Category Archives: General

Patch-Burn Grazing in Missouri Prairies

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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.

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

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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...

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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.

Report from the 2011 Grassland Restoration Network – Part 2: Grassland Birds

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The Grassland Restoration Network’s 2011 annual meeting was at The Nature Conservancy’s Kankakee Sands prairie/wetland restoration site in Indiana.  This year, we focused more than usual on creating habitat for various animal taxa, and I previously reported on the herpetology portion of the meeting.  Here is a summary of the discussions we had regarding grassland birds.

While the diversity of insects in a prairie is strongly tied to plant diversity, grassland birds have no such relationship.  The species richness, abundance, and breeding success of grassland birds are mainly related to variables such as vegetation structure, habitat patch size, and the amount of grassland in the neighborhood around their nesting sites.  At Kankakee Sands, the 6,000 acres of restored prairie/wetland habitat are obviously increasing both the patch size and total amount of grassland in the neighborhood, so our discussions focused on vegetation structure.  The ideal situation, of course, is to have a diversity of vegetation structure scattered across the site so that all grassland bird species can find the habitat they require for nesting.

This kind of tall vegetation is typical of most of the restored prairie at Kankakee Sands (and most other tallgrass prairie restoration sites). While valuable for many species, it's not much good for grasshopper sparrows and other animals that require short or patchy habitat structure.

We talked mainly about two different approaches to creating habitat structure in order to accomodate a rich variety of bird species.  The first approach is to design seed mixes for each desired habitat structure type, and the second is to design seed mixes that promote overall biological diversity, and then manage for structure with fire, grazing, and other tools.  Kankakee Sands is employing both strategies, so we were able to look up close at each.

We first looked at a restored prairie that had been seeded with about 60 species of short and medium-height plant species, and that included bunchgrasses like dropseeds and little bluestem instead of tall and strongly rhizomatous species like big bluestem.  The resulting structure was very favorable for grasshopper sparrows and other species that prefer that short to mid-height structure.  The seeding was nearly a decade old and seemed to be maintaining its structure and species composition with only a couple of prescribed fires as management.  The short patchy vegetation is definitely a contrast to the majority of other seedings at Kankakee Sands (and most other tallgrass prairie restoration sites) which are mainly tall and rank.  Those taller sites provide excellent habitat for Henslow’s sparrows and species with similar habitat preferences, but don’t do much for grasshopper sparrows.

Chip O'Leary (left) describes grassland bird habitat and research results with participants of the 2011 Grassland Restoration Network workshop. This restored prairie was seeded with short and medium-height plant species (including bunchgrasses instead of tall and strongly rhizomatous species).

The second example we visited was one of the first seedings done at Kankakee Sands (in the late 1990’s).  From the beginning, the several hundred acre prairie has been dominated by grasses and has been low on forb species diversity.  For the last several years, the Conservancy has been experimenting with patch-burn grazing as a way to create more heterogenous vegetation structure and to increase forb diversity in this prairie.  To date, forb diversity has neither increased nor decreased, but habitat structure has certainly changed.  The recently burned (and thus currently grazed) portions of the prairie provided excellent grasshopper sparrow habitat, while other portions were more tall and rank.  Though no change has been detected in forb abundance or diversity, the staff has noticed that a few forb species seem to bloom less abundantly than in the past – including compass plant, prairie dock, and Canada milkvetch.  Because of that, we discussed the value of fencing out a significant portion of the prairie each year to ensure that those species were given a complete break from grazing pressure periodically.

The two methods of creating bird habitat (seeding design vs. active management) both seem to be working well so far.  Both the prairie seeded with short/bunchy vegetation and the grazed prairie had significantly different vegetation structure than did the majority of the tall rank prairies around them – and birds are responding to that structure.  However, there are still plenty of questions about the long-term future of both approaches to creating bird habitat. 

In terms of the seeding design approach, one potential downfall is that the site was seeded with considerably fewer plant species than most other tallgrass prairie seedings at Kankakee Sands.  The potential effect of this lower diversity on insects and other species is unknown.  In addition, planting short and medium height plant species in soil/climate conditions that typically favor tall species could result in a relatively unstable prairie community.  In the long term, the fact that those shorter plant species aren’t using all of the available light/soil/moisture resources could lead to encroachment by either tall grasses (defeating the purpose of the design) or invasive species (which create obvious problems).  The planting we looked at was located on dry sandy soils with very low organic matter, so it probably is less at risk for that kind of instability than if it had been located in wetter or heavier soils. 

A final potential disadvantage of the seeding design approach is that the location of the short/medium habitat structure is static.  Grazing and other management tools for manipulating structure can be moved around a site from year to year, creating a shifting mosaic of habitat conditions.  That kind of mobility could help keep predator or pathogen populations from building up under consistently favorable conditions at any one site (this is speculation).  In addition, the staff will have to be careful to avoid repetitive management treatments aimed at maintaining the same structure year after year – that management could consistently favor some plant species over others, further reducing the plant (and insect?) diversity of the prairie.

There are plenty of concerns about the patch-burn grazing strategy as well.  To date, the plant diversity in the grazed prairie we looked at has not gone down, but neither has it increased – though increasing plant diversity in a grass-dominated prairie is very difficult with any strategy.  Because the prairie started with few forbs, it’s hard to know what the impact of patch-burn grazing would be on a more diverse plant community, but that needs investigating.  We discussed the possibility that a higher stocking rate and the addition of a large exclosure that changes location each year could help with both habitat and plant diversity over time. 

The burned patch of the patch-burn grazed prairie at Kankakee Sands. While the compass plant in this photo is blooming under grazing, other individuals (of compass plant, prairie dock, Canada milkvetch, and others) appear to be blooming less frequently than they did prior to the introduction of cattle. While this doesn't kill the plants over the short-term, it is a concern down the road, and the Kankakee Sands staff is considering strategies to mitigate those potential impacts.

A higher stocking rate would lead to more intense grazing of the dominant grasses such as big bluestem that are likely preventing existing forbs from becoming more abundant.  Currently many of the grass plants inside the most-recently burned patch are only being moderately grazed, and that can actually induce those plants to divert extra resources into rhizome production – leading them to expand their footprint (not the objective here).  More intense grazing on those grasses could create better opportunities for seed germination and seedling establishment around those plants, and would create even shorter vegetation structure, which might help attract upland sandpipers and as well as grasshopper sparrows. 

Regardless of stocking rate, the use of a grazing exclosure would help ensure a periodic break from grazing for plant species that otherwise be vulnerable to annual grazing – even in the unburned (and lightly grazed) portions of the prairie.  With a higher stocking rate, the exclosure would become even more important.  In addition to protecting plants from grazing, it would also protect fuel for the next year’s burn.  An exclosure roughly 1/4 or 1/3 of the size of the prairie would probably sufficient for protecting both plants and fuel, and would still leave cattle access to both burned and unburned portions of the prairie – something is important when promoting selective grazing. 

Even with those potential alterations to the current patch-burn grazing system, there are still plenty of unknowns about the long-term impacts of cattle grazing at Kankakee Sands.  It seems clear that grazing can create a shifting mosaic of habitat structure, but whether or not it can maintain the kind of plant diversity (and other diversity) desired by the Conservancy at this site is still an open question.

Discussing those kinds of questions while standing on the ground, however, is the best part of our Grassland Restoration Network workshops.  We don’t all agree on the best strategies, because we are all still experimenting with our own ideas on our own sites – and none of us feel like we have all the answers.  Being able to see for ourselves what various restoration and management treatment results look like helps us better compare those results to what we see on our own sites.  While we don’t have all the answers yet, we’re certainly moving much closer to them as a group than we would be individually.