Last Friday, I wandered through the small prairie we burned back on March 10. Even though it is still very early spring, there were already a number of prairie plants popping out of the ground. I posted photos of this site right after the fire was completed. Today, I’m posting some photos taken 10 days later at the same site, along with some discussion of the impacts and effectiveness of prescribed prairie fires.
Purple poppy mallow (Callirhoe involucrata) begins its new year of growth.
Most prairie plants grow from belowground buds, making them much less vulnerable to fire than trees and shrubs, which start their new growth above ground – from buds at the tips of branches. When fire burns woody plants, those aerial buds and living tissue are destroyed, stressing the plants and forcing them to start over from ground level. However, fire (at least during the dormant season) simply burns up the old stems and leaves of non-woody prairie plants, causing no injury. Instead removing those dead stems helps stimulate growth in the coming season, especially via increased sunlight, which warms the ground and is available to new shoots as they first emerge.
Scribner’s panicum (Panicum oligosanthes), a native cool-season grass. In this photo, you can see that the tips of the grass leaves had just started to grow when the fire came through ten days earlier. Since the leaves grow from the base, those burned tips don’t impede plant growth.
Increased sunlight hitting the ground has helped the small area we burned on March 10 green up much faster than unburned prairie nearby. Our main objective for the fire was to remove thatch in order to improve the effectiveness of planned herbicide treatment/re-seeding of some smooth brome patches within the small prairie. The brome is responding very strongly to the fire, and its rapid growth (and the absence of thatch to intercept spray droplets) will make the grass more susceptible to our herbicide treatment. However, since many other plants are also popping up, we’ll carefully spray only the thickest patches of brome where no other species are growing.
Green sage (Artemisia campestre) growing next to its old stem from last year.
Prescribed fire can be a useful tool when trying to temporarily flip the balance of power from cool-season invasive grasses (smooth brome, Kentucky bluegrass, etc.) to native warm-season grasses (big bluestem, indiangrass, etc.). However, timing is critically important. A dormant season or early spring fire is actually counterproductive unless it is followed by herbicide treatment, mowing or grazing. Those early fires stimulate the growth of cool-season plants – including smooth brome and Kentucky bluegrass – giving them a big advantage over later-season plants which won’t start growth until late April or early May. By the time those warm-season plants start growing, the early plants will have had a month or more to extract soil moisture and nutrients, and will be big enough to dominate competition for light and root space.
If we’d wanted to suppress smooth brome solely with fire (and not follow up with herbicide), we would have waited until late April or early May to burn. That late season burn would have stressed the actively-growing brome and bluegrass and provided direct sunlight to freshly emerging shoots of big bluestem and other warm-season grasses. More often, we combine periodic fire and grazing to suppress brome and bluegrass and facilitate greater plant diversity.
Along with smooth brome (Bromus inermis), Kentucky bluegrass (Poa pratensis) also responded well to the fire. This particular plant will likely have a very good year, but the brome and bluegrass in the thicker patches of this prairie will be sprayed with glyphosate herbicide and re-seeded.
The regrowth of prairie plants after fire can seem almost magical. Fire is absolutely an important natural process and a very useful tool for prairie managers. However, prescribed fire is not magic, and doesn’t automatically lead to better prairies. As with any tool, fire has to be applied thoughtfully (and carefully!) in order to meet objectives.
The timing of fire dramatically impacts the way prairie plant communities respond. Early spring, late spring, summer, and fall fires each have different effects on plants, and those effects are also influenced by soil moisture, the presence/absence of grazers, and many other factors. Prescribed fire can also have serious impacts on some animals, even during the dormant season. Many invertebrates, for example, overwinter in the aboveground plant stems or thatch, making them very vulnerable to fire. It’s important not to burn an entire prairie at once – especially if that prairie is isolated from other grasslands.
I’m not sure what species of wildflower this is but I’m looking forward to finding out as it gets bigger!
Fire plays many critical roles in prairie ecology – suppressing woody plants, removing thatch, stimulating microbial activity, aiding in nutrient cycling, and more. However, while fire is important and its effects are both useful and aesthetically pleasing, it is not automatically positive. Safe use of prescribed fire requires training, experience, and caution. The effective use of fire requires clear objectives and careful planning that ensures those objectives will be met.
As I’ve discussed before, the actual process of conducting a fire can be very stressful. However, once the smoke clears and I can relax, its easy to appreciate both the beauty and ecological benefits of prairie fires. The emergence of bright green prairie plants through black ash is one of my favorite sights, and I love watching plant and animal communities respond and adapt to changing habitat conditions.
In prairies, rising from the ashes is more than a metaphor – it’s a way of life.
The Prairie Ecologist 
Will the brome and such you spray give up at some point so you will not have to keep using herbicides? I enjoyed your photos. I love seeing the new spring growth of plants.
Good question. We don’t often use herbicide to control brome because it’s tricky to hit only what we want to kill – especially in native prairie. In this case, we’re dealing with a small area near our field headquarters that is almost a big prairie garden (about an acre in size). We hope to get enough suppression on the brome that we can establish a more diverse mixture of plants within those thicker patches. More typically, we attack brome and bluegrass with a mixture of fire and grazing – just trying to suppress the plants periodically and keep them from becoming too dominant – but grazing isn’t an option for us on this little area. Unfortunately, I don’t think the brome will ever give up, and there’s enough in nearby roadsides and other prairies that it would find its way back in even if we could eliminate it.
Have you tried a grass specific herbicide like Select 2EC (clethodin). There are many generics available with that active ingredient also and may be lower cost. The highest label rates probably won’t control the smooth brome and bluegrass as effective as glyphosate, but clethodin chemistry will not touch broadleaves or sedges. It will also cost more that glyphosate. Seems like we have visited about this in the past. I used some on small plots on east Dahms in the mid 1990’s.
Hi Orvin – yeah, we’ve played with Select and Poast Plus some with mixed results. They would certainly be an option worth considering in this situation too. I sure like their selectivity. In this case, the prairie we’re treating is pretty degraded (at least the areas with the most brome) and there’s not much else growing in the worst spots we hope to treat and overseed. Still, it’s a point. We’ll talk it over. Thanks.
I’d be curious to see photos of these species from an unburned prairie for comparison.
Each spring the prairie phlox in my garden starts growing before prescribed burns are conducted. I expect a spring burn would set back prairie phlox, violets, and other species that emerge early in spring. The ecologists have been burning the higher quality areas in fall for the last few years. I expect the spring flora is the primary reason for the fall burns. I still wonder why these early spring species emerge right before the beginning of prescribed burn season. It is only logical that natural selection would have chosen individuals that emerged a couple of weeks later. I have been contemplating this disconnect without finding any answers.
The “spring burn season” is a post-settlement artifact and an abomination! Okay, a bit over-dramatic, but spring burning as the only form of management doesn’t make sense to me, because it’s so destructive to early flora and waking fauna. It does have a place as a management though, as Chris describes here, but most evidence points to fall as the most frequent time of burning in pre-European central North America.
Go dormant – dormant season burning, that is!
Interesting the effects that latitude have on the same species. We burned Feb 26th at a property here in East Central TX and I went out 2 weeks ago and there was already about 1-2 inches of new growth on the little bluestem and switchgrass plants on the burn units. Areas that went unburned had no growth as of yet. Indian painbrush (Castilleja indivisa, I think) and bluebonnets (Lupinus texensis) are just starting to pop into bloom. Good post, Chris.
Hi Chris,
I am curious if you ever had any success frequently burning mixed prairie and brome patches in dormant season and interseeding desirable species? This technique is used all the time in our area (WI) with success. Dormant season burns are used so as not to set back early prairie forbs or excessively stimulate existing warm-season grass. I should note that I have not seen cow grazing used on any of these sites so that may be a factor in the final outcome with respect to the brome grass?
David
David – interesting question. We’ve done some of that, but have found (mostly) that without something to suppress the brome after a dormant season fire, it (or bluegrass, or fescue, or canarygrass, etc) exerts its dominance to such effect that our seeding doesn’t accomplish much. Grazing, mowing, or herbicide is needed to counteract the flush of growth from those grasses. I think further east, where soil moisture is less limiting, the biggest limiting factors for seed establishment might be light and seed/soil contact, in which case a dormant season burn alone might be sufficient. Here where we have less rainfall, soil moisture is more limited and those early season grasses can more easily monopolize what’s available, leaving little for other species. I’m not saying this is all true – it’s what I have inferred from experience and conversations with others.
Have you tried the herbicide Plateau for suppressing cool season grasses? It’s worked pretty effectively for me in the past when applied at the right rate/time.
Mark – yes, a long time ago. More selective than Roundup, but pricier and not as selective as Poast/Select. A good option in some cases, for sure.
The facts back up Mr. Trager’s statement about Spring fire being “post settlement”; however, due to the very exotics discussed in this article, we are dealing with much different fuel models than days of old. Dormant fires in restorations that struggle with CSG invasives like brome and fescue and/or deciduous woody encroachment do little more than turn things black and encourage those species. Early fall burns often scorch woody plants and promote forbs far better than spring burns; however, leave at least 50 days of soil temps that get brome/fescue to shine like diamonds by December. Also, a lot has been made about providing refugia (for a wide array of species) within a burn unit. When a practitioner employs a dormant burn, every stitch of natural cover is “available” fuel and will be consumed without dramatic and often risky intervention; however, growing season burns utilize material with live fuel moisture which inherently result in patchier burns.
I know there are probably 100+ different ideas about what is the correct fire regime, but I thought I would share what we do in the fire management of our property (WI). We try very hard to burn dormant season. Fall burns tend to be difficult for us to get in due to a short weather window. We wait until asters and gentians are finished which pushes burn timing into mid November. We also limit total burn acreage of fall burns because it removes a lot of important winter wildlife food and cover. Our burn season of choice is during snow melt. South aspect slopes followed by west aspect slopes followed by east and finally north. Many of the early burns are contained by snow. The burns leave lots of unburned plant matter due to the higher humidity and cold/partially frozen ground. It is the best and easiest method we have found for creating a highly varied patch-work burn with a lot of different vegetation structural elements. As I stated in an earlier post, we have good luck intereseeding brome areas after dormant season burns. And there is research that hints (?) to why this works with the soil carbon/nitrogen balance tipping to favor natives. For the land we manage, an early spring burn (after green up) to suppress brome grass would also suppress cool-season natives such as small panicums, June grass, needle grass, poverty oat grass, a wide variety of sedges, etc. It would also likely eliminate flower production of many early blooming forbs and reduce herptiles numbers due to direct fire contact mortality. I can’t speak to thatch overwintering insects, but our reasoning is that our snow melt burns are much kinder to them? As to woody control, we see fire kill very young seedlings but most species with a few years of establishment will require manual removal. Our snow melt burns are good at exposing any woody invaders but typically do not kill the woody tissue near the ground. We come along later after the fire and basal bark any species we do not want with triclopyr in oil.
David
I think the primary reason my county burns in spring is due to resource limitations. My county has 68,000 acres of forest preserves. They are lucky to get 3000 acres burned in fall. Burning in spring allows them to turn another 2,500 acres black in a good year. Once reptiles start coming out of the ground they stop burning.
I still wish more could get burned in fall. I grew a large number of plugs of high quality sedge meadow species from local seed and planted them in a wetland at a large site where prairie is being restored. Since the area is a restoration, it does not get to the top of the list like high quality prairie, savanna, and woodland. The fuel in this old agricultural field restoration is still sparse. The wetland is dry in fall and would likely burn, but in spring there is often standing water stopping the fire. The disturbance this wetland has received has resulted in dense young saplings of cottonwood and willow species. The county has been mowing this woody growth in summer. This mowing is great, but I really wish the wetland area could get burned. At least the spring burns are eliminating the dense cottonwood saplings from the upland areas.