Tag Archives: wildflowers

Lessons from a Fenceline

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Last week, I spent some time collecting data and thinking about next year’s plans for managing our Platte River Prairies.  While I was out, I made an interesting observation along the boundary of one of our properties and that of the neighbor.

About two years ago, we replaced a section of fence that separated our prairie from the prairie to the west.  The fenceline had become overgrown with shrubs – something that is great for some species of birds but really hard on a barbed-wire fence.  We ended up treating the shrubs with herbicide, pulling out the fence, and shredding the remains of the shrubs before re-building the fence.

This fenceline was cleared of shrubs two years ago so we could re-build the fence. The photo shows the vegetation that came in after the shrubs were removed (left side of the fence). Note the lack of flowering plants in our property to the right.

The above photo shows that fenceline as it looks now.  In place of the shrubs, there is now a stand of thick prairie vegetation, including grasses, sedges, and forbs.  Ok, there’s also some smooth brome and even the beginnings of a stand of Phragmites (the thick-leaved grass in the photo).  But the interesting thing to me is the species that are blooming right now.  If you look at our prairie – which is shown on the right side of the photo – you don’t see any flowers blooming.  That’s not a photography trick.  There really are very few plants blooming right now in that prairie.  Yet in the fence row, Maximilian sunflower and Canada goldenrod are abundant and showy, and there are a few other flower species blooming as well.

So what’s the deal?  Here’s what I think is happening.  Our prairie had a long history of annual summer haying – as far as we can tell.  I don’t think it’s been sprayed with 2,4-D, though I’m not 100% sure, because it has a pretty good abundance of spring and early summer flowers, including pale poppymallow, blue-eyed grass, violets, prairie clovers, Illinois bundleflower, and others.  However, I think many years of annual haying likely eliminated late-blooming flowers from our prairie.  If perennial plants aren’t allowed to bloom and complete their annual life cycle they don’t produce seeds.  Perhaps more importantly, annual defoliation while the plants are still actively growing removes the plants’ ability to produce food for their root systems that were, until they were defoliated, gathering enough resources to support tall vigorous plants.  If wildflowers are like grasses (don’t know if there is research that has tested this) that sudden loss of aboveground vegetation causes an abandonment of large segments of roots – because there is no food coming in to maintain them.  If those plants are defoliated at the same growing stage every year without a break, it’s easy to see how they would eventually die without replacing themselves.

The Maximilian sunflower and Canada goldenrod plants growing in the fenceline are not rare plants, or even plants that are particularly difficult to maintain in most prairies.  But they’re almost non-existent in our prairie.  We’ve begun to overseed some late-season-flowering plants into the prairie, and species such as Maximilian sunflower, stiff sunflower, wild bergamot,  and a few others are slowly establishing – and seem to be surviving well under our patch-burn grazing management.  I hope we can bring them back so that late-summer pollinators (for example) can have something to eat other than what they can find in the fenceline!

A closer view of some of the plant species growing in the unhayed/ungrazed portion of the prairie along the fenceline. The prairie to the left in this photo is our neighbor's prairie - which is annually hayed.

So, if the wildflower species that are missing from our historically-hayed prairie are common in the fenceline where they weren’t being mowed, burned, or grazed, does that mean we should manage (or not manage) our prairie by perennially idling it?  No, I don’t think so.  First, remember that although those flowers are blooming in the fenceline now, they weren’t two years ago because they were covered up by tall vigorous shrubs.  Prairies managed without fire – or something that sets back trees and shrubs – tend to grow quickly to woody vegetation, changing their very nature pretty dramatically.  In addition, though I haven’t looked carefully, I would guess that the fenceline “prairie” is missing many of the early season plants that are so abundant in our prairie because there is nothing that removes each successive year’s thatch along the fence to allow those small plants to get sunshine.  I think one lesson of these plants along the fenceline is that it’s important to provide a periodic rest period for plant species – especially when a site is being managed with the same treatment every year.

One could, I suppose, make the argument that we should manage some portions of the prairie for late-season plants and other portions for early-season plants, and everything will be fine.   Unfortunately, by doing that, we would be reducing the plant diversity – and ecological resilience – of those individual portions by not facilitating the full range of biological diversity and ecological function.  As a result, the entire prairie would be weakened.  This is, by the way, why I disagree with biologists who promote leaving portions of prairies permanently unburned in order to protect insect species that are vulnerable to prescribed fire.  I completely agree that small isolated prairies should not be completely burned (or hayed) in any one year, helping to ensure that refuges are left behind for those species that might be harmed by the management treatment.  Shifting the location of management treatments from year to year should allow species to find appropriate habitat, especially if (as in small isolated prairies) the distance between one management treatment and another is short.  If that’s insufficient, it might be that the real issue is not management, but size and isolation of the prairie – something that can only be solved by strategic prairie restoration of surrounding land parcels.  Reducing the ecological resilience of small prairies by managing them for a small suite of species is certainly not a good long-term solution for those species or the larger community.  (Baby with the bathwater…)

There is one more observation that’s too important not to mention.  The plants that are blooming in these photos somehow survived being covered by dense shrubs for at least a couple decades, and also survived the foliar herbicide application that removed those shrubs.  Plants are tough.  Granted, the wildflower species we’re talking about are species that have a reputation for toughness anyway, but I still think their survival is worthy of note.

I’m not completely sure I’m right about why those flowers are in the fenceline and not my prairie, but even if I’m wrong, just going through the thought process is valuable!  If nothing else, it gives me a hypothesis I can test (and sufficient fodder for an entire blog post).  Isn’t it amazing what we can learn just by looking around us?

A Guide to Patch-Burn Grazing for Biological Diversity

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Patch-burn grazing is getting a lot of attention from a wide variety of audiences these days.  The management system has generated substantial enthusiasm among some people – particularly those interested in improving habitat for prairie wildlife species.  It has also generated substantial skepticism among others – particularly those concerned about potential negative impacts of grazing in eastern tallgrass prairies.

To date, the majority of research on and demonstration of patch-burn grazing has been oriented toward influencing agricultural grassland management because of the system’s potential to improve wildlife habitat at those sites.  Research has largely shown that farmers and ranchers can reap the habitat benefits of patch-burn grazing without compromising current stocking rates or livestock performance.  Because wider adoption of patch-burn grazing techniques on private lands could have tremendous positive impacts on prairie wildlife populations, those research results are exciting, and the continuation of work toward that objective is very appropriate and important.

However, the emphasis on developing and testing patch-burn grazing as an agricultural tool has also somewhat limited our ability to evaluate the system’s impacts (current and potential) on biological diversity.  Variables such as stocking rates, timing and intensity of grazing, fire season and frequency, and others tend to be defined such that they are compatible with local grazing systems and cultures.  Again, this is very appropriate, but it also narrows the range of possible modifications to the basic patch-burn grazing model that are being tested.

In contrast to research projects oriented toward balancing agricultural production with wildlife habitat, our work with patch-burn grazing in the Platte River Prairies of Nebraska is targeted only at building and sustaining biological diversity.  Our stocking rates, fire frequency, and other variables are all primarily designed to favor plant diversity.  Because few others are experimenting with patch-burn grazing from the same standpoint, we have tried to gather as much data as we can about the impacts of our various patch-burn grazing modifications – especially related to impacts on plant species and plant communities.  We’re taking the approach that if we can learn how to optimize management for plant diversity and overall biological diversity, we can then help translate and modify those methods to fit the specific needs of private landowners, public land managers, and others.

A burned patch in restored prairie along the Platte River in Nebraska. Cattle are concentrating their grazing in this area, but the light stocking rate employed means that while many grasses are being grazed, most forbs are not. In this case, ungrazed forbs include opportunistic plants such as black-eyed susan and hoary vervain, but also compass plant and Canada milkvetch, which are often viewed as negatively affected by cattle grazing.

This week I attempted to capture what we’ve learned about patch-burn grazing to this point and incorporate it into a single document.  We certainly don’t have all the answers, and the document should not be read as a prescription for precisely how to employ patch-burn grazing.  Rather, it is a description of the kinds of things we’re trying on our sites and the results we’ve seen so far.  I hope it will stimulate thought and discussion among other prairie managers looking for new ideas and options for dealing with prairie management challenges.

As I’ve said before on this blog, patch-burn grazing is not an appropriate management system for all prairies.  Moreover, patch-burn grazing often gets treated as a single narrow management system, but should really be seen as a basic template – and should rarely be implemented without tailoring it to meet particular objectives.   This new document describes some of the modifications of that template being tested at our sites and the responses we’ve seen from the prairie communities we manage.

If you’re interested, you can download the document here.