Effective Forestry Tools: Understory burns
The tremendous wildfires of the summer 2023 really got the attention of Louisiana residents.
These fires were bad; they were terrible. The amount of timber lost and damaged in these fires was staggering. We don’t normally think of large wildfires occurring in the South — they happen out West.
Hurricane Laura hit the southwest portion of the state in August 2020, causing tremendous damage to everything in its path. Trees were blown over, snapped off and damaged to the point where many died a year later. The damage was so widespread salvage operations were greatly limited. Three years later the amount of fuel laying on the ground had dried out and was just waiting for a fire and some wind. That scenario played out much to the dismay of the forest community.
There was not a whole lot that could have been done to prevent what happened last year. We had a lot of rain in the spring then it shut off. We got really dry in a short period of time; then we got really hot. This summer certainly looks like it could follow in the footsteps of the Summer 2023.
One forest management tool which can be implemented to reduce the threat of wildfires is understory burning. I remember being in a fire class at Louisiana Tech in 1980 with Dr. Jim Dyer. Someone used the term “control burn” in addressing the subject of the understory burns. Dr. Dyer quickly pointed out that there is nothing we control in a fire. “We do prescribed burns.” We write a prescription to accomplish a desired goal.
You can do fall burns, spring burns or warm season burns. Many of the understory burns are done for fuel reduction, with many beneficial components. The prescription for the burn takes into account the time of the year of the burn; the temperature, wind speed and direction, relative humidity, time since the last rain, and moisture content of the fuel. The prescription will also factor in the height, direction and speed of the transport winds. The transport winds help to move the smoke out of the area. The prescription will assess the burn in relation to the location to highways, towns and airports.
We do the burns under prescribed conditions. A large number of understory burns are done in the spring (March-May), when the temperature is lower, there is ample moisture and winds are more favorable. Spring burns can clean up a stand by burning the pine straw and limbs and killing back some of the sweetgum and yaupon. The ash from the debris on the ground will be able to go back into the soil as fertilizer for the trees. The young, tender vegetation which comes in, is excellent deer food. The burned area makes for preferred wild turkey brood habitat. Plus, all the fuel on the ground is eliminated.
A burn program is just that, a management program which is repeated. The one thing you do not want to do is, burn your stand one time and walk away from burning. You will create a monster! Your understory will be amazingly thick, so thick you cannot walk through it. The wildlife managers suggest doing a burn about every three to four years.
Another suggestion is that you don’t want to burn your whole tract at one time. You would want to break up the burn into smaller blocks and rotate around your property. If you have a 40-acre tract, this concept may not work. You would just burn the whole 40 acres. A tract of 100 acres and bigger will work great by dividing into blocks. You could set up the tract with three blocks of 20, 40, 80 or 100 acres. The first year you will burn Block 1; the second year you will burn Block 2 and the third year you will burn Block 3. Year four you start over with Block 1 and work through the rotation each year. Each block will be burned every three years.
You want to burn stands which are a little more mature and which have been thinned. You do not want to burn a young, first thinning pine pulpwood stand. One of the problems with trying to burn a young stand is that the heat cannot get out of the stand. The tree canopy is so tight, the heat cannot escape and there could be a huge build up of heat, and it will blow out through the crown when enough heat builds up, killing many of the trees.
Thinned stands are the normal candidate for a burn. You will want to wait about a year to a year and a half after the thinning operation to do the burn. Waiting 12-18 months will allow for the debris on the ground to start to break down some and therefore burn a little cleaner. It depends on the time of the year the thinning operation is completed.
You burn your stand in the spring of 2024 and you get a very nice burn. Then during the late summer of 2024, your neighbor is burning some trash in his backyard. It is dry, it is hot and it is windy. The fire gets away from him and heads toward your tract. The fire may burn into your tract, but it will not do any damage. There is no fuel on the ground to carry the fire. The fire may go out on its own or the Louisiana Department of Agriculture and Forestry may plow it out. Either way, there will be little to no damage.
The burns can be funded under the state’s Forest Productivity Program (FPP) which can be a big financial boost. The burns have a cost, normally somewhere between $35 and $50 per acre. The reimbursement from the incentive program can make a burn program manageable.
(Tim Holland is a consulting forester for Mudd & Holland Consulting Foresters LLC in Shreveport.)
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