Patch-Burn Grazing in Missouri Prairies

If you read this blog frequently, you know I manage many of our prairies with combinations of prescribed fire and grazing.  I like the heterogeneous habitat structure I get from patch-burn grazing, and have documented benefits to plant diversity in our prairies.  (I’ve summarized the experiences I’ve had with multiple variations of patch-burn grazing here.)

Patch-burn grazing with cattle is still viewed with skepticism by many people – especially some in eastern tallgrass prairies.  I can understand why people would be concerned about the potential impacts of cattle grazing on some plant species and prairie communities, and I certainly don’t advocate cattle grazing for all prairies.  However, I also think that many common concerns stem from limited experience with cattle grazing.  If the only cattle grazing I’d ever seen was the kind that annually beat grasslands down to the ground and resulted in soil erosion and a gradual loss of native plant diversity I’d be skeptical too – to say the least! 

When you see a prairie like this, it's easy to see how prairie enthusiasts could be nervous about cattle grazing. This Nebraska prairie has never been plowed, but it's missing many prairie plant species - though that is likely due more to past herbicide practices than cattle grazing.

However, chronic overgrazing is one extreme in a broad spectrum of grazing regimes, and cattle can also be used in ways that produce very positive results for plant diversity and wildlife habitat.  The first time I saw a prairie being stomped and chomped by lots of cattle it was pretty unsettling.  However, watching that prairie recover the next year after cattle had been removed gave me a much greater respect for prairies than I’d had before.  Over the last 20 years, I’ve seen that process over and over in many tallgrass and mixed-grass prairies, and the resilience of prairie plants never ceases to amaze me.  Of course, I’ve also seen instances where repeated overgrazing has degraded prairie communities, but that degradation has usually come from not giving plants sufficient opportunity to rest and recover from grazing bouts – not from grazing per se.  (And often because of a history of broadcast herbicide use as well.)

Most of my personal experience with grazing (and patch-burn grazing in particular) has come from mixed-grass and lowland tallgrass prairies in east-central Nebraska.  I’ve also seen a lot of grazing on western tallgrass prairies in Kansas and Oklahoma.  However, my experience with cattle grazing in eastern tallgrass prairies is much more limited – mostly because it is such a rarity.  This summer has given me two chances to observe the impacts of patch-burn grazing on eastern prairies in Indiana and Missouri.  I wrote briefly about the Indiana experience in a previous post, but I want to spend more time on what I saw in Missouri last week.

The Missouri Department of Conservation (MDC) began a research project on the use of patch-burn grazing on public lands prairies back in 2005.  One of their hopes was to increase the habitat quality of those grasslands for prairie chickens and many other grassland species without hurting the diversity or quality of the plant communities.  Many of the prairies they grazed during the project were considered to be some of the higher-quality prairies in Missouri (botanically speaking) so protecting the diversity of those plant communities – and the rare and conservative plant species in them – was extremely important.  Several people, including me, with prior experience using patch-burn grazing provided input to MDC as they designed the project.  During the summer of 2007, I finally got the chance to see some of the grazed prairies during the third year of the research project.  One of those prairies was Taberville Prairie, north of Eldorado Springs.

The burned patch of Taberville Prairie in 2007 (part of the MDC's patch-burn grazing research project). The grazing was pretty intensive in the burned patch, with only a few plant species remaining ungrazed. Even I was a little unsettled by the way the prairie looked. (Sorry about the photo quality, the tour was during the middle of a bright sunny day...)

I remember being a little shocked as I walked around Taberville Prairie back in September 2007, because the cattle had grazed it much harder than I’d expected to see.  The most recently burned patches of the prairie were nearly universally cropped close to the ground, with only a few plant species remaining lightly grazed or ungrazed.  That was pretty different from my own sites, where our relatively light stocking rates lead cattle to graze pretty selectively in burned areas, leaving many forb species ungrazed – even many that are typically considered to be favorites of cattle.  At Taberville, even unburned portions of the prairie showed evidence of moderate grazing, and it was difficult to find conservative plant species such as compass plant, purple coneflower, blazing star, and leadplant.  What I was seeing at Taberville made me wonder whether MDC had pushed the prairie a little further than was prudent.  Of course, the plan was to rest the prairie for several years following the three years of patch-burn grazing, so logic and experience told me this was something the prairie could easily recover from – but even so, I’ll admit it was a little disturbing to see.

This photo shows the patch that was burned in 2006 (the year before the photo was taken). Though grazed less intensively than the 2007 burn patch, there are still few conservative plants visible.

Since my 2007 trip there has been considerable discussion (to put it mildly) among prairie enthusiasts and biologists in Missouri about the impacts of cattle grazing in those prairies where patch-burn grazing was tested, especially on conservative plant species.  I can easily understand why people were concerned – especially after my own experience at Taberville.  I was anxious to see for myself how the prairies had recovered, so I was glad to accept an invitation from MDC to participate in a grassland ecology workshop last week.  The day before the workshop started, I got a tour from Len Gilmore and Matt Hill of MDC, and made my return to Taberville prairie.

MDC's Len Gilmore manages Taberville Prairie. In this photo, he's showing me the kind of vegetation structure favored by nesting prairie chickens. This is a portion of the prairie currently open to cattle - but is not the most recently burned patch.

We started the tour in a portion of Taberville than had not been included in the grazing back in 2005-2007, but that was currently in year three of a patch-burn grazing rotation.  Len, who manages Taberville Prairie, showed me the kinds of habitat structure they’re trying to create with patch-burn grazing, including nesting habitat for prairie chickens.  We also discussed other aspects of patch-burn grazing MDC is concerned about (and testing) – including potential impacts to headwater streams, most of which are currently fenced out.  The overall look of the prairies under patch-burn grazing this year was similar to those I saw in 2007.  This time, however, I looked harder for conservative plants, and was able to find them in the patches that weren’t the most recently burned.  Most weren’t blooming, but they were certainly alive and well.

This is the most recently-burned patch in the current grazing area at Taberville Prairie. The grazing was obviously very intense (the cattle had been removed the week before my visit).

What I really wanted to see, however, were the portions of the prairie I’d seen in 2007 that had been rested (with one burn) since I’d last seen them.  When we arrived, I think I let out an audible sigh of relief.  The prairie looked great.  Even in what was a very dry summer, the prairie looked like my visual image of Missouri tallgrass prairie.  Lots of showy blazing star flowers and abundant conservative plants, including leadplant, compass plant, purple coneflower, rattlesnake master, and others.  Len took me to several locations where they had built grazing exclosures during the original patch-burn grazing research project.  The exclosures had allowed MDC researchers to compare the ungrazed plant community inside the exclosures to adjacent plots that were exposed to cattle grazing.  Even without seeing the data, being able to walk through and compare those areas that had never been grazed with those that had been exposed to three years of patch-burn grazing (the exclosures had been removed but their locations were still marked) was a powerful testament to prairie resilience.  I looked hard for differences, but the truth is, if Len hadn’t told me which areas had been the grazed areas and which had been the exclosures, I never would have known. 

This is the portion of Taberville prairie shown in my 2007 photo above when there was almost nothing taller than a couple inches. Several years of rest (and a fire) following the three years of patch-burn grazing changed the look of the prairie considerably. Even in a summer during which the prairie had almost no rain in June or July, the plant community looks tall and vibrant.

.

The same portion of Taberville Prairie. Compass plant, and many other conservative plant species were abundant.

.

Another photo from the same portion of Taberville Prairie (grazed 2005-2007, but rested since then.) Eastern gamagrass (the thick leafy grass with tall stems) was abundant and full of vigor across the prairie. In the burned/grazed patches of Taberville and other MDC prairies gamagrass was being grazed extremely hard - even to the point where I could see rhizomes the cattle had pulled out of the ground. Clearly, gamagrass recovers well from that kind of treatment...

.

A final photo from the area grazed 2005-2007 but rested (and burned once) since. This photo shows leadplant in the foreground. Rattlesnake master and purple coneflower (two other conservative plants) were also abundant, but not shown in these photos.

During the next several days at the grassland workshop, I listened to MDC biologists from wildlife and fisheries divisions talk about what they like and don’t like about their experiences so far with patch-burn grazing.  One of the interesting issues they (and I) are wrestling with has to do with the appropriate length of grazing and rest periods.  Figuring out how to mix grazing and rest periods in a way that allows all plant and animal species to “win” periodically is a major challenge.  There was also considerable discussion about how to better evaluate potential impacts to plant communities and streams – as well as exploration of ideas about how to modify current management to better address needs of pollinators, amphibians, and other species.  I think those who are worried about patch-burn grazing in Missouri would have been comforted to hear the thoughtful discussion and see the obvious dedication of MDC staff to the prairies in their charge. 

This bush katydid was one of many insects I saw at Taberville Prairie. I don't think this species is necessarily rare or conservative, but the regal fritillary and Henslow's sparrow I saw nearby are (not that seeing one of each necessarily determines success...)

There are still plenty of important questions about whether, where, and how cattle grazing should be used to manage eastern tallgrass prairies, but the Missouri Department of Conservation is leading the effort to answer some of those.  Early results show improvements in habitat structure for many species of insects and animals, including greater prairie chickens – where they occur.  MDC has asked faculty from two universities to help evaluate impacts on streams, and is fencing out the majority of headwater streams until that evaluation is complete.   The responses of plant species and communities to various fire, grazing, and rest treatments is still being evaluated, and probably will be for some time.  In the meantime, it was good to see confirmation of the ability of plants to bounce back from periodic grazing, even in prairies that are pretty different from the ones I know best.  I think the knowledge that plants (even conservative species) don’t immediately die from being grazed for a season or two gives us a little cushion as we forge ahead with our attempts to find appropriate tools and strategies for maintain the broad array of biological diversity in what remains of tallgrass prairie.  If you live and/or work in the tallgrass prairie region, I hope you’ll be a productive part of that effort.  We need all the help we can get.

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.