Tag Archives: reconstruction

Trying to Figure Out What We Did Right

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When converting crop land to restored prairie, it’s always hard to predict what you’re going to get.  Numerous examples prove that even when you control as many variables as possible – including soil conditions and the rate, timing, and technique of planting – no two seedings turn out alike.  Sometimes, you can use hindsight to explain what happened (weather conditions, herbicide carryover, etc.) but most of the time it’s clear that we just don’t understand much of what’s happening out there.

I’ve been analyzing some data from one particular restored prairie lately, and trying to puzzle out what’s going on.  In this case, the results are good – which is nice.  It’d be nicer, of course, if I could explain WHY things worked so well and then replicate whatever happened…

The Dahms 2000 prairie restoration has turned into one of the most aesthetically pleasing prairies we manage along the Platte. It has tremendous diversity and abundance of wildflowers. Most importantly, its plant diversity is still increasing fairly rapidly after twelve field seasons.

The prairie in question was seeded with a mixture of about 200 plant species onto 69 acres of disked cropland that had been in corn the previous season.  The seed was planted sporadically between December 1999 and April 2000.  Wetlands were added to the site by excavating down close to groundwater and recreating the kind of swale/ridge topography that is typical of nearby Platte River meadows.  Those wetlands and sandy spoil piles (ridges) were seeded with appropriate seed as well. 

All of the seed was broadcast onto the site – some by fertilizer spreader and some by hand (I was experimenting) and no harrowing or packing of the soil was done.  Unfortunately, this was the last year BEFORE I started keeping good records of the amount of seed from each plant species I included in the mixture, so I only have a list of the species we harvested seed from that year.  What I know is that my seeding rate per acre was about 15 gallons of grass seed (mostly big warm-season natives) that was harvested by combine from nearby prairies, and about 1/2 gallon of hand-harvested forbs, grasses, and sedges.  That’s roughly 12 bulk pounds of grass seed and 1/2 pound of forb (wildflower) seed per acre.  I have no idea what germination rates were that year, but it was a pretty light seeding rate compared to what many others around the country use.  Today, our typical mix is a little lighter on grass and includes about twice the forbs.

To cut to the results, this prairie has turned into our most diverse and showy restoration we’ve ever done.  You’d never know we’d used such a light seeding rate of forbs by looking at the site now – its appearance is dominated by big showy wildflowers.  By every measure I use to look at the plant communities of our restored prairies, it comes out high.  I’ve found 178 plant species in the site so far, which is excellent.  The mean Floristic Quality (combination of species number and “conservatism values”) is high, and still climbing rapidly.  It averages twelve plant species per square meter, which is higher than most other restored or remnant prairies in the area.  (Yes, I know that seems like a very low number to you eastern tallgrass prairie folks, but it’s good for out here.  Don’t rain on my parade, ok?)  Twelve years after it was planted, tall warm-season grass species are still not very dominant.  The species found at the highest frequency is big bluestem, and it was only in about 80% of 1m2  plots stratified across the site last June.  In short, it’s a beautiful prairie.  And I don’t know why.

I know most of you are ITCHING to see the actual data tables and graphs, but because there are a few who aren’t, I’m including them as a PDF file, which you see by clicking here.  The PDF also includes a cumulative list of plant species found in the restored prairie.

Flower species such as black-eyed Susan (foreground) and bee balm (pink flowers in the background) are still dominating the plant community in this photo from 2009 (the 10th growing season of this seeding). The lasting abundance of those species is, I think, tied to the lack of dominance by major grass species.

It’s particularly impressive that this seeding turned out so well, because the odds seemed stacked against it early on.  It was seeded right at the beginning of a 7 year drought.  The first several years were dominated (as usual) by weedy species and a few colonizing native species such as Canada wild rye and common evening primrose, but in this prairie those species remained dominant for several more years than is typical.  Once other plant species started breaking through, there were few legumes present – and we don’t typically have problems establishing legumes in our prairies.  Those legumes are still more scarce than in other nearby sites, but they’re increasing over time.  Finally, in about its eighth season, the site stopped looking like a weed patch and matured into something that most people would recognize as a prairie.

As I’ve discussed in other blog posts, I’m still struggling to define success in our overall prairie restoration efforts, but at the scale of individual seedings, there are a couple things I look for.  First, I want to see a good diversity of plant species, and I want to see that diversity sustain itself over time.  Second, I don’t want to see invasive species increasing at the expense of that overall plant diversity, even as the prairie is exposed to disturbances such as drought, fire, and grazing.  So far, this restored prairie passes those tests with flying colors.  We’re moving toward implementing some measures of invertebrate use as well, but aren’t there yet.  Initial data and observations, however, show higher butterfly abundance and diversity in this site than in other nearby restored prairies – for whatever that’s worth.

The prairie has been managed with some periodic fire and grazing, which should be helping to suppress dominant grasses. However, this site has gotten much less of that kind of management than nearby restored prairies, and those other prairies have stronger populations of major grasses, so management can't explain the whole phenomenon. In this photo, cattle are grazing in the burned portion of this site - within a patch-burn grazing system. The grasses are primarily grazed short, helping to showcase the abundance of the forbs.

So why did this restoration turn out so well?  I really have no idea.  It caught a couple nice rains during its first spring, but the rest of the summer was awfully dry.  The overall seeding rate for forbs was considerably lower than we use now, but I don’t know how much seed we had of individual species.  I wish I understood why it has taken the big grasses so long to fill in, but I don’t.  I think the delayed grass dominance probably plays a role in encouraging the abundance and diversity of wildflowers at the site, but I don’t know how to replicate it.  The soils at the site are a little sandier than some of our other sites, but we’ve worked on sandier soils and had very quick grass establishment, so it seems unlikely that the sand is the key.

Besides its aesthetic appeal, the prairie is also a great seed harvest site because of its wildflower abundance. Nanette Whitten (left) and Mardell Jasnowski (right) are harvesting seeds in this photo.

The vast majority of our prairie restorations turn out pretty well, but this one is extraordinary, and I can’t explain it.  Was it something about our technique?  Something about the weather or soil conditions?  I know I should probably just be happy with the results, but I want to know WHY! 

Success is sure frustrating.

(What We Have Here is) A Failure to Communicate

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Picture a grassland dominated by little bluestem and other grass species.  One that has an abundance of wildflowers, including bird’s foot violet, goat’s rue, partridge pea, and numerous varieties of goldenrod, bushclover, and tickclover – among many others.  This prairie is one of only a few remnant prairies remaining in an ecosystem that once covered large swaths of North America.  Less than 1% of that ecosystem now remains in good condition, and most of its remnants are on sandy soils or steep slopes where farming and other human practices are difficult.  Sound familiar?  What if I told you this grassland ecosystem is found in places like North Carolina, Alabama, and Florida?  Oh, and that when it’s in really good condition, it’s full of pine trees…

Longleaf pine woodland (grassland?) in North Carolina.

If you live in the Midwest or Great Plains regions of North America, you were likely picturing a nearby tallgrass or mixed-grass prairie as I was describing that grassland.  Our prairies here sound, look, and function very much like the grasslands of the longleaf pine ecosystems in the southeastern United States.  Both rely heavily on frequent fire to maintain the species and habitat structure their species rely on.  The main difference is that longleaf pine grasslands have longleaf pine.

So if longleaf and midwestern prairies are so similar, why is there so little interaction between those of us working in the two ecosystem types?  It’s a question that has bothered me for years.  I’m not anywhere close to an expert on longleaf, having visited only twice during prescribed fire training courses.  On the other hand, I felt very much at home while I was there.  I recognized many of the plants – if not the species, at least the genus – and it wasn’t hard to imagine that I was walking through a midwestern oak savanna (with pine cones).  Click HERE to see some photos of longleaf pine wildflowers.

Frequent fire is used to keep longleaf ecosystems in good condition. Mature longleaf pine trees are very resistant to fire, and the fire keeps woody species from becoming overly abundant in the understory.

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Deciduous trees and shrubs can quickly start to encroach in longleaf pine communities when fire frequency decreases.

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Young longleaf pines - not just older ones - are resistant to fire. When very young, longleaf pines spend several years in a "grass stage" in which the growing point is at the ground level. In the grass stage, the tree invests in root growth belowground and resembles a bunchgrass aboveground - protecting it from fires. The tree in this photo is in the "bottle brush" stage, a phase in between the grass stage and a more mature tree. During this stage, the tree is at its most vulnerable to fire - until it reaches a size that it can again withstand burning.

It seems crazy to me that we’re not consistently exchanging ideas and strategies between midwestern prairies and longleaf pine grasslands – especially because we’re both struggling with many of the same issues.  Both systems become choked with brush and trees in the absence of frequent fire.  Invasive species are a major issue.  Perhaps most importantly, both midwestern prairie and longleaf pine are nearly gone, making restoration a critical need if the ecosystems are to survive.  Restoration efforts involve both the rehabilitation of degraded remnant natural areas and the reconversion of farm land to native vegetation.

I’ve been part of a couple efforts to start information exchanges through The Nature Conservancy and through the Grassland Restoration Network.  Both have mostly fizzled, but the little bit of exchange we managed only strengthened my conviction that we need to keep trying.  From what I can tell, many midwestern prairie ecologists could learn a lot from the way longleaf ecologists focus on ecosystem function – especially fire – as a way to measure success and manipulate habitat.  That heavy emphasis on restoring ecological process is very different from the more species composition-oriented thinking among many midwestern prairie ecologist.  At the same time, I think many longleaf ecologists could gain from infusing their process-oriented approach with more emphasis on plant diversity and the insect and animal diversity associated with those plant species.  In some ways, the differences between longleaf and tallgrass prairie thinking are similar to those between eastern and western prairie thinking within the Central U.S. (as discussed in an earlier post).

One specific opportunity I see is to provide longleaf ecologists better access to lessons learned from the long history of diverse prairie restoration efforts in the Midwest, in which hundreds of plant species are included in seed mixtures.  Most efforts to convert farm fields to longleaf pine communities (with notable exceptions) focus mainly on establishing longleaf pines and grass – largely as a way to facilitate reintroduction of fire.  Increasing the diversity of herbaceous plant species could have some big benefits ecologically, and shouldn’t slow down process of reintroducing fire.  The extent to which midwestern techniques would transfer south is something we should be exploring together.

How do we build the connections?  If I knew the answer, I wouldn’t be writing this post.  However, I do think there are some important steps.  One would be to ensure that longleaf pine ecologists are encouraged and invited to attend the meetings such as the biennial North American Prairie Conference.  Getting us all in the same place to share ideas is absolutely the best way to exchange information.  Better yet, maybe someone in Alabama or South Carolina can host an upcoming prairie conference so that Midwestern prairie folks are forced to come down and see for themselves the wonderful longleaf grasslands.  Facilitating involvement from Midwestern prairie ecologists in existing longleaf conferences would also be valuable (to everyone).

In addition, I think organizations like The Nature Conservancy and others that span multiple states have a responsibility to lead the way in facilitating communication and collaboration.  It’s certainly not easy.  It’s hard enough to work between adjacent states, let alone regions.  On the other hand, none of us have figured out all the challenges in grassland conservation, so we need all the help we can get.  Working and experimenting in separate laboratories without sharing results is just silly.

If anyone sees an opportunity for building bridges between north and south on this issue, please let me know if I can help.

For more information about longleaf pine ecosystems, visit the Longleaf Alliance website.