Choosing Your Destination Before You Choose Your Mode of Transport

Last week, I attended a science and stewardship conference of The Nature Conservancy in Madison, Wisconsin.  It was an inspiring and thought-provoking week.  There were a lot of topics that will provide fodder for future blog posts, but I wanted to start with an issue that came up in several sessions.  The topic had to do with setting appropriate objectives for conservation strategies, and for land management in particular.  In short, it’s really important to make sure we’re not setting objectives that are focused on strategies rather than outcomes.

This mixed-grass prairie is managed with both prescribed fire and grazing.  However,  neither fire nor grazing is the objective, they are tools that are strategically employed to create desired outcomes.  Gjerloff Prairie – Prairie Plains Resource Institute

Here’s an illustration of what I mean.  If I was planning a vacation for next summer, I probably wouldn’t start with the following question: “What mode of transportation should I take on my vacation next year?”

Clearly, it’s tough to answer that question without knowing more about the ultimate objectives of the vacation.  Where do I want to go?  What time of year am I going?  How many people are going with me?  If I’m planning to travel from Nebraska to Ireland, I probably won’t be able to do that by bus.  I could conceivably travel by motorcycle (if I had one) to the Rocky Mountains, but probably not if I was going during the winter or planning to take little kids with me.

It seems silly to start by thinking about how to get somewhere before deciding where to go, but as land managers, it’s easy to fall into exactly that mindset.  We sometimes set objectives about using fire or grazing, for example, instead of first defining the outcome we want and then thinking about what tools and strategies might get us there (which may or may not include fire or grazing).  In this post, I’ve provided examples of how this trap can present itself, both to managers of conservation land and private landowners, and some thoughts about how to avoid the trap.

Significant research has helped us understand the kinds of fire and grazing patterns under which North American prairies developed.  For example, in many places, we have a pretty good idea how often a particular site burned, on average, before European settlement.  We also have reasonably good information on the presence, abundance, and behavior of historic grazers.  Based on that information, a land manager could decide that the best management for their prairie would be to reinstate, as closely as possible, the timing and intensity of historic fire and grazing that site likely evolved under. 

Historically, prairies in this region probably burned on an average of every 4-5 years.  However, within that average range, there would have been wide variation.  More importantly, this prairie sits within a very different landscape today, with challenges not faced by those historic prairies.

Patch-burn grazing is often described, for example, as “mimicking historic fire and grazing patterns.”  Mob grazing advocates trumpet (though I’m skeptical) that their system replicates the way bison moved across a landscape.  Some in the Upper Midwest region of North America point to research showing high populations of indigenous people and scarce evidence of abundant bison and argue that their prairies should be managed only with fire.  We can argue about all three of those examples – and many more – but the bigger point is that none of those arguments should determine our management strategies.  Again, we shouldn’t be setting objectives about the strategy we want to use without first identifying the outcome we want.

To make a clunky return to my vacation travel analogy, it would be silly of me to choose horseback as my preferred mode of transportation across the Great Plains to the Rocky Mountains just because it’s what worked several hundred years ago.  Today’s landscape is broken up into countless fenced off private land parcels, which would make cross-country horse travel difficult, to say the least.  In addition, there is a pretty nice set of modern opportunities (roads and vehicles) I can take advantage of nowadays.

Likewise, our prairies exist within a different world today, with a new set of challenges and opportunities.  Mimicking historic disturbance regimes won’t necessarily keep prairies in good shape in a world with habitat fragmentation, massive invasive species pressure, climate change, nitrogen deposition, and other factors.  And speaking of good shape, our first and primary concern should really be to define what “good shape” is, right?  Are we managing for plant diversity or a few rare plants?  Are we trying to sustain diverse bird populations?  Habitat heterogeneity? Is ecological resilience the goal?  If so, what are the factors driving resilience, and how to we sustain those?  There are countless reasonable goals for land managers to choose from, many dependent upon scale, but those goals should be based on the outcome we want.

This annually-hayed prairie maintains high plant diversity but provides only one type of habitat structure for nesting birds and other wildlife species.  Depending upon the objectives for the site, that could be fine, but it very much depends upon what the manager wants to accomplish.

I feel it’s important to say this here:  I am a big proponent of both fire and grazing as management tools – you can find myriad examples of that by searching through my previous blog posts.  However, while I think combining fire and grazing can create some fantastic results, those strategies/results don’t fit all objectives.  More importantly, your particular site may or may not respond well to those kinds of fire and grazing combinations.

Let’s say your primary objective is to provide habitat for as many species of grassland birds as possible.  First, you’ll need a pretty big swath of land – many bird species have minimum habitat size requirements.  Assuming you’ve got sufficient land, the major factor grassland nesting birds respond to is habitat structure.  Some birds prefer tall thatchy structure, others like short/sparse vegetation, and others want something in-between.  A reasonable outcome-based objective might be that you want to provide all three of those habitat types across your prairie each year (and you’ll want to make sure the habitat are being successfully used by a diverse bird community).  Perfect.  Now, how will you create those habitat types?

 Grasshopper sparrows tend to nest in prairies with relatively short structure, but with some thatch (which they use to build nests) along the ground.  Some of the highest abundances of grasshopper sparrows around here are found in relatively heavily-grazed prairie.

Fall or spring fires can create short habitat structure that some birds really like to nest in.  However, some bird species (e.g., grasshopper sparrows) usually like short habitat with a little more thatch in the ground layer than is usually found in recently burned prairies.  Also, while burned areas are short and unburned areas are tall, it’s difficult to create in-between height/density habitats using only fire.  This is where other tools such as mowing and grazing might be helpful.  Mowing can reduce the height of tall vegetation and create short or mid-height structure that grasshopper sparrows, meadowlarks, and other species prefer.  Grazing can do the same and can have the advantage that cattle or bison are selective grazers, eating some plants and leaving others.  This can create structure with both tall and short vegetation mixed together and can also help suppress grasses and allow for greater expression of forbs (broadleaf plants) – something birds such as dickcissels often prefer.

Upland sandpipers prefer to nest where vegetation structure is short, but often move to sites with strong forb cover and a little patchier structure when their chicks become active.

If we’re trying to create optimal bird habitat, then, fire, mowing and grazing might all be useful tools to consider.  It’s important to understand how each tool can be used to affect habitat structure, as well as the potential risks of using each (fire can sometimes kill aboveground animals and stimulate invasive plants, grazers can sometimes target vulnerable plants and create issues via trampling).  With all of that information, you can start putting together strategies that employ the right tools, and then test those strategies against the OUTCOMES you desire.  Notice that the process I’ve just described is independent of the kinds of historic fire returns for your area or whether or not you think grazing was a significant factor in the evolution of regional plant communities.  Define your objective by the outcomes you want and test/adapt strategies based on that objective.

Other examples: At my family prairie, we aren’t using prescribed fire because we’ve been able to use grazing to meet our objectives of habitat heterogeneity and increasing plant diversity, and we use loppers/herbicide to successfully control woody invasion.  In small prairies where preserving particular plant species is the objective, a strategy using only fire or mowing could be most appropriate.  If that small prairie has rare insects or reptiles that are especially vulnerable to fire, maybe mowing is the best tool.  Regardless, the right tools and strategies depend upon the outcome-based objective.

This photo was taken in the burned patch of a patch-burn grazed prairie at Konza prairie, near Manhattan, Kansas.  The grazing created varied habitat structure because of the selective grazing by cattle.  Leadplant and other ungrazed forbs contrast with surrounding short grasses.

For ranchers and farmers who manage prairies, this same objective setting process should apply, but of course those prairies also have to help provide sufficient income to keep a family or business thriving.  Even in those cases, however, it’s still important to start with outcome-based objectives.  Those objectives can include a certain amount of needed income but should also include specific habitat or other ecological objectives.  Once you’ve decided, for example, that you really want to manage in a way that provides a certain amount of quail habitat or provides consistent pollinator resources through the season, you can look for ways to accomplish that while still providing the needed income.  When a conflict between income and habitat objectives arises, you can make the decisions that make sense to you, but at least you’re making those decisions with all the information needed to fully consider the options.

Prescribed fire can be a great tool for accomplishing some objectives, but it can also be difficult to implement for some managers.  While it is an important ecological process in prairies, employing prescribed fire should still be seen as a tool/strategy, rather than as an objective in and of itself.

There are plenty of reasonable prairie management objectives to choose from, but they should be based on outcomes rather than on tools and strategies.  Employing more frequent prescribed fire is not a good objective.  However, using more frequent prescribed fire might be a great strategy to reach a particular outcome.  (It could also be a terrible strategy, depending upon your objective.)  Don’t fall into the trap of choosing your transportation method before you know where you want to go. 

P.S. I’m sure some of you are thinking it, so let me address what might appear to be a weakness of my vacation transportation analogy.  Yes, it’s perfectly fine to start vacation planning by deciding that you want to take a cruise ship or motorcycle if the OUTCOME you really want is to ride on a ship or motorcycle.  If you don’t care where you go, the destination isn’t the outcome, it’s just a by-product of your mode of travel.  Fine.  But I think you understand what I was trying to say, right?  Sure, you could argue that conducting prescribed fires could be your objective if all you want is a legal way to light things on fire and watch them burn.  If that’s your objective, though, you’re not managing prairies, you’re lighting things on fire – and there’s a big difference.  Ok?  Ok.

A Closer Look at Prairie Roots

One of the biggest jobs of a prairie steward is to manage the competition between plants, ensuring that no species becomes too dominant and no species is pushed out of the community.  In our prairies, much of our effort is directed toward some of the stronger grass species, including big bluestem, indiangrass, smooth brome, and Kentucky bluegrass.  Left unchecked, those grasses (and a few others) can monopolize both light and soil resources and reduce plant diversity.  Our management targets those grasses with fire and grazing, often using season-long defoliation by cattle or bison to weaken the competitive ability of those grasses, opening up space and resources for other plants to flourish.  Our long-term plant data show that we’ve been able to maintain species richness and a full complement of plant species with this kind of management.

When those major grasses are weakened, one of the most obvious responses is a flush of “weedy” vegetation that quickly takes advantage of the soil and light resources that have become available.  Research has shown that growing season defoliation temporarily causes grasses to abandon some of their roots (until defoliation stops and the grasses recover), opening up space for nearby plants to grow larger and more abundant.  However, there are still many questions about the actual physical responses of grass roots to defoliation, and gaining a better understanding of that could be really important to prairie managers.  Researchers at Kansas State University are actively working on those questions right now.  Dr. Jesse Nippert, in particular, has done a lot of work on this subject, including some work on prairie shrubs that I wrote about a few years ago.

Last week, a couple of Jesse’s graduate students, Seton Bachle and Marissa Zaricor, were at our Platte River Prairies, collecting data on roots under grazed and ungrazed conditions.  In addition, Seton brought along a nifty tool called an air spade, which uses compressed air to dig into prairie soil with enough force to expel soil particles, but not so much that it tears apart the roots of plants (with the exception of the tiny rootlets at the tips).  Seton and I started talking about a year ago about the possibility of getting the air spade up here so we can look for visual evidence of grazing impacts to roots.  Marissa and Seton are both doing very in-depth (ha!) measurements of plant root responses, but I also wanted to see what’s those roots really look like.  The air spade seemed like a great way to do that.

Here is our sampling area, as seen by our drone. The bottom right portion was burned this spring and has been grazed fairly intensively since. The top left portion is unburned and has had very little grazing pressure.
Dust erupts out of the ground as Seton excavates with the air spade.

For this initial trial, we chose a part of the prairie that was burned this spring and was being grazed intensively by cattle as part of our patch-burn grazing management.  Abundant rain this year has meant that the cattle aren’t keeping the grasses as short as we’d really like, but we were still able to find some big bluestem plants that have been cropped pretty short.  As a comparison, we went across the burn line to part of the prairie that hasn’t had much grazing pressure in recent years and, because it is unburned, hasn’t had much attention from cattle this year either.  As a result, we were (ok, Seton was) able to excavate around the roots of big bluestem plants that had been grazed off to just a few inches of leaf height, as well as ungrazed plants with leaves around 12 inches high.

Here is the excavation spot in the burned/grazed patch.
Here is the unburned/ungrazed excavation site.

As Seton started blowing soil away from the roots (and I photographed the process with my camera and our drone), one of the first things that became obvious was the relatively shallow depth of the main root mass.  The work of J.E. Weaver and others has shown that prairie plants, including grasses, have some very deep roots.  However, more recent work, including that of Jesse Nippert of Kansas State, Dave Wedin at the University of Nebraska, and others, has shown that those grasses don’t appear to actually use those deep roots for much.  In fact, grasses tend to concentrate the vast majority of their root masses in the top foot or so of the soil profile, effectively monopolizing most of the moisture and nutrients there.  Forbs tend to pull most of their resources from below that, and shrubs work at even greater depths.  I’ll write about this more in a future post, but for now, just trust me when I say that this is abundant evidence for this (and many more questions being pursued).  Prairie grasses can have deep roots, but it’s the incredible root density at shallow depths that they most rely on, even during drought.

With the air spade, we could pretty easily see that most of the big bluestem roots were in that shallow depth, and only a few extended down below that.  However, as Seton pulled out fully-excavated clumps of big bluestem shoots and roots, my initial reaction was one of disappointment.  There didn’t seem to be any obvious difference in the density of roots or size of the overall root mass between the grazed and ungrazed plants.

Marissa and Seton examine the roots in the partially excavated grazed site.
Seton examines some of the roots dug out of the burned/grazed site.

My immediate thought was that because these plants had only been exposed to grazing for about a month, maybe there hadn’t been enough time to see changes in their root masses.  In addition, it might be that some of the roots were no longer active, but were still connected to the root mass for now.  We’ll be repeating this excavation process later in the season, and might see differences then that aren’t yet obvious.  In addition, we’ll look at some roots of grasses that were heavily grazed all of last season and see what those look like.  Still, I was a little disappointed not to see a bigger visual difference.

However, when Seton and Marissa looked at the roots, they pointed out something I hadn’t initially seen because I was so focused on root length and density.  The diameter of most of the roots of the ungrazed bluestem appeared to be considerably larger than those of the grazed plants.  We were working with a small sample size, but among all the plants we dug up, that size difference seemed to be pretty consistent.

An ungrazed clump of big bluestem on the left and grazed on the right.  You can’t see the length of all the roots in this image (they were similar between plants) but the ungrazed roots are noticeably thicker than the roots of the grazed plant.
Here’s another look at the difference in root thickness between the grazed plants (top) and ungrazed (bottom).

Marissa explained that thicker roots have more carbohydrates stored in them.  Plants that have been defoliated, and are trying to regrow shoots, have to pull carbohydrates from their reserves to do so – pulling them out of their roots and putting them into aboveground growth.  Whether those roots kind of deflate as the carbohydrates are pulled from them or stressed plants just create skinnier roots is something Marissa and Seton are hoping to learn from their work.  Regardless, carbohydrate storage plays into competitive ability.  Grasses rely on their storage capacity to fuel growth and withstand further stress, so differences in root diameter could be part of the answer to why grazed grasses are less competitive.  Seton and Marissa plan to examine some cross sections of the roots we dug up to see if they can see more under a microscope than we could by just looking at the roots with our naked eye.

Seton and Marissa’s actual scientific explorations will give us much better answers to questions about grazing impacts on grass roots than simply looking at a few samples, but it was fun to see the actual roots themselves.  While the differences between grazed and ungrazed plants weren’t as stark as I’d expected, I’m still looking forward to our next effort later this summer – especially because all I have to do is photograph the results of the hard work Marissa and Seton are doing!

If you’re interested, here is a short 1 minute drone video showing the excavation process.  You can also check out Seton’s science website here.

Special thank you to the Nebraska Environmental Trust for funding our drone purchase through a PIE (Public Information and Education) minigrant, administered through the Nebraska Academy of Sciences.

Diversity, Redundancy, and Resilience

Grasslands face a long list of challenges.  In many regions, habitat loss and fragmentation top that list, leaving prairies to struggle for survival as tiny isolated patches of habitat.  In addition, invasive plants and animals keep finding new footholds within both fragmented and unfragmented prairies.  Many of those invaders are aided by nutrient pollution – increasing levels of nitrogen, for example, which help species like reed canarygrass and smooth brome monopolize formerly diverse plant communities.  Most of all, the climate continues to flail crazily about, ratcheting up the temperature and tossing out more and more extreme weather events.

How can grasslands possibly survive all of that?

I’m actually pretty optimistic about the future of prairies.  Prairies are inherently resilient, and if we do our jobs as land managers and supporters of conservation, we can help ensure their continued resilience and survival.  Resilience in prairies and other ecosystems is the capacity to absorb and adapt to whatever challenges are thrown at them, while sustaining their essential functions and processes.  That resilience is built largely upon two pillars: biological diversity and the size/connectivity of the habitats that biological diversity depends upon.

Plant diversity is a key component of ecological resilience, along with the other biological diversity associated with it.  Taberville Prairie, Missouri.

We’ve severely compromised the “habitat size/connectivity” pillar in many regions of North America, but even in little prairie fragments, there is an incredible diversity of organisms, providing the countless services needed to sustain life and productivity.  In a healthy and diverse prairie, not only are all the bases covered, there is considerable redundancy built in to the system because of the number of different species present.  If one plant, animal, or microbe is unable to do its job because of drought, fire, predation or disease, another can step up and fill the role. Diversity provides redundancy, and redundancy helps ensure that prairie systems stay healthy and productive, regardless of circumstances.

It’s not hard to find examples of this kind of built-in redundancy in prairies.  In fact, you can find it within some very recognizable groups of species.  Let’s start with sunflowers.

While most people know what a sunflower looks like, you might not realize how many different kinds there are.  Here in Nebraska, we have at least nine different sunflower species, plus a lot of other flower species that look and act much like sunflowers.  Two of our official sunflowers are annuals, often classified as weeds because of their ability to quickly colonize areas of bare or disturbed soil.  The other seven species are long-lived perennials, each with its own set of preferred habitat conditions.

Plains sunflower, an annual, is a rapid colonizer of exposed in sandy prairies around Nebraska. The Nature Conservancy’s Niobrara Valley Preserve.

All sunflowers are tremendously important providers of food and shelter to wildlife and invertebrates.  There’s a reason sunflower seeds are so prevalent in bird feeders – they pack an enormous amount of nutrition into a little package.  Because of that, a wide array of both vertebrate and invertebrate animals feed eagerly on sunflower seeds when they can find them.  Sunflowers also produce an abundance of pollen and nectar, and make it very accessible to pollinators and many other creatures by laying it out on a big open platter.  It’s rare to find a sunflower in full bloom that doesn’t have at least one little creature feeding on its nectar, pollen, or both.  Grazing animals can get a lot from sunflowers as well; the forage quality of sunflowers is very high, especially before they bloom.

During or after droughts, intensive grazing bouts, fires or other events that leave bare soil exposed, annual sunflowers thrive, and they can provide abundant resources at a time when many other plant species can’t.  We see this often in the Nebraska Sandhills, where plains sunflower (Helianthus petiolaris) turns the hills yellow during the summer after a spring fire or the year after a big drought.  Plains sunflower isn’t the only plant that flourishes under those conditions, but its presence in plant communities is a great example of the kind of built in redundancy that helps ensure there are plants for animals to eat, even when many normally-abundant prairie plants are scarce or weakened.

Nebraska’s perennial sunflowers span a wide range of habitats, from wet to dry and sunny to shady.  You can find a sunflower in just about any habitat type in Nebraska.  That’s another great example of built-in redundancy, and a reason for optimism about the future.  As climate change alters the growing conditions across much of Nebraska, it seems unlikely that any habitat will change so dramatically that it will become devoid of sunflowers.  Instead we’ll probably see changes in the relative abundance of each species from place to place.  In addition, remember that what we call a sunflower is a fairly arbitrary categorization; there are lots of other wildflowers that provide very similar resources/services, including plants like rosinweed (Silphium integrifolium), false sunflower (Heliopsis helianthoides), sneezeweed (Helenium autumnale), and many more.  Those sunflowerish plants also span a wide range of habitat preferences and growth strategies, making it likely that some of them will be blooming abundantly every year, no matter what drought, fire, or grazing conditions are thrown at them.

An illustration of the general habitat preferences of several perennial sunflowers found in Nebraska.  The variety among habitats used by these species makes it likely that some kind of perennial sunflower will persist in most locations, regardless of how climate and disturbance patterns change over time.

Milkweeds are another group of organisms that demonstrate the diversity and redundancy in prairie ecosystems.  There are 17 milkweed species here in Nebraska, along with several other related species (like dogbane) that produce the same kind of sticky white latex.  While that latex is toxic to most creatures, a number of invertebrates have figured out how to feed on milkweed plants without suffering harmful effects.  Many have actually turned the toxin into an advantage by ingesting the substance and making themselves toxic to potential predators.  The most famous of these critters, of course, is the monarch butterfly, which uses milkweeds as larval hosts.

A selection of milkweed species found in Nebraska, demonstrating the variety in flower colors and shapes among the group.

When you picture a monarch caterpillar on a milkweed plant, you probably envision a tall plant with a big pink flower.  In reality, monarchs can use many (maybe all?) milkweed species as larval hosts.  Because each species of milkweed has its own unique set of preferred habitat and growing conditions, the diversity of milkweed species in Nebraska should help monarchs find a place to lay eggs regardless of weather, disease outbreaks, or other events.

The spring of 2017 provided a compelling example of this.  In most years, monarchs overwintering in Mexico fly into the southern United States and lay eggs on milkweed plants there.  The subsequent generation than flies northward into Nebraska and other  nearby states.  For some reason, many monarchs broke from that pattern in 2017, and arrived in Nebraska much earlier than normal.  This caused a great deal of concern because the milkweed most commonly used for egg laying – common milkweed (Asclepias syriaca) wasn’t up yet, and just as it started emerging, a freeze knocked it back down.  Fortunately, common milkweed wasn’t the only option available to monarchs.  Whorled milkweed (Asclepias verticillata) is also fairly common, starts growing earlier in the year than common milkweed, and is more resistant to cold weather.  Monarchs seemed happy to lay their eggs on the skinny leaves of whorled milkweed, and those of us worried about monarchs breathed a sigh of relief.  Once again, diversity created redundancy, and monarchs found habitat for their babies, even though they arrived well ahead of schedule.

A monarch egg and caterpillar on whorled milkweed earlier this spring (April 27, 2017) in Nebraska.

A broader example of redundancy and resilience in prairies includes the interdependence between bees and plants.  If you’ve followed this blog for long, you’re surely aware that there are thousands of bee species in North America, and potentially 80-100 or more species in a single prairie.  Most of those bees can feed on the pollen and nectar from many kinds of wildflowers, though some are restricted by their size or tongue length from accessing certain species. Because most plants only bloom for a few weeks, and most bees need considerably longer than that to successfully raise a family, bees require more than one kind of wildflower near their nest.  In fact, in order to support a broad diversity of bee species, a prairie needs an equally diverse set of wildflower species.  That way, a bee can find sufficient food throughout the growing season, even if drought, grazing, or other events keep some plant species from blooming in a particular year.

On the flip side, most wildflowers rely on the diversity of bees and other pollinators to ensure successful pollination.  While some insect-pollinated plants are very selective about who they let in, most rely on the availability of many potential pollinators.  If some species of bees are suffering from a disease, or have a weather-related population crash, it’s awfully nice to know that there are other bees (along with butterflies, moths, wasps, and other insects) that will still be able to transfer pollen from one flower to another.  A diverse pollinator community relies on a diverse wildflower community, and vice versa.  Diversity, redundancy, and resilience.  No matter what happens, flowers make fruits and seeds – which, by the way, is pretty important all the various creatures that rely on those fruits and seeds for food.

Bees rely on plant diversity to ensure a consistent supply of pollen and nectar across the growing season. In this case, tall thistle, an important native wildflower, is supplying food to a bee in return for pollination services.

All of us have our favorite prairie species, whether we’re fans of flowers, butterflies, birds, or some other group of organisms.  It’s easy to focus our attention on those favorite species, and worry about whether they will survive all the challenges that face prairies today.  If we really care about prairies, however, we should probably focus more on (and celebrate) the richness of species that keep prairies humming along, no matter what gets thrown at them.  The variety of yellow-flowered sunflowerish plants, the broad array of latex-producing milkweed-like plants, the complexity of the plant-pollinator relationship, and countless other examples of diversity and redundancy help ensure the survival of prairies well into the future.  That resilience is why I remain optimistic about the future of prairies.

Does Dotted Gayfeather Flower More Under Reduced Competition?

Late summer is definitely a season of yellow flowers in prairies, with goldenrods and sunflowers in the vanguard.  However, there are exceptions to the yellow rule, and one of the most prominent of those in our prairies right now is dotted gayfeather (Liatris punctata).

Dotted gayfeather punctuated an otherwise yellow-dominated plant community last week at our family prairie south of Aurora, Nebraska.

Last week, I was collecting data on the number of flowering stems within various management treatments at our Platte River Prairies, and noticed an apparent pattern with dotted gayfeather.  In particular, I thought I was seeing more flowering stems on gayfeather plants in one treatment than another right next to it.  I had a little extra time, so I tested the observation by counting the stems on a bunch of plants in each treatment, and sure enough – I was right.  Where we had burned and intensively grazed the prairie last year, there were more than twice as many flowering stems per plant (on average) as there were in the unburned, lightly grazed patch right next to it.  Both areas were in the same restored prairie (planted in 2000).  You might recall a post I wrote back in mid-August about this same site, which included photos of both the 2016 burn and unburned areas…

Error bars represent 95% confidence intervals

I collected my dotted gayfeather data pretty simply – I just walked through each part of the prairie and counted the ramets (stems) of every plant I encountered.  In total, I counted stems on 58 plants in the unburned patch and 53 plants in the 2016 burn.  The average number of stems per plant in the unburned/lightly grazed patch was 6.12, compared to 12.5 in the burned/grazed patch.  A big majority (76%) of the plants in the unburned area had 10 or fewer stems per plant, and the highest number of stems on any plant was 17.  By comparison, only 56% of the plants in the 2016 burn patch had 10 or fewer stems and eleven plants (21%) had more than 17 stems.  There were some extraordinarily large plants in the 2016 burn patch, including plants with 39, 40, 42, and even 51 stems!

One of the larger plants in the 2016 burn patch

Now, this is a single site and it’s really important not to draw too many conclusions from a one year sample.  I’ll be looking at the same site again over the next couple years to see how things change as future management is applied differently to each patch.  The unburned area is slated to be burned and grazed in 2018, for example, so it will be really interesting to see how dotted gayfeather plants look in both 2018 and 2019.  I’m not sharing my data from this year because I think there are conclusions to be drawn from it, but rather because it’s fun to speculate about what might have caused the apparent pattern.  I’m hoping some of you will enjoy speculating with me, and maybe even look around in prairies near you for similar patterns.

In that spirit, here are a few thoughts running through my head.  First of all, the 2016 burn patch in this restored prairie was grazed really intensively all of last season, which severely weakened the vigor of dominant grasses.  Coming into this season, most of those grasses were very short in stature, allowing a lot of light to hit the ground, and their root systems were greatly reduced, allowing space for a flush of opportunistic plants to flourish – including dandelions (Taraxacum officinale), yarrow (Achillea millefolium), hoary vervain (Verbena stricta), stiff goldenrod (Solidago rigida) and many others.  However, we also saw abundant seedlings of long-lived, more conservative plants as well, especially white and purple prairie clover (Dalea sp).

Many of the opportunistic plants that flourish in times of abundant light and root space do so through establishment of new plants from seeds waiting in the soil.  However, that’s not the only way plants can respond.   Most perennial plants, including dotted gayfeather, grow new stems each year from buds that are produced at the base of the plant or on rhizomes (underground stems).  Each bud represents a potential future flowering stem, and healthy plants can have quite a few of those buds and deploy them as needed.

Here is the 2016 burn patch about a year ago, after a spring burn and season-long intensive grazing. You can see ungrazed dotted gayfeather flowers blooming. but most grass leaves have been grazed short.

It makes sense to me that dotted gayfeather plants in our 2016 burn patch deployed more buds this spring than plants in the nearby unburned patch where surrounding vegetation is more dense.  Long-lived plants like dotted gayfeather should benefit from producing extra flowers/seeds in years when their competition is weakened.  Maybe abundant bud deployment happened because gayfeather plants were able to expand their root systems last year and reach new resources, or maybe the short stature of surrounding vegetation allowed more light to hit the base of the plant this spring, triggering buds to open.

Of course it’s also possible that all my speculation is complete bunk.  Maybe the plants in the 2016 burn patch are always bigger than those to the east, regardless of management, and I just hadn’t noticed before.  If so, I’ll know that after a couple more years of sampling.  Either way, it’s sure fun to wonder what might be happening and then collect data to test whether or not I’m right.  Opportunities like that are exactly why I love being a scientist.

Please share your thoughts and experiences related to this topic, and if you get a chance to go look at dotted gayfeather plants in patch-burned grazed prairie or other similar situations, let me know what you see!

Trying to Create Something Different in the Nebraska Sandhills

At our Niobrara Valley Preserve (NVP), we’re experimenting with prairie management techniques to see if we can create a wider range of habitat conditions than is found throughout much of the Nebraska Sandhills.  On many Sandhills ranches, pastures look fairly similar to each other in terms of vegetation structure.  That’s because Sandhills ranchers tend to be careful in their grazing management to avoid wind erosion that can cause “blowouts” of bare sand.  As a result, pastures are rarely grazed intensively enough to create wide expanses of bare ground.  If intensive grazing does happen, it’s usually on a small scale and/or for short periods of time, which allows for quick recovery of grasses.

The Nebraska Sandhills have tremendous innate heterogeneity.  Just in this photo, you can see areas of bare sand created by pocket gophers and/or other animals, habitat structure created by various kinds of plants, including grasses, wildflowers, yucca, and shrubs.  Vegetation height varies greatly across small areas.

Overall, the ecology of the Nebraska Sandhills seems very healthy.  It’s a huge and mostly intact grassland landscape, and because of the dry sandy soils, topography and diversity of vegetation, there is quite a bit of habitat heterogeneity that is independent of management.  As you walk across most Sandhills pastures, you will move through both short/sparse vegetation and taller/dense vegetation, and occasionally come across other structural components like yucca plants or plum thickets.  Wildlife and insect species can often find the habitat structure they need somewhere in that pasture, though it might be in a small patch surrounded by other habitat types.  That seems to be true even for many bird species, which have relatively large breeding territories.  As an example, in pastures with fairly tall vegetation, we often see and hear horned larks that are (apparently) nesting in a few small and scattered patches of the short vegetation structure they prefer.  Those patches of short habitat often occur in gravelly flat areas or in favorite feeding areas for cattle, where grass growth is weak because of frequent grazing.

This late July photo shows a portion of our west bison pasture that was burned this spring and has been grazed intensively by bison all year. Because bison are in the pasture year round, they had immediate access to the burned area and started grazing regrowth as soon as it was available.

We’re trying to figure out more about how management with patch-burn grazing or other similar grazing systems affects Sandhills ecology.  Patch-burn grazing has part of the management of our bison pastures at NVP since the early 1990’s.  Because of that, we know Sandhills vegetation can recover from fires that are followed immediately by season-long intensive grazing.  However, we still don’t know much about how many animal species might respond – positively or negatively – to the kind of large patch heterogeneity created by this kind of management.  Instead of pastures with interspersed small areas of tall and short vegetation, we’re trying to create large patches (500-1000 acre patches within 10,000-12,000 acre pastures) of each habitat type and then shift the location of those patches between years.

Plains sunflower (an annual) often becomes very abundant after fires because it germinates well in exposed soil and then thrives in the absence of strong competition from perennial grasses.  This is the current year’s burn patch in our east bison pasture, where plains sunflower tall and blooming, surrounded by short-cropped grasses.

Creating large patches of various habitat types could bring both advantages and disadvantages to different species.  As an example, large patches could create an abundance of resources that support larger and more viable populations of some animal species. On the other hand, a vole who likes thatchy habitat could wake up in the middle of a 1000 acre burn, and it would have to make a long dangerous trip to find a more suitable place to live.  Trying to evaluate those potential costs and benefits is a big challenge for us.

This landscape shot shows the abundance of plains sunflower across the entire burned patch.

One possible advantage of the kind of shifting mosaic of habitat approach we’re trying is that it helps avoid risks that come from having the same habitat conditions in the same place year after year.  Just as crop rotation can help avoid buildups of pests and pathogens, shifting habitat types from place to place could have important benefits.  For example varying the location of habitat types from year to year could limit disease outbreaks and help prevent predators or herbivores from building up large and potentially destabilizing populations.

Showy evening primrose, aka fourpoint evening primrose (Oenothera rhombipetala) where the prairie was burned in 2015 and grazed intensively in both 2015 and 2016.  This opportunistic biennial is taking advantage of a long period where grasses are weakened by prior intensive grazing and haven’t yet recovered.

The most intriguing part of our experimentation for me, though, is the idea that we could create large ‘recovery patches’ where grasses have been weakened by a full season of intensive grazing and the plant community is temporarily dominated by opportunistic, mostly short-lived plant species.  That combination of short grasses and tall ‘weedy’ wildflowers can provide excellent brood-rearing habitat for some birds and important structure for reptiles and invertebrates that need to regulate their body temperature by moving quickly from sun to shade as needed.  Studies in other landscapes have shown that this kind of recovery patch habitat creates pulses of high insect biomass, which could have numerous impacts – including the provision of an awful lot of food for wildlife.  In addition, if an abundance of opportunistic plants include species beneficial to pollinators, that could provide quite a bonanza of resources for bees, butterflies, and other insects.

Zoomed out

In most of the Sandhills, patches of  ‘weedy’ habitat tend to be in small, static and widely scattered locations such as around windmills or other places where cattle or bison frequently congregate.  We’re wondering what might happen if we created big patches of the same habitat type and shifted their location from year to year.  In our Platte River Prairies, patch-burn grazing (and similar strategies) has sustained prairie plant diversity over many years, but we haven’t looked closely for similar responses in the Sandhills.  In addition, we know a little about how birds respond to patch-burn grazing in the Sandhills, but not much about impacts on other species like lizards, pollinators, small mammals, or invertebrates.  Now we’re trying to collect data on the responses from all those different organisms.

The lesser earless lizard is often found in and around sand blowouts or other habitat patches with abundant bare sand.  Will they respond positively to much larger patches of sparse vegetation?  Can they successfully shift their population locations as we burn/graze new sites?
Will pollinators such as this plasterer bee (Colletes sp) benefit from higher abundances of flowering plants in big patches of Sandhills prairie that are recovering from season-long intensive grazing?
This is part of our east bison pasture that hasn’t burned since 2012, and has been only lightly grazed during that time period.  It should support a different array of wildlife and allow different plant species to thrive than more recently-grazed areas.  Providing a wide range of habitat types across the prairie seems beneficial for biological diversity, but we still need to test that idea in the Sandhills.

I’ve really enjoyed digging into all the questions we have about our attempts to create more habitat heterogeneity in the Sandhills.  We haven’t had time to answer many questions yet, but we feel like we’re at least creating something different than what exists throughout most of the Sandhills landscape.  A few years from now, we might conclude that the heterogeneity we created didn’t really result in any significant positive or negative impacts compared to what exists elsewhere.  If that’s the conclusion, we’ll move forward with that in mind.  On the other hand, we might find that there are some important positive (and/or negative) impacts of the shifting mosaic approach we’re testing.  In the meantime, it’s exciting to have the opportunity to try something different and watch what happens.  Stay tuned…

If nothing else, huge populations of Plains sunflower like this one in our west bison pasture provide a different (and I think beautiful) look to parts of the Sandhills landscape at the Niobrara Valley Preserve.

Should We Manage for Rare Species or Species Diversity?

Land managers constantly make difficult decisions without really knowing the long-term consequences of their choices.

Balancing the sometimes conflicting needs of rare plants like Canada milkvetch (Astragalus canadensis), pollinators, and many other components of prairie communities can be a major challenge. 

For those of you who aren’t ecologists, here are some important vocabulary terms you’ll need to know for this post. 

 1. Conservative species – plants or animals primarily restricted to “intact” or “high-quality” natural areas, as opposed to species that commonly occur in degraded habitats.

2. Species richness – the number of species found in a certain area. High species richness means there are lots of different kinds of plants and/or animals present

3. Species diversity – a kind of modified species richness that also takes into account the evenness, or relative abundance, of each species. When one site has a few dominant species and lots of uncommon ones, it is less diverse than another site with the same total number of species but with more evenly distributed numbers of individuals.


Imagine this situation:  You’re put in charge of managing a tallgrass prairie with thriving populations of several rare plant species.  The prairie is located in a highly fragmented landscape dominated by rowcrop agriculture.  The prairie has been managed with frequent spring burning for many years, and the populations of those rare plants has been pretty stable for at least the last couple of decades.  As you take over, the previous manager tells you she’d recently been considering management changes that might increase overall plant and animal diversity but would likely reduce the population sizes of some rare plant species.  You have to decide whether to stick with the existing management regime or try something different.  What would you do?

Culver’s root (Veronicastrum virginicum) is a conservative plant species found in a small subset of today’s tallgrass prairies.

It would be perfectly rational and defensible to stick with the strategy that has sustained healthy populations of rare plants for a long time.  Because those plants aren’t found at many other sites, prioritizing them in this prairie makes good sense.  However, before you lock in that choice, let’s consider some other information.

First, there is often an assumption that an abundance of rare plants is an indication that the rest of the prairie community is also intact and healthy. While that assumption seems logical, it’s not always the case.  A good example of this comes from an Illinois study by Ron Panzer and Mark Schwartz.  Their research in the Chicago region showed that neither the number of conservative plant species or rare plant species predicted the number of conservative or rare insect species at a site.  Instead, Panzer and Schwartz concluded that overall plant species richness was more important for insect conservation.

Plant diversity also helps support healthy populations of pollinators and herbivores (invertebrate and vertebrate) by ensuring a consistent supply of food throughout the year.  A wide variety of plant species allows pollinators and herbivores to find high quality food at all times, even though each plant provides those resources at different times of the season.  For this and other reasons, increasing plant species richness can increase both the abundance and diversity of animals, especially invertebrates.  In addition, managing for a variety of vegetation structure types (including a wide range of both plant stature and density) can also help support more animal diversity, including birds, mammals, reptiles, and insects.

Grazing can decrease the size of rare plant populations, especially in comparison to sites under repetitive haying or burning management. However, carefully planned grazing can also increase plant diversity and provide more varied habitat structure for wildlife and invertebrates.

Every species of plant and animal plays a certain role within the prairie community.  High species richness provides redundancy of function and helps ensure that if one species disappears or can’t fill its role, others can cover for it.  That contributes to ecological resilience – the ability of an ecological community to respond to stress without losing its integrity.  Ecological resilience may be the most important attribute for any natural system, especially in the face of rapid climate change, continuing loss and degradation of habitat, encroaching invasive species and other threats.

Aside from the benefits of managing for species richness, a strict management focus on the needs of a few species can put others at risk.  The use of prescribed fire, for example, provides a competitive edge to some plant species, but has negative impacts on other plants, as well as on some animals.  There have been vigorous arguments between advocates for frequent burning and people concerned about rare butterflies and other insects, as well as reptiles and other animals that can be extremely vulnerable to prairie fires.  Repeated intensive grazing by cattle or bison is another management strategy that favors some plant and animal species, but can negatively impact many others, especially without adequate rest periods between grazing bouts. Management that consistently provides favorable conditions for a few species at the expense of others may eventually eliminate some species from a prairie altogether, or at least reduce their ability to effectively contribute to ecosystem functioning.  If those losses lead to decreased ecological resilience, the resulting impacts may end up negatively affecting the same species a site manager is trying to promote.

Regal fritillary butterflies are very sensitive to fire, and can be eliminated from isolated prairies if the entire site is burned at an inopportune time. However, populations can also thrive in large prairies managed with a combination of fire and grazing, as long as sufficient unburned areas are available, and many of their favorite nectar plants (like this Verbena stricta) are common, or even weedy.

So, what’s the right path?  Should we prioritize management for rare or conservative species, assuming that other species don’t need as much help?  Or should we focus on species diversity and ecological resilience because we need the strongest possible natural communities in today’s challenging environment?  How should scale (size of prairie) influence decisions?

There are plenty of potential benefits and risks associated with each path, and I’m not here to tell anyone which they should choose.  In most cases, my own tendency is to focus on diversity and resilience, but I completely understand why managers would go the other way, and I think every situation needs to be evaluated independently.  For example, if a species is teetering on the brink of extinction and we need to keep it alive while we create more habitat elsewhere, I’m perfectly fine with prioritizing management to favor that species.

In other cases, I worry that we’re too sometimes unwilling to manage prairies in ways that promote changes in plant composition.  Years of repetitive management (especially frequent haying or burning) create conditions under which plant communities seem very stable.  However, that stability may be a response to consistent management rather than an intrinsic quality.  Allowing plant populations, even of rare species, to fluctuate in size, or even persist at a lower abundance than we’re used to is not the same as driving those species to extinction.  If rare species survive in smaller populations but the surrounding community is more resilient, that may be a win.  Having said that, reducing the size of rare species’ populations can make them more vulnerable to local extinction, and I don’t take that kind of risk lightly.  These are challenging issues.

This bottle gentian plant (Gentiana andrewsii) is an extremely conservative plant, and was growing in a hayed meadow in the Nebraska Sandhills where management conditions are very stable from year to year.

The hard truth is that we don’t yet understand enough about ecological systems to make these kinds of decisions confidently.  I understand the impulse to manage conservatively, sticking with what seems to have been working for a long time – especially in small and isolated prairies.  At the same time, I also think we need to build as much diversity and resilience in our prairies as we can – focusing on both plants and animals – especially in landscapes where we don’t have many left.  I’m glad managers are experimenting lots of different strategies, but we should all take responsibility for collecting data that help us evaluate our management, and keep open minds as we share what we learn with each other.  None of this is easy, but it is certainly important.

The Risks of Managing Prairies Exclusively for Plants

Prairies are often defined as plant communities dominated by grasses, sedges, and wildflowers.  However, prairies are also home to thousands of animal species, not to mention countless varieties of fungi, bacteria, and other microbes.  Animals are just as much part of the prairie as plants, and they can have immense impacts on the plant community and overall prairie function.

Mixed-grass prairie managed with periodic fire and intensive grazing. Gjerloff Prairie - Prairie Plains Resource Institute.
For most of us, prairies are characterized by the plants we see when we walk through them. Gjerloff Prairie – Prairie Plains Resource Institute. Nebraska mixed-grass prairie managed with periodic fire and intensive grazing.

Despite the importance of animals, many prairie managers and biologists focus largely on plants when evaluating the quality of a prairie or when making management decisions.  Interestingly, many ranchers do the same thing, though they tend to focus mostly on dominant grasses while biologists often look more at plant species diversity and/or rare plant species. Regardless, it is rare that the needs of harvest mice, leafhoppers, or smooth green snakes are incorporated into management plans or evaluations of prairie quality.  (A major caveat is that some prairies are managed primarily for bird habitat – either song birds or game birds – a practice that has its own set of ramifications.)

Deer mice and other small mammals are rarely considered during management planning. Small mammals and other animals have specific needs for habitat structure, however, and are also vulnerable
Deer mice and other small mammals are rarely considered during management planning. Small mammals and other animals have specific needs for habitat structure, however, and their populations can decline or disappear after several years of unfavorable habitat conditions.

To be fair, there are good reasons to give plants primary consideration in management planning.  Cattle ranchers correctly recognize that cattle feed mostly on grass, so maintaining robust stands of grasses is critical for a successful ranching operation.  For biologists and conservation land managers, plants are often good indicators of prairie health.  Plant communities are easier to assess than insect or small mammal communities, and they provide the foundation for many ecological processes.  Pollinators, for example, rely on plant diversity and abundance of flowering plants.  Many other insect species need particular plant species or groups of plant species for food and/or living quarters.  A diverse plant community also provides a consistent supply of vegetative growth and seed production for plant-eating animals.

Bees and other pollinators rely upon plant diversity to provide a consistent supply of flowers throughout the growing season. This bee (Svastra sp) is on a native tall thistle (Cirsium altissimum) in September.
Bees and other pollinators rely upon plant diversity to provide a consistent supply of flowers throughout the growing season. This bee (Svastra sp) is on a native tall thistle (Cirsium altissimum) in September.

Not only are plants helpful in assessing prairies, every plant species is also significant and worthy of conservation for its own sake. However, the same is also true for animal species.  A prairie without birds, ants, butterflies, or grasshoppers just wouldn’t be the same, and not just from an aesthetic standpoint.  The complex interactions between all the various organisms in prairies are difficult to study, but absolutely critical to ecological function.  Studies that have excluded or suppressed populations of small mammals or insects have documented tremendous changes to the plant community – usually resulting in lower plant diversity and dominance by a few species at the expense of others.

Animal communities are vital to prairie communities and ecological function, and conserving healthy animal communities relies on at least two broad factors: plant diversity and a variety of habitat structure. As mentioned earlier, most pollinators and herbivores rely upon a wide range of plant species in order to be able to find food at all times of the season, and many insects depend upon particular plant species for survival.  However, habitat structure is also critically important for animal communities, and because every animal has its own unique habitat requirements, prairies need to provide a wide variety of habitat conditions.

Habitat structure for animals is driven by factors such as the amount of plant litter covering the ground and the height and density of the vegetation.  Some animals depend upon short vegetation with lots of exposed bare ground, some need tall dense vegetation, and still others prefer something in-between – or combinations of several habitat types.  The size and distribution of habitat patches is also important.  For example, some animal species need fairly large areas of a particular habitat structure, while others thrive best in situations where small patches of short and tall vegetation are intermixed.

A variety of habitat structure types across a prairie helps ensure a diversity of animal species, including invertebrates, will thrive.
A variety of habitat structure types across a prairie helps ensure that a diversity of animal species, including invertebrates, will thrive.  This area of intensive grazing is adjacent to other patches of taller and thicker vegetation.  Restored prairie in The Nature Conservancy’s Platte River Prairies, Nebraska.
This is the same restored prairie as shown above, but in a diffrent yet
This is the same restored prairie as shown in the previous photo, but in a year when management provided different habitat structure.  Cattle have grazed much of the grass, but have left behind a diversity of blooming plants, including Canada milkvetch (Astragalus canadensis), compass plant (Silphium laciniatum), black-eyed Susans (Rudbeckia hirta), bergamot (Monarda fistulosa), and many others.  Platte River Prairies, Nebraska.

Prairie management regimes that don’t consider animals’ needs can lead to problems.  For example, prairies with relatively uniform vegetation structure provide limited options for animals, regardless of whether that structure is uniformly short, tall, or somewhere in the middle.  A subset of animal species will thrive in those prairies, but other species can experience significant population declines.  If those same conditions persist for too long, some animal species can disappear completely.  Whether or not those species return depends upon the mobility of the animals and the degree of habitat fragmentation around the prairie.

Some management tactics can also cause animal populations to disappear or decline dramatically.  While it is an important part of prairie management, prescribed burning can be particularly dangerous to animals, especially if an entire prairie is burned at once. Fire can directly kill animals, including insects overwintering or living inside plants, but animals can also suffer from the sudden loss of habitat.  These impacts are especially severe in fragmented landscapes where there is nowhere for animals with limited mobility to go for better habitat, and no way for recolonization by species wiped out by fire.  Uniform haying and intensive grazing can have some similar impacts to fire, although both tend to leave a little more habitat for at least some species.

Snakes like this red-sided garter can be vulnerable to fires that occur during the growing season. However, dormant season fires can also be very damaging for insects and other species that overwinter in grass litter or in aboveground stems of plants.
Snakes like this red-sided garter can be vulnerable to fires that occur during the growing season. However, dormant season fires can also be very damaging for insects and other species that overwinter in grass litter or in aboveground stems of plants.

Plant diversity and the survival of rare plant species are important objectives for prairie management.  However, the same can be said for animal diversity and rare animal species.  In some cases, well-planned management can largely account for the needs of both.  Providing a shifting mosaic of habitat patches across big prairies can usually facilitate plant and animal diversity, and accommodations can be made for rare species or species sensitive to particular management tactics such as fire or grazing.  Understanding the needs and evaluating responses of various groups of plants and animals, however, is crucial to successfully adapting management strategies over time.

Conserving all species is much more difficult in small and/or isolated prairies.  A single prescribed fire can potentially wipe out animal species, and repetitive use of any management tactic, including fire, grazing, haying or rest risks eliminating species as well.  Read more about the challenges of managing small prairies here.

In both large and small prairies, setting clear objectives for management is very important.  Ideally, those objectives will accommodate the needs of most or all animal and plant species and sustain ecological resilience.  In reality, it’s more likely that the needs of some species will have to be sacrificed or given less priority than others.  As an example, frequent burns might sustain high populations of many plants (including some rare species) and help suppress invasive trees or grasses, but are likely to eliminate some species of butterflies and other invertebrates, and potentially some snakes and other vertebrates as well.  Alternatively, applying periodic patchy grazing and rest treatments in the same prairie could increase habitat heterogeneity to the benefit of many animals, but could reduce the relative abundance of some sensitive plant species while stimulating higher populations of more grazing tolerant plants.

These kinds of management decisions can be extremely difficult, and there are no easy answers.  The disappearance of any species from a prairie is a big loss, particularly at isolated sites, and we don’t yet know how to predict the ripple effects of losing most species.  Even when management decisions don’t directly eliminate species, reducing population sizes can make species more vulnerable to diseases or other factors that could eventually wipe them out.

Regal fritillaries are
The regal fritillary butterfly is one of many prairie animals that has been shown to be vulnerable to disappearing from prairies because of incompatible management.  Even for fairly mobile species like butterflies, recolonization after local extinction is far from assured, especially in fragmented landscapes.

No matter what management decisions are made, it’s crucial that land managers consider the needs of as many species as possible – including both plants and animals.  It’s not necessarily wrong to manage a prairie primarily for plant diversity or to sustain populations of rare plants.  It’s also understandable that a cattle rancher would want to sustain consistent vigorous stands of grass.  However, in both cases, managers need to acknowledge and accept that optimizing conditions for a particular suite of plant species will lead to negative consequences for other species, including both animals and plants.

Hopefully, continuing research and experience will help us better understand the inescapable tradeoffs that come with these kinds of difficult decisions.  For now, the impacts of losing plant or animal species and the potential for those losses to affect ecological resilience are still very unpredictable.  The best we can do is to be clear and honest with ourselves and others about why we’re making decisions, and do our best to evaluate the results and learn as we go.

 

If you’re interested in learning more about how excluding or suppressing animal populations can lead to unexpected and complex reactions in grassland communities, here are a couple example research papers.

Herbivory and Plant Species Coexistence: Community Regulation by an Outbreaking Phyotophagous Insect.  Walter P. Carson and Richard B. Root.  2000.  Ecological Monographs 70(1):73-99.

 Secondary plant succession: how is it modified by insect herbivory?  V.K. Brown and A.C. Gange. 1992. Vegetatio 101:3-13

Massive and Distinctive Effects of Meadow Voles on Grassland Vegetation.  2006.  Henry F. Howe, Barbara Zorn-Arnold, Amy Sullivan and Joel S. Brown, Ecology 87(12):3007-3013

Effects of Coyote Removal on the Faunal Community in Western Texas.  1999.  Scott E. Henke and Fred C. Bryant.  Journal of Wildlife Management 63(4):1066-1081

Trusting the Resilience of Prairies

Note to my son (and others who mainly follow this blog to see if there are cool pictures or pictures of them):  This is a pretty long and involved post – sorry.  The first picture is probably the best one, though there are a couple other decent prairie photos further down (though none with you in them).  The other pictures are more instructional than aesthetically pleasing.  Don’t worry, I’ll put up some better photos later this week.

Restored sand prairie at The Nature Conservancy's Platte River Prairies, Nebraska. This prairie
Restored sand prairie at The Nature Conservancy’s Platte River Prairies, Nebraska. This prairie was seeded in 2002 and has been managed with sporadic intensive grazing and fire.

Great Plains grasslands are more resilient than most of us give them credit for.  Just recently, for example, they survived the drought of 2012, the worst single year drought on record in many places (including at our Platte River Prairies).  In a post I wrote during 2012, I compared that drought to similar conditions described by famous prairie ecologist J.E. Weaver back in the 1934.  In both cases, prairies recovered nicely.  In fact, in a 1944 paper, Weaver and collaborator Frederick Alberts provided a detailed summary of how prairies in Iowa, Nebraska, and east-central Kansas persevered and recovered from repeated drought conditions between 1933 and 1943.

This is a brief summary
This brief summary was part of the 1944 paper referenced above that documented how prairies reacted to the drought years of the 1930’s.  The paper is worth reading if you’re interested in how prairies might respond to droughts in the future.  You can click on the image to make the print larger.

Nebraska prairies have also shown resilience to intensive fire and grazing – historically by bison and currently by cattle.  Chronic overgrazing, of course, can decrease plant diversity and cause cascading negative impacts on prairie animals and critical ecological processes.  However, most prairies can easily withstand periodic bouts of intensive grazing followed by comparable rest periods.  We’ve been tracking plant community responses to this kind of fire/cattle grazing management in our Platte River Prairies since 2002 and have seen plant diversity remain stable.  Even grazing-sensitive plants such as rosinweed (Silphium integrifolium), Canada milkvetch (Astragalus canadensis), prairie clovers (Dalea sp.) and others have maintained their populations.  Likewise, at our Niobrara Valley Preserve in the Nebraska Sandhills, prairies managed with more than 25 years of periodic fire and intensive bison grazing are still healthy, diverse, and full of wildlife.

Since coming to dominance in the Great Plains after the last ice age, prairies have survived and thrived through long droughts (some lasting multiple decades), severe fires, and intensive grazing episodes.  Yes, we’ve managed to destroy and degrade many prairies through tillage, herbicide use, and chronic overgrazing, but those are departures from the kinds of stresses prairies have evolved with over time.  The more time I spend in Nebraska prairies, the more important I think it is to run prairies through their paces now and then.  That includes beating them up with periodic intensive grazing.

Ragweed
Western ragweed is visually dominant this summer in this part of my family prairie which is recovering from being grazed hard most of last year.  Big bluestem and other grasses are still present, but are weakened from last year’s grazing.  Stiff sunflower and other perennial forb populations are expanding.

Not only can prairies rebound from droughts and intensive grazing, some aspects of prairies seem to depend upon those patterns of disturbance and recovery.  As we’ve experimented with variations of patch-burn grazing over the years, I’ve observed a consistent response pattern from plant communities.   We burn a patch of prairie, let cattle or bison graze it hard all season and then provide a different burn patch for the grazers the following year.  In the year following fire and grazing, prairie patches get a weedy look to them because dominant grasses are weakened by the previous year’s grazing and there is open space for new plants to establish.  Often, I see an increase of roughly 25-30% in the number of plant species found at the 1 m2 scale in the year after grazing.

Many of the plants that fill spaces left by weakened grasses are opportunistic (‘weedy’) species that grow, bloom, and produce copious amounts of seed within a year or two – and most of those plants disappear within a year or two as grasses reassert their dominance.  In addition to those short-lived plants, however, I also see expansion of long-lived perennial plant populations that are taking advantage of weakened competition.  Prairie clovers, leadplant, perennial sunflowers, and many others spread via both rhizome and seed during those periods when grasses are weakened.  What I don’t see is the death or disappearance of plants following intensive grazing bouts that last a year or two.  Even plants – both grasses and forbs – that are cropped close to the ground and kept that way by repeated grazing regain their vigor within a few years of rest.

Prairie animals also seem to benefit when prairies go through periods of severe stress and recovery.  For example, many of the plant species that flourish following intensive grazing (and/or severe drought) are very attractive plants for pollinators.  Annual sunflowers, hoary vervain (Verbena stricta), black-eyed Susans (Rudbeckia hirta), and biennial primroses (Oenothera sp.) are just a few examples.  The prolific seed production by those opportunistic plants also provides a bonanza of food for insects and wildlife species.

Annual plains sunflowers (Helianthus petiolaris) were super abundant throughout the Nebraska Sandhills in 2013, following the severe 2012 drought. I would love to see this kind of prolific blooming of short-lived plants on portions of our Niobrara Valley Preserve each year.
Plains sunflower (Helianthus petiolaris), an annual, was super abundant throughout the Nebraska Sandhills in 2013, following the severe 2012 drought. I would love to see this kind of prolific blooming of short-lived plants on scattered areas of our Niobrara Valley Preserve each year.  We are trying to create that scenario by intensively grazing selected pastures/patches of prairie each season and then letting them recover while others are hit hard.

Animals also benefit from habitat structure created by patterns of intensive grazing and recovery.  Because every animal has its own individual habitat preferences, the highest diversity of animals are found in prairies with patches of intensively grazed vegetation, patches of recovering vegetation, and patches of tall/thatchy vegetation.  Mobile animals can move to their favorite habitat structure and less mobile animals need only wait a few years for conditions that allow them to prosper.

Vegetation recovering from intensive grazing can provide particularly unique and valuable habitat.  Habitat structure consisting of short, weakened grasses and tall ‘weedy’ forbs provides wonderful brood-rearing habitat for birds such as grouse, quail, and pheasants, for example.  The low density of grass leaves and litter at ground level makes it easy for young birds (and other wildlife) to move around and feed beneath a canopy of protective cover.  Coincidentally, insect abundance also skyrockets under those same conditions, which is good for insects and also for the wildlife that eats them.

This 2013 photo shows a restored Platte River Prairie recovering from severe drought, fire, and intensive grazing from the previous year. Grasses are weak, but opportunistic forbs are prolific, including many that provide excellent resources for pollinators and lots of seeds for insects and wildlife.
This 2013 photo shows a restored Platte River Prairie recovering from severe drought, fire, and intensive grazing from the previous year. Grasses are weak, but opportunistic forbs are prolific, including many that provide excellent resources for pollinators and lots of seeds for insects and wildlife.

What are we afraid of?

I’m more and more convinced of the importance of putting prairies through periods of stress and recovery, especially when those stresses are applied in a way that provides a shifting mosaic of stressed, recovering, and full strength vegetation patches across a prairie.  No matter how hard we have grazed prairies, even during severe and extended drought periods, the plant communities have always bounced back during the recovery periods that follow.  In addition, my own observations and data collected by many researchers have documented benefits to wildlife and invertebrates that come from the variety of habitats provided by this kind of management.  (You can read more about patch-burn grazing here and the way I manage my family prairie here.)

While I’m confident that it’s valuable to beat prairies up now and then, I’m having a hard time convincing others to try it.  Both ranchers and public land managers tend to have strong visceral reactions when I walk them through patches of really intensively grazed prairie.  Ranchers are often convinced that I’ve killed the grasses and created weed and erosion problems that will never go away.  Conservation area managers worry about potential weed invasions too, and some also wonder if sensitive wildflowers will survive the stress.  Many of those land managers also flinch at the lack of habitat structure for wildlife species they care about.

Walking tour participants from an intensively grazed patch into a nearby area of recovering vegetation doesn’t usually help things.  Ranchers tend to see the flush of opportunistic plants as validation of their fears about dead grass and weed problems, even when I next show them patches where the grasses have regained dominance after a few years of rest.  Some wildlife managers recognize the value of the weedy vegetation as habitat, but worry about the perceptions of neighbors and the public who just see weeds, not habitat.  Others see the weedy vegetation as a sign that the plant community has been degraded, despite the fact that the plant species they like better haven’t gone away.

This fenceline photo from our family prairie was taken in September 2014. The pasture on the left had been grazed hard all season, while the one on the right had been largely rested for more than a year.
This fenceline photo from our family prairie was taken in September 2014. The pasture on the left had been grazed hard all season (the grass is about 2-3 inches tall), while the one on the right had been mostly rested for more than a year.  Besides helping to increase plant diversity, this kind of grazing also creates a variety of habitat conditions across the prairie.
This is the same fenceline as shown above (just slightly uphill). The grasses on the left have recovered from the long intensive grazing in 2014 and are ready to be hit hard again next season. The ragweed on the right is enjoying a good year after that area was grazed intensively for most of 2015.
This is the same fenceline as shown above (just slightly uphill) as it looked in mid-August of 2016. The grasses on the left have recovered from the long intensive grazing in 2014 and are ready to be hit hard again next season. The ragweed on the right is enjoying a good year while the competing grasses are recovering from being grazed intensively for most of 2015

To be clear, I’m not suggesting that all prairies would benefit from the kind of periodic intensive grazing I’m talking about here.  Some prairies, for example, are simply too small and isolated.  There are big logistical challenges associated with fencing and providing livestock water in small prairies.  More importantly, there just isn’t space to graze some portions of small prairies while leaving other areas to rest and recover.  (Small prairies have a number of other challenges that make any kind of management difficult.  If you’re interested, I tried to address some of those in a blog post several years ago.)

I also have a number of lingering questions about how best to apply intensive grazing and recovery periods to prairies.  For example, I strongly suspect that the best results come from intensive grazing bouts that last between a couple months and a full growing season.  Grazing for only days or weeks doesn’t seem to stress the grasses as much as longer periods of repeated grazing on those plants.  In addition, different grass species grow strongly at different times of year.  Because of that, grazing for a short time can just shift dominance from the grasses growing strongly during the grazing bout to species that peak in their growth after grazers leave.  Since my objective is to really weaken the entire grass community, I don’t think short grazing periods will do the job – but I’d like to test that more.

This is one of our restored prairies at the end of August of this year. The grasses were grazed hard all season, and eventually went dormant during a hot dry spell. Many of the forbs were also grazed, but not all of them. This site will likely be very weedy looking next year.
This is one of our restored Platte River Prairies at the end of August of this year. The grasses were grazed hard all season, and eventually went dormant during a hot dry spell. Many of the forbs were also grazed, but not all of them. This part of the site will likely be very weedy looking next year.
This is the same restored prairie as shown above, but the photo was taken several years ago during a year it wasn't being grazed. It will look like this again in a few years.
This is the same restored prairie as shown above, but the photo was taken several years ago during a year it wasn’t being grazed. It will look like this again in a few years.

I’d also love to see more data on the responses of various vertebrate and invertebrate populations to intensive grazing, recovery periods, and the overall mix of habitat provided by the kind of management I think is important.  There is strong research showing benefits to small mammal and bird communities, and some information on invertebrates, but only some of them.  Learning more about the response of reptiles and a wider selection of invertebrates to this kind of grazing management would be really helpful.

In the meantime, however, I’m going to keep beating up my prairies.  Not only do I think they can take it, I think the prairie communities I work with thrive best under that kind of management.  (I will keep an eye on what happens, however, constantly vigilant for signs that I’ve gone a little too far.)  I’ll also keep trying to convince others to stop babying their prairies so much.  I’m hoping I can find a few ranchers willing to push pastures a little harder than they usually do – allowing longer rest periods to compensate, of course.  That shouldn’t require changing stocking rates, but might provide some really nice benefits for pollinators and wildlife species.  I know I’m going to continue to face skepticism from many corners, but I really think this concept needs to be explored further.  Prairies have shown their resilience over thousands of years.  I think we can trust that kind of track record.

So…who’s with me?

The Role of History In Today’s Prairie Management

Past performance is not necessarily indicative of future results.

I’m no expert in financial investing, but I’d like to retire someday, so I muddle along the best I can.  As I skim through various financial statements and investment newsletters, I often see some variation of the disclaimer above.  The concise statement emphasizes that while history is important, many factors change over time, and we shouldn’t simply assume that what happened previously should drive what we do now.

I was thinking about this statement and its implications while attending the North American Prairie Conference last month.  During presentations and hallway discussions, the topic of history came up frequently.  How often did prairies burn prior to European settlement?  Were bison only abundant in eastern tallgrass prairies after human populations crashed during the smallpox catastrophe?  What was the role of big native ungulates like elk in suppressing woody plants?

Fire
We have reasonably good data on the historic fire frequency in prairies around the U.S.  How should that information drive today’s prairie management?

Questions like those are fascinating to contemplate, and important to our understanding of how prairies have changed over time.  Which of us wouldn’t jump at the opportunity to step into a time machine and go see North American prairies in the 1400’s or other historic times?  Wouldn’t it be fantastic to somehow find and pore over hundreds of years of data on bison population numbers, plant species composition, elk feeding patterns, and lots of other grassland phenomena?  While, that kind historic data is very limited, mining what we do have is fascinating and instructive.

However, just as with stock market investments, we can’t just look to the past to guide what we should do in the future.  The business world has evolved over time.  Simply investing today in the same corporate stocks that were profitable 30 or 60 years ago wouldn’t make a lot of sense.  Instead, we need investment strategies that fit today’s world.  Many companies disappeared over time because their products became obsolete.  Those that are still around, like General Electric, Nokia, and IBM, reinvented themselves.  Why?  The business landscape changed and they changed with it.

The prairie landscape has changed too.  Row crop agriculture and other human developments have replaced grassland across huge swaths of our country, leaving many prairies relatively small and isolated.  Trees and shrubs have flourished in landscapes where they were once scarce, and woody encroachment into small prairies now comes from all directions.  Many new species of plants and animals have found their way into North America, and some have become very aggressive.  Significant amounts of nitrogen from industrial and agricultural sources now enter grasslands by both air and water, changing soil chemistry to favor some plants over others.  Finally, prairies have endured a century or two of impacts from factors such as fire suppression, livestock grazing, haying, and broadcast herbicide use.  Today’s remaining prairies don’t look or function as they did a century or two ago.

corn
Prairies today exist within landscapes that are dramatically different from what they looked like historically.  Row crop agriculture has replaced grassland across much of the Midwest and Great Plains, and trees, invasive species, and many other factors threaten the remaining patches of prairie.

Big changes to prairies and surrounding landscapes mean that land managers face equally big challenges as we try to sustain biological diversity and ecological function.  For most managers, invasive species suppression is our most time consuming and expensive task.  Because of that, we are always searching for new ideas, strategies, and technologies to help us be more effective and efficient.  The herbicides we use to kill invasive plants were not part of the prairie ecosystem a couple hundred years ago, but I can’t imagine trying to do our job without them.  Similarly, brush mowers and the tractors that pull them are certainly not historically accurate, but they are invaluable when creating firebreaks or mowing down large patches of encroaching brush.

Today, land managers’ decisions about when to burn a prairie should be based on the myriad management objectives we face rather than on what the historic average fire frequency might have been at that site.  In many prairies, managers struggle to weigh the benefits of frequent fire to control brush and other invasive species against the potential impacts of frequent fire on vulnerable insects, reptiles, and other species.  Looking at historic fire patterns can help us understand how prairies developed, but today’s fire patterns need to address current challenges and help us sustain our imperiled grasslands.

Similarly, studying the historical population abundance of bison or elk can teach us about how those species influenced prairie communities long ago, but decisions about grazing as a contemporary management strategy need to be made based on today’s objectives and needs.  I wrote last week about the introduction of bison into the Nachusa Grasslands in Illinois, and attempts to capture the impacts of bison grazing at that site.  I’m sure the staff at Nachusa have been in numerous discussions about what historic bison populations were like in what is now northern Illinois.  The decision to bring bison in, however, was not based on history, but rather on defined needs for habitat structure and plant community management.  Nachusa staff are hoping to see more diverse grassland bird communities, for example, and positive effects on a wide variety of mammals, reptiles, and invertebrates.  They also hope bison will help maintain high plant diversity.  In particular, they hope to increase the long-term survival of relatively short-lived plant species that often disappear over time in restored prairie.

bison
Bison and cattle grazing can be useful in meeting some prairie objectives, but is not appropriate for all sites.

Here in Nebraska, The Nature Conservancy uses both cattle and bison to achieve prairie management objectives.  Grazing strategies are designed with specific objectives in mind, and we collect as much data as we can to evaluate the impacts of grazing on plant and animal communities.  Grazing helps us suppress the vigor of both non-native invasive grasses and aggressive native grasses and foster a more diverse plant community.  Plant species that would otherwise be outcompeted by dominant grasses can usually maintain strong populations under various combinations of intensive grazing and long rest periods.  Both cattle and bison can also help us create a wide variety of habitat conditions, including large areas of both short/sparse and tall/rank vegetation and other areas where patches of short and tall vegetation are intermixed.

Just as with fire, mowing, and herbicide use, the value of grazing as a prairie management tool needs to be evaluated not by its historic role in local grasslands but on its potential utility today.  In many prairies, grazing is not feasible or does not fit with management objectives.  For example, grazing is unlikely to make sense in small isolated prairies where wildlife/insect diversity is limited more by habitat quantity than habitat structure, and where plant composition objectives can be met through other means.  At larger sites, however, grazing may allow managers to provide more habitat variety and/or manipulate plant competition in positive ways.  Regardless, decisions about whether or not to graze should be based upon how grazing might help address current management challenges, not upon historic populations of bison or elk.

Prairie management is complicated and we have a lot left to learn.  We can’t afford to be overly conservative or rely too much on what happened long ago.  Imagination and experimentation are crucial components of adaptation, and we desperately need to keep adapting to new challenges if prairies are going to survive.  Companies like General Electric, Nokia and IBM rightly celebrate their history, but they also have to innovate and evolve to keep up with the changing landscape.  Prairie managers need to innovate and evolve to keep up with changing landscapes too.  Let’s learn what we can from the past but keep looking for new ideas and tactics so we can keep prairies healthy and vibrant well into the future.

After all, prairie conservation is worth the investment, right?

Returning to Nachusa Grasslands

Last week, the Hubbard Fellows and I attended the 24th North American Prairie Conference (NAPC) in Normal, Illinois.  The NAPC is always an enjoyable and thought-provoking conference that brings together scientists, photographers, land managers, poets, and prairie enthusiasts from across the country.  This one was no exception, and it was great to be back in Illinois, where there is very little remnant prairie left but much concern about the remaining pieces.

Prairie dock (Silphium terebinthinaceum) at The Nature Conservancy's Nachusa Grasslands near Franklin Grove, IL. We don't have prairie dock in Nebraska and I love seeing its gigantic basal leaves when I travel east.
Prairie dock (Silphium terebinthinaceum) at The Nature Conservancy’s Nachusa Grasslands near Franklin Grove, IL. We don’t have prairie dock in Nebraska and I love seeing its gigantic basal leaves when I travel east.

On Tuesday, the Fellows and I joined the field trip to The Nature Conservancy’s Nachusa Grasslands, one of my very favorite places on earth.  Bill Kleiman, Cody Considine, and an impressive array of volunteer stewards do fantastic work to restore and manage prairie on about 3,500 acres of land.  The diversity and beauty of their restored prairies is unmatched at any site I’ve been to.  However, the restorations are not there as flower gardens, but as habitat designed to defragment and enhance the prairie landscape.

Bumblebees and other invertebrates were abundant at Nachusa (including Japanese beetles like the one right above the bumblebee - I've never seen so many in a prairie before).
Bumblebees and other invertebrates were abundant at Nachusa. They contributed to the cacophany of color, movement, and noise at the site.
Former Nachusa staffer Mike Saxton led us through a young prairie planting where the plant diversity was already impressively high.
Former Nachusa staffer Mike Saxton led us through a 3rd year prairie planting where the plant diversity was already impressively high.
The abundance of showy flowers is almost overwhelming in some of the restored prairies, but the plant communities are also full of smaller and less auspicious species that help build the ecological integrity of the site.
The abundance of showy flowers is almost overwhelming in some of the restored prairies, but the plant communities are also full of smaller and less auspicious species that help build ecological function.
Carl Kurtz, a well-known prairie restoration guru in Iowa stands next to a thimbleweed plant we were admiring. Neither of us had ever seen the plant grow so large.
Carl Kurtz, a well-known prairie restoration guru in Iowa, stands next to a thimbleweed (Anemone cylindrica) plant we were admiring. Neither of us had ever seen the plant grow so large.

I last visited Nachusa a couple years ago as they were preparing to introduce bison to the site.  The bison are settled in now, and it was fascinating to get a brief look at how those animals are interacting with the tallgrass prairie there.  Nachusa Grasslands staff did a great job of engaging scientists to collect baseline data prior to the bison’s arrival and they are now measuring some of the early impacts.  Watching how grazing bison change the plant and animal communities at the site will be a long-term but invaluable addition to our understanding of tallgrass prairie ecology.

I only saw the Nachusa bison from a distance, so didn't get any photographs of them. I did, however, photograph the signs they have posted around the perimeter of the bison-grazed prairie.
I only saw the Nachusa bison from a distance, so didn’t get any photographs of them. I did, however, photograph the signs they have posted around the perimeter of the bison-grazed prairie.  I am a big fan of these signs.
Interestingly, the bison seemed to have been spending most of their time grazing in some of the less diverse restored prairies. However, they were certainly impacting the vegetation structure of those places they grazed.
Interestingly, the bison have been spending much of their time grazing in some of the less diverse restored prairies. However, they were certainly impacting the vegetation structure of those places they grazed – creating many patches of short-cropped plants in and amongst the taller flowers.

For various reasons, about 3/4 of the bison area was burned this spring.  The bison were certainly preferentially grazing the burned area, but because so much was burned this year, they didn’t create large areas of short vegetation.  Instead they created sporadic small grazing lawns throughout much of the burned area.  It will be really interesting to watch how that habitat heterogeneity changes which animals use the prairie and how they use it.  We were already seeing evidence of critters that like short vegetation (e.g., thirteen-lined ground squirrels) in areas where the plants normally grow too thick for them.

The bison were grazing primarily (though not exclusively) grasses, punching holes in the tall vegetation.
The bison were grazing primarily (though not exclusively) grasses – punching holes in the tall vegetation.  Those “grazing lawns” can be really valuable as sunning spots for invertebrates and reptiles, and can also create opportunities for new plants to germinate and establish.
This thirteen-lined ground squirrel burrow was evidence of habitat changes favoring animals that like short vegetation. Researchers will be looking for more of that among bird, mammal, insect and other communities.
This thirteen-lined ground squirrel burrow was evidence of habitat changes already favoring animals that like short vegetation, even in small patches.  Larger areas of concentrated grazing can provide habitat for birds (like upland sandpipers) and other species that need short vegetation on a larger scale.
We saw plenty of spots where new plants were germinating where bison had cropped off competing grasses, including these ragwort (Packera sp) seedlings and the purple coneflower (Echinacea sp.) seedling in the bottom right.
We saw plenty of spots in which new plants had germinating where bison had cropped off competing grasses, including these ragwort (Packera sp.) seedlings and the purple coneflower (Echinacea sp.) seedling in the bottom right.
Interestingly, most of the common milkweed plants we saw in the bison area had been grazed. We see the same thing in cattle pastures in Nebraska. We assumed bison were eating the milkweed, but deer, box turtles, and other animals could also be culprits.
Interestingly, most of the common milkweed plants we saw in the bison area had been grazed. We see the same thing in cattle pastures in Nebraska. We assumed bison were eating the milkweed, but deer, box turtles, and other animals could also be culprits.
Some bison impacts are unrelated to cropped vegetation, including bare ground created by wallowing, and the concentration and redistribution of nutrients through manure - something capitalized on by this mushroom.
Some bison impacts are unrelated to cropped vegetation, including bare ground created by wallowing, and the concentration and redistribution of nutrients through manure – something capitalized on by this mushroom.

There was much discussion at the conference about the historical abundance and impacts of bison in eastern tallgrass prairie (more on that in a future post) but the introduction of bison to Nachusa Grasslands was not done because of history.  Instead, staff and volunteers are hoping that bison will catalyze more diversity in plant and animal communities in ways that weren’t possible with only fire and mowing management.  The science used to evaluate those impacts should teach us more about tallgrass prairie, it’s ecology, and its potential.

Nachusa's Cody Considine surveys the prairie where bison are augmenting an already complex prairie community.
Nachusa’s Cody Considine surveys the prairie where bison are augmenting an already complex prairie community.