One point that I often forget to mention about woodland burns: we are burning the leaf litter, not the trees! With a national media, most folks only hear about fire in the context of out-of-control Western wildfires ripping through the canopies of pine forests. But in the lower Midwest, we are dealing mostly with deciduous forests filled with species that drop their leaves annually. The fire’s fuel is on the ground, not up in the air. Fire-adapted trees, especially oak species, have thick layers of bark that prevent them from catching fire, in addition to being full of moisture. (Last year I wrote a little about why we burn).
Well… now that I say that, there are a couple pines in this photo. We decided to save these individuals because it wasn’t too much work and we like having some around. We just wet the trunks down and passed the fire slowly underneath them. Pines can be susceptible to catching fire as the live leaves (needles) are flammable; they also lack the thick protective bark of the oaks. What you don’t see in this photo is that these white pines are isolated and wouldn’t have threatened any other trees or structures even if they did catch.
Anyway, no large trees were harmed in the making of this photo! We didn’t just run up to the woods and light a match either… this photo was actually after a good 45 minutes of careful work. At this point, we knew with a good amount of certainty exactly what the fire was going to do as we laid it down.
So let’s go back to the beginning…
The following two photos are from a tiny burn unit (0.7 acres) that we affectionately call the “Brother Bob Savanna” (some readers can guess where it might be). The overstory (tallest trees) are mature black and white oaks and hickories. The understory has a large amount of rasperries and small diameter oaks and sassafras. The ground floor is a thick layer of oak leaf litter. Our management goal is not a dark, closed forest, but a more open oak woodland/savanna with both an oak overstory and plenty of herbaceous (non-woody) grasses, sedges, and wildflowers on the ground. We expect that these communities, especially on our soils, will be the best adapted to carry biodiversity through the hot and dry climate we are expecting to prevail.
Ok, let’s not get into theory, I said photos!
The photo below shows a “backburn” or “backfire.” It is the safest and most common way to initiate a prescribed fire.
I started the fire at the red star, by the large oak tree. This is at the most downwind portion of the unit. I then moved towards the yellow star, parallel to the wind. The flames lean downwind, over the firebreak (mowed grass). They move “backward” into the wind, creeping along at a slow rate. In a few minutes, this created an expanding “blackline” of burned fuel, increasing our margin of safety on that end of the unit. Once a fire burns across the oak leaves, the fuel is spent.
By the green star is one of our staff. He has the somewhat unfortunate task of staying downwind in the smoke and watching outside the unit for any escaping fire. Given the wide expanse of mowed lawn are this unit and the calm nature of the backburn, that was almost impossible, but I like to have eyes everywhere there is active flames.
The backfire may be creeping along at just a few feet per minute. Well… we don’t have all day and night. So we move next to a “strip-head fire” or “strip fire.” This is “a series of lines of fire [that] are set progressively upwind of a firebreak in such a manner that no individual line of fire can develop to a high energy level before it reaches either a firebreak or another line of fire” (source). Basically, it helps us move through the unit faster without compromising safety.
Now, you’ll have to flip around the photo perspective, the next photo was shot from the opposite direction, but its the same fire just 5-10 minutes later..
I initiated the strip burn at the red star, and moved in a line to the yellow star. I walked far enough in front of the first backburn to make it worth my while, but not so much that it would gather too much speed burning downwind. The wind was fairly strong. As you can tell in the photo, the flames on the strip burn are already larger than either backburn, just seconds after I laid down fire.
There is plenty of work associated with prescribed fire that’s not terribly exciting. Below is a photo from an adjacent woods that just wasn’t burning as hot and complete as we’d expected. The backburn I had initially set didn’t make a nice wide and solid black line, it was a little sporadic. With unburned fuel near the burn break (which separates the burn unit from the exterior) there was a small chance of a wind shift or other event reigniting that fuel. Additionally, the burn break we created here was not very wide as we wanted to minimize disturbance.
Here, Cheri had the not-so-glamorous (but important) job of slowly patrolling this end of the fire while the rest of us were continuing through the unit while we were sending smoke her direction. Thanks Cheri!
Even with a meticulously-written burn plan, the burn boss ultimately has to constantly assess the weather, fuel, fire behavior, wind, and the status of his/her equipment and staff. I always try to start each burn reminding the team of our ranked priorities:
1) Everyone gets home safe
2) Protect buildings and property
3) Achieve the burn’s objectives
4) Have fun!
Well, so much for “just a few photos.” Behind every photo is a lot of prep work, a choreography of dedicated staff, and several ecology lessons!
Very informative lesson. Thanks!
Excellent work, however, I wonder about burning too much. I.e. Every year the same patterns. I’m concerned about losing Forbes and Mantises not to mention, many other insects and herps.
Sr. Mary –
Yes, all things we take into consideration. Landscape context is also important… no burning in adjacent areas.
Nice job Adam. Very informative. I enjoyed it.
Why, thank you for reading! You are welcome to assist at anytime… “I got a little job for ya!” 🙂