Profile of a 20-Year-Old Prairie

I’ve said many times that prairie and wetland restoration work has been some of the most gratifying of my career.  The opportunity to literally build new prairie from the ground up is pretty tough to beat.  Perhaps the only thing better is the chance to watch that new prairie become a mature, dynamic community of plants that supports a broad diversity of animals as well. 

I’ll apologize up front that this post might be a little too ‘inside baseball’ for some readers.  I’m going to share a lot of details about a restoration project that I think are fascinating.  I’m hoping at least a few others will enjoy it, but I won’t be offended (and I won’t know anyway) if some of you skim this pretty quickly and move on. The last three paragraphs summarize the story pretty well if you want to skip ahead.

An early June 2021 photo from the Derr West 2002 Restoration. Serrate-leaf primrose (Calylophus serrulatus), yarrow (Achillea millefolium) and Junegrass (Koeleria macrantha) are in flower.

Last summer, a couple of my favorite restored prairies hit their 20th growing seasons.  One of them, the Derr West 2002 Restoration, has been particularly interesting to watch for several reasons.  First, it was planted with the most diverse seed mix we’ve ever created – a total of 218 plant species (all locally-harvested).  Second, when we started grazing the site, we built a permanent exclosure in one corner that has given us some ability to compare fire only management with fire/grazing management.  Finally, and related to the first two, I’ve been collecting intensive plant community data at the site every season since the site’s 3rd growing season in 2004.

Site Description, Management, and Evaluation Methods

The 68 acre former cropfield includes 6,000 linear feet of slough wetlands we created by excavating shallow channels that have standing water when groundwater is high.  Spoil from those excavations were used to create curvilinear (there’s a word!) sand ridges.  Those wetlands and ridges were planted with tailored seed mixes and the remainder of the site was planted with a mix of mesic plant species that included some of the wet and sandy species too.  Seed was broadcast in February, 2002 with an EZ-Flow fertilizer spreader that dropped the seed onto soil that had been disked after corn was harvested the previous fall.

The Derr West 2002 Restoration. This is a 2020 photo, showing the sandy alluvial (river formed) soils during a dry summer.

Starting in 2009, we combined this restored prairie with adjacent prairies to make a 370 acre management unit and began a modified patch-burn grazing approach that included a year of complete rest from grazing every once in a while.  Within that large management, units were burned (usually either early or late spring) and then intensively grazed for a full growing season. At any one time, there were patches being grazed hard and others that were in the midst of a multiple year recovery period from the last grazing treatment.  The exception was a 9 acre grazing exclosure we built at the northwest corner of this restored prairie, which got burned at about the same frequency as the rest of the site (average = 3-4 year frequency), but never grazed.

Cows grazing the Derr West restoration this past summer (2021) in a burned patch. You can see a lot of big bluestem and other grasses grazed very short (but many still blooming), as well as both perennial and annual sunflowers – some of which are grazed. This kind of grazing intensity is always followed by a few years of recovery before the next burn/graze event.

It’s been fascinating to watch the site mature and evolve.  In addition to frequent wandering around the site, I also collected annual data on plant composition.  Dating back to 2004, I’ve stomped through the prairie every year with a 1×1 meter plot frame, plopping it down about 70 times in the grazed area and 25-30 times in the ungrazed exclosure (random stratified design – not permanent plots).  Each time I laid the frame down, I listed all the plant species I could see within it.


Between 2004 and 2021, I’ve found a cumulative total of 175 different plant species within those plots.  I only sample from the mesic portions of the site, (skipping the wetlands and sand ridges) so I feel like 175 species is pretty good.  There are probably a few I’ve missed because they aren’t common enough to have show up within those little plots yet (the sum total of all those plots is about 1/5 acre, so I’m sampling a very small portion of the total each year).  I also haven’t crosschecked against the initial planting list to see what we planted that isn’t yet on that list, but there can’t be too many absences. 

For those of you who might want to dig into the full details of the following results, here’s a link to a PDF so you can peruse at will.  For the rest of you, here are a few highlights:

Mean floristic quality through time. Error bars indicate 95% confidence intervals. For context, grazing began in 2009 and 2012 was the most severe single-year drought in recorded history for the area.

Floristic quality is a metric that combines species richness (# of species) with a rating of how tolerant a species is to degraded conditions. Species found mainly in non-degraded sites get higher values. I averaged the floristic quality of all the 1×1 subplots I sampled from each year to get a mean floristic quality number. If you look at the above graph, mean floristic quality grew during the late establishment phase of the site. You can also see a brief dip in 2013, a year after a severe drought in 2012. Apart from that, there has been little change over time, which I take as a sign of ecological resilience.

The 9 acre grazing exclosure from the air in 2021. You can tell from the orange-color that there’s a lot higher density of flowering big bluestem and Indiangrass in the exclosure than in the surrounding grazed area, which was burned in the spring and in the midst of intense grazing when this photo was taken.
This is a cell phone photo of the exclosure (right) and grazed area (left) during a point of high contrast when both were burned but the grazed area was being hit hard by cattle (same year as the above aerial photo). In other years, the height/density contrast is much lower, but the exclosure is still ‘grassier’ in appearance.

The next two graphs show the same time period depicted in the first graph, but include comparisons between the data from the grazed portion of the site and the ungrazed exclosure. The first graph shows mean floristic quality again and the second graph shows mean species richness, which is simply the average number of plant species found within those 1x1m plots each year.

Mean floristic quality started out slightly higher in the exclosure (dark bars) and stayed higher in most years, but that gap seemed to close somewhat over time. Again, grazing started in 2009, so the initial gap was probably due mostly to soils and was unrelated to grazing. Error bars indicate 95% confidence intervals.
While mean floristic quality was very similar between grazed and ungrazed, plant species richness was consistently higher in the grazed area. It started out a little higher (unrelated to grazing) but the widening of the gap was almost surely because of grazing. Error bars indicate 95% confidence intervals.

My interpretation of the above graphs is that the seeded plant community has been remarkably resilient over time. Through fire, drought, floods, and grazing (in the grazed area), the community has maintained its diversity. Grazing doesn’t seem to have had a negative impact on floristic quality and has had a positive impact on species richness (number of species per plot) in most years. Some of that higher species richness is due to ‘weedy’ species that benefit from periodically weakened grass dominance, but as the graphs below show, there’s more to the story.

It’s interesting how obvious the effects of the 2012 drought are. Mean floristic quality dropped in both the grazed and ungrazed areas in 2013 but recovered within a year or two. Mean species richness in 2013 dropped in the exclosure (but not in a statistically significant way) but rose strongly in the grazed portion of the site, likely because a broad suite of plants took advantage of lower competition from species stressed by the drought. Both floristic quality and species richness leveled back off quickly, however. Again, I feel like this is positive evidence that this constructed community is able to adapt and withstand stressors.

The following graphs show example species and their individual changes in frequency of occurrence through time. Frequency of occurrence is the % of 1×1 plots the species was found within each year. The orange lines show species occurrence frequency in the grazed area and the dark blue represents the same for the ungrazed exclosure. I find it fascinating to see the differing patterns. I can make informed guesses about the reasons for some of them, but others just raise fun questions that would be fun to explore.

As you look at the graphs, remember that there’s just a single exclosure, it is considerably smaller than the grazed area (9 acres compared to 59 acres) and includes less variation in soil conditions. In addition, there are fewer than half as many samples from the exclosure as from the grazed area. As a result, be cautious in interpreting too much. This isn’t a replicated study, it’s just a comparison to help interpret what’s going on and to trigger questions to follow up on. I focus mostly on the initial difference between occurrence frequency within grazed vs. ungrazed areas in 2009 and whether that difference grew or shrank over time.

Big bluestem is remarkably consistent in both grazed and ungrazed areas, while Indiangrass has become much more abundant in the grazed areas. (Also why did Indiangrass increase so quickly in the 2 years following the drought within the exclosure??). Both tall dropseed and Canada wildrye have declined somewhat over time, but wildrye seems to have done that independent of grazing status, where dropseed seems to like the grazed area better.
Stiff sunflower does well in both grazed and ungrazed areas, but Maximilian sunflower seems like like the exclosure best (but is persisting in the grazed area at about the same level as before grazing was introduced.) Common groundcherry (Physalis longifolia) seems to respond positively to grazing. Interestingly, marestail (Conyza canadensis) seems to pulse in abundance independent of grazing (what happened in 2015??)
Canada goldenrod hasn’t changed much over time and seems unaffected by grazing. Stiff goldenrod and heath aster look like they do a little better outside the exclosure, but that difference is stronger in heath aster than the goldenrod. Purple prairie clover is found mostly in localized patches across the site, so the overall frequency of occurrence numbers are too small to draw too much from. However, it looks like it might be doing less well in the exclosure than in the grazed area.
Illinois bundleflower is a favorite of cows, so likes the exclosure best, and germinates in large numbers after fires (it’s holding steady in the grazed area too, though). Upright coneflower has largely disappeared in the exclosure, but started out in lower numbers there too. Hoary vervain and yarrow both respond well to grazing, which fits what I would have guessed.
Sweet clover (biennial) has an episodic pattern, but seems to be growing more abundant in the exclosure, while declining somewhat in the grazed area. Black medic does its own thing. Both Kentucky bluegrass and smooth brome are increasing steadily over time in the grazed area. However, as I’ve seen in our other older restored sites, those increases in invasive grasses don’t seem to be causing decreases in species diversity or mean floristic quality. Maybe our grazing management keeps their dominance suppressed, even as they spread, but we will continue to watch that very closely.

I’m really encouraged by the apparent resilience of this site over time. Most species vary in abundance from year to year, but I don’t know of any that have disappeared altogether. The plant communities within the exclosure and grazed areas have become different from each other over time, but neither is necessarily better. The exclosure is less diverse and more grass-dominated, but also has higher abundances of some forb species that seem to thrive better in the absence of grazing (but are surviving in the grazed area as well).

Most importantly to me, the grazed area, which definitely has more heterogeneous habitat (other data not shown here) doesn’t seem to be showing signs of degradation due to the grazing management we use to manage it. Mean floristic quality remains stable and we’re not seeing local extinctions of any plant species. We’re creating a wider range of habitat while still maintaining a diverse plant community.

However, our restoration objective is not just to create a diverse prairie plant community in what used to be crop land. The primary objective is to use that restoration project to enlarge and reconnect neighboring prairies. A diverse plant community contributes toward that, but it’s also important that the new habitat acts as ‘connective tissue’ and provides places for animal species to feed, live, and travel.

We’ve collected data on bees, ants, small mammals, and grasshoppers/katydids that indicate we’re doing well on the habitat front, in addition to maintaining plant diversity. If we can create habitat that helps defragment the landscape, manage it for a diversity of animals, and maintain plant diversity over long periods of time, that’s pretty sweet. We still have a lot to learn, and our oldest sites are still less than 30 years old, so a lot might happen that will make us reconsider, but so far so good!

An American bumble bee (Bombus pensylvanicus) feeds busily in a patch of prairie larkspur in the Derr West 2002 Restoration last summer.

Photos of the Week – January 21, 2022

It’s been an interesting week. One of the reasons is that my two-year-old parody Roadside Wildflower Guide (full of blurry wildflower photos) has caught people’s attention on social media again. Somebody on Twitter came across it and their tweet got picked up on Instagram and Facebook and shared many times. As a result, I’ve been fielding questions all week from people asking whether I’m planning to make the guide into a physical book (no), but also telling me how much they enjoy it (thank you!).

That one goofy project has gotten way more attention than anything else I’ve ever done. I’ve joked with people this week that when I’m dead and gone all my thoughtful conservation work and crisp close-up photography will be forgotten – I’ll just be remembered as ‘that guy with the blurry flower pictures’. I guess as long as I’m remembered, I should be happy?

Anyway, today’s post… At the very end of 2021, Kim and I spent a few quiet and blissfully isolated days at the Niobrara Valley Preserve. While there, I ventured out multiple times with my camera, mostly along the edges of the Niobrara River and some small tributary streams. Before I could share photos from that trip, I got excited about ice bubbles on the restored wetland at the Platte River Prairies and shared photos of those instead. As a result, today’s post has photos from several weeks ago. It’s a hodge podge of ice and frost images. I’m sorry they’re not more blurry. I hope you enjoy them anyway.

The Norden Chute. Nikon 10.5mm fisheye lens. ISO 100, f/22, 1/13 sec.

The Norden Chute is a well-known local landmark on the Niobrara River, located just upstream of the Norden Bridge in the middle of the Niobrara Valley Preserve. The chute is gorgeous, but I’ve always struggled a little with photos of it. Compositionally, if you’re standing down by the chute, it’s hard for me to find a way to avoid the water flowing out of the edge of the frame, rather than into the frame. That tends to make the resulting photos seem a little out of balance. Here, above and below, are two examples of that. I still like the images, but maybe you can see what I mean. It would be ideal to stand on the other (south) side of the river, but there isn’t a great place to stand there and all the action (shallow flowing water and patterns) is on the north side. Oh well.

The Norden Chute. Tokina 11-20mm lens @11mm. ISO 100, f/22, 1/13 sec.
Patterns in the ice along the edge of the Norden Chute. Nikon 105mm macro lens. ISO 320, f/14, 1/80 sec.
Small chunks of ice in the mud near the Norden Chute. Nikon 10.5mm fisheye lens. ISO 320, f/22, 1/80 sec.

Here’s a very short video clip of the water going over the falls at the Chute. The cascading water, with rafts of ice in it, was really mesmerizing to watch. The video captures some of that feeling, but I spent a long time just staring at it in real life.

Ice and flowing water in a small stream. Nikon 105mm macro lens. ISO 250, f/16, 1/100 sec.
More ice and flowing water – in a different stream. Nikon 105mm macro lens. ISO 250, f/9, 1/320 sec.
Raccoon track and ice on a stream bank. Nikon 105mm macro lens. ISO 400, f/11, 1/100 sec.
Frosty grass along the edge of a stream. Nikon 105mm macro lens. ISO 400, f/14, 1/60 sec.
Accumulated frost above the water along the edge of a stream. Nikon 105mm macro lens. ISO 500, f/13, 1/200 sec.

I took lots of photos of the little ‘Christmas trees’ of frost (above) on emergent vegetation along the edge of a small stream. The stream was strongly groundwater fed, and so wasn’t frozen over, but that warmer water and the cold air combined to make some pretty fantastic frost on plants in and along its banks.

Ice and open water on a small stream. Nikon 10.5mm fisheye lens. ISO 500, f/18, 1/60 sec.
A small opening in the frozen Niobrara River. Nikon 10.5mm fisheye lens. ISO 500, f/20, 1/640 sec.