How It’s Made: Parsnip Predators

How It’s Made: Parsnip Predators

How It’s Made: Parsnip Predators

Summer 2024 Chapter Update by Rebecca Gilman and Charles Harmon. Photos by Rebecca Gilman.

Nick Faessler, Jerry Newman, Den Oostdik, Chris Roberts, Fred Faessler and Tom Mitchell with a crate of finished Predators

What’s a Prairie Enthusiast to do when the skies of February turn gloomy? Members of the Prairie Bluff Chapter spent the short days of winter—as they have for years—producing the tool that tames the nightmare that is wild parsnip (Pastinaca sativa). 

If you’re lucky enough not to know it, wild parsnip is an aggressive invasive that spreads like wildfire and burns like it too. Handling the plant without proper protection can be dangerous. If an unsuspecting weed-puller gets sap from wild parsnip on their skin and the sap is then exposed to UV light, it causes phytophotodermatitis, or burn-like blisters. That’s the scenario that faced George and Kay Barry, stewards of a prairie planting at Honey Creek Park in Monroe, WI, in the early 1990’s. Presented with a field full of parsnip, Kay turned to The Prairie Enthusiasts for help. 

As chapter member Rob Baller recalls, “I contacted Mark Martin, (of the Wisconsin DNR), and asked how the State Natural Area crew treated parsnip. He told me that crew members sharpen spades, and on prairie remnants they jab the plant a couple inches from the base, angling the blade so it intercepts and slices the root an inch or two below-ground. Then, with gloves on, they pull out the severed plant. A parsnip with the root crown so severed will not resprout.” 

Rob took Mark Martin’s idea and ran with it, straight back to his workbench. Using scrap metal, the handle from an old snow shovel, and plenty of nuts and bolts, he fashioned the prototype of what we now call the “Parsnip Predator.” After trying it out, “Kay was all smiles,” Rob says.   “’Can you make more of these?’ she asked.”   

Rob turned to Nick and Fred Faessler and asked the brothers if they thought the tool could be put into mass production. Another chapter member, Julia O’Reilly, saw commercial potential in the tool and volunteered to be the implement’s first dealer. Nick and Fred retired to Nick’s shop and began experimenting. Eventually, they settled on a modified number two shovel with a notched blade as the best design. The tool allows users to cut the parsnip root crown and is strong enough to pry the parsnip out of the ground once severed.  (“Everyone wants to pry,” Rob notes.) 

Nick Faessler remembers that they made the first batch of 30 Parsnip Predators with no idea of whether or not any of them would sell. The predator was an instant hit, however. Over the years, the Prairie Bluff Chapter saw sales increase yearly and shipped the tool from coast-to-coast. Now sales and shipping are handled by The Prairie Enthusiasts awesome staff in Viroqua, with Prairie Bluff Chapter and the organization as a whole sharing the profits. 

Nick Faessler cuts Predator blades

Chris Roberts secures handles

This past February, a visitor to Nick’s shop witnessed what is now a well-oiled, Parsnip Predator assembly line. Nick begins the process by cutting a notched tip in the shovel’s blade with a plasma-cutter. At the next station, the rivets that attach the shovel’s handle to the blade are ground off so that the handle can be turned 90-degrees and carefully aligned. During the next step, a new hole is drilled in the handle and a bolt is inserted, tightened and ground downAnother group of volunteers then polishes the sharp edges on the blade and applies a protective coating of paint. The final step is to brand the handle of each shovel with the registered “Parsnip Predator” trademark. (The “Parsnip Predator” moniker was coined by Rob Baller’s landlord and adopted in lieu of another suggestion, “The Root Canaller.”) 

The group of volunteers on hand in Nick’s shop that day made the work look easy. But take it from that visitor who briefly wielded a power tool herself, crafting a Parsnip Predator is not as easy as it looks. Only through years of working together have the volunteers on hand that day—Nick Faessler, Chris Roberts, Billy Eisenhuth, Fred Faessler, Jackson Lancaster, Tom Mitchell, Todd Argall, John Ochsner, Steve Hubner, Den Oostdik and Jerry Newman—created a seamless system that was beautiful to behold.   

Over the years, sales of the Parsnip Predator have not only helped to eradicate a noxious invasive, they’ve also helped to preserve and protect the prairies we cherish. If you’re not already a proud owner of a predator, consider purchasing one today. Every Parsnip Predator is handmade in Wisconsin, with love. 

John Ochsner applies protective coats of paint

Den Oostdik grinds off the original bolts

This article appeared in the Summer 2024 edition of The Prairie Promoter, a publication of news, art and writing from The Prairie Enthusiasts community. Explore the full collection and learn how to submit your work here.

Positive Changes on Pleasant Bluff

Positive Changes on Pleasant Bluff

Positive Changes on Pleasant Bluff

Story by Eric Ressel, Minnesota Driftless Chapter volunteer 

Drone image of prescribed burn at Pleasant Bluff.

As I approached Pleasant Bluff, just south of Winona, MN, I asked myself if this was the same location I visited a few years earlier, since this hillside was once densely infested with an onslaught of buckthorn and encroaching eastern red cedars. Since then, the Minnesota Driftless Chapter of The Prairie Enthusiasts has contributed substantially to ecological restoration on this impressive prairie remnant. Over 18 acres along the spine of this formidable bluff, which sits above the banks of the Mississippi River, have been restored due to the diligent, hard work from folks like Gabe Ericksen, who has spent countless hours traversing the steep terrain to cut and remove the cedars, eradicate invasive brush, and implement numerous prescribed burns over the years. Gabe is a restoration practitioner through his contracting business, Land Spirit Design Landscaping, and he has been the tip of the restoration spear on Pleasant Bluff, assisted by the landowners and the Minnesota Driftless Chapter.

At a mid-March occasion in 2023, a diverse crew was assembled to assist Gabe with an 11-acre prescribed burn on this precipitous goat prairie. Thirty people of all ages and backgrounds, from children to seniors, joined together to conduct a safe and successful prescribed burn. Many of the participants were members of the Minnesota Driftless Chapter of The Prairie Enthusiasts, but many of the participants weren’t. A substantive way in which the Minnesota Driftless Chapter of The Prairie Enthusiasts contributed to the burn was by loaning the Chapter’s prescribed burn equipment to Gabe for the day’s burn.

The slope of this lofty bluff approaches 60% and is nothing short of intimidating. On this day, thanks to restoration efforts, the fuel-bed consisted primarily of native warm-season grasses and wildflowers, with some scattered pockets of shrubs. The climb up the mowed firebreak was grueling for the whole group. At the top, along the ridge overlooking the Mississippi River, Steve Winter having been designated as the burn boss by Gabe, provided the crew with an overview of why we burn such fire-dependent ecosystems, and he demonstrated fire behavior on steep terrain. He also highlighted numerous safety considerations, such as tumbling rocks and tripping hazards. Steve educated the group on the importance of clear communication, being familiar with the weather and environmental conditions, such as the optimal wind direction and humidity, and being aware of the safety zones and escape routes at this particular site. Once everyone confirmed they were comfortable implementing the burn, we broke into several smaller crews that were positioned along the ridge and others down the steep firebreak on the northwestern side. 

 

From the ridge we patiently waited for the progression of the fire from the ignition point, which was slow-going due to the calm conditions. My crew discussed strategy and stayed in contact with Steve and Gabe over the radio. We kept a careful watch as the gradually growing flames moved diagonally down the hillside. However, with barely a breeze the fire crept ever slowly, so Steve instructed me and fellow member Bill Hovell to ignite a shirt strip fire directly down the slope, which allowed the flames to spread more quickly in both lateral directions in the dense Indian grass (Sorghastrum nutans), side-oats grama (Bouteloua curtipendula), and little bluestem (Schizachyrium scoparium). Bill and I worked our way down the steep slope towards the county road on the lower edge of the prairie where we rendezvoused with our other crew members, whom I literally passed the torch to so they could get some ignition experience. It was in that moment that I watched my greener group members become less fearful, and more comfortable and excited to use fire as an ecological tool! 

In the meantime, another crew worked the line along the northern edge of the burn unit as the flames continued to consume the fuel down the slope. In the heat of the moment, the landowner, Paul Richards, was able to capture some stunning drone footage. I wondered what the children, who were positioned in a safety zone at the top of the ridge, and upwind from the fire, were thinking as they watched the fire grow from a safe distance. I’m sure this experience proved to be exhilarating, educational, and memorable for them. Along with the children, I hoped our new participants and the students that attended Steve’s burn school would also be inspired to continue with the restoration legacy. 

Volunteer Gabe Ericksen burning. Photo by Laurie Arzaga.

Our crew continued to walk along the lower edge. We eventually met up with Gabe and his partner, and we extended the line as far east as possible. As the heat intensified above us and behind us, we ducked down into the refuge of a safety zone represented by a buckthorn thicket, which had little flammable fuel on the ground, as the flames progressed through the portions of the burn unit. I turned around and gave a gleeful smile as the sweltering flames made contact with many stems of the aggressive woody plants that are constantly trying to establish in prairies such as the one we were burning that day. We then moved again to our county road safety zone farther below, which we followed back to meet the main group. Gabe once again targeted the buckthorn as he ignited the strip of vegetation along the roadside edge, allowing the fire to burn up the slope and make contact with many buckthorn stems. We allowed the fire to spread up the slope into a grove of old white oaks that will surely benefit from the fire with more space to stretch their limbs.

We met to start mopping up and to review the outcome of the successful burn. Most of the group members then left, but I was greatly impressed by those devoted enthusiasts who decided to stay well into the evening. Gabe and Josh Lallaman led this late-night effort, which was carefully supervised into the early morning hours, and they were able to effectively burn an additional 3-acre area. The night burn looked equally serene and intensely dramatic. To me, this illuminating scene was the perfect illustration of the power of fire. It showed why prescribed burning promotes creation through destruction, making it an essential tool to encourage natural rejuvenation and regrowth, which helps to maintain prairies and savannas by preventing their conversion to other vegetation communities. Once again, demonstrating that fire is the ultimate management method to set back undesirable invasive vegetation, while stimulating the growth and reproduction of native grasses and wildflowers.  

As I drove south to head home along the mighty river, I reflected on the progress of this goat prairie from its previous poor condition, choked by buckthorn, to a thriving, fully functional ecosystem that is driven and dependent on fire. Now this unique ecological community can thrive in the southwestern-facing sunshine, while supporting an array of rare plant and animal species. I contemplated the logistics and timeframe for completing restoration efforts on similar sites, since the majority of the goat prairies in the Driftless Area, along with associated oak savannas and woodlands, have become degraded in part because of altered fire regimes. I thought of the historic photos portraying a landscape where trees weren’t as abundant along the Mississippi River Valley. Those historic conditions were largely due to frequent landscape burning by Indigenous Peoples. As Indigenous Peoples were displaced by European Americans, Indigenous land stewardship practices like prescribed burning were also displaced. Fires were often viewed as harmful by European Americans, and woody vegetation increased greatly in the Driftless Area, including on Pleasant Bluff. With the increasing prevalence of woody vegetation, including invasive species such as buckthorn, we’re witnessing a correlated decline in health of rare plant communities and an overall decrease in plant diversity.

“It made me proud to be a part of such an ambitious chapter of like-minded, well-educated enthusiasts who are passionate about ecological restoration and conservation education.”

The Pleasant Bluff prescribed burn was just one example of how dedicated members of the Minnesota Driftless Chapter are eager to save ecosystems. Their tireless restoration work, outreach efforts and mentorship are also an inspiration for others. It made me proud to be part of such an ambitious chapter of like-minded, well-educated enthusiasts who are passionate about ecological restoration and conservation education.

I want to thank the Pleasant Bluff landowners, Paul and Melissa (Missy) Richards, for their ongoing involvement and enthusiasm for the restoration and management of Pleasant Bluff. Their commitment to conservation and stewardship of the beautiful bluff prairies, woodlands, and oak savannas on their Winona County property is exemplary. Missy summarizes the continual progress of their beloved prairie: “We have deep appreciation for all the collaborative work between The Prairie Enthusiasts volunteers, experts in the field, U.S. Fish and Wildlife Service and Land Spirit Design Landscaping. We recognize and appreciate being a part of something so much bigger than us. It gives us the opportunity to showcase the importance and impact of land restoration to our neighbors, family and friends. The ability to have a community partner with us on this journey makes Pleasant Bluff so much better.”

 

You, too, can follow their inspirational journey on the Richards’ Instagram page (@pleasantbluff_winonamn). Since the burn last spring, with help from Gabe, the Richards have continued their brush management efforts to lessen the buckthorn pressure across additional areas on the bluff. They have also documented dozens of native wildflowers on the bluff and often find new species. We encourage you to follow the Minnesota Driftless Chapter Facebook page to learn what additional prescribed burns and restoration efforts will take place.

I’ll be thrilled for the opportunity to return to this unique and productive dry bluff prairie to work once again with our devoted chapter members and these dedicated landowners, and to observe the positive and dynamic changes to this ecological gem along the river. On behalf of the Minnesota Driftless Chapter, we hope you can come join us.

Seven people and a dog gathered around a table and smiling at the camera.

Nighttime prescribed burn mop-up. Photo by Joshua Lallaman.

This article appeared in the Spring 2024 edition of  The Prairie Promoter, a publication of news, art and writing from The Prairie Enthusiasts community. Explore the full collection and learn how to submit your work here

Management Toolbox: How to Prioritize Removing Invasive Species

Management Toolbox: How to Prioritize Removing Invasive Species

Management Toolbox: How to Prioritize Removing Invasive Species  

Story by Jim Rogala, President 

The purpose of this regular section of The Prairie Promoter is to keep proper management methods fresh in your mind. These short articles will sometimes reference past or future articles that contain details on the selected topic. Others will just be some food for thought. I encourage others to provide ideas for articles. You can send those ideas to me at jrogala@theprairieenthusiasts.org.

Prioritizing the sometimes-long list of invasive species to combat  

Oftentimes serving on a committee seems like a burden, albeit necessary. However, those meetings provide an opportunity for committee members to engage in interesting discussions. A recent Land Management Committee meeting found its members talking about strategies for dealing with a long list of invasive species in a management plan. Seldom do we have the resources to control all the invasive species present, so how do we prioritize our management actions?

Let me offer an example of a process that might be used. There are several factors leading to my decision to control a species. The first factor I consider is whether the species has shown up because of a disturbance. Many species take advantage of the lack of competition but can’t compete in the long-term as other more conservative plants establish. Some examples are Queen Anne’s Lace, Mullein, and Canada Thistle. I realize it is difficult to just ignore these and wait them out, but leaving each species can be justified. Both Queen Anne’s Lace and Mullein are biennials and could be controlled by pulling. However, remember why they showed up in the first place, and consider how the additional soil disturbance might perpetuate the problem. Canada Thistle is a deeply rooted perennial that one might suspect could outcompete establishing prairie plants but that is not the case, as it will succumb to solid competition from native plants given enough time. 

In contrast to species that respond to disturbance, there are those that can invade remnant sod. These pesky species require attention because once established they can spread and have an impact on prairie species. Some of these heavy hitters include Crown Vetch, Leafy Spurge, and Spotted Knapweed (I won’t list more because it can be depressing!). These usually require herbicide use, although there are some biocontrol methods that can at least keep populations controlled to some degree. 

I’ve just scratched the surface of this topic here. Look for an upcoming article by Dan Carter in which he will delve into the factors behind why to prioritize control of some invasive species over others.

What timescale do you plan at?

Keeping with the theme of topics discussed at Land Management Committee meetings, one of the committee’s primary responsibilities is to approve land management plans. These are required for all lands owned by The Prairie Enthusiasts, land with easements and areas with management agreements. These are long-term plans, although we are now planning to update them in a 10-year interval. We have also formally added some goals for a 10-year period in our management plans, a period that might require a substantial amount of work for new sites. Although these plans provide valuable context for conducting management, actions are usually planned at much shorter timescales. I like to develop 1-year plans that focus work for the upcoming year. These plans can be much more detailed and therefore provide the basis for scheduling specific work throughout the year. I’d encourage anyone managing lands to consider having plans at several scales, preferably written plans rather than ones just floating around in our heads.

This article appeared in the Fall 2024 edition of The Prairie Promoter, a publication of news, art and writing from The Prairie Enthusiasts community. Explore the full collection and learn how to submit your work here

Invasive Queen Anne’s Lace. Unknown photographer.

Stability Part Three: Promoting Old Growth and Controlling Unwanted Vegetation Should Go Hand in Hand

Stability Part Three: Promoting Old Growth and Controlling Unwanted Vegetation Should Go Hand in Hand

Stability Part Three: Promoting Old Growth and Controlling Unwanted Vegetation Should Go Hand in Hand   

Story and Photos by Ecologist Dan Carter
April 2, 2025

Figure 1: Spring view of an area where glossy buckthorn (Frangula alnus) was removed the previous fall and winter. Little herbaceous vegetation remained beneath. What is visible here is a mix of species seeded immediately after brush work and opportunistic natives like burnweed (Erechtites hieraciifolius). Quaking aspen (Populus deltoides) was subsequently girdled. Here seeding, aspen girdling, prescribed fire, and targeted removal of unwanted vegetation (e.g., pulling and flaming of glossy buckthorn seedings, pulling of small Canada thistles, Cirsium arvense) are being combined in close sequence.  

This article is the third in a series on promoting stability—or perhaps doing the least damage to it—as we encourage and sustain old-growth prairie, savanna, and oak woodland sods. Prescribed fire1 and grazing2 were obvious topics that were addressed earlier, but the other management practices we use, particularly those that kill or remove excessive woody vegetation or invasive/aggressive herbaceous species, deserve attention. Removing unwanted species represents much of what we do in defense of fire dependent ecosystems. As with fire and grazing, its effects relate to physical parameters like nutrient availability, light, and microclimate, but those effects also relate to direct impacts to what we’re trying to save. Sometimes it just comes down to not injuring or killing the good stuff by accident.

Woody encroachment and many non-native herbaceous plants can destabilize old growth composition, structure, and ecological process if not addressed. They do this by altering light, water, nutrients, and air movement. Some species produce allelochemicals that cause local changes to vegetation. A good example of a species that alters most or all of those parameters is common buckthorn (Rhamnus cathartica), which casts excessive shade and produces emodin, a likely allelochemical. What I find more sinister is the microbial community associated with buckthorn3, which supports more free-living nitrogen fixing (diazotrophic) bacteria; these ensure that the buckthorn has a continual supply of nitrogen to fertilize the area under its canopy with its fast-decomposing (labile) leaf litter. The increased nutrient cycling and availability from leaf litter inputs of many problem species, woody4 and herbaceous5, are a big part of why intervention is needed. However, practices that remove unwanted vegetation usually create physical disturbance or leave behind excessive available nutrients in their wake. These wounds require mending, and their healing requires sustained care.

A common mistake is instead to assume that the ecosystem will heal on its own, either by natural dispersal or from the seed bank. Three inconvenient realities work against that hope. Opportunistic species (most herbaceous invasive species, sometimes “weedy natives” like tall goldenrod, Solidago altissima), many of which are problems in the communities we manage, are better at dispersing to open spaces where unwanted species have previously been removed. In many instances the landscape is too fragmented for old-growth-associated species to have any chance to get there, However, disturbed areas overrun with opportunistic species surround the places we care for. Second, physical conditions continue to be altered even after areas are daylit (e.g., nitrogen availability is greater), which further favors re-colonization by opportunistic species. Finally, many long-lived, old-growth-associated species do not persist in seed banks6,7, which means recovery in the wake of invasive species removal relies on remaining vegetative plants. Often when plants have persisted, they have not flowered and set seed for a long time, so use of heavy-handed management practices should not assume that the seed bank is an insurance policy, but I hear that exact claim or assumption again, and again! It is true that there are native species in the seed bank, including uncommon native species8 (especially where seed inputs are still ongoing), but flora that may lead to the restoration of ecological integrity9 do not reside where old growth vegetation has been suppressed or absent for any length of time.

Figure 2: Winter application of 20% triclopyr ester in mineral oil with basal dye by drip from a pump sprayer to a fresh glossy buckthorn stump in the areas shown in Figure 1. 

Figure 3: Representative late winter / early spring sap flow in a previously treated glossy buckthorn stump.  

Healing the damage caused by unwanted species requires integrating approaches that both control those species and actively promote the establishment and persistence of species associated with old growth. In cases where desirable species have been lost or gaps in desirable vegetation have been created in the wake of removing unwanted species, we should gather and broadcast seed or propagate and plant plugs. We can also ameliorate the excessive nutrient availability by facilitating the early establishment of species that produce relatively slow-decomposing litter (native grasses and sedges especially10), the decomposition of which requires microbes to draw more nutrients from the surrounding environment. Grassier and sedgier vegetation also allows us to reestablish flammability and volatilize excess nitrogen out of the ecosystem using frequent dormant fire. Finally, establishing grassy vegetation (and probably the vegetation of our restoration target community more generally) may slow re-invasion by providing competition for the seedlings of invasive species (e.g., buckthorn11), though I believe complementing the establishment of desirable vegetation with the use frequent fire is important for suppressing invasive species in the longer term. Removal of unwanted species ought to be combined with restoration of core ecological processes—by facilitating dispersal and using frequent dormant fire to promote and sustain conditions (low litter, low nitrogen availability) that allow species associated with old growth to establish and begin to stitch themselves back into a functioning ecosystem.

We often make faulty assumptions about how safe certain applications of herbicide are for ecosystems, but we can also do damage even when we follow herbicide labels to the letter. In old growth the use of herbicide should be very judicious. Where necessary, it should utilize only the most targeted applications of the chemicals that pose the lowest risk, either because they are the most selective or they can be applied in very targeted ways and do not tend to persist in or migrate through the soil. Do not assume that overspray from herbicide treatments in winter will not affect native vegetation, many old-growth-associated species maintain green tissues above ground that can be impacted. Assessment of that risk is where most mistakes happen. We need to start paying closer attention to and sharing accounts the collateral impacts treatments have.  I’ll describe and share photographs of a couple examples from my experience.

The first involves a degraded area where I oversaw the cutting and stump treatment of glossy buckthorn (Frangula alnus), common buckthorn and several other unwanted woody species in a dense thicket between late autumn and late winter. I applied 20% triclopyr ester, either in mineral oil with basal dye or basal oil with dye, to cut stumps using a hand-held pump sprayer on low pressure. This allowed me to carefully drip herbicide onto the cut stumps. Herbaceous vegetation was very sparse in the wake of clearing, so the area was seeded heavily with wild ryes (Elymus spp.) to quickly establish grassy cover. I also seeded conservative, old-growth-associated species appropriate for the site. In late February and very early March when the ground began to thaw and warm, I noticed that glossy buckthorn stumps, most treated weeks or months before, began oozing sap. None of the other treated species oozed sap in the same way. By midsummer it was obvious that treatment had effectively killed the buckthorn and other unwanted species. Nearly all treated stumps were dead, but around each glossy buckthorn stump was a dead zone where no herbaceous vegetation (including seedlings—even those of wild ryes) grew. While the extent of these dead areas and their impact was minor in this instance, the experience has made me wary of treating cut stumps with triclopyr ester in areas with high quality vegetation, especially where the density of treated stumps would be high. It will be worth investigating whether herbicides that are mixed with water (vs. oil) or applications made in summer that potentially have more time to kill stumps ahead of the following spring could produce fewer negative effects.

Figure 4: Broader cut-stump treatment area where damage to pointed-leaf tick-trefoil occurred. Ten years ago when this area was in the early stages of common buckthorn (Rhamnus cathartica) and gray dogwood (Cornus racemosa) invasion/encroachment, it supported a low woodland sod of false toadflax (Comandra umbellata, still visible), Pennsylvania sedge (Carex pensylvanica), poverty oats (Danthonia spicata), kittentails (Synthyris bullii), Carolina vetch, alumroot (Heuchera richardsonii), etc. In the wake of brush work, opportunistic species like woodland sunflowers (Helianthus spp.) and clonal goldenrods (Solidago spp.) are poised to increase unless other actions are implemented.  

Figure 5: Representative late July view of a treated glossy buckthorn stump with surrounding bare area inferred to be result of spring sap flow. Away from stumps seeded species as well as seed bank species like burnweed and biennial evening primrose (Oenothera biennis) grow. In this setting this collateral effect is probably acceptable, but in cases with remnant old growth-associated vegetation, it would not have been.  

Recently, I visited a site where several months prior 20% triclopyr ester in basal oil had been used to treat mostly common buckthorn cut stumps with a wick-type applicator. That treatment had been performed in the winter when there was a shallow layer of snow. Still, there was obvious damage to the herbaceous woodland and savanna vegetation, presumably from herbicide that had come in contact with the snow or moist soil and spread out, and probably also leached into the sandy soil without being immobilized or broken down by soil organic matter or microbial activity. Triclopyr has a relatively short half-life, but that half-life depends on temperature, moisture, and sun exposure. In summer we worry about volatilization of triclopyr ester and some other herbicides due to heat, but in winter reduced microbial activity and solar irradiance might allow herbicides more time to migrate to where they can cause damage, even if they are being applied in targeted ways.

In both cases I was surprised by the collateral effects. My own calculation of risk versus reward for my actions and the advice I offer changed. I urge readers to take a second look at practices that are often taken for granted. Don’t just track the efficacy of treatments against unwanted species; also monitor surrounding vegetation before and after treatment. Do areas that receive treatment continue to be problem areas? Perhaps there were collateral impacts to native vegetation that further destabilized the community, or perhaps additional types of care (e.g., seeding, monitoring for re-invasion, more fire) are needed to address underlying problems and get things on the right track. Last year on his Strategies for Stewards blog12 Stephen Packard offered the following wisdom:

“Is killing invasives our goal? Or restoring integrity and health to the ecosystem? Herbicides are needed. But herbicide treatments may solve one problem while ultimately not helping, or even making things worse. Restoration requires a wise overall plan with appropriate sequencing. The work then needs close oversight by someone who has a good working knowledge of the site’s ecology and the long-range impact of possible treatments.”

Figure 6: February view of green Carolina vetch, a conservative and old growth-associated species of oak woodlands that would have been vulnerable had late fall foliar spray of buckthorn or winter overspray or drip from basal or cut stump treatment occurred in its vicinity.  

Figure 7: Pointed-leaved tick-trefoil in the same area that was presumably impacted by herbicide dripped on snow during a winter, 2023 cut stump treatment.  

References

1 Carter, D. (2024). Stability part one: Why I recommend frequent dormant season burning. Prairie Promoter, Spring: 14-19. https://theprairieenthusiasts.org/stability-part-one/

2 Carter, D. (2024). Stability part two: Stability Part Two: Why I Seldom Recommend Grazing. Prairie Promoter, Summer: 12-17.  https://theprairieenthusiasts.org/blog_dan-carter/

3 Rodrigues, R. R., Pineda, R. P., Barney, J. N., Nilsen, E. T., Barrett, J. E., & Williams, M. A. (2015). Plant invasions associated with change in root-zone microbial community structure and diversity. PLoS One, 10(10), e0141424. (Shown in Rhamnus davurica, which is nearly identical to R. carthartica, similar ecologically, and also occurs in the Upper Midwest where it may often be mistaken for R. cathartica).

4 Ashton, Isabel W., et al. “Invasive species accelerate decomposition and litter nitrogen loss in a mixed deciduous forest.” Ecological Applications 15.4 (2005): 1263-1272.

5 Edwards, J. D., Cook, A. M., Yannarell, A. C., & Yang, W. H. (2022). Accelerated gross nitrogen cycling following garlic mustard invasion is linked with abiotic and biotic changes to soils. Frontiers in Forests and Global Change, 5, 1050542.

6 Schott, G. W., & Hamburg, S. P. (1997). The seed rain and seed bank of an adjacent native tallgrass prairie and old field. Canadian Journal of Botany, 75(1), 1-7.

7 Lamb, N., Havens, K., Holloway, J., Steffen, J. F., Zeldin, J., & Kramer, A. T. (2022). Low passive restoration potential following invasive woody species removal in oak woodlands. Restoration ecology, 30(4), e13568.

8 Abella, S. R., Hodel, J. L., & Schetter, T. A. (2020). Unusually high‐quality soil seed banks in a Midwestern US oak savanna region: variation with land use history, habitat restoration, and soil properties. Restoration Ecology, 28(5), 1100-1112.

9 Ecological integrity is the condition of an ecosystem where composition, structure, and function operate within the natural range of variation for that region.

10 These are an important element for restoring ecological processes like fire and nutrient dynamics, but so are some forbs and forbs should not be neglected, because they support much of the biodiversity.

11 Schuster, M. J., Wragg, P. D., Roth, A. M., Bockenstedt, P., Frelich, L., & Reich, P. B. (2025). Revegetation of Elymus grasses suppresses invasive Rhamnus cathartica in deciduous forest understories. Ecological Engineering, 210, 107438.

12Packard, Stephen. (2024) Destructive herbicide in the ecosystem. Strategies for Stewards blog. https://woodsandprairie.blogspot.com/2024/01/destructive-herbicide-in-ecosystem.html

This article appeared in the Spring 2025 edition of The Prairie Promoter, a publication of news, art and writing from The Prairie Enthusiasts community. Explore the full collection and learn how to submit your work here

About The Prairie Enthusiasts 

The Prairie Enthusiasts is an accredited land trust that seeks to ensure the perpetuation and recovery of prairie, oak savanna, and other fire-dependent ecosystems of the Upper Midwest through protection, management, restoration, and education. In doing so, they strive to work openly and cooperatively with private landowners and other private and public conservation groups. Their management and stewardship centers on high-quality remnants, which contain nearly all the components of endangered prairie communities. 

Stability Part Two: Why I Seldom Recommend Grazing

Stability Part Two: Why I Seldom Recommend Grazing

Stability Part Two: Why I Seldom Recommend Grazing   

Written by Dan Carter. Photos by Dan Carter
September 23, 2024

In the previous issue of The Prairie Promoter,[1] I introduced stability and discussed how fire can be stabilizing or destabilizing depending on how we use it. Here I will discuss grazing and browsing in the context of managing old-growth Midwestern prairie and oak ecosystems or projects seeking to restore old-growth-like characteristics to degraded sites. Keep that scope in mind. There are cultural reasons for repatriating native herbivores and conservation objectives for which grazing and browsing practices might be explored in surrogate grasslands[2] or for initial opening of brush where there is high confidence that collateral damage will not occur to native biota[3], but there are many reasons to caution against using those practices on remnant old-growth or projects attempting to promote old-growth characteristics. Grassland and savanna species declines are not the result of failure to graze prairie and oak ecosystems; those declines arise from loss of grassland and savanna habitat across the landscape and changes in land use. At one time tremendous variation in habitat existed among the prairie and oak ecosystems that were expressed along gradients of moisture, soil texture and chemistry, aspect, slope, etcetera in the Midwest; and our agriculture was more varied and less industrial. To promote the biotic expressions in need of protection, we should restore landscapes and all the unique ecosystem types that comprise them—not force exquisite and unique remnants to do work that simple plantings or conservation agricultural practices can do.

 

Large Ungulate Grazing is not Necessary to Maintain or Encourage Old-Growth Characteristics

I became aware of The Prairie Enthusiasts during my graduate study at Kansas State. I was drafting a manuscript, and most publications from the Konza Prairie Biological Station referenced a paper by Knapp et al. (1999)[4]. Knapp et al. argued that bison (Bison bison) played a keystone role promoting “biotic integrity” and healthy plant communities in tallgrass prairie. Having spent a few years working on Konza, I felt uneasy passing along the breadth of their conclusions. While I was in awe of the grassland landscape there, I was underwhelmed by the condition of Konza’s experimental watersheds. Unburned watersheds were becoming forests of eastern redcedar (Juniperus virginiana), frequently burned watersheds (burned after spring green-up) were over-dominated by big bluestem (Andropogon gerardii) and Indiangrass (Sorghastrum nutans). Bison-grazed watersheds were experiencing woody encroachment, and while forbs were conspicuously more abundant, they were predominantly species like plains ragweed (Ambrosia psilostachya), gumweed (Grindelia squarrosa), and goldenrods (Solidago spp.). Except for a few low statured species (e.g., ground plum, Astragalus canadensis), greater concentrations of old-growth-associated species (conservative species)[5] occurred mostly on the steep, rocky slopes. There was little of Konza that I saw as high quality, remnant prairie. As I followed citations of Knapp et al., I stumbled across the letter that Mark Leach, Rich Henderson, and Thomas Givnish[6] published in response, and I found their concerns entirely consistent with my experience. Research into the authors led me to The Prairie Enthusiasts, and I was relieved that there were people that understood what high quality, old-growth prairie was!

How did Knapp et al.3, and later Manning et al. (2017)[7] and Ratajczak et al. (2022)[8] conclude that disturbance from confined bison grazing was beneficial to prairie plant communities?[9] One problem is a reliance on primary productivity, species richness, and other metrics of which richness is part (i.e., diversity and floristic quality index). I explained the spring issue1 how primary productivity and richness can increase while plant communities degrade, as generalist or opportunistic species colonize space opened by disturbance, and competition becomes less driven by low nutrient availability. Manning et al. reported higher floristic quality index in bison-grazed watersheds at Konza, but that effect was driven by richness; mean coefficient of conservatism (affinity of species for remnants—old-growth) was lower with bison grazing. Long-term disturbance history is another important factor at Konza. Frequent early growing season burning (vs. dormant season burning) practices aimed at maximizing grass production for livestock have held sway for a century in the Flint Hills. Those practices favor big bluestem and Indiangrass and had already changed prairie composition by the second half of the twentieth century[10],[11]. Before the 1970s Konza’s prairies were pastured ranchland[12], and there is no reason to suspect they would have been managed differently. Post green-up spring burning between March and May was carried forward in Konza’s most-replicated burn treatments. Spring phenology there is several weeks ahead of southern Wisconsin[13]. This has sustained big bluestem and Indiangrass over-dominance in the frequently burned, ungrazed watersheds that are used to make comparisons with bison-grazed watersheds. In that setting, bison grazing breaks the over-dominance of big bluestem and Indiangrass and allows more opportunistic or generalist plant species to grow, and that leads to higher species richness. Neither condition is like that of less degraded, remnant tallgrass prairies or savannas[14],[15].

Bison roamed the prairies, especially westward, so how could their presence be anything but salubrious? I don’t blame bison so much as settler culture and fences. I suspect there are differences between the effects of bison under confinement—even on thousands of acres—and unfenced bison. Bison were migratory, their behavior was subject to influence by hunting and predation, and their use of the landscape was and still is heterogeneous. We don’t have data to compare the effects bison had historically under those circumstances to those of contemporary confined bison, but the few historical descriptions of tallgrass prairie plant composition we have suggest historical bison numbers and behaviors, whatever they were, led to different expressions of prairie than result from contemporary bison grazing or any fenced scheme involving domesticated herbivores[16][17]. Estimates of past bison populations vary widely and mostly either extrapolate historical observations to large landscapes (e.g., Seton 1929[18]) or estimate carrying capacities based on different levels of consumption of plant biomass that cannot be adequately disentangled from that consumed by other vertebrate consumers, invertebrate consumers, and fire (e.g., Weber 2001).[19] These are only snapshots of the dynamic situation in the historical period. It’s possible that effects of bison as we see them now are more intense in space or time than they were for the several thousand years the tallgrass prairie was developing—even westward where bison numbers were greater.

Bison occurred eastward, but their populations east of the Mississippi River increased vastly following the plagues of disease inflicted by Europeans on Indigenous people. Henderson (2001)[20] summarized evidence, or the lack-thereof, for significant presence of modern bison in Wisconsin before the historical period. Similarly, McMillan (2006)[21] concluded that bison were present in “small scattered herds” in Illinois during that time. Any presence of bison prior to the historical period may have been culturally significant, or ecologically significant in terms of seed dispersal, but bison grazing probably was not a significant factor shaping community structure and composition on most of the landscape for most of the past several thousand years, at least away from localized areas bison may have concentrated.

The restoration or maintenance of high small-scale species richness and conservative vegetation in the absence of prescribed grazing (with frequent dormant season fire) provides additional evidence that bison are not essential to the maintenance of community structure or composition in tallgrass prairie and savanna ecosystems. Even prairie remnants farther west where bison were historically abundant look remarkably like remnant eastern prairies when they share similar European land use histories and contemporary management. These are often remnants along railroad rights of way or areas that were hayed rather than grazed or cultivated. The life history strategies of many conservative species make it unlikely that their assemblage in these areas has been a recent response to cessation of grazing and suggests that prior effects of free bison were less intense in the tallgrass region than those of confined bison. I suspect that as fire’s effects vary with intensity and seasonality, so do bison’s effects by their access to an intact broader landscape replete with elements that affect bison behavior.

I’ve focused on bison because their perceived role is used to justify practices involving other herbivores. More generally, how can fenced grazers and browsers destabilize prairie and savanna ecosystems? As with growing season fire, nitrogen may be part of the story. Herbivores consume the living tissues of herbaceous plants and deposit nutrients that had been held within those tissues during times when opportunistic plant species can capitalize. Frequent burning in the absence of fenced grazing volatilizes nitrogen from fuels and results in less plant-available nitrogen in the soil, but the nitrogen made available in animal waste counters that, and the proportion of plant production consumed by fire is concurrently reduced. Continuous fenced bison grazing leads to as much as six-fold increases in nitrogen mineralization and nitrification[22],[23], which result in increased plant-available nitrogen. Cattle have similar effects[24]. This can promote opportunistic versus old-growth-associated vegetation by shifting the community away from one shaped by competition for nitrogen towards one shaped by tolerance to or avoidance of herbivory or trampling, or competition for light upon cessation of grazing. Plant-available nitrogen may also stimulate germination of opportunistic species, including woody species. Briggs et al. 2005[25] report that introduction of bison to Konza was associated with four- to forty-fold increases in woody encroachment within four years. They speculate about mechanisms without considering the above, but the second to last line below stands out (emphasis added, grammatical error notwithstanding):

“…woody vegetation was restricted to riparian areas or protected escarpments…. Thus, even when bison removed fine fuel by grazing, there was a low probability that seeds of woody plants would reach these patches. In the current fragmented landscape, which is characterized by a higher cover of woody plants…, there is a greater chance that the seeds of woody plants will reach a grazed area with low fire intensity. In addition, bison were migratory grazers; thus, grazing in any given area were probably not chronic. Fuels could accumulate in years when there were no bison grazing in the area and therefore could support intense fires.”

They recognize bison’s past effects may have differed. Indeed, large portions of the bison grazing treatments receiving ignitions at Konza do not burn because of sparse fuels. More than once while serving on Konza burn crews, I was sent deep into bison watersheds searching for patches of adequate fuels to carry ignitions.

Fenced grazing and browsing can also compact soil (e.g., Manning et al. 20066), though there are exceptions, at least with short-term grazing (e.g., Harrington and Kathol 2009[26]). When compaction does occur, it can reduce water infiltration and retention, cause erosion and sedimentation, and physically change the soil growing environment for microbes and plants. Nonetheless, effects of compaction on prairie and oak community structure and composition are poorly understood, in part because changes arising from effects on soil physical properties are difficult to separate from those arising from soil chemical changes and direct effects of herbivores on plants. Also, many studies (e.g., Teague et al. 2011[27]) only compare soil and vegetation effects of different grazing practices in the absence ungrazed controls.

Grazing or browsing with goats or cattle are sometimes used to specifically target problematic woody species. These are seen by some as alternatives to herbicides or fire. Goats can also reach brush on steep terrain. However, goats and cattle also consume a wide range of conservative native plants, sometimes preferentially. On a visit to an open savanna restoration in Iowa that I’ve known since the 1990s, a recent change in management involved introduction of goats in lieu of burning. Inside the goat fence and in areas where goats had recently been, I could find browsed prairie forbs and defoliated oak grubs, but the goats had not yet worked over the smooth sumac (Rhus glabra) and Amur honeysuckle (Lonicera maackii)! Likewise, on a visit to a bluff prairie in southeastern Minnesota, I saw something similar where goats had browsed—heavy impacts to prairie forbs, but unwanted woody species were clearly going to recover. The prairie’s biological crust, important for stabilizing soil and itself capable of  , was battered by hooves. In contrast to other bluff prairies in the Driftless, there was no midsummer bloom. I wonder if lepidopterans or oligolectic bees emerged to find the hillside bereft of resources. I am not aware of any study showing a benefit of prescribed goat browsing to old-growth-associated vegetation in the Midwest, nor have I seen one. I have seen photographs showing immediate after-effects—typically reductions of woody vegetation taken shortly after browsing treatments. Longer-term outcomes and effects on conservative species are conspicuously absent.

There is more study of cattle grazing in restoration or conservation contexts. In a Minnesota experiment on effects of canopy thinning, burning, and light cattle grazing treatments in a savanna restoration setting, Yantes et al. (2023)[28] found that cattle grazing did not yield benefits above combined thinning and burning, but that study did not consider effects on mean coefficient of conservatism—just richness, diversity, density, and cover. Harrington and Kothol19 showed reductions in unwanted shrubs in degraded oak savanna and prairie in response to treatment with highland cattle, but fire alone caused greater or similar reductions in savanna and prairie, respectively. Briggler’s (2017)[29] study of short-term effects of patch-burn grazing (one cycle) in Missouri seams to show positive effects on floristic quality index, but the authors don’t report mean coefficient of conservatism. In contrast, Buckles and Harmon-Threatt (2019)[30] show reductions in floristic quality and habitat quality for ground-nesting bees at patch-burn-grazed sites, and Thomas[31] showed longer-term collapse of mean coefficient of conservatism in response to patch-burn-grazing at Taberville Prairie in Missouri. It is worth noting that effects of grazing and burning in Missouri patch-burn grazed sites could also result from a recent tendency to burn sites later in spring versus the dormant season. Regardless, the declines of Taberville and other premier Missouri prairies (e.g., Niawathe Prairie, see Paul Nelson’s presentation[32]) offer cautionary tales and gut-wrenching imagery of well-intended practices profoundly damaging previously well-maintained (with dormant season fire, without prescribed herbivory) old-growth sites. Nor should this be a surprise. Hayden17, Curtis[33], and Weaver16 wrote about how quickly and profoundly fenced livestock can ruin prairie based on research and observations from the late 1800s through the mid-1900s. From Weaver:

“Climax grassland, when grazed lightly, retains essentially its natural composition. It is only when grazing animals are circumscribed in their range by fences and when too large a number are thus confined, that grazing and trampling become so excessive that normal plant cover can not be maintained. Numerous changes in the vegetation then occur…. Where prairie is grazed intensively, in only a few years almost unbelievable changes occur.”

Sometimes the hope is to set the stage for restoration through the temporary use of goats or cattle to remove brush. That may be worth a try where no old-growth-associated biota remain that may be lost. However, unless grazing and browsing treatments are repeated or continuous over long periods, other means of treatment of resprouting woody vegetation are necessary.

Resilience of old-growth prairie and savanna is a myth based on research conducted predominantly on sites already degraded by past land use[34]. The more remnants are disturbed, the more effort is required to promote recovery. Still, remnants are highly resistant to change if the stabilizing ecological processes that promote low nutrient availability, remove smothering thatch and leaf litter, and otherwise maintain healthy and genetically diverse populations[35] are maintained, chief among them is frequent dormant season fire. That’s the common thread among rare sites maintaining or improving condition despite fragmentation, climate change, and nitrogen deposition due to agricultural and industrial practices. Fenced grazing and browsing practices can impair that resistance, destabilizing plant community composition, structure, and everything connected to those in response. While greater site-scale diversity often results, that occurs at the expense of unique and tightly interwoven old-growth, because opportunistic species increase that are much more common on the broader, degraded landscape. Regionally, these site-level increases in diversity represent homogenization—as old-growth loses unique characteristics and becomes more similar to old fields, roadsides, and other disturbed habitats.

 

References 

[1] Carter, D. (2024). Stability part one: Why I recommend frequent dormant season burning. Prairie Promoter, Spring: 14-19.

[2] Surrogate grasslands are grassland types associated with or arising from European land use practices. Examples of surrogate grasslands include agricultural hayfields, pastures, fallow fields, and certain lower diversity native or non-native conservation grassland plantings. Most grassland habitat consists of surrogate grasslands (vs. old-growth or old-growth-like), so they are important to the conservation of grassland Species of Greatest Conservation Need. In these settings certain grazing practices may be used towards specific habitat goals with lower risk to the ecological integrity of old-growth or old-growth-like prairie and oak ecosystems.

[3] Even at very degraded sites populations of a few to many highly desirable old-growth-associated species often persist as exceedingly small vegetative plants dying slow deaths from shade and excessive litter. These are particularly vulnerable to extirpation from disturbance associated with restoration practices, and it takes skill and luck to detect them.

[4] Knapp, A., et al. (1999). The keystone role of bison in North American tallgrass prairie: Bison increase habitat heterogeneity and alter a broad array of plant, community, and ecosystem processes. BioScience 49: 39-50.

[5] Conservative plant species are those that are relatively intolerant of degradation. Species are assigned coefficients ranging from zero to ten; those with higher coefficients are more indicative of a relatively stable and undisturbed conditions where they occur. The limited dispersal ability of these species, and the abundance and richness of these species on sites least subject to excessive thatch build-up, European grazing practices, soil disturbance, and regular growing season burning; as well as early historical accounts of tallgrass prairie composition suggest that these are associated with old growth and high quality/integrity sites. There are many native plant species, but these are the ones that define remnant sites.

[6] Leach, M., et al. (1999). A caution against grazing. Bioscience 49: 599-600.

[7] Manning, G., et al. (2017). Effects of grazing and fire frequency on floristic quality and its relationship to indicators of soil quality in tallgrass prairie. Environmental Management, 60: 1062-1075.

[8] Ratajczak, Z., et al. (2022). Reintroducing bison results in long-running and resilient increases in grassland diversity.” Proceedings of the National Academy of Sciences, 119.36: e2210433119.

[9] It is worth noting that in addition to my graduate advisor, two of my dissertation committee members and a former office mate are authors/co-authors on these papers. They are all brilliant and well-meaning people.

[10] Towne, G., & C. Owensby. (1984). Long-term effects of annual burning at different dates in ungrazed Kansas tallgrass prairie. Journal of Range Management 37: 392-397.

[11] Hensel, R. (1923). Recent studies of the effect of burning on grassland vegetation. Ecology 4: 183-188.

[12] Given, C. (2004). History of the Dewey Ranch: https://kpbs.konza.k-state.edu/history/land.html

[13] This means Konza spring burn treatments are phenologically equivalent to burning between mid-April and mid-June in southern Wisconsin. In southern Wisconsin depending on the year, consistently burning after some time roughly between the spring equinox and the second week of April risks destabilizing remnant prairie.

[14] Carter, D. (2023). Change and persistence among prairie grasses. Prairie Promoter, Summer, 10-12.

[15] Many would argue that the degraded condition was the ancestral condition, but the earliest data we have in that region and elsewhere do not support that, fragmentary though it may be. High small-scale richness and high relative abundance of conservative species most likely did not self-assemble into the small fragments we still have today, because the individual life history strategies and complex ecological interactions of those species would make that implausible. They need stability, time, and intact means of dispersal.

[16] Weaver, J. E. (1954). North American prairie. University of Nebraska—Lincoln, URL: https://digitalcommons.unl.edu/agronweaver/15/

[17] Hayden, A. (1918). Notes on the floristic features of a prairie province in central Iowa. In Proceedings of the Iowa Academy of Science, Vol. 25: 369-389.

[18] Seton, E. (1929). The lives of game animals. Doubleday, Doran and Co., Garden City, N.J.

[19] Weber, K. (2001). Historic bison populations: A GIS-based estimate. Proceedings of the 2001 Intermountain GIS Users’ Conference: 45-51.

[20] Henderson, R. (2001). Where did the elk and the buffalo roam? Prairie Promoter. Fall: 15-16.

[21] McMillan, R. (2006). Perspectives on the biogeography and archaeology of Bison in Illinois in Records of early bison in Illinois. Illinois State Museum Scientific Papers, 31: 67-146

[22] Nitrogen mineralization is the conversion of organically bound nitrogen into inorganic forms (e.g., nitrate and ammonium), and nitrification is a microbial process by which primarily ammonia is oxidized to nitrate and nitrate. The important product of these reactions is plant-available nitrogen in the forms of nitrate and ammonium.

[23] Konza bison fact sheet: http://lter.konza.ksu.edu/sites/default/files/BisonFact17.pdf

[24] Johnson, L., & Matchett, J. (2001). Fire and grazing regulate belowground processes in tallgrass prairie. Ecology, 82: 3377-3389.

[25] Briggs, J. et al. (2005). An ecosystem in transition: causes and consequences of the conversion of mesic grassland to shrubland. BioScience, 55: 243-254.

[26] Harrington, J., & Kathol, E. (2009). Responses of shrub midstory and herbaceous layers to managed grazing and fire in a North American savanna (oak woodland) and prairie landscape. Restoration Ecology, 17: 234-244. Note: Grazing treatment duration was two days on several rotations over two years. Also, there were some differences in the woody species more reduced by grazing versus fire.

[27] Teague, W. et al. (2011). Grazing management impacts on vegetation, soil biota and soil chemical, physical and hydrological properties in tall grass prairie. Agriculture, ecosystems & environment, 141: 310-322.

[28] Yantes, A, et al. (2023). Oak savanna vegetation response to layered restoration approaches: Thinning, burning, and grazing. Forest Ecology and Management, 537, 120931.

[29] Briggler, M., et al. (2017). Effects of patchburn grazing on vegetative composition of tallgrass prairie remnants in Missouri. Natural Areas Journal, 37(3), 322-331.

[30] Buckles, B. J., & Harmon‐Threatt, A. (2019). Bee diversity in tallgrass prairies affected by management and its effects on above‐and below‐ground resources. Journal of Applied Ecology, 56(11), 2443-2453.

[31] Thomas, J. (unpublished). The effects of patch burn grazing on a high quality prairie. NatureCite, URL: https://drive.google.com/file/d/0BwTps-dBuxNCenpYbTJWNEVIOWc/view

[32] Nelson, P. (2012). Patch-burn grazing: Is it right for Missouri’s remaining high quality prairies: https://www.youtube.com/watch?v=cqwu5jG96tc

[33] Curtis, J. T. (1959). The vegetation of Wisconsin: an ordination of plant communities. University of Wisconsin Press.

[34] As discussed earlier in this article, most of the western tallgrass prairie has long been utilized as prairie pasture and been dramatically altered in composition and structure for many decades to more than a century prior to more recent study. Research and observation from such areas is not directly applicable to the conservation management of old-growth, true prairie or oak ecosystems.

[35] Don’t mistake this to mean maximizing populations of species. I mean maintaining viable populations within the context of an ecosystem with ecological integrity versus maximizing populations of specific flora or fauna.

 

Figure 2: A vegetation sampling quadrat in a bison-grazed, biennially burned watershed at Konza in August. Tall goldenrod (Solidago altissima, C=1), stiff goldenrod (Solidago rigida, C=3), plains ragweed (Ambrosia psilostachya, C=3), hoary vervain (Verbena stricta C=1), and Baldwin’s ironweed (Vernonia baldwinii C=2) are the most prominent forbs in the vicinity, none of which are conservative (Coefficients of conservatism are for Kansas).

Figures 3 and 4: Views of minimally grazed/ungrazed (at least by European livestock), mesic prairie in western Iowa (left) and southeast Wisconsin (right). Note the similarity. It is only possible to differentiate them by the presence of nodding onion (Allium cernuum, left of center) in the photo on the right. All other species visible in both images are at least present at both sites at the transect (vs. plot) scale.

Figure 5: This is a reference, old-growth prairie (The Prairie Enthusiasts’ Black Earth Rettenmund Prairie)—not the prairie pastures so often used for research on grazing and fire effects.

Figure 6: Another reference, old-growth prairie, this one on private land in western Iowa. 

This article appeared in the Summer 2024 edition of the Prairie Promoter, a publication of news, art and writing from The Prairie Enthusiasts community. Explore the full collection and learn how to submit your work here

About The Prairie Enthusiasts 

The Prairie Enthusiasts is an accredited land trust that seeks to ensure the perpetuation and recovery of prairie, oak savanna, and other fire-dependent ecosystems of the Upper Midwest through protection, management, restoration, and education. In doing so, they strive to work openly and cooperatively with private landowners and other private and public conservation groups. Their management and stewardship centers on high-quality remnants, which contain nearly all the components of endangered prairie communities. 

Stability Part One: Why I Recommend Frequent Dormant Season Burning

Stability Part One: Why I Recommend Frequent Dormant Season Burning

Stability Part One: Why I Recommend Frequent Dormant Season Burning

Photos and Written by Dan Carter

Prairie and Oak Ecosystems Depend on Stability

A central organizing concept of my ecological education was that prairie and oak ecosystems are “disturbance dependent.” This view emphasizes that we stop these ecosystems from becoming something else and deemphasizes that they are something in and of themselves—old growth. Disturbance-centric thinking remains prominent in prairie and oak ecosystem science and management. For example, under the heading “Managing Prairies” the Minnesota DNR website[1] states:

“Prairie is a ‘disturbance-driven’ ecosystem: plants and animals have adapted to withstand and even thrive with regular disturbance—fire, grazing, and periodic droughts. Each disturbance favors different plants and animals, so it is important to include a variety of disturbance types, timing, and frequency.”

The advice to mix things up sounds reasonable, disturbances do favor different plants and animals, and certain events or conditions must occur to prevent oak and prairie ecosystems from becoming something else.

The problem is that disturbance[2] can simplify ecosystems and promote species that are not conservation priorities at the expense of the old growth that we would like to conserve or emulate. Given what we know about historical structure, composition, and the individual ecologies of the species that comprise old-growth prairie and oak ecosystems, I believe that the prevailing view about how these ecosystems sustain themselves—disturbance—is wrong. Instead, stability should be a central organizing idea guiding our stewardship.

Centering management around a core principle of stability does not mean doing less. Indigenous Peoples’ use of dormant season fire and its interaction with landscape, climate, and biota was the lattice over which our prairie and oak ecosystems came together over thousands of years. Managing for stability means keeping this in mind and building an understanding of how it governs ecological processes. In this article I will discuss prescribed fire, and how it can function as a stabilizer or a destructive disturbance depending on how we use it. I intend to discuss other management practices in turn.

A fire-starved remnant prairie that persisted long enough to be protected because haying prevented build-up of smothering thatch and removed nutrients.

A close-up showing the deep accumulation of thatch in the fire-starved remnant prairie. It would be difficult to burn at this point without producing high fire intensity, particularly long duration of burning near the soil surface.

Excessive leaf litter accumulation in an oak woodland.

Both high intensity and growing season fires have destabilized this former savanna.

Frequent Dormant Season Fire is Stabilizing; Infrequent, Intense, and Growing Season Fire is Destabilizing

First, recognize that critical areas of fire ecology in Midwestern prairie and oak ecosystems are forgotten, understudied or not studied through the posing of questions and collection of data that informs our mission. Synthesis of what we do know is also in short supply. What follows is my earnest attempt using applicable science, cases of success and failure, and historical information to explain why I often advocate for very frequent[3] dormant season burning. This topic is also difficult to flatten into a linear narrative, such are the ecological relationships. Many threads could be drawn from this that merit their own separate discussions.

I don’t refer to prescribed fire as a tool. A Pulaski is a tool. Fire is an integral part of Upper Midwestern prairie and oak ecosystems. Fire is their primary stabilizing agent and was probably the greatest single consumer of their plant production in the past (Wendt et al. 2023[4]). The more frequently contemporary Midwestern prairie and oak ecosystems burn in the dormant season, the more they retain historical or old-growth composition over time (Towne and Owensby 1984[5], seasonality of fire; Milbauer and Leach 2007[6], Bowles and Jones 2013[7] and Alstad et al. 2016[8], frequency of burns mostly in early spring or fall). See my article in the 2023 fall issue of The Prairie Promoter[9] for a discussion specifically about how fire exclusion and altered fire seasonality have affected prairie grass species composition. With enough dormant season fire and other appropriate management, incredibly diverse and complex examples of prairie and oak ecosystems have recovered and persist. Black Earth-Rettenmund Prairie and Sugar River Savanna are excellent examples. Unfortunately, few places are managed this way. We need more demonstrative examples for science and inspiration[10]. Sites burned too infrequently lose old-growth-associated composition and structure—conservative[11] plant species and the fauna they support, so do sites that receive too many growing season fires. Hopefully, what follows provides insights into how lack of fire and growing season fire can be destabilizing.

Most historical accounts describe ignitions preceding Indigenous Peoples’ displacement as anthropogenic, autumnal[12], and frequent over large areas (Stewart 2002[13]; Wilhelm and Rericha 2007[14], 2012[15]; McLain et al. 2021[16]). Wilhelm and Rericha refer to this as the “ancient, culturally mediated rhythm,” and it prevented smothering thatch and litter accumulation, reduced fire intensity (especially duration), and minimized growing season nutrient availability. Fire in the dormant season is not unlike frost to prairie or oak ecosystems, something that in its proper season falls within the parameters that governed their original formation and the subsequent evolution. Fidelity to that seasonal rhythm is not anachronistic; it is important for the restoration and maintenance of prairie and oak ecosystems. It has served us well as the climate has changed dramatically over the last several decades, and it will probably continue to do so if we allow it.

There is disagreement between historical accounts and scientific estimates of fire frequency based on fire scars (e.g., Allen et al. 2011[17]), which typically estimate fire-return intervals of several years to a decade. The fire regimes that best-maintain prairie and oak ecosystems on the contemporary landscape lend strong support to the historical accounts. Fire scar studies capture fire events sufficiently intense to scar oaks on landscape positions where trees historically occurred—not prairies. Very frequent or annual fires in oak woodlands have low intensity due to reduced fuel loads and may fail to scar oak trees and subsequently be detected in the fire scar record (McEwan et al. 2006[18], Knapp et al. 2017[19]). Climate change and other anthropogenic changes at scales ranging from local to global may also necessitate that we burn differently, regardless of historical frequency. We should strive to do what works, regardless which estimates of historical frequency are right.

The benign removal of litter and thatch that would otherwise smother and weaken the sod of native graminoids and forbs typical of prairies and oak ecosystems is among the most important stabilizing roles of fire. When prairie fire is too infrequent, thatch accumulation thins the herbaceous vegetation and “prairie understory” species fade while composition shifts in favor of taller species and those with longer-elongating rhizomes that can grow up through the debris (e.g., Weaver 1952[20]). A similar phenomenon occurs in remnant oak woodlands, which support continuous grassy / sedgy, often forb-rich herbaceous vegetation. Without removal of oak leaf litter by fire or another agent like wind (as on convex topography and windswept slopes), many woodland herbaceous species are smothered. Midland shooting star (Primula meadia) is an example from both prairies and woodlands that is diminished in this way. When searching for remnant woodland vegetation at long fire-starved sites, I’ve learned to seek topography that is subject to removal of fallen leaf litter by wind. Perhaps because this is such a plain mechanism, direct smothering effects of leaf litter are under-researched in woodland ecosystems (but see Sydes and Grime 1981[21], Vander Yacht et al. 2020[22]). Once the herbaceous sod in a prairie, savanna, or woodland is thinned and degraded, it becomes more vulnerable to invasion and woody encroachment.

Thatch and leaf litter don’t only smother. Increased fuel loads lead to greater fire intensity as fire burns down through accumulated debris. This can injure herbaceous species whose regenerating buds are held at or above the soil surface, species like little bluestem (Schizachyrium scoparium) and prairie dropseed (Sporobolus heterolepis) and cause greater harm to certain invertebrates overwintering at or just below the soil surface (e.g., Dana 1991[23]). Intense fire can injure mature, healthy oak trees and lead to abrupt changes in canopy closure. In relatively nutrient poor oak and pine ecosystems, long periods without fire can lead to duff development (an organic layer below the leaf litter), and when trees proliferate roots in the duff, fire can subsequently consume those roots with lethal results (Carpenter et al. 2021[24]).

Frequent prairie fires can reduce nitrogen availability (e.g., Ojima et al. 1993[25]) through volitilization, and the same may be true in woodlands where fire is frequent and consumes primarily fine fuels. Frequent fire may also contribute higher carbon to nitrogen ratios in oak litter, which can then immobilize more nitrogen and reduce nitrogen availability (Hernández and Hobbie 2008[26]), but it does not necessarily lead to nutrient losses from the ecosystem (Sharenbroch 2010[27]). Conversely, adding nitrogen destabilizes prairie composition (Koerner et al. 2016[28]). Old-growth vegetation in fire-dependent ecosystems is comprised largely of species that rely more on year-to-year survival versus annual reproductive output or seed banks for population persistence. Old-growth vegetation also tends to be nutrient efficient and produce slower-decomposing, flammable litter. Dormant season fire sustains that vegetation by removing accumulated detritus without significant injury to established herbaceous plants. Conversely, the strategy of most weedy species is to persist in the seed bank or disperse widely and respond to available nutrients and light by growing and reproducing rapidly. The litter they produce tends to be less flammable and decompose rapidly, which promotes faster nutrient cycling and greater nutrient availability. Growing season fires cook the aboveground living tissues of conservative herbaceous plants. In addition to that direct harm, which can be substantial and lead to compositional changesrelated to plant growth form and regeneration strategy, it results in the hard-won nutrients present in their tissues and light intercepted by their foliage being made available. This creates an environment where soil warmth, light, and nutrient cues align to encourage the establishment of opportunistic, weedy species. Nitrogen (nitrate), for example, serves as a germination cue for raspberries (e.g., Jobidon 1993[29]) and a variety of herbaceous weeds, particularly in combination with light (Soltani et al. 2022[30]). Heat from fire also has more opportunity to penetrate the soil during the growing season, because the latent heat of water buffers soil temperature, and near-surface soil moisture content usually decreases as the growing season proceeds. Exposure to heat can break seed dormancy in smooth sumac (Li et al. 1999[31]), which I think is worth considering! Where late spring or summer burning has occurred and sumac is on the landscape, look for sumac seedlings. Setting the flora aside, greater direct negative impacts of growing season burning on certain fauna are well known (e.g., Harris et al. 2020[32]); these magnify tensions between the use of prescribed fire and rare animal species. Dormant season burning minimizes them.

Conservation-oriented land managers often burn during the growing season to maximize injury to unwanted woody vegetation. The evidence that this makes a meaningful difference is scant. Meunier et al. (2021)[33] showed decreases in resprouts per individual (not mortality) for northern pin oak (Quercus ellipsoidalis) and bush honeysuckle (Lonicera spp.) with August burning relative to April or June burning, but they found no similar benefit for common buckthorn (Rhamnus cathartica). Hartnett and Wilson (2011)[34] found that spring and summer growing season burns led to increases in smooth sumac relative to fall and winter burns.

Another argument for burning during the growing season is that it can be associated with increased herbaceous plant richness and primary productivity[35]. These may be go-to response variables for research ecologists and agronomists, but they tell us little about ecological integrity[36] and can indicate ecosystem degradation. As fire-dependent ecosystems degrade their richness is a function of extirpation of the species that were originally present and colonization by opportunistic species or those associated with other ecosystem types[7,8]. For example, widely dispersed woodland species like stickseed (Hackelia virginiana) can accompany woody encroachment into the prairie. Inventories of degrading sites are often packed with such species—even while the original species are hanging on by a thread. Likewise, primary productivity can increase with ecosystem degradation—even when an ecosystem undergoes profound change that impairs other ecosystem functions and resilience (De Leo and Levin 1997)[37]. Imagine a sedge meadow that transitions to Phragmites dominance. Productivity is used as a measure of ecosystem efficiency, but the sun’s energy does not just go into biomass production; it also fuels production secondary metabolites, which are the basis for countless specialized interactions between plants, fungi, bacteria, and both invertebrate and vertebrate fauna! High quality prairie and oak ecosystem herbaceous sods are often low in stature, but that does not mean that they are thermodynamically inefficient. They are just doing different things—more interesting things if you ask me! Increased productivity aboveground may be indicative of nutrient availability destabilizing composition by causing a shift from belowground competition to aboveground competition for light (e.g., Wilson and Tilman 1993[38]; Goldberg et al. 2017[39]), which favors species with opportunistic strategies.

Frequent dormant season burning can keep most woody encroachment at bay when the sod is strong, and frequent dormant season burning results in a strong sod. When they occur together, dormant season fire and high integrity herbaceous sods are stable and autocatalytic. For example, quaking aspen (Populus tremuloides) has remained a minor presence at Sugar River Savanna for fifty years with near-annual burning[40]. Aspen would most likely overwhelm a similar site in the absence of frequent fire, but the herbaceous sod there is tightly interwoven. The same is true for sumac in more degraded Flint Hills prairie in Kansas[33]. Upon cessation of frequent fire, species like aspen, smooth sumac, and gray dogwood (Cornus racemosa) quickly take over, if they have a toehold, and the ecosystem changes states. This isn’t because fire is ineffective. It’s because very frequent dormant season fire is a defining part of the autocatalytic system, and it is underutilized.

Sugar River Savanna has been managed with near-annual early spring (dormant) fire for fifty years.

Frequent dormant season burns stabilize prairie and oak ecosystem composition, structure, and ecological processes by removing smothering debris and minimizing growing season nutrient availability without injury to conservative, old growth vegetation. Are there situations where less frequent fires, or disturbance-inducing intense or growing season fires are appropriate? I can think of examples related to specific management needs or goals. Many are applicable to degraded sites where conservation of one or a few species or the need to generate income outweigh other considerations in the short term. Those instances have merit, but such decisions should be based on an understanding of the relevant ecological processes and both direct and indirect effects. Historically, disturbance fires did occur. Some fire scars were laid down during the growing season. Lightning can ignite summer fires in drought years. Those fires may have had important effects on ecosystem structure, composition, and processes in the past, but the fire-dependent ecosystems of the past were also buffered by intact ecological landscapes free of invasive species. Remaining prairie and oak ecosystems can no longer rely on landscape ecological processes for resilience. This should give us pause when we consider deviating from the “ancient, culturally mediated rhythm” to mix things up, hit woody vegetation hard, or simply get more fire on the ground.

References

[1] Minnesota Department of Natural Resources Website (accessed 1/12/24): https://www.dnr.state.mn.us/prairie/manage/managing-prairie.html

[2] For the sake of this discussion, disturbance is an event that causes mortality, injury or stress to an ecosystem or one of its components that causes deviation from a reference state.

[3] How frequent is frequent? It depends on the ecosystem type. Relatively productive mesic prairies may need to be burned more often than every other year maintain structure, composition, and ecological processes. Some dry, sandy sites require multiple seasons to build up enough fuel to burn.

[4] Wendt, J., et al. (2023) Past and present biomass consumption by herbivores and fire across productivity gradients in North America. Environmental Research Letters 18.12: 124038.

[5] Towne, G., & Owensby, C. (1984). Long-term effects of annual burning at different dates in ungrazed Kansas tallgrass prairie. Rangeland Ecology & Management, 37(5), 392-397.

[6] Milbauer, M. L., & Leach, M. K. (2007). Influence of species pool, fire history, and woody canopy on plant species density and composition in tallgrass prairie1. The Journal of the Torrey Botanical Society, 134(1), 53-62.

[7] Bowles, M.L., & Jones, M.D. (2013). Repeated burning of eastern tallgrass prairie increases richness and diversity, stabilizing late successional vegetation. Ecological Applications, 23(2), 464-478.

[8] Alstad, A.O. et al. (2016). The pace of plant community change is accelerating in remnant prairies. Science Advances, 2(2), e1500975.

[9] Carter, D. (2023). Change and persistence among prairie grasses. Prairie Promoter, Summer, 10-12.

[10] Very few sites in most research cited are burned very frequently, for example in Milbauer and Leach (2007), burn frequency was divided into three classes, the most frequent class including sites that had been burned between four and seventeen times in twenty years. We need more sites that are burned more often than every other year, including annually for greater resolution of fire’s effects.

[11] Conservative plant species are those that are relatively intolerant of degradation. Species are assigned coefficients ranging from zero to ten; those with higher coefficients are more indicative of a relatively stable and undisturbed conditions where they occur. The three most frequent grasses on WI mesic prairie, for example, all have coefficients of nine or ten. About 80 percent of Wisconsin’s native flora have C-values of four or greater.

[12] A bias based on more travel in fall or early winter versus when conditions were muddy in early spring has been raised, but if that were the case, fires were overwhelmingly at the edge of or within the dormant season, and there is as of present no evidence beyond conjecture to suggest early spring fires were as or more common or extensive than autumnal fires. We need more science to elucidate ecological differences, but practically it may be advantageous to utilize fall burning opportunities to guard against the possibility of rapid spring green-up, as happened in 2023.

[13] Stewart, O.C. (2002). Forgotten fires: Native Americans and the transient wilderness. University of Oklahoma Press.

[14] Wilhelm, G., & Rericha, L. (2007). Timberhill savanna assessment of landscape management. Conservation Research Institute, Elmhurst, IL.

[15] Wilhelm, G. & Rericha, L. (2012). Inventory and Assessment Plan for Stewardship and Monitoring at Hitchcock Nature Center. Conservation Research Institute, Elmhurst, IL.

[16] McClain, W. et al. (2021). Patterns of anthropogenic fire within the midwestern tallgrass prairie 1673–1905: Evidence from written accounts. Natural Areas Journal, 41(4), 283-300.

[17] Allen, M. S., & Palmer, M. W. (2011). Fire history of a prairie/forest boundary: more than 250 years of frequent fire in a North American tallgrass prairie. Journal of Vegetation Science, 22(3), 436-444.

[18] McEwan, R. W., et al. (2007). An experimental evaluation of fire history reconstruction using dendrochronology in white oak (Quercus alba). Canadian Journal of Forest Research 37(4), 806-816.

[19] Knapp, B. O., Marschall, J. M., & Stambaugh, M. C. (2017). Effects of long-term prescribed burning on timber value in hardwood forests of the Missouri Ozarks. In Proceedings of the 20th Central Hardwood Forest Conference (pp. 304-313). USDA Forest Service Gen. Tech. Rep. GTR-NRS-P-167, Northern Research Station, Newtown Square, PA.

[20] Weaver, J. & Rowland, N. (1952). Effects of excessive natural mulch on development, yield, and structure of native grassland. Botanical Gazette 114: 1-19.

[21] Sydes, C., & Grime, J.P. (1981). Effects of tree leaf litter on herbaceous vegetation in deciduous woodland: I. Field investigations. The journal of ecology, 237-248.

[22] Vander Yacht, A.L. et al. (2020). Litter to glitter: promoting herbaceous groundcover and diversity in mid-southern USA oak forests using canopy disturbance and fire. Fire Ecology, 16(1), 1-19.

[23] Dana R., (1991) Conservation management of the prairie skippers Hesperia dacotae and Hesperia ottoe. Minnesota Agricultural Experiment Station Bulletin 594, University of Minnesota

[24] Carpenter, D.O. et al. (2021). Benefit or liability? The ectomycorrhizal association may undermine tree adaptations to fire after long-term fire exclusion. Ecosystems, 24, 1059-1074.

[25] Ojima, D.S. et al. (1994). Long-term and short-term effects of fire on nitrogen cycling in tallgrass prairie. Biogeochemistry 24:67–84.

[26] Hernández, D.L., & Hobbie, S.E. (2008). Effects of fire frequency on oak litter decomposition and nitrogen dynamics. Oecologia, 158: 535-543.

[27] Sharenbroch, B.C. (2010). Ecological impacts of long-term, low intensity prescribed fire in Midwestern oak forest. Report to: The Illinois Department of Natural Resources: 1-102.

[28] Koerner, S.E. et al. (2016). Nutrient additions cause divergence of tallgrass prairie plant communities resulting in loss of ecosystem stability. Journal of Ecology, 104(5), 1478-1487.

[29] Jobidon, R. (1993). Nitrate fertilization stimulates emergence of red raspberry (Rubus idaeus L.) under forest canopy. Fertilizer research36, 91-94.

[30] Soltani, E. et al. (2022). An overview of environmental cues that affect germination of nondormant seeds. Seeds, 1(2), 146-151.

[31] Li, X. et al. (1999). Anatomy of two mechanisms of breaking physical dormancy by experimental treatments in seeds of two North American Rhus species (Anacardiaceae). American Journal of Botany, 86(11), 1505-1511.

[32] Harris, K.A., et al. (2020). Direct and indirect effects of fire on eastern box turtles. The Journal of Wildlife Management, 84(7), 1384-1395.

[33] Meunier, J., et al. (2021). Effects of fire seasonality and intensity on resprouting woody plants in prairie‐forest communities. Restoration Ecology, 29(8), e13451.

[34] Hajny, K.M., et al. (2011). Rhus glabra response to season and intensity of fire in tallgrass prairie. International Journal of Wildland Fire, 20(5), 709-720.

[35] The biomass produced by primary producers (e.g., plants).

[36] An ecosystem with ecological integrity is comprised of the full range of parts and processes expected for a region and has its evolutionary legacy intact.

[37] De Leo, G.A., & Levin, S. (1997). The multifaceted aspects of ecosystem integrity. Conservation ecology, 1(1).

[38] Wilson, S.D., & Tilman, D. (1993). Plant competition and resource availability in response to disturbance and fertilization. Ecology, 74(2), 599-611.

[39] Goldberg, D.E., et al. (2017). Plant size and competitive dynamics along nutrient gradients. The American Naturalist, 190(2), 229-243.

[40] Henderson, R. (2022). Effect of long-term annual fire on tree establishment and growth in an oak savanna (Poster). The Prairie Enthusiasts Annual Conference: Inspired by Resilience.

This article appeared in the Spring 2024 edition of the Prairie Promoter, a publication of news, art and writing from The Prairie Enthusiasts community. Explore the full collection and learn how to submit your work here