Tag Archives: management

Learning How to Live With Shrubbier Grasslands – Part 2: Experimentation

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In Part 1 of this topic, I wrote about the uncomfortable situation many prairie stewards find ourselves in – that our grasslands are getting “shrubbier” and it’s increasingly difficult to prevent that. Because the drivers for that change are mostly beyond our control, it seems obvious that we need to start thinking differently about grassland management.

There are still plenty of grasslands where we should work to prevent woody encroachment. However, there are also a lot of prairies where trees or shrubs have already become part of the community. In many other places, it appears to be just a matter of time. It seems smart for us to try to get ahead of this and figure out how to manage woodier grasslands for biodiversity and productivity.

Most of us haven’t focused much on how to manage the height and density of shrubs in our prairies because we’ve been thinking mostly about how to repel them. That means we need to start experimenting, and quickly. My team has implemented a couple different field trials in the last couple years and I’m going to share some preliminary results with you. I hope those results will spur others to share their experiences and, more importantly, ramp up their own experimentation efforts.

Our first trials focus on clonal deciduous shrubs (smooth sumac and rough-leaved dogwood). We started with the hypothesis that if we could hit them twice (or more) in the same growing season, we might get multiple years of suppressed height and density as a result. This hypothesis was informed by helpful conversations with people like Dean Kettle at the Kansas Biological Survey and several others.

Field Trial #1 – Smooth Sumac at The Nature Conservancy’s Niobrara Valley Preserve

In 2023, we treated a number of smooth sumac patches with treatments (often in combination) that included prescribed fire, mowing, and a non-lethal “burn-down” herbicide. The photos shown here illustrate what those sumac patches looked like on June 16, 2025.

Quick summary of preliminary results:

  • Mowing sumac in June and August really reduced both the height and density of stems, and that impact has persisted for at least 2 years.
  • An August mowing, followed by a dormant season fire (November, in our case), showed pretty similar results.
  • June mowing followed by herbicide in August seemed slightly less effective than the above two treatments, but much better than any single treatment alone.
  • June mowing followed by a November fire was the least effective of all the combinations listed so far, but still better than a single mowing treatment.
  • All single treatment applications (June mowing, August mowing, November fire) showed quick recovery within two years.
June 16, 2025 Photo of smooth sumac that received no treatment in 2023. You can just barely see my spade in the center of the photo, with sumac looming well above it.
This patch received a single prescribed fire treatment in November of 2023. If you look really closely, you can see just the handle of my spade. The sumac rebounded very well. This is similar to what both single mowing treatments (June and August) looked like by June 2025.

Treatments were applied on June 13, August 9, and November 29, 2023. The photos below show sumac patches with various treatment combinations.

This patch was mowed in June and August of 2023 and experienced a significant decrease in both height and density of stems (the slope in the background was untreated).
August mowing followed by November fire also had a significant impact.
June mowing followed by a November fire was better than any single treatment, but not nearly as effective as the other combinations.

The herbicide we used contained the active ingredient Carfentrazone-ethyl, which disrupts cell membranes in leaves and essentially defoliates plants. The hope was that it would act much like a prescribed fire – injuring the shrubs without killing them or any surrounding plants. We mixed 17.5 ml (0.7 ml/gal) of AIM herbicide and 47.5 oz (1.9 oz/gal) of crop oil in 25 gallons of water and applied a heavy foliar spray.

We tested this on full-sized sumac plants in June, but the spray didn’t penetrate the canopy well, and only burned up the top layer of leaves. It seemed to work much better in August as a follow-up treatment to resprouted sumac plants mowed in June.

The brown-leaved sumac plants on the right were mowed in June and the regrowth was sprayed with AIM herbicide in August. This photo was taken 1 week after spraying.

As we’d hoped, we saw no mortality of sumac or any other plants from the herbicide treatment. Instead, it seemed to act much like a prescribed fire, in that it just injured the shrubs. We’d expected it to do some temporary damage to surrounding vegetation as well, but saw very little evidence of that.

Here is the June 2025 photo of the sumac sprayed with AIM herbicide in June 2023. Height and density are both much reduced compared to untreated patches.

My takeaway from the herbicide application was that it is worth more testing, but seems less effective than mowing or fire. In places/situations where spraying might be feasible, but mowing isn’t, it might be a decent follow-up treatment to extend the impacts of prescribed fire. Maybe. We’ll see. Either way, it didn’t seem to cause any damage to the plant community around the sumac, which reinforces my interest in more experimentation.

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Field Trial #2 – Rough-Leaved Dogwood at The Nature Conservancy’s Platte River Prairies

For a few years now, I’ve been paying attention to fenceline differences and other evidence that cattle grazing has potential to help manage deciduous shrub height and density. This spring (2024) we set up a quick experiment to test that with rough-leaved dogwood. Cattle were brought into the unit in early June and will be present through October (part of our larger open gate grazing experiment.)

A fenceline photo showing grazed prairie on the left and ungrazed on the right. Note the height and density of the dogwood and plum on the ungrazed side.

Forty cow/calf pairs were introduced to a 49 acre pasture in late May, 2025. In early July, they were given another 25 acres (in addition to the initial 49) and later this summer, they’ll gain access to an additional 69 acres. The photos below, though, were all taken on June 10 – about 2 weeks after cattle were brought into the pasture. In other words, the grazing impacts shown below happened pretty quickly after cattle were brought in. It’s not like they waited to graze dogwood leaves until they’d eaten everything else.

We set up four treatments:

  • Grazed (unmowed)
  • Ungrazed (unmowed)
  • Mowed/Grazed
  • Mowed/Ungrazed

The height of all dogwood stems included in the study was measured on April 22, 2025 and some of those stems were mowed immediately afterward. Small exclosures were set up to exclude grazing from some treatments.

Quick summary of preliminary results (as of June 16, 2025):

  • Cattle are definitely grazing the leaves of dogwood. Stems outside the exclosures looked very ragged compared to ungrazed plants.
  • Dogwood stems mowed in April were being kept cropped off at just a few inches in height.
  • Dogwood stems mowed in April but excluded from grazing had already reached about 10-12 inches in height by June 16.
Grazed dogwood (left) and ungrazed dogwood (right, in the exclosure).
Dogwood stems inside the triangle of red flags were mowed in late April and cattle are keeping them grazed off close to the ground.
Dogwood mowed in April but excluded from grazing had grown 10-12 inches by June 16.

This project is just getting started, but it’s gratifying to see that cattle are grazing dogwood as we’d expected (see photos below for further confirmation). The most promising result so far is that the mowed dogwoods seem particularly attractive to cattle and we hope repeated grazing of those resprouting stems will lead to several years of much-reduced growth compared to stems in the other treatments. Time will tell, but we’re off to a good start.

My real hope is that we can find ways that cattle grazing can play into our larger efforts to manage shrub height and density. For example, burning every 4-5 years isn’t enough on its own to suppress shrub growth. However, burning followed by a season of grazing on the regrowth of those shrubs might lead to significantly reduced growth over the next several years. By the time the next fire comes through, those shrubs might not have grown very tall at all.

We have lots of experience (and data) showing that some kinds of cattle grazing can benefit habitat heterogeneity without reducing plant diversity. If similar grazing approaches can also suppress the height and density of shrubs, that’ll be a huge help.

This (including the sumac work above) is just the start of a long experimental path, but I’m excited by the early results.

A cow grazing dogwood on July 2, 2025
Even the calves are working on the dogwood.

I’m sharing these very early results in the hope that I can encourage others to do similar experimentation. Please don’t interpret these preliminary findings as anything more than what they are. We’re seeing some hopeful signs, but need to follow these trials for more years to see the longer-term impacts of what we’re trying. We also need to greatly expand the treatments and combinations to really understand what various options can do.

Please help! If you are a land manager in the Central U.S. and have shrubs in your grassland, it would be terrific if you could test these or similar approaches to managing shrub height and density and report back. Just as importantly, we need researchers to help us learn about the impacts of different degrees of shrub height and density on plant communities, pollinators and other invertebrates, birds, mammals, and much more. That information will be crucial to land management and help tell us what to aim for.

As I said in the first post, the increase in woody plants in our grasslands doesn’t have to be a catastrophe. It might just be one more factor we need to include in the way we think about managing prairies for various objectives. If we ignore the issue until the shrubs have filled in and taken over, though, we’ll definitely lose. Let’s not lose, ok?

The Show Must Go On

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Almost a decade ago, I wrote about two competing metaphors for prairie restoration. I suggested we view prairie restoration like the reconstruction of a city after a disaster rather than like the restoration of an historic building.  We need to concentrate on the roles and functions of prairie ecosystems rather than how closely a restored patch of prairie resembled what it used to be in the past.

Today, I’m hoping to stimulate conversation about the difficult decisions we face as we try to conserve prairies in the face of rapid climate change.  One conservation planning approach is to focus on conserving the stage, not the actors.  It advocates prioritization of sites with geophysical diversity because those abiotic conditions influence habitat heterogeneity, which supports biodiversity.  The hope is that we might be able to conserve “an abiotically diverse ‘stage’ upon which evolution will play out and support many actors (biodiversity).”

The varied topography and the habitat size and connectivity found in Flint Hills of Kansas makes it a ‘stage’ that can potentially sustain biodiversity – but only with thoughtful, persistent, and adaptive management.

I think the ‘conserve the stage’ approach has merit, but it’s just a first step, especially for prairie conservation.  We don’t just want to save the stage; we want to make sure the show goes on.  Thus, I present to you a long (and potentially ridiculous) metaphor for prairie conservation that builds upon the ‘conserve the stage’ approach.

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Every actor in a theatrical production plays a role that helps tell a story.  Likewise, every species in a prairie plays a role that contributes to the overall functioning of the ecosystem.  In a healthy and resilient prairie, all the key roles in are filled. 

Fortunately, there is a lot of redundancy built into prairie communities.  We have lots of species that provide pollination, seed dispersal, nutrient cycling, and all the other essential functions that keep prairies going.  We have a big cast, or maybe a big actors’ union.

Today’s prairie ‘show’ already looks different than it did in the past.  Prairie landscapes are fragmented, invasive species have joined the cast, and the climate is changing.  Those and other factors mean that some actors who played key roles in the past are no longer part of the show, at least at some venues.  Other actors remain in the cast but don’t play their roles as effectively as they used to.  Despite those changes, there are still really good versions of the prairie show being presented on various stages, though the versions vary quite a bit from place to place.

To keep the show going, we, as producers and directors, have to be creative and adaptable.  We face really difficult decisions, especially when it comes to actors who aren’t well suited for their roles anymore.  Continuing to direct the show with those actors as the main focus can weaken the performance of others and drag the whole production down. 

Making changes to the cast of a show comes with a lot of risk, however.  We don’t have a lot of experience with that process and we’re likely to make mistakes. Fortunately, in most cases, there are existing cast members that have the potential to adapt their roles and take on new challenges.  With some guidance, those actors will find new ways to collaborate with each other and put on a show that might not be exactly the same as we’re used to but will still have a plot we can follow and enjoy.

More frequent and severe flooding is occurring as a result of climate change. That increased flooding will likely affect which plant and animal species will persist in low-lying prairies like this one. Can we predict those changes and help guide them in ways that don’t lead to reduced biodiversity?

If more drastic actions are needed, we might recognize that some actors are on their way out and start training understudies who can gradually take over roles as needed.  If necessary, we might decide to recruit actors that are playing diminished roles on other stages and bring them in to rejuvenate their careers in a more suitable situation.  Similarly, we might help some of our own long-term stars find new opportunities elsewhere, rather than just watching them slowly fade away. 

In some cases, the world around us might force major a rewriting of the show itself.  We might find ourselves directing a shrubland or woodland production rather than a prairie show.  That doesn’t mean the show will stop or become less important, but it will require a different approach, a significantly altered cast, and a lot of adaptation by all involved.  However, if we stick with the mantra of ‘The Show Must Go On’, we’ll need to figure out how to adjust on the fly and sustain as much biodiversity and ecological function as we can.

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Ok, I have to break away from this tedious metaphor.  The real point here is that we can’t afford to be so invested in current or past versions of our prairies that we don’t allow them to adapt to changing conditions.  At the risk of sliding back into my metaphor, there are lots of old movies and plays that don’t hold up well today.  Jokes that used to be funny 20 or 30 years ago aren’t funny today.  Old references don’t land with new audiences.  In most cases, the basic stories themselves are still solid – they just need to be adapted for today’s world.  Prairies and their species also exist in a different world than they used to, and that world continues to change (very quickly) around them.

The resilience and function of prairies is highly dependent upon biodiversity, which depends upon habitat size and heterogeneity, along with other factors.  Maintaining high biodiversity in prairies that exist in fragmented landscapes comes with huge challenges, which are compounded by a rapidly changing climate.  Plant and animal communities aren’t the same as they were in the past and they’ll continue to change over the next few decades and beyond.  In fragmented landscapes, unless we take an active role, those alterations will largely take place in isolation, with limited opportunities for species to travel between one prairie fragment and another.  Even in landscapes with large contiguous grasslands, we’ll need to be very thoughtful about how we shepherd those prairie communities through the coming years.

These tent caterpillars probably aren’t causing serious impacts to this patch of wild plum, despite appearances. How will climate change, habitat fragmentation, and increased woody encroachment affect this insect species and its impacts on other species in the future? (This is just a random example – I’m not saying tent caterpillars are going to become a major problem!)

It’s really hard to look at the prairies we know best and imagine them with a different composition of species.  We’re used to measuring stewardship success by our ability to sustain the status quo.  Watching the population of a species diminish in size – or disappear entirely – feels like a major failure.  Most of us have also looked skeptically at any new species that show up in a prairie, worrying about potential negative impacts of that species on the existing community. 

I don’t have a lot of answers to the big questions we face.  I’m certainly not ready to lay out a plan or advocate for a particular approach to managing these changing prairies.  As I did in another recent post, I’m mainly trying to get some conversation going on this topic. 

The best I can do right now is offer a few ideas for discussion.  For example, I think we might be smart to reevaluate the way we look at our objectives for prairie management.  Instead of trying to maintain the current composition of plants and animals, maybe we should focus more on biodiversity and less on which particular species are present or abundant within those communities.  (That doesn’t mean we welcome invasive species, by the way.  Any species – plant, animal, or otherwise – that acts to reduce biodiversity is still a problem.)  

I also think we need more serious conversation about when to resist ‘state changes’ like the transition from grassland to shrubland and when to facilitate those transformations, while trying to preserve as much biodiversity and productivity as we can.  Again, I have little to offer in terms of specifics, but it seems clear that we’re not going to be able to stave off those state changes forever in at least some places.  Let’s start thinking about contingencies instead of just waiting for those sites to collapse.

There’s a lot of woody encroachment in this prairie. The number of trees in the surrounding landscape and a changing climate are both spurring that invasion. At what point does the fight against this kind of encroachment become fruitless? What do we do then?

Finally, it’s never been more important to find opportunities to enlarge and reconnect prairie fragments through prairie restoration.  The chances are slim that a small, isolated prairie fragment is going to adapt well to a rapidly changing world.  Growing the size of those fragments by restoring adjacent patches should be a top priority.  Can we find new approaches for creating those restoration opportunities in strategic locations? As we do that restoration work, we should also continue to test and discuss seed sourcing strategies, including the regional admixture approach, to see if we can further bolster the adaptive capacity of those small sites.

We’ll be figuring this out as we go, and we’ll surely screw some things up, but we can’t afford to just continue reacting.  At the very least, we need to be thinking ahead about the changes that are taking place and how those will affect prairies.  In some cases, we should probably be ‘acting ahead’ to guide state transitions, migration of species, or simply changes in species composition within individual prairie sites. 

What we can’t afford to do is live in the past.  We’re hurtling into the future whether we like it or not.  Let’s make sure we bring prairies along with us.