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.

A Visual Illustration of Plant Diversity’s Importance

Last week, I took some photos that powerfully demonstrate the importance of plant diversity.

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Research plots at The Nature Conservancy’s Platte River Prairies.

Several years ago, we created some research plots to help us learn more about how plant diversity interacts with ecosystem function.  As you can see above, the plots include a grid of squares (3/4 acre in size), each planted with one of three seed mixtures: monoculture (big bluestem), low diversity (grasses and a few forbs harvested in the fall), and high diversity (100 species).  Working with academic partners, we have several research projects underway, including a couple that demonstrate the influence plant diversity has on the spread of invasive plant species.

Other researchers have found similar relationships between plant diversity and resistance to invasive species, but that is only one of many benefits from having a wide variety of plants in a prairie.  Both herbivores and pollinators benefit from having a broad selection of food choices available to them.  During extreme weather conditions (hot, dry, wet, cold), high diversity prairies always have plants that flourish under those conditions and help provide habitat and food conditions for animals.  Most importantly, because of these and other reasons, prairies with high plant diversity also have high total biological diversity, including more species of microbes, insects, other invertebrates and vertebrates.  That overall diversity is important for its own sake, but also because of the role each species plays in the functioning of the ecosystem.

The aerial photo I took from our small drone last week illustrates another benefit of plant diversity; prairies with high plant diversity have green vegetation for more of the growing season.  Every plant species starts and ends their growth period at different times.  Some start early, bloom, and are done before summer even starts.  Others bide their time and don’t bloom until late in the fall.  When you mix all those species together in one prairie, you end up with consistent, but ever-changing, availability of nutritious vegetation and flowers throughout the growing season.

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Labeled plots, showing the location of the various treatments.

Our monoculture research plots (big bluestem only) looked very different from our other plots last week because big bluestem was just starting to grow (on April 23).  Even after we burned all the plots this spring, allowing the soil to warm earlier than it otherwise would have, the most advanced big bluestem plants only had leaves of a few inches in length.  Our low diversity plots (mostly grasses) showed more green, but only due to the presence of one grass species, Canada wildrye (Elymus canadensis), a cool-season grass that begins its grown early in the year.  By contrast, the high-diversity plots had many plant species growing, with some close to blooming.

The monoculture plots were planted only with big bluestem,
The monoculture plots were planted only with big bluestem, which was just barely starting to grow last week.
Low diversity
The low diversity plots were slightly greener than the monoculture plots, mainly because Canada wildrye was growing quickly (most of the other grasses were just breaking dormancy).
high diversity
The high diversity plots had numerous species showing vigorous growth, even early in the season.

Although the visual differences between plots on April 23 are striking, they are ecologically significant as well.  Invertebrate and vertebrate herbivores (including cattle, if the plots were grazed) can find a variety of forage options in the high diversity plots right now – far more than in the low diversity or monoculture plots.  Within a week or so, the high diversity plots will also have several different kinds of wildflowers in bloom, providing resources for early-season bees and other pollinators.  The low diversity and monoculture plots will have far fewer resources for pollinators throughout the season.  Furthermore, invasive plants species trying to establish themselves within the high diversity plots face stiff competition from plants using wide range of growth strategies.  They will find a smaller amount of resistance in the other plots, where less diverse plant communities are not as efficient at taking up space and fully utilizing resources.

Plant diversity is incredibly important in natural systems for a variety of reasons, only a few of which are mentioned here.  We still have a lot to learn about how plant communities function, and how plant diversity plays into that.  However, we already know enough to recognize the value of having numerous players in the game.  It was fun to see a visual demonstration of that value last week.

 

Media Coverage of Our Restoration Work

Our friends at Platte Basin Timelapse (PBT) created a very nice radio piece about our restoration work that aired on NET Radio (Nebraska Educational Telecommunications) today.   The link below includes that audio, along with a transcript and short video of our staff harvesting, mixing, and planting seed.  You can also see video of me describing what we’re doing and why.

It’s always difficult to distill the complexities of land management and restoration into sound bites and video clips, but this was a very good description of our work.  I really appreciate the time and consideration that Ariana Brocious, Peter Stegen, and others at PBT put into this project.

If you’re interested, you can see and hear the story HERE.

Ariana Brocious (with headphones) and Pete Stegen (green coat) collect audio and video footage as we prepare to overseed a degraded prairie back in January of this year.
Ariana Brocious (with headphones) and Pete Stegen (green coat) collect audio and video footage as we prepare to overseed a degraded prairie in January of this year.

 

 

Why Does Plant Diversity Matter? Help Us Figure It Out!

How important is plant diversity in restored prairies?

Are diverse prairies more resistant to drought and invasive species than less diverse prairies?

How does plant diversity influence invertebrate communities and their ecological functions?

These kinds of questions have been the focus of multiple research projects in our Platte River Prairies over the last decade or so.  We have numerous restored (reseeded) and remnant (unplowed) prairies that provide excellent field sites, and have also established two sets of experimental research plots to help focus specifically on questions related to plant diversity.  Those plots are 3/4 acre (1/3 ha) in size and represent varying levels of plant diversity, allowing us to investigate the functional differences between them.  Researchers from the University of Nebraska, Kansas State University, the University of Illinois, and Simpson College have been involved in data collection efforts so far.

2013 photos from
2013 photos from our experimental research plots.  The plots from left to right were planted to a monoculture (big bluestem), a low diversity mixture (mostly grasses and a few late season wildflowers) and a high diversity mixture (100 plant species).  We are investigating functional differences between these kinds of plant communities.

Craig Allen, Leader of the Nebraska Cooperative Fish & Wildlife Research Unit, and I are hoping to take the next step in these efforts by bringing on either a PhD or Post-Doctoral Research Associate.  We have data to build upon, including some intriguing results regarding invasive species and insect herbivory rates at varying levels of plant diversity, but want to greatly expand upon those data.  If you or someone you know is interested in these kinds of questions, please read below and contact Craig or me with questions.

Here is the official description of the position:

Ph.D. or Post-Doctoral Research Opportunity:  Grassland diversity, restoration and resilience

Ph.D. graduate research assistantship or Post-Doctoral Research Associate.  Available starting in May 2015, to investigate the relationship between grassland restorations and ecosystem services and resilience.  The assistantship (or Post-Doc) is with the Nebraska Cooperative Fish and Wildlife Research Unit, in the School of Natural Resources at the University of Nebraska, working closely with the Nature Conservancy scientists and resource managers.   The research project will include a synthesis of literature to identify prominent knowledge gaps related to the restoration of grasslands and resilience.  In addition to synthesis, field work will occur on a suite of restorations in central Nebraska.  Some questions of interest are listed below, but ultimately, successful candidates will be expected to develop a specific research project(s).  The candidate could approach this project from a broadly ecological, or botanical, or entomological frame.

The successful applicants will be highly motivated, with a strong work ethic, strong and demonstrated writing skills, a passion for field work, and the ability to work in collaboration.  Experience in restoration ecology is helpful, but not required.  Ph.D. applicants should possess a M.S. in Wildlife, Biology, Zoology, Botany, or Entomology, or a related field and have a valid driver’s license.  Post-doctoral applicants should possess a Ph.D.

Interested applicants should send a cover letter, names and emails of 3 references, GPA and GRE scores, and an updated CV as an electronic PDF or Word document to Craig Allen, allencr@unl.edu

Review of applications will begin March 15 and continue until a qualified candidate is identified.  For more information on the Nebraska Coop. Unit and the University of Nebraska-Lincoln please visit us at:

http://snr.unl.edu/necoopunit/default.asp

Applicants should also review:

https://prairieecologist.com/

Specific projects could include all or part of the following:

Relationship between restoration diversity and ecosystem services, such as invasion resistance and herbivory; interactive effects that might mediate some resilience properties; responses to multiple disturbances; how invasions might weaken the ability to cope with disturbance; microbial diversity and ecosystem function and services; response to pulse and press disturbances and mechanisms driving responses; functional trait diversity and redundancy and resilience.

Konza Prairie Trip Part 3 – Questions About Frequent Prairie Burning

A few weeks ago, I wrote about our trip to the Konza Prairie Biological Station in eastern Kansas.  On that trip, we learned about research results showing that frequent spring fires (one or two year frequency) can prevent encroachment of tallgrass prairie by trees and shrubs.  Less frequent fire allows shrubs, especially dogwood and sumac, to invade.  Pretty simple – we should be burning tallgrass prairie at least every two years, right?

Hang on just a minute, Sparky.

As you might expect, there is more to the story.  It turns out that the frequent spring fire (with no grazing) regimes at Konza has other impacts.  One example is that frequent fire favors grasses over forbs and decreases plant diversity over time.  Prairies that are burned every year or ever two years develop a grass-dominated plant community in which many forb species are difficult to find.  So, frequent fire is bad for plant communities…  Right?

Annually-burned tallgrass prairie at Konza Prairie, in the Flint Hills of eastern Kansas.
Annually-burned tallgrass prairie at Konza Prairie, in the Flint Hills of eastern Kansas.  August 2014.

But in other tallgrass prairies, especially in more eastern prairies such as those in Illinois, researchers are seeing very different impacts of frequent fire.  A paper by Marlin Bowles and Michael Jones, for example, found that frequent fire “stabilizes” plant communities in the Chicago, Illinois area, and that plant diversity was positively correlated with fire frequency.  In fact, their results are almost the exact opposite of what was seen at Konza.  In the Illinois study, frequent fire decreased the dominance of warm-season grasses and increased the diversity of summer wildflowers.

Frequently-burned prairie at the University of Wisconsin-Madison Arboretum.  Clearly, frequent fire is not incompatible with plant diversity...
Frequently-burned prairie at the University of Wisconsin-Madison Arboretum. Clearly, frequent fire is not incompatible with plant diversity…

What the heck is going on??

If we could answer that question, we’d be miles ahead of where we are now in terms of understanding prairie ecology.  I can come up with lots of potential reasons for the difference between frequent fire application in Illinois versus Kansas, but I can’t confirm or deny any of them – we simply don’t know.  As I think about why prairie plant communities might become more dominated by grasses over time, I wonder about factors such as small scale plant diversity, soil productivity, and the soil microbe community – all of which may correlated with each other.

Eastern remnant (unplowed) prairies tend to have a higher density of plant species (e.g., plant species per square meter) than western prairies. High species density could potentially help suppress grass dominance because of the variety of competition strategies each of those plant species employs to take and defend territory.  Those strategies include allelopathy (releasing chemicals that retard growth of nearby plants), rhizomes (underground stems that can connect even fairly distant stems of the same plant together), root density/depth, and many others.  It seems logical that communities with that kind of well-established complex competitive environment would present a major challenge for any species (grasses or otherwise) trying to become dominant.  Maintaining consistent growing conditions by burning or haying annually might facilitate stability within those plant communities because it essentially maintains a stalemate; no plant species is ever given a window of opportunity to gain advantage over its neighbors.  Or this could all be balderdash – I’m just throwing out ideas here.

Does the rich soil organic matter content of eastern tallgrass prairies help suppress grass dominance?  It’s probably the major reason for the higher plant species density in those prairies, so maybe.  On the other hand, research at Konza and elsewhere in more western prairies shows that adding nitrogen to prairies (increasing productivity) increases grass dominance and lowers plant diversity.  Hmm.

Soil microbial communities surely have a very important influence on plant diversity, but (as discussed in a previous post) we don’t know much about them yet.  I’m optimistic that our understanding of soil microbes will grow tremendously during the next few decades, but the complexity of that world might mean that it will take many more decades before we start to get a grasp on it.  In the meantime, we can use it as a convenient scapegoat.  If something you don’t like is happening to your prairie, it’s probably a soil microbe problem…

Those of you who read this blog frequently may be surprised that I haven’t mentioned insects or other animals yet.  Let’s talk about them now, shall we?

It’s very important to remember that even if frequent burning seems to maintain high plant diversity in (some) prairies, a prairie is much more than just plants.  The use of frequent fire tends to create fairly homogenous habitat conditions across a prairie.  Regrowth rates are similar across the whole burned area, so vegetation height and density is relatively uniform.  Dead material, including both litter and standing dead vegetation, is scarce.  Because habitat diversity is limited, so is the diversity of creatures that rely on that habitat.  In taxonomic groups ranging from grasshoppers and spiders to mice and birds, research shows that habitat diversity is positively correlated with species diversity.  Creating habitat heterogeneity – through grazing, patchy mowing, or other means can help facilitate a more diverse animal community.  Burning in a less regimented way can help too, especially if that means splitting a prairie into multiple management units and burning only a subset of those each year.

Habitat
Heterogeneous habitat structure, including tall, short, and mixed-height vegetation – like that shown here – can help maintain diverse invertebrate and wildlife communities.  Grazing is one great way to manipulate vegetation structure, but isn’t feasible at all sites.  Grazed prairie at The Nature Conservancy’s Platte River Prairies, Nebraska.

In small isolated prairies, it’s also critically important not to burn (or mow) the entire prairie at the same time.  With limited opportunities for species to recolonize from other prairies, a fire that kills all of the individuals of a particular species (e.g., an insect that overwinters in the stems of grasses or in the litter along the ground) can mean the end of that species’ existence in that prairie.  Maintaining a floristically diverse prairie without a full complement of invertebrates doesn’t seem like success to me.  On the other hand, I also appreciate the difficulties associated with managing small prairies.

To wrap this up, I think there are two really important points to make about fire frequency in prairie management.  First, there are some big questions about why frequent fire seems to maintain high plant diversity in some prairies but encourages grass dominance in others.  Figuring out the answers to those questions may be one of the more important keys to prairie conservation success.  Second, even if frequent fire maintains high plant diversity and repels invasion by shrubs and trees, it still might not be the best choice for a prairie management strategy.  There is much more to a prairie than its plants, and even if you don’t much care for invertebrates, birds, reptiles, or mammals (and how could you not?) those species – especially the invertebrates – are strongly tied to the long-term viability of the plant community, so it’s probably not good to ignore them.  To be clear, I’m not saying people who use frequent fire are evil destroyers of animals.  I’m just raising a flag of caution and pointing out some potential tradeoffs.

Prescribed burning is an important management tool, but its impacts on prairie communities can be complicated.
Prescribed burning is a valuable management tool, but its impacts on prairie communities can be complicated.  It’s important for prairie managers to recognize and account for both the negative and positive impacts of fire.

Those of us who work with prairies are used to the seemingly overwhelming complexity of grassland communities and the way those communities respond to management.  In fact, for many of us, it’s a big reason we love prairies as much as we do.  While we still have more questions than answers about effective prairie management, we have enough information to go forward with.  Most importantly, prairies are pretty tough, so excepting drastic measures such as broadcast spraying with 2,4-D (and maybe burning an entire tiny prairie), we have the latitude to try out lots of ideas and see what works.  We’ll learn as we go.

In the meantime, it’d be great if all you researchers out there would get cracking on the issue of disparate effects of frequent fire in eastern versus western prairies.  It should only take a few decades to figure it out…  Right?

 

Conservation Grazing in Iowa

I got the chance to spend a couple days in Iowa last week, talking about conservation grazing with staff of the Iowa Department of Natural Resources.  They invited me to join a two day workshop discussing various ways to use grazing for conservation objectives.  My main role was to kick off the meeting by providing various examples of objectives that can be addressed through grazing.  Beyond that, I was asked to participate in the remainder of the workshop and contribute thoughts and ideas as appropriate.  I am grateful to have had the opportunity to participate, and came away with a better appreciation for the challenges faced by Iowa prairie managers.

Staff of the Iowa Department of Natural Resources discuss conservation grazing at the Kellerton Wildlife Management Area in south-central Iowa.
Staff of the Iowa Department of Natural Resources discuss conservation grazing at the Kellerton Wildlife Management Area in south-central Iowa.

I thought I’d share some of what I covered in my presentation.  Essentially, I focused on two broad categories of prairie management objectives that can be addressed through cattle grazing.  Those are:

  1. Reducing grass dominance to increase plant diversity
  2. Increasing heterogeneity of habitat

Reducing Grass Dominance

Dominant grass species can sometimes suppress prairie plant diversity by monopolizing soil and light resources.  Two categories of prairies seem particularly vulnerable to this: 1) prairies that have been degraded by chronic overgrazing or broadcast herbicide use, and 2) restored (reconstructed) prairies.  In Nebraska and Iowa, dominant grasses can include non-native invasive species such as smooth brome (Bromus inermis), Kentucky bluegrass (Poa pratensis), tall fescue (Schedonorus arundinaceus), and reed canarygrass (Phalaris arundinacea), as well as native species such as big bluestem (Andropogon gerardii).

When attempting to reduce the dominance of these grasses, it’s important to be clear about what you’re trying to accomplish.  If the ultimate goal is to increase plant diversity, it’s not enough to just suppress the vigor of grasses.  In order to be successful, a variety of other plant species have to colonize territory abandoned by that weakened grass.  A late-spring prescribed fire can temporarily suppress the growth and vigor of smooth brome or Kentucky bluegrass, but often results in robust growth of big bluestem later that season.  Trading a dominant invasive grass for an aggressive native grass may not be success if wildflower diversity remains low.

Grazing can play an important role in increasing plant diversity by repeatedly defoliating  major grass species that limit plant diversity.  The timing, stocking rate, and frequency of grazing can all be adjusted based on the grass species and objectives at a particular site.  As an example, we sometimes combine an early spring prescribed fire with intensive grazing (through about June 1) to suppress cool-season invasive grasses such as smooth brome and Kentucky bluegrass.  If big bluestem is abundant in the same place, we’ll leave cattle in for much of the summer as well, but at a lower stocking rate.  The strategy is to suppress both the invasive cool-season grasses and the native warm-season big bluestem while allowing other plants to thrive and expand their footprint.

At low stocking rates, cattle tend to keep big bluestem closely cropped, but don’t target most wildflower species.  We usually see an abundance of new plants growing in and amongst the weakened brome, bluegrass, and bluestem during the year of grazing and the following year.  Those new plants include both short-lived “opportunistic” plants and longer-lived perennial plants.  The result is a bump in plant diversity.  If we repeat the same kind of treatment every few years, we can often maintain a richer plant community than we can with other management options such as fire or mowing alone.

The rattlesnake master plant (Eryngium yuccifolium) in the foreground of this photo was ungrazed, in  spite of being the burned patch of this patch-burn grazed prairie.  A light stocking rate meant that even this often-favored plant was being rarely grazed in this Iowa DNR prairie.  Staff were hoping to reduce the dominance of tall fescue and allow species such as rattlesnake master to increase in abundance.
The rattlesnake master plant (Eryngium yuccifolium) in the foreground of this photo was ungrazed, in spite of being the burned patch of this patch-burn grazed prairie at Kellerton WMA.  A light stocking rate meant that even this often-favored plant escaped grazing in this Iowa DNR prairie. Staff were hoping to reduce the dominance of tall fescue and allow species such as rattlesnake master to increase in abundance.

There are countless ways to employ cattle grazing to weaken dominant plants and stimulate higher plant diversity.  I’ve written about other examples previously.  You can find a couple of those here and here.

Increasing Habitat Heterogeneity

Cattle grazing can create habitat structure that other management options such as fire and mowing can’t.  As they work to meet their nutritional needs, cattle graze some plant species (mostly their favorite grasses) preferentially.  Stocking rate, or the intensity of grazing, correlates with grazing selectivity.  At low stocking rates, cattle are free to eat only what they really want, resulting in closely cropped patches of grass interspersed with taller clumps of less palatable grasses and wildflowers.  When stocking rates are higher, cattle are forced to eat a wider range of plant species, creating a more uniformly short vegetation structure.  Both the “lower-stocking-rate-patchy-habitat” and “higher-stocking-rate-uniformly-short-habitat” can be valuable to wildlife and invertebrate species.

The ideal situation is to provide the widest possible range of habitat types within a prairie, or within a series of adjacent or connected prairies.  That way, regardless of their habitat needs, most wildlife and invertebrate species will be able to find a place to live.  Changing the location of each of those various habitat types from year to year helps keep any species (plant or animal) from becoming so abundant that it impacts other species to the point of reducing diversity.

Because of the unique vegetation structure created by grazing, a wider range of habitat types can be created with grazing than with either fire or mowing.  However, it’s also very important to ensure that grazing doesn’t have a detrimental impact on plant diversity in the name of creating wildlife habitat.  Significant periods of rest from grazing and careful monitoring of grazing impacts and populations of sensitive plant species are important.  If conservation is the primary goal, grazing should be used only when there are specific objectives to meet, not as a default strategy.

This seeded prairie has been part of a grazing system in every year since it was planted in 2003, and has maintained an excellent diversity of prairie plants.  Examples in the foreground include leadplant (Amorpha canescens).
This seeded prairie has been part of a grazing system in every year since it was planted in 2003, and has maintained an excellent diversity of prairie plants. Examples in the foreground include leadplant and Ohio spiderwort (blooming) but many others, including rare and conservative species, were abundant as well.

I’ve written much more on the topic of creating heterogeneous habitat with grazing in previous posts as well, and you can find a couple examples here and here.

Setting Useful Objectives – And Then Using Them

Regardless of the management tool(s) being employed, the biggest challenge for a prairie manager is to set clear objectives and then follow up on them.  Start by defining the outcome you want (different habitat structure, more plant diversity, etc.) and then describe precisely what success looks like.  Monitoring doesn’t have to mean spending hours on your knees with a plot frame, it just means measuring the outcome you desired.

For example, if you want more habitat diversity, you could start by listing the types of habitat structure you want (tall/dense, short sparse, patchy forbs with short grass, etc.) and how much of the prairie you’d like to be in each category.  Then, you could make a rough map of how the site looks before the treatment and estimate percentages of each habitat type.  After your grazing, fire, or mowing treatment, make another map and see if you reached your objective.

If plant diversity is important, decide how you will measure that.  This is where a plot frame and repeated sampling across a prairie can be helpful, but there are simpler ways as well.  You could pick out 3-5 small areas (less than 10 square meters) that you can find each year and then annually list the plant species you find in each area to see if that number changes over time.  You don’t have to identify all the species, just list how many there are.  If you are using grazing, it’s also important to figure out which plant species are favorites of the cattle and use that information to ensure that your management allows those plants enough rest from grazing that they can bloom and make seed every few years.

Most importantly, your objectives should drive the adjustments you make to management from day to day and season to season.  If you can define what you want, you can see if your management is moving you in the right direction.   It’s fine to change objectives as you learn, or as conditions change.  In fact, in our Platte River Prairies, while we have some broad objectives (plant and habitat diversity), we set new specific objectives and management strategies each year to respond to what we’re seeing on the ground.

Cattle grazing is just another tool that can be used for the conservation of prairies.  It’s not appropriate for all prairies or situations, but can help meet some objectives in ways that other tools (fire, mowing, herbicides) can’t.  Conservation grazing differs from ranching in that income doesn’t have to be a major part of the decision-making process each year.  On land where conservation is the primary objective, managers can decide when and how to employ grazing (or not) based purely on the conservation challenges they face.

Thanks again to the Iowa Department of Natural Resources for inviting me to their conservation grazing discussion last week.  I was impressed by the thoughtfulness and creativity of the staff I met, and I look forward to hearing more about their prairie management and restoration work down the road.

 

 

 

 

 

Is Poison Hemlock Repelled By Plant Diversity? Early Results Say Yes

How important is plant diversity?  Most ecologists think it’s a critical component of resilient ecosystems.  Last week I collected some data that lends support to that view.  In some experimental prairie plantings we’ve established in our Platte River Prairies, plant diversity appears to be suppressing the invasion of poison hemlock (Conium maculatum).

A floristically rich restored prairie, in which prescribed fire and grazing are being used to maintain high plant diversity.  The Nature Conservancy's Platte River Prairies, Nebraska.
A floristically rich restored prairie, in which prescribed fire and grazing are being used to maintain high plant diversity. The Nature Conservancy’s Platte River Prairies, Nebraska.

Back in 2006, I established some research plots in our Platte River Prairies so we could take a more experimental approach to our work to understant how plant diversity affects prairie ecosystems.  Those research plots consist of 24 squares, each of which is 3/4 acre in size.  Half of those plots were planted with a high diversity seed mixture of about 100 plant species.  The other half was planted with a lower diversity mixture of 8 grass and 7 wildflower species.  Since then, several university researchers have helped us collect data on the differences between those high and low diversity plantings.  We’ve looked at a number of variables, including soils, drought response, insect populations, insect herbivory rates, and resistance to invasive species.

An aerial photo of our 2006 diversity research plots.  Each plot is 3/4 ac (1/3 ha) in size and is planted with either a high diverisity (100 species) or low diversity (15 species) seed mixture.
An aerial photo of our 2006 diversity research plots. Each plot is 3/4 ac (1/3 ha) in size and is planted with either a high diverisity (100 species) or low diversity (15 species) seed mixture.

Kristine Nemec, a recent PhD from the University of Nebraska-Lincoln, has done the bulk of the data collection and analysis from those experimental plots.  A soon-to-be-published research paper from that work will report that plant diversity appears to be suppressing the spread of two invasive species: bull thistle (Cirsium vulgare) and smooth brome (Bromus inermis).  Poison hemlock wasn’t included in that project because the methods we chose for measuring vegetation weren’t well suited to capture its presence and abundance.  However, from a purely observational standpoint, it’s always appeared that a lot less hemlock grows in the high diversity plots than in the low diversity plots.  Last week, I decided to test that observation by collecting some data.

Poison hemlock (Conium maculatum) has invaded portions of our research plots, sometimes forming large colonies that are near monocultures.
Poison hemlock (Conium maculatum) has invaded portions of our research plots, sometimes forming large colonies that are near monocultures.

Since hemlock is abundant mainly in the southern half of our 24 plots, I only collected data from those 12 plots for this pilot effort.  Half of those 12 plots had been seeded with a high diversity mixture and the other half with a low diversity mixture.  I walked three transects across each of those plots, and counted the number of last season’s hemlock stems that were within a meter of me on either side.  I only counted stems that still had seed heads to help ensure that I wasn’t counting stems from multiple years’ production.  You can see the results of my counts in the graph below.

The number of poison hemlock flowering stems found by transect in low diversity and high diversity plots.  Platte River Prairies - Diversity Research Plots.  April 2013
The number of poison hemlock flowering stems found by transect in low diversity and high diversity plots. Platte River Prairies – Diversity Research Plots. April 2013

Although I haven’t yet run any statistics on these data, there is a striking difference in the number of poison hemlock plants between the two treatments.  Hemlock was rare in the high-diversity plots, but was found in large numbers in many of the transects through the low-diversity plots.  This was just a quick and dirty pilot effort to see if there was enough difference to warrant a full-fledged research project, but I feel pretty comfortable that plant diversity is having an impact on hemlock abundance.

I plan to collect some more comprehensive data on poison hemlock this summer.  I’d also like to collect the same kind of data from an adjacent set of plots we established in 2010.  Those newer plots are the same size as those from 2006, but include three different seed mixtures: high diversity, low diversity, and a monoculture of big bluestem.  If I see a similar pattern of hemlock abundance there, that will go a long way to confirm what I think I’m seeing in the 2006 plots.

I’ve never considered poison hemlock to be a particularly dangerous invasive species in our Platte River Prairies.  It seems to be most abundant in old woodlots, and doesn’t often show up in our native or restored prairies.  On the other hand, the plant’s toxicity can cause big problems, especially from an agricultural perspective.  In fact, we’d considered haying our research plots last summer but couldn’t find anyone to harvest them because hay containing poison hemlock can’t be fed to livestock.  If prairie plantings with a high diversity of plant species resist invasion from hemlock, that could have important ramifications for farmers who want to establish new grasslands for hay or grazing production.

Poison hemlock is most often found in old woodlots along the Platte River.  It's unusual for us to find it in our diverse prairies.
Poison hemlock is most often found in old woodlots along the Platte River. We don’t usually see it in our diverse prairies.

My little pilot study is a small addition to a growing list of other research projects demonstrating the value(s) of plant diversity.  Unfortunately, high diversity prairie plantings are more expensive than lower diversity plantings, so it’s important for landowners and conservation organizations to know exactly what they get for that higher cost.  High plant diversity provides nectar and pollen resources for pollinators, improves total vegetative production, and has other benefits, including quality wildlife habitat.  However, one of the most intriguing aspects of plant diversity is its potential to help suppress invasive species.  If we continue to find that more diverse plantings help repel species such as bull thistle and poison hemlock, that will have important implications for both agricultural producers and wildlife/prairie managers.

Stay tuned as we keep learning…

Dealing With a Pervasive Invasive – Kentucky Bluegrass in Prairies

Many of the prairies we manage have pretty degraded plant communities, characterized by low plant diversity and dominance by a few grass species – including the invasive Kentucky bluegrass (Poa pratensis).  Our primary objective for these prairies is to increase plant diversity, which, in turn, bolsters ecological resilience and improves habitat quality for a wide range of prairie species.  Because bluegrass is so pervasive in our prairies, we’ve had to modify our objectives and strategies from those we use to address most other invasive species.

Kentucky bluegrass can stifle plant diversity by crowding out other plants. In many prairies degraded by years of overgrazing and/or broadcast herbicide use, bluegrass is now the dominant plant species and few other plants can compete with it.

When attacking invasive plant species, a common strategy is to contain, and (hopefully) shrink, patches of invasive plants in order to protect plant diversity in non-invaded areas.  In the case of Kentucky bluegrass, however, we have to take a different approach because the species already spans the entire prairie.  Kentucky bluegrass acts like a thick blanket of interwoven stems, roots, and rhizomes – smothering most other plant species beneath it.  Because our goal is to increase plant diversity, we want to make that blanket thin and porous enough that a wide variety of other plant species can grow up through it.   

An illustration of a floristically diverse prairie (left) with several large patches of an invasive plant.  When dealing with many invasive species, we can focus on reducing the size of infestations in order to restore a more diverse plant community.

   

Kentucky bluegrass acts as a thick blanket that smothers most other plant species.  In a case like this, we need to manage the prairie in a way that increases the mesh size of that blanket and allows a more diverse plant community to poke through.

Our primary strategy for suppressing Kentucky bluegrass is the periodic application of prescribed fire and grazing.  We can weaken bluegrass by burning prairies when bluegrass is just starting to flower and/or by grazing prairies harder in the spring than in the summer.  We mix those treatments with rest periods within a patch-burn grazing regime.  The result has been a steady increase in plant diversity in most of our degraded prairies.

If we were fighting a different invasive species, we might expect that if plant diversity was increasing, the amount of territory occupied by the invasive species would be decreasing.  With Kentucky bluegrass, however, our bluegrass blanket is getting thinner, but still covers the whole prairie – something that shows up clearly in data I’ve been collecting over the last decade.  Through the use of nested sampling plots of 1m2, 1/10m2, and 1/100m2, I’ve been tracking plant diversity and floristic quality through time, along with changes in the frequency of various plant species (the percentage of plots in which they occur).  Over the last 8-10 years, as plant diversity within 1m2 plots has increased, the frequency of Kentucky bluegrass has stayed about the same.   Even at smaller plot sizes, which are more sensitive to changes in the frequency of very abundant species, bluegrass is still in nearly every plot.

We also have a number of restored (reconstructed) prairies in and around our remnant prairies.  Within restored prairies, plant diversity is in pretty good shape, but Kentucky bluegrass is rapidly invading.  In one particular prairie, Kentucky bluegrass is now in almost 90% of 1m2 plots and more than 50% of 1/100m2 plots.  That sounds bad, but as bluegrass becomes more abundant, plant diversity – and the frequency of other prairie plant species – is actually holding steady.  There are a few small areas in which bluegrass appears to be forming near monocultures, but for the most part, it looks like bluegrass is just filling in around the other plants instead of actually displacing them.  My guess is that some soil conditions provide such ideal growing conditions for bluegrass, it’s going to be king of those areas no matter what we do.  Elsewhere, however, I think our management is preventing it from becoming dominant.

Here’s the take home lesson for me:  When trying to manage for plant diversity in the face of a pervasive species such as Kentucky bluegrass, it’s more important to track plant diversity than to worry about how much territory bluegrass occupies. 

Just consider the data from our prairies… if I concentrated only on how much Kentucky bluegrass is in our prairies, it would look like we’re failing miserably in our management attempts.  We’ve got just as much bluegrass as we ever did in our degraded remnant (unplowed) prairies, and we’re quickly losing ground in some of our restored prairies.  However, my data also shows that plant diversity is increasing in remnant prairies and holding steady in restored prairies.  Since the ultimate goal is to have a diverse plant community, that’s success! 

Click here to see a PDF showing some of the data I mentioned in this post.

Quantifying the Value of Plant Diversity

Why is plant diversity important? 

I can come up with lots of reasons, including the value to pollinators, correlations between plant and insect diversity, and contributions to ecological resilience – among others.   But it’s much more difficult to quantify the specific functional differences between high-diversity and low-diversity prairie plantings.  Even basic questions are difficult – for example, how many plant species does it take to see benefits?

Most of us who spend time in prairies know intuitively that plant diversity is important, but if we’re going to influence environmental policy, agricultural practices, and other large-scale conservation strategies, we’re going to need stronger and more quantified answers than intuition provides us.

In an attempt to help find some of those more specific answers, we have built some research plots within our Platte River Prairies, in which we’ve established prairie plantings of various plant diversity.  Each treatment plot is 3/4 acre (1/3 ha) in size – big enough that we hope to compare patterns of invertebrate species composition and activity,  soil changes, differences in the resistance to invasive species, and more.  We’ve actually established two sets of plots now; one in 2006 and the second in 2010.  The 2006 set consists of low diversity (15 species) and high diversity (100 species) plots, and the 2010 set consists of three treatments: a monoculture of big bluestem, low diversity (mostly grasses, with a few forbs), and high diversity (100 or more plant species).  Each treatment is replicated at least 4 times.

Clint Meyer, of Simpson College (Iowa), was out last week doing some sampling of ground-dwelling invertebrates.  Here he examines insects caught in a pitfall trap within our 2010 diversity research plots.
A close-up view of a vial of insects caught in a pitfall trap. There are least two species of ground beetles in the vial (floaters and sinkers!) as well as springtails (the little specks floating in the lower left hand portion of the vial).

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Patch-Burn Grazing in Missouri Prairies

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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