With a growing body of science urging deer managers to diversify the timing of prescribed fire, I planned and lit my first growing-season fire on June 14 last year. It was a success, and I plan more spring and summer burns this year. If you hesitate to burn outside your familiar winter window, or to burn at all, consider what I learned when I burned last summer.
Like many deer and forest managers, we’ve traditionally burned the woods in winter on our Georgia land. But experts are encouraging deer managers to break out of that rut and expand the calendar to add spring and summer to our burn-unit rotation. The Longleaf Alliance even produced a bumper sticker: “Pyrodiversity Enkindles Biodiversity.” Using fire in different seasons increases and extends the supply of high-quality forage for deer, and it enhances plant and wildlife diversity.
Yes, it is a little tougher in spring and summer to find those ideal days when all the conditions are just right. A 28-year study of prescribed fire conditions at the Jones Center ecological research site in Georgia found good burning conditions on 52% of days in the dormant season (January to March) and 44% of days in the growing season (April to September). Narrow the growing season down to summer months, June through August, and it was only 34% of days.
For my first summer fire, I was shooting for a May-June window (more on why later). I got lucky in mid-June when a free weekend aligned with satisfactory weather. I freshened the firebreaks around the target 4-acre unit of thinned loblolly pine, scattered oaks, and longleaf pine saplings in the understory. Grace Acres, our family land, borders both a small town and a four-lane state highway. Thus, fire control and smoke management are our highest priorities.
The Fire Weather Forecast looked good from a few days out. At 9 a.m. on the morning of the burn, the forecasted conditions from 11 a.m. to 5 p.m. were within acceptable ranges.
- Relative Humidity: 57% at 11 a.m. dropping to 43% by mid-afternoon. Even on a hot June afternoon in Georgia, it would not fall below the recommended floor of 30%.
- Eye-Level Wind Speed: 2 mph. Bottom of the preferred range of 2-6 mph.
- 20-Foot Wind Speed: 5-6 mph. Bottom of the preferred range of 5-15 mph.
- Wind Direction: NE shifting to E by 4 p.m. No danger of smoking the highway or neighboring town.
- Mixing Height: 3,900 to 6,900 feet. Well above the floor of 1,650 feet, as well as above the 2,200 feet recommended near sensitive areas like highways.
- Transport Winds: 12 mph dropping to 9 mph. In the range of 9-20 mph.
- Fine Fuel Moisture: 10-15%. Above the floor of 8%.
- Dispersion Index: 42-77. In the ideal range of 40 to 90.
I plugged the conditions into V-Smoke, and the model predicted safe smoke dispersal. Reviewing the conditions and my location, the Georgia Forestry Commission granted me a burn permit that morning, though the forester I spoke with on the phone cautioned me that conditions were starting to get on the dry side. In the end, this actually worked to my advantage.
Winds on June 14 were just barely what I needed, and conditions overall were a little “stable” for the best smoke dispersion. But considering wind direction and the small size of my burn unit, there was no chance of putting smoke anywhere it could become a safety factor. The relatively dry fuels meant less smoke anyway, and it also made up for lighter winds.
After a small test fire in a firebreak, and with orange flagging tape confirming steady wind direction, I lit my first growing-season prescribed fire. Here are a few observations of mine about how the day, and the results, differed from the winter burning I’m used to.
The Sound of Summer Fire
The noise of a growing-season fire is very different than winter fire. Green leaves and stems snap, crackle and pop loudly as the moisture is released. Bigger stems hiss, steam and whistle as they burn. It’s a unique and interesting soundtrack – and yet it’s a natural one. Historically, most wildfire occurred in summer when it was ignited by lightning from summer thunderstorms. It’s amazing to hear summer fire return to woodlands that need it but haven’t seen it in a century or more.
One bad thing about the sounds of summer fire: Some of the crackling noise sounds an awful lot like the buzz of a rattlesnake. Several times the noise sent a chill up my spine. It’s a reminder that snakes are active in the growing season. Be careful walking in cover ahead of an active fire and be on the lookout for snakes crawling into firebreaks.
Worries About Wildlife
We started with a backing fire on the downwind firebreak then gradually added a little flanking fire on the sides of the unit. Since the unit was relatively small and the fuel burning well, I let the backing fire do most of the work. As the fire reached to within about 10 yards of the firebreak on the upwind edge of the unit, I noticed a lot of movement in the brush. Insects! Grasshoppers, beetles, spiders and other insects crawled, hopped or flew across the firebreak into the adjacent cover. I saw a few tree frogs and lizards in the mix, too.
This emphasizes an important point about prescribed fire: the impact on wildlife is not nearly as bad as most people imagine, even in the growing season. If spiders and tree frogs can outrun a fire, then fawns, turkey poults, rabbits, quail chicks and other wildlife larger than insects are certainly likely to escape.
This unit was surrounded on all sides by good escape cover. When I walked the unit one last time before lighting it, I did not see any fawns, turkey poults, quail or other animals. When I inspected it the day after the fire, I did not find any evidence of any wildlife killed by the fire, not even a snake or box turtle. However, if any insects didn’t make it out, I’m sure turkeys found them to be a delicious toasted snack.
Prescribed fire is not wildfire. If you plan and prepare to ensure slow, safe fires that burn at low intensity, as you should, then you’re minimizing unintended harm to living creatures – as well as valuable trees. New research is showing turkeys prefer to nest in areas more recently burned, not in the type of cover that’s ready for fire’s return. On the contrary, the benefits of fire for wildlife populations will far outweigh any incidental losses to individual animals. If you still have concerns, do like I did: Start with a small unit for your first growing-season fire. The idea is not to burn every unit in summer but to add a little seasonal diversity to your fire plan.
Heat Exhaustion: Take It Seriously
I once listened to a presentation by a physician and wildland firefighter on the health risks of prescribed fire, and I wrote an article about it. He talked about heat exhaustion, especially with summer fire. Now that I’ve run a growing-season fire I can fully appreciate how easily it can creep up on you. I lit our June 14 fire at 11:15 a.m., and we were mopping up at 4 p.m. Air temperatures that day reached 92 by the time we finished – not even a really hot day for South Georgia. By that time, I felt like I was moving in slow motion. Lifting the drip-torch or the fire rake was like lifting a 50-lb. bag of fertilizer.
I brought plenty of ice-cold water to the site and paused to drink regularly. It was a steady but slow-burning fire, so there were frequent breaks to lean on my fire rake and just watch. Yet, the combination of sunlight, air temperature, the heat of the fire, and the steady exertion of walking and carrying the drip-torch wore me down. Had I kept working any longer that afternoon, I probably would have been pushing into heat exhaustion territory.
No matter how much you prepare, burning woods in summer puts a much greater strain on you than in winter. Tackle small burn units that can be finished in a few hours. Stay hydrated. Take breaks to sit in the shade and rest. Invite plenty of friends to help, and make sure they stay hydrated, too.
Does Green Vegetation Burn?
I wondered about this and thought it would be more difficult. However, the block I burned had not seen fire in three years and there was a good layer of duff and dry grass underneath the green plants. Additionally, I hit the humidity and moisture levels just right: we were just about a week away from being too dry to burn. It was one of the most efficient and thorough fires I’ve ever conducted.
The dry fuel burned completely, and fire climbed up into almost all of the green understory vegetation and consumed it. This unit had a lot of gallberry and palmetto, which usually burn easily, but even young maples, wax myrtle and ferns burned well. Even if the tops weren’t burned, the temperature was hot enough to girdle the stems. That’s good, because controlling a lot of these species was my goal with a June fire.
There were no gaps in the fire. I didn’t have to go back and try to re-ignite islands of unburned cover. The strings of fire held together across the burn unit. So, growing-season fire is just like winter fire: You get a good burn if you wait for good conditions.
The Results: Pyrodiversity Works
As expected, the growing-season fire was very effective at killing small hardwood shrubs like gallberry, maples and wax myrtle. The 4-acre unit borders a 3-acre unit I had burned in January, making for a great side-by-side comparison. We got two completely different results. In the January burn, we only set the cover back in age, we didn’t change the species composition much. The gallberry, maple, wax myrtle and bracken fern survived and grew back from the roots. Still, blackberry responded well to the space created by setting other plants back.
However, in the June burn unit, hardwood shrubs and ferns were much more effectively killed. When I walked the site three months post-fire in September, I was amazed at the diversity of broadleaf forbs I saw, including partridge pea, butterfly pea, blackberry, passionflower vines, and many others I didn’t know. Many plants were in flower in mid-September, and butterflies were everywhere. It was as if the June fire had brought spring back in September.
That’s a primary goal of growing-season fire, according to habitat researchers: To create a new pulse of high-quality, high-protein deer forage at a time when the spring pulse is long gone. The evidence I saw of deer browsing on forbs in the June burn unit was proof of success.
Additionally, I was extremely pleased to see wiregrass responding with a burst of growth. Wiregrass is a native warm-season grass of the Coastal Plain. I’d learned from local biologists that fire in May or June is important to stimulate strong seed production in wiregrass, and that’s why I chose the timing. It worked.
Deer don’t eat wiregrass, so why do I care? In the longleaf pine ecosystem, wiregrass is one of the fire-adapted species. It helps carry fire, helps us to burn more frequently, and it even helps diversify our fire timing. I learned this from Brandon Rutledge, a deer hunter and wildlife biologist at the Jones Center.
“Wiregrass provides a broader window of conditions under which you can burn,” said Brandon. “You can burn wiregrass under much wetter conditions and during different times of the year than old-field vegetation, which typically does not burn well after green-up. Unlike pasture grasses, wiregrass provides space for other plant species to occur. Many of the native legumes that co-occur with wiregrass are beneficial deer browse.”
Most deer managers in North America don’t have wiregrass where they hunt, but the point is that we all have native forage and cover species that respond to fire. They respond in different ways to being burned in different seasons. This year, set aside a small unit for your first growing-season fire, and start learning how deer, native plants and other wildlife benefit from pyrodiversity.