Lessons From a Project to Improve Prairie Quality – Part 1: Patch-Burn Grazing, Plant Diversity, and Butterflies

We recently completed a large multi-year restoration and management project at our Platte River Prairies.  Our specific objectives were to improve habitat quality for various at-risk prairie species and evaluate the impacts of our management on at-risk butterflies – particularly regal fritillaries.  The project was supported by the Nebraska Game and Parks Commission, who funded our work with two State Wildlife Grants (U.S. Fish and Wildlife Service money).  Over five years, we conducted fire/grazing management in our prairies and enhanced plant diversity through overseeding and seedling plugs.  We measured the results of that work by measuring changes in prairie plant communities and by looking at the use of our prairies by regal fritillaries and other butterflies.

Plant diversity and buttterfly habitat were the objectives of our 5-year project.

We’ve worked hard to get plant diversity in our restored prairies, including this one.  We wanted to know whether or not our management was maintaining that diversity, and also how it was affecting butterflies.  The prairie shown here was being grazed at the time of the photo – July 2009.  The Nature Conservancy’s Platte River Prairies, Nebraska.

The following is a brief summary of the major lessons we’ve gleaned from the fire/grazing component of the project, including implications for future management and restoration work.  I will summarize the overseeding/seedling work in a separate upcoming post.  If you want more details, you can see our entire final report to the funding agencies here.  As a warning, the report is 14 pages long, with an additional 21 pages of Appendices, full of tables and graphs.

What We Did
Between 2008 and 2012, we treated over 1,500 acres of prairie with varying applications of patch-burn grazing management.  During that time, we altered the timing of burning and the intensity of grazing from year to year, and included years of complete rest from grazing in some prairies.  For the purposes of this project, we evaluated the results of our work in two main ways:

–          We measured changes in plant diversity and mean floristic quality.

–          We conducted three years of butterfly surveys to evaluate how regal fritillaries and other butterfly species responded to our restoration and management work.

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Grandpa’s “Accidental” Prairie Restoration Project

In the late 1950’s, my grandfather bought a quarter section of farmland just southwest of Stockham, Nebraska.  At the time, all but about 26 acres of that 160 acre land parcel was in row crops.  The unfarmed areas (the steepest slopes and wettest draws) were a combination of native prairie and other “waste” ground.  From what I understand, Grandpa’s intent was to buy the land and put much of the cropland back to native grass pasture, keeping only the flattest areas and most productive soils to farm.  Regardless of whether or not that was his initial intent, he did indeed do that restoration project in 1962 – using the Soil Conservation Service’s Great Plains Program to provide cost-share for the seeding and construction of a livestock dam.  Approximately 87 acres of cropland was planted with a mixture of native grasses, including primarily big bluestem, indiangrass, switchgrass, little bluestem, side oats grama, and western wheatgrass – with a little blue grama thrown in too.  (We still have the receipts from the seed company.)

Starting in 1964, Grandpa started grazing the new pasture – including the unfarmed portions – and it’s been grazed annually ever since.  The pasture grazing was designed to be both profitable and sustainable, and as far as I can tell it has been.  There is no evidence of chronic overgrazing, and a number of “grazing sensitive” plant species are still abundant, especially in the old remnant areas.  My grandpa died in 1990, and Grandma died earlier this year.  After Grandma’s death, most of the other family farm land was sold, but after some long discussions, we kept the ¼ section in the family.  My wife and I now own a 2/3 interest and my aunt and uncle own the other 1/3.  Although I was helping Grandma manage the pasture for more than a decade before her death, actually owning the land makes me see the pasture in a much different way.  Before we shelled out our hard-earned money to buy it, the pasture was an interesting place to go cut cedar trees and walk around, and I tried to help Grandma set up the grazing leases to ensure that the land stayed in good condition while bringing in a reasonable income.  Now, as an owner, that lease income means a whole lot more, as does the current and future condition of the grassland.  Decisions about how to balance stocking rate and income with plant community impacts are a little more real!

I bring all this up as background discussion for the real subject of this post.  Though I’m sure it wasn’t Grandpa’s intent when he seeded the site back to grassland in 1962, he actually did some pretty great prairie conservation work.  He took a series of very small isolated remnant prairie islands and filled the space between them with grassland habitat.  It’s hard to know how many plant and insect species populations have larger and more viable populations now because of his work.  Certainly the site has improved habitat conditions for the grasshopper sparrows, western meadowlarks, and other grassland birds that are nesting there.

A portion of remnant (unplowed) prairie on our farm. It has retained a good mixed-grass plant community, with fairly abundant leadplant, stiff sunflower, prairie clovers, and other characteristic prairie plants. Shown here are Missouri goldenrod, white sage, stiff goldenrod, and many others.

While any grassland is better than no grassland, the re-seeded areas of the prairie are still distinct in appearance and composition from the unplowed areas.  Many of the prairie remnants contain fairly abundant populations of conservative forb species, including leadplant, stiff sunflower, prairie violet, prairie clovers, and many others.  A few of those species have moved into the re-seeded areas, but mostly at low abundances.  The re-seeded areas are dominated by grasses, but also have an abundance of many common forb species such as goldenrods, white sage, ironweed, hoary vervain, yellow prairie coneflower, dotted gayfeather, yarrow, and others – along with strong populations of sweet clover.

This photo shows some of the re-seeded prairie. Many native forbs have moved into the stand of grass that Grandpa planted, but others are still rare or missing.

I only recently found some hand-drawn maps showing the exact locations of the unplowed areas, and was able to cross-check those with old aerial photos from before and after the 1962 seeding.  Now that I know those locations more exactly, I’ll be able to start making even better comparisons between the remnant and re-seeded areas.  I started that process this last weekend, taking an inventory of plant species in the re-seeded areas (I found 65 species).  I’m sure I’ll add to that list over time, but that’s not too bad, considering only 6-7 grasses were planted there initially.  I don’t know yet how many plant species are in the remnant portions – I’m still working on that.

This aerial photo from 1956 shows our 1/4 section just prior to Grandpa buying it. The darkest areas are the unfarmed portions. You can see how small and isolated many of them were. Only the steepest and wettest areas avoided the plow.

In some ways, it’s amazing to see the diversity of plants in those previously farmed areas.  If I took a botanist to the site without divulging its history, I’m pretty they’d have no idea it had once been farmed.  At the same time, while there is good plant diversity at the site, it’s interesting to see how few conservative plant species have made their way into the previously farmed areas.  I’ve seen a few individuals of leadplant, a few patches of purple and white prairie clover, some areas of purple coneflower, and a few stiff sunflower colonies.  Prairie violets have begun creeping from the remnants into the re-seeded areas too – but in 50 years, they’ve only made it about 20 or 30 yards.

All of this points out the importance of protecting and managing remnant prairies to avoid losing those conservative plant species.  Once they’re gone, it’s not realistic to expect them to just come waltzing back in from nearby sites.  During the last 10 years or so, I’ve been overseeding portions of the re-seeded prairie with locally harvested seed.  As is typical, the results of that have been fairly muted, but I’m hoping my work gets those plants to establish a little faster than they otherwise would have…

This false sunflower is one of a handful of species that is showing up here and there across the old farmed portions of the prairie as a result of our overseeding efforts. It's a slow process, but one that will, I hope, pay long-term dividends.

Of course, if Grandpa’s restoration project was being done today, and the main goal was really to ecologically reconnect those small prairie islands, the cropland around the prairie remnants would be seeded with a high-diversity mixture of prairie plant species.  That would help ensure that the seeded area facilitated a number of ecological needs, including the availability of host plants for a variety of insects and genetic flow between plant species.  In 1962, no one in Nebraska was even thinking about anything like that, and Grandpa’s goal was (I think) simply to take a piece of land that was being overused and make it into productive agricultural land.  I’m pretty sure he’d never heard of a grasshopper sparrow.  Regardless of his initial goal, there is now a 108 acre prairie in southern Hamilton County, Nebraska – and that’s a rare and valuable commodity.  The nearest prairie to ours is at least several miles away, across many acres of cropland.

I don’t know exactly know how to measure the ecological value of our prairie, but I’m sure proud to own it.