Difficult Decisions – Growing Season Fires and Other Prairie Management Choices

Would you purposefully destroy the nest of a wild turkey or grasshopper sparrow?  Of course not.  But what if that destruction was a consequence of a land management action that benefits the larger prairie community?  That was the situation we were faced with last week as we mulled over whether or not to conduct a late spring (early summer?) prescribed burn.

Michelle Biodrowski ignites a prescribed fire last week (June 6) at a wet-mesic prairie.  The Nature Conservancy's Platte River Prairies.
Michelle Biodrowski ignites a prescribed fire last week (June 6) at a wet-mesic prairie. The Nature Conservancy’s Platte River Prairies.

In the aftermath of any prescribed fire, there are winners and losers.  Fire rapidly and dramatically alters habitat and growing conditions in ways that favor some plant and animal species and put others at a disadvantage.  Fires also kill some insects and other animals outright.  For example, dormant season (late fall through early spring) fires burn up a lot of invertebrates that overwinter in prairie thatch.  Growing season fires, of course, can kill numerous small animals – especially slow-moving non-flying ones.  We usually don’t see the evidence of those impacts, but when we do, it’s no fun.  Over the years, I’ve seen way too many fried snakes and scorched nests, in addition to animals who suffered injuries from our fires.  It can be tough to deal with the knowledge that I made the decision to light the fires that killed or maimed those animals.

Regal
I’m sure we burned up a number of regal fritillaries in our fire last week because the females are within a few weeks of emerging as adults, and the kind of thatchy prairie we burned is prime habitat for overwintering larvae.  However, we would have done the same damage to those caterpillars if we’d burned the prairie any time between October and July.  Fortunately, regal fritillaries are very common in our prairies, so I know the overall population will be fine.

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garter
Snakes are common victims of growing season fires.  It’s likely we killed some snakes last week, though I didn’t see any corpses as I walked around the next day.  I did, however, find a live red-sided garter in one of the small unburned patches in the middle of the burn unit – so at least one survived…

While it can certainly be deadly to insects and animals, fire is also an important part of our strategies to maintain diverse and healthy prairie communities.  Fire can help suppress invasive species, remove thatch and stimulate vigorous plant growth, and attract grazing activity – among many other things.   Prairies that aren’t burned fairly frequently often suffer from tree/shrub encroachment, excessive build-up of litter, and/or dominance by a few native grass species.  Other tools, including grazing and haying, can be used instead of fire (or in addition to it) but those can also have negative impacts, and can’t replicate everything fire can do.  Knowing that fire can cause problems for some species, we try to minimize those impacts as much as we can.  For example, we usually only burn a portion of a larger prairie so that any impacts are not likely to affect the entire population of a species.

A smooth brome
Smooth brome was mostly done blooming when we burned, and starting to make seed.  I’m not sure how much we sapped the vigor out of the brome (a week or two earlier might have been better) but I guess we at least prevented it from making seed this year.

The main objective for our burn last week was to create an attractive patch of nutritious grass to concentrate cattle grazing in that portion of the prairie – part of our patch-burn grazing system.  We are using a light stocking rate of cattle this year, so we expect the grazing in the burned patch to be selective (the cattle should eat mostly grass) and to favor wildflower diversity by suppressing dominant grasses.  Meanwhile, unburned areas won’t be grazed much at all, allowing them to rest from previous years’ grazing and last year’s drought.  The result should be a messy mixture of habitat types and growing conditions across the prairie that will allow just about every species to thrive somewhere.

We’d hoped to burn the site earlier in the spring, but never got the right weather window to do it.  In other sites where we didn’t get our planned burns done this year, we’re using electric fence to temporarily enclose the cattle in what were supposed to be the burned patches.  The idea is to get the cattle to graze the areas down sufficiently that when we take the fence down in early July the cattle will continue to graze the regrowth (which will then be the best quality forage in the prairie) in those patches for the remainder of the season – similar to what we’d see in burned patches.  It’s far from a perfect subsitute for burning, but it does at least concentrate grazing pretty well in one portion of the prairie and allow other areas to rest.  The biggest disadvantage of the temporary grazing enclosure method is that cattle aren’t very selective in their grazing within that enclosure, so we lose some of the benefits we in burned patches when cattle graze mainly grasses.

patches of green
It was a pretty complete (though pretty slow and smoky) burn last week, but there were a few patches that didn’t burn – mostly in low, wet areas where the thatch was moist enough it didn’t carry fire.  The green strip shown here is at the bottom of a wetland swale and is also where I found the surviving red-sided garter snake mentioned earlier.

After weighing the pros and cons of burning in early June, we decided to go ahead with last week’s fire.  We certainly burned up nests of meadowlarks, grasshopper sparrows, and at least one turkey (a forlorn-looking female was wandering around after the fire).  I expect most of those will have time to re-nest, but that only makes me feel marginally better about it.  I’m sure we also killed lots of insects and some wildlife species.  On the other hand, the burn allows us to move ahead with our management strategy to improve the wildflower diversity of the entire prairie.  That increase in wildflower diversity will benefit a wide range of insect and wildlife species in coming years, as will the habitat structure created in both the burned and unburned patches.  We burned about 65 acres, but left more than 300 acres of the prairie unburned.  Actually, there is much more unburned prairie than that, since there are more than 1,000 acres of unburned grassland on adjacent land as well.  That unburned prairie should be a great refuge for fire-sensitive species and give them opportunities to recolonize last week’s burn over the next several years.

eastern red cedar
This eastern red cedar burned brown after the fire, but it’s unlikely to die.  Experience has shown us that growing season fires rarely “cook” cedar trees enough to kill them.  Even when they turn brown, they tend to green up again.  However, this prairie has had numerous dormant season fires, so cedar control was not an objective for last week’s fire.  We’ll get this one next time.

The kind of difficult decision we made last week is a regular part of land management.  Every management treatment leads to the improvement of conditions for some species but hurts others – often literally.  Just letting “nature take its course” by not managing at all isn’t any better.  An idled prairie eventually becomes dominated by trees and shrubs, along with just a few grass and wildflower species.  That degradation of habitat kills or evicts more animals and plants than active management, which maintains diverse plant and animal communities.

Right or wrong, I guess I’ve trained myself to focus on the long-term positive outcomes of our management and not to dwell on the short-term negative impacts.  I’m not sure if that makes me insensitive or just sensible.  One thing that helps me justify our actions to myself is that we’re collecting as much data as we can about the overall impacts of our management.  If we’re going to make tough decisions that have negative consequences for other living creatures, I want to KNOW that those decisions are leading to the long-term benefits we think they are.  We can never collect enough data to know everything we want to, but we collect enough that I’m convinced most of our management strategies are working as planned, and we constantly tweak those strategies as we learn more.

Ants
The ants in these mounds appeared to survive the fire just fine.  I assume they’ll be able to find plenty of food, and satisfy their other needs, as the prairie greens up around them over the next few weeks.

Regardless of the tough decisions we have to make, I love my job.  I feel good that we’re improving the condition of our prairies, and that we’re sharing successes and failures with other prairie managers so they can do the same.  It’s difficult for me to imagine a more fulfilling career.  I always try to focus on the big picture instead of dwelling on the immediate negative impacts of some of our actions.  At the same time, I try to be ethical about what we do, and not cause harm when it’s not necessary.

It’s a messy world and a messy job, but I wouldn’t have it any other way.

Early Recovery from the Wildfire at the Niobrara Valley Preserve

I was back up at the Niobrara Valley Preserve last week to help with a roundup and sorting of the east bison herd (more on that later this week).  While I was there, I was glad to see the prairies starting to green up again.  It had been about three weeks since the wildfire, and the area had received an inch of rain one week prior to my visit. 

Grasses and other prairie plants are sticking their heads up from the ash in the sandhill prairie of the east bison pasture.

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From a distance, the sandhills still appear black, but at the right angle, you can see the thin green grasses starting to pop up.

Of all the areas of the Preserve that burned, I’m the least concerned about the sandhills prairie.  We’ve done enough summer burning in the sandhills – as well as in sand prairie along the Platte River – that we know what to expect there.  The only question is about how the drought will affect the recovery.  Because many of the plants, especially those that had been grazed, were already dormant because of the drought, I’m guessing they’ll wait until next year to resprout.  If that’s the case, we may see immediate greening mainly of those plants that had escaped grazing or that have particularly deep roots.  Either way, next spring will bring recovery of the entire sandhills plant community.  In the meantime, our east bison herd would appreciate it if enough plants greened up to keep them fed through the winter.  We’ll see – some more rain would sure help.

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Leadplant is one of the fastest-recovering plants in the prairie – likely because of its very deep root system and the fact that it is rarely grazed in our bison pasture.

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This ground cherry is re-emerging from the base of its old stem.

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Smooth sumac appears to be recovering quickly and vigorously. The prairie has always had large patches of sumac, but at 7,200 acres, the east bison pasture can absorb fairly large patches of shrubs without losing its open grassy nature.

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In contrast to the prairies, the woodlands are not yet greening up.  I’m not sure what to expect with pine trees – will the survivors start to put on new needles yet this fall?  Or next year? 

We have a lot more questions about what comes next.  I’ve put out feelers to some colleagues who have been through similar wildfires to see if they can share some lessons that would help us be proactive.  If anyone reading this has experience that could help us, I’d appreciate hearing from you as well.  You can add comments to this post or contact me separately.  Thanks!

This photo was taken just a few days following the wildfire (and used in an earlier post). Notice the trails beneath the powerlines, and compare those to the next photo (below).

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About three weeks after the fire, the shallow trails beneath the powerlines appear to be eroding somewhat. There has been about an inch of rain since the fire. I think some degree of erosion is to be expected, but I’m not sure whether or not it’s something we should worry about – or what we’d do if we wanted to… This is one of many questions we need to be thinking about in the weeks and months ahead.

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Are Botanists Ruining Prairies?

No, I’m not saying they do.  I’m merely conducting a thought exercise, and inviting you to come along for the ride.    …No, really – some of my best friends are botanists!  And I’m pretty sure they have a good sense of humor…

Why is it that we define prairies and prairie quality by their plant communities?  Are we making a mistake by letting botanists drive the prairie conservation bus?  Let’s review the current situation:

Today’s prairies are generally categorized as high or low quality based mainly on the composition of their plant community.  More specifically, prairies achieve high quality status by containing an abundance of “conservative” plants.  Conservative plants are essentially defined as plant species that are rare in most of today’s prairies, don’t do well in prairies that are heavily disturbed by grazing, and don’t colonize quickly into fallowed fields, etc.  Another way to think about it is that conservative plants are those deemed to be “fragile”.  Whether they really are or not is another subject for another time.

Compass plant is usually considered to be a conservative wildflower in prairies.

So, a prairie filled with lots of fragile plants is considered to be a high quality prairie.  Conversely, a prairie filled with prairie plant species that are tough and scrappy is considered to be degraded.  Come to think of it, we tend to think about human society in much the same way.  Speaking stereotypically, high society consists of fragile people with clean fingernails and uncalloused hands who have to hire low-society people to cook, clean, garden, and take care of their fancy cars.  Those low-society people work hard to feed themselves and their families, wear functional clothes (without designer labels), and often employ double negatives and words like “ain’t”.  Success in life is supposed to be measured by our ability to move from low to high, right?  I suppose it makes sense that we think of prairie conservation in the same way.

Now it’s certainly understandable that people who dedicate their lives to plants would be concerned about preserving those plant species that are the most difficult to preserve.  Conservative plants are important because they’re rare.  Most grasslands in today’s landscapes have to earn their keep, and are managed in ways that tend to favor species that are tough and scrappy, rather than those that are fragile.  In those landscapes, conservative species find hiding places on steep hillsides, in wet or sandy soils, outside fences, and in small, oddly shaped land parcels that don’t fit into agricultural systems.  The question of whether conservative plants were distributed in similar ways historically or were more widespread is a topic of much debate in prairie conservation circles.  Regardless, botanists today tend to focus their conservation energy on prairies that contain lots of fragile plants because they don’t want to see them disappear.

Botanists from the Illinois Natural History Survey look at a tallgrass prairie in southeast Nebraska as part of a research project on insects in fragmented prairies. By including a photo of them in this blog post, I am in NO way representing their opinions on conservative plants, prairie quality, or anything else. It's just a nice photo of botanists.

And conserving prairies full of conservative plants makes sense for the larger conservation effort anyway, right?  Because prairies with lots of rare plants also have lots of rare insects, rare bird species, etc.  Right?  Well – maybe not.  In fact, while there are a few instances in which that’s true (some rare butterflies, for example) there are many more cases where it’s not.  For instance, I’ve spoken with several entomologists working in eastern tallgrass prairies who have found that large and relatively “degraded” prairies tend to have much higher numbers of rare insect species than small “high quality” prairies.  In addition, two groups of Illinois entomologists have each developed their own index of prairie quality based on “conservative” insect species.  You can learn more about those indices here and here.   Both of them have found that there is often little correlation between the number of conservative insect species and the number of conservative plant species in a prairie.  In other words, even if we saved all of the remaining prairies with “high quality” plant communities, we could still lose a lot of rare insect species.

A specific insect example, and a notable exception to the aforementioned connection between rare butterflies and high quality prairies, is the regal fritillary butterfly.  States with highly fragmented grasslands, and thus a heavy emphasis on conservation of small prairies with lots of conservative plants, have very few regal fritillaries left.  In contrast, regals are among the most common butterfly species found in places like eastern Nebraska and Kansas – places full of prairies scorned by many eastern botanists as having been long-ago “ruined” by cattle grazing because they don’t have abundant conservative plant species.  Gorgone’s checkerspot is another butterfly with a relatively similar pattern of occurrence.

Gorgone's checkerspot butterfly in restored prairie in east-central Nebraska. This is a fairly common species in Nebraska, but is very rare in many eastern tallgrass prairies.

Grassland birds are rightly of great conservation concern to many people.  In fact, I think it’s a requirement that ornithologists working with grassland birds have to start every paper or presentation with the phrase, “Grassland birds are the fastest declining group of birds in North America”.  And it’s true.  So where do we find the strongest populations of grassland birds?  In landscapes full of large prairies – which typically have relatively low abundances of fragile plant species.  With a few exceptions, high quality prairies – using the botanists’ definition – tend to be small.  Again, they’re found in those hidden corners that have escaped having to work for a living.  However, grassland birds are notoriously unsuccessful when they try to nest in small prairies, and most don’t even try because the predation risk is too high, and the prairies are often surrounded by trees and/or relatively intense human activity.  Give an upland sandpiper or prairie chicken a big landscape full of nothing but cows and grass and they’re in high heaven.

Grasshopper sparrows are a species of concern, but they do very well on "degraded" grasslands with both historic and current intensive grazing. This juvenile bird is sitting on a hemp plant in a grazed prairie.

What does this all mean?  I’m not sure.  I’m certainly not saying that prairies full of conservative plants aren’t of great value.  Clearly, they contain plant species that are rare elsewhere – and some rare butterflies and other species as well.  However, it’s also clear that those prairies can’t be the sole focus of conservation if we’re going to preserve the entirety of prairie species diversity.  I also wonder whether at least some of those prairies (especially those larger than 40-50 acres or so) could play a larger role in prairie conservation if they were managed a little differently.  For example, if some of those prairies were managed for more heterogeneous vegetation structure they might become more valuable to many insect and wildlife species.   If we could improve habitat for rare wildlife and insect species while decreasing the abundance (but maintaining viable populations) of conservative plants, would that be a reasonable trade-off?

It seems to me that some of those larger prairies could accommodate some experimentation with summer fire, fire-driven grazing, and/or other less traditional management strategies by testing those strategies on a portion of each prairie.  If the results of those insects showed benefits to wildlife/insects without catastrophic impacts on conservative plant populations, it might be beneficial to periodically apply those kinds of treatments to all parts of the prairie over time.  Again, that management might reduce the overall abundance of conservative plant species somewhat – it would certainly periodically change the visual dominance of them.  Either way, the added benefits to a wider range of prairie species might be worth the trade-off.  Or, they might not.  It seems important to find out, however, since we have a lot of prairie species (other than plants) that are in need of good habitat right now.

Tallgrass prairie in southeast Nebraska. This hayed prairie has leadplant (a conservative plant species) scattered throughout, but not dense populations of it. How abundant do plant species like leadplant need to be for a prairie to be considered "high quality"?

I live in work primarily in east-central Nebraska, so the prairies I’m most familiar with are those that are dismissed by some botanists as already having been ruined by grazing.  It’s true that many of them have been severely degraded, not just by chronic overgrazing, but also by broadcast herbicide use.  However while Nebraska prairies are rarely dominated by conservative plant species, those species aren’t absent either.  Moreover, many of our restored (reconstructed) prairies have strong populations of many conservative species.  Watching those species respond to disturbances like summer fire and periodic grazing has been instructive.  Species like Canada milkvetch, compass plant, and leadplant, for example, that are often considered to be easily eliminated by cattle grazing, are thriving under a mixture of fire and grazing on our sites.  While there are still lots of questions about how/whether to use grazing on high quality prairies, we’ve certainly busted the myth that cattle automatically pick out conservative forb species for grazing (see my report on our use of lightly-stocked patch-burn grazing for details).  My hope is that the work we’re doing here can serve as a catalyst for similar experimental work in more “high quality” tallgrass prairies to the east of us.  Will those prairies benefit from shaking up their management?  I’m not sure.  Will they be ruined by the attempt?  I have a hard time believing that, but until we do some small scale experimentation we’ll never know.

These cattle are grazing selectively in the burned patch of a lightly-stocked patch-burn grazing system. (At the time of this July photo, the cattle had been in the prairie since April) Within the burned patch, some conservative forbs will be grazed - though most won't. Those grazed forbs may or may not bloom the year they're grazed, but typically do bloom the following year. Are short-term impacts on those species worth the wildlife and insect habitat benefits gained from the heterogeneous habitat structure?

Regardless of answers to the above questions, there is one thing I feel very strongly about:  Good prairie managers consider more than just their favorite plant species as they think about how to manage their prairies.  Yes, plant diversity is very important -a growing number of ecological functions and non-plant species needs are being tied to plant diversity as we continue to learn more about prairies.  But the importance of dense populations of conservative plants versus less abundant – but still viable – numbers of those species is less clear.  More importantly, we know that many species of insects (and probably other taxa) are doing better in prairies with low numbers of conservative plants.  We need to learn more about whether that’s tied to the way those prairies are managed, the landscape surrounding them, or the plant composition of those sites – or (most likely) a combination of those factors.

Are botanists ruining our prairies?  I don’t really think that’s the case, though it’s fun to poke them a little.  Most of the botanists I know are relatively well-rounded naturalists that care deeply about the conservation of prairies and other natural areas.  I do think, however, that all of us can become too attached to certain species or groups of species, to the point where it hamstrings our creativity (see my earlier post on “Calendar Prairies”).  Plants are often the easiest group to become attached to for prairie managers because they’re easy to find, relatively easy to identify (especially the big showy ones), and are comforting to see every time they bloom.  Birds and butterflies are also very popular, and easy to become attached to, but many small prairies don’t have many bird species, and butterflies are less familiar to most people than are plants.  On the other hand, beetles, leaf hoppers, flies, micro moths, ants, and the other species that actually make up the vast majority of prairies’ biological diversity are really easy for most of us to overlook.  Yet they’re really important, both for their own sake and because they play critical roles in keeping the larger prairie machine running – which supports those pretty flowers and birds.

We can all benefit from stepping outside our own comfort zone in terms of how we evaluate prairie conservation success.  As I said in a recent post, looking at my prairies through the eyes of pollinators has changed my perspective considerably over the last couple of years.  I’m working hard to learn more about other species like voles, beetles, and snakes so I can better think about their needs as well.  If nothing else, it’s fun.  But I think it’s quite a bit more important than that.

Even for botanists.