It’s always fun to hang out with innovative people, especially when they’re working on the same kinds of challenges I am. I was invited to spend several days last week at a South Dakota prairie restoration (reconstruction) workshop, organized by and for staff of the U.S. Fish and Wildlife Service. Tom Koerner, an old friend from when he worked in central Nebraska, asked me to come up and share what we’ve been doing with prairies, and I was glad for the chance to see what’s happening up north.
The Fish and Wildlife Service refuges in the Dakotas have a long history of restoring and managing wetlands and surrounding uplands as primarily duck habitat. Recently, a few biologists and managers have begun questioning the relatively narrow focus on ducks, in view of the much broader mission of the agency (“The U.S. Fish and Wildlife Service’s mission is, working with others, to conserve, protect and enhance fish, wildlife, and plants and their habitats for the continuing benefit of the American people.”). Rather than planting non-native grasses and legumes as duck nesting cover, they say, the Service could be adapting high-diversity restoration techniques used in nearby states to better accomplish their broad mission. To those of us who have been working with high-diversity prairie/wetland restoration for years, the decision seems like a no-brainer, but there are several significant obstacles standing in the way for the Fish and Wildlife Service.
The first obstacle is really inertia. The refuge system in the Dakotas has established a strong reputation as a duck production area among the public, and refuge managers have established techniques and strategies that have been consistently used for many years. It’s difficult to convince someone to change what they’ve been doing over their entire career, especially when you’re asking them to start using a technique they’re unfamiliar with. To those who haven’t used it, high-diversity restoration sounds expensive and risky – and what if it isn’t good for ducks?
The second obstacle is invasive species. In much of the Dakotas, and certainly on the sites we visited near Madison, South Dakota, Canada thistle is a pervasive and invasive threat. Taking land out of crop production and planting perennial vegetation often produces large dense crops of Canada thistle (except when it doesn’t – but there isn’t currently a good way to predict that outcome!). Because Canada thistle is both aggressive and a state-listed noxious weed, the Service can’t ignore large populations of the species in restored grassland areas, and has to act to control it. Small patches can be spot-sprayed, but many areas become infested so heavily that they have to be broadcast-sprayed. This makes planting a diversity of plant species a risky endeavor, because there’s a pretty good chance much of that diversity will have to be sacrificed during Canada thistle control efforts.
The third obstacle is the cost. The perception is that high-diversity restoration is much more expensive than simply planting several species of exotic grasses and some alfalfa. There is obviously some truth to that. Particularly if you’re buying the seed you use, a diverse mixture of native prairie seed can be very expensive. However, there are several other ways to measure and mitigate costs. For example, if seed is harvested by agency staff and volunteers, a lot of seed can be obtained pretty cheaply. It’s amazing how much seed a few people can harvest in just a little bit of time when they’re organized and efficient about doing it. In addition, the alternative is Dense Nesting Cover (DNC), consisting of exotic grasses and alfalfa, which typically has to be torn up and replanted every 7 years or so when the alfalfa starts to disappear, so over the long term, the costs of that method are higher than it might seem at first. Combining the Canada thistle threat with the perceived cost, however, makes a pretty strong counter argument to those pushing for high-diversity – and that argument was the main subject of the workshop last week.
Madison, South Dakota was chosen as the location for the workshop because that Wetland Management District has been experimenting with high-diversity restoration for the last several years. Kyle Kelsey and Bryan Schultz are leading that charge, harvesting seed and experimenting with techniques for establishing it in the face of tight budgets and Canada thistle. Bryan, like Tom Koerner, has ties to prairie restoration work in Nebraska, having worked at the Boyer Chute National Wildlife Refuge on the Nebraska side of the Missouri River earlier in his career. (I’m sure these Nebraska ties are just coincidence, but it IS interesting that John Leisner with the South Dakota Game, Fish & Parks, who is helping lead the way for high-diversity within that agency, also started his career in Nebraska…)
To account for Canada thistle and build diverse prairie restorations, Bryan and Kyle are trying a combination of strategies. First, they are harvesting as much seed as they can – from local sources. Their diversity is increasing each year, as they find more seed sources (and create their own in newly-restored prairies). Second, they are dealing with first-year weeds by applying Plateau herbicide in the first spring. That herbicide application helps suppress Canada thistle, along with some annual weeds such as foxtail. They also do some mowing of annual weeds when they grow so densely that they block sunlight from hitting the ground. Finally, if Canada thistle does appear, they control it by spot spraying, if possible, and broadcast spraying only when absolutely necessary.
Both the Plateau herbicide in the spring and the Milestone herbicide for later thistle control are relatively selective herbicides – though grass and wildflower species that are tolerant of one are not necessarily tolerant of the other. As we walked around the sites, it appeared to some of us that the Plateau herbicide might not be necessary, judging by some areas that were not sprayed. The herbicide application appeared to increase the speed with which dominant warm-season grasses established, and knocked out some wildlflower species – both of which run counter to Bryan and Kyle’s objectives. The weed control provided by the herbicide did alter the weed species composition, but it looked like the unsprayed areas were going to establish equally well (maybe better) compared to the sprayed areas – and might actually have better species diversity in the long run. Experimentation over time will provide better answers than our brief observations last week.
The Milestone herbicide applications seem to be effective, because the chemical is certainly effective at controlling Canada thistle, and there are quite a number of wildflower species that are tolerant (recover within a year or two) to being sprayed. Broadcast spraying definitely reduces plant diversity, but that’s only used when absolutely necessary, and spot spraying is used much more often. That spot spraying helps maintain diversity by only applying chemical to small areas and the selectivity of the herbicide means that even sprayed areas maintain some plant diversity.
In addition to chemical control, Service staff are working on a research project with Dr. Jack Norland of North Dakota State University to see if they can find ways to increasing seed rates of forb species that might compete strongly with Canada thistle without decreasing overall prairie diversity. This study is intriguing because, in contrast to a couple similar projects I’m aware of, they’re targeting a single invasive species and are trying to find forb species with similar life strategies to compete with the invader. They’re only in their second field season, so it’s difficult to say how the project will work out, but I like the way they’re thinking.
Bryan, Kyle, Tom, and the rest of the Fish and Wildlife Service staff in the Dakotas have a long learning curve ahead of them, but they’re doing great work. Most importantly, they’re jumping in with both feet and building some experiment/demonstration sites that will help address the questions being asked by themselves and others about the potential for high-diversity seedings to work in the Dakotas. Some of their young seedings are already looking great, and it’s hard to imagine standing in one of them and thinking that a seeding of exotic grasses and alfalfa would be superior. On the other hand, success hasn’t been consistent yet (Canada thistle has come in strongly in some seedings) and it’ll be interesting to see how their plant diversity looks over time. They’re getting tremendous growth of warm-season grasses in first and second year seedings, which is nice in some respects, but may make it difficult to obtain and maintain plant diversity in the long term. However, as trips around the country constantly remind me, techniques and results that apply to one site often don’t apply elsewhere, so it’s good to try many different things to see what works best locally.
Lots of questions, lots of ideas, and lots of experimentation. Sounds like prairie restoration to me!
Just wondering what species they’re looking at to compete with thistle, northern bedstraw, Canada anemone? My experience with thistle in Minnesota is quite similar, some locations end up with bad infestations, some have little or no thistle. And are they planning to manage their prairie seedings with grazing? Thank you.
Second question first – yes, they’re planning to incorporate grazing into their long-term management. First question – they’re including species such as prairie clover, yarrow, black-eyed susan, and some others I don’t recall right now. Some, like the yarrow are anticipated to largely fade away over time.
Thank you so much for joining us in South Dakota! You have a wealth of knowledge and a great ability to communicate.
We are trying to out compete thistle by filling niches with a high species richness mix, and restore the ecological processes that exist in native praires that are very resistant to invasion by exotics (if managed properly). In the spike project we are putting a lot of a few species (purple prairie clover, yarrow, black-eyed susan, blue vervain, and plains coreopis), on top of our high diverstiy mix. Basically we are looking for species with a huge amount of seeds per pound (economically viable) and we are trying to get species that express over the season so we are not going to boom or bust, to blanket the seeding and make it very difficult for thistle to establish. Most of the species we are targeting are not long lasting and will fade over time due to disease and or fungus infections. Then, in theory the high diversity mix will express and dominate. Lets hope it works!
Kyle and company
What is likely causing the Cirsium arvense problem is continuing disturbance. This could be coming from introduced non-native earth worms or even native fauna. I have read about toads hibernating in groups causing a patch disturbance regime that would fit the descripition of the Cirsium arvense outbreaks. Selective herbicide application is useful, but the question is then “How do you prevent it from coming back?” I have seen patches of Spartina pectinata and a highly rhizomous variety of Physotegia virginiana adjacent to areas dominated by Cirsium arvense, but the Spartina and Physotegia patches effectively excluded the thistle. Maybe some effort should be put into determining how to keep it from coming back instead of just focusing on what effectively kills it.
You’re correct, continued disturbance is the likely cause, the trick is we need disturbance to create bird habitat (the primary objectives of the grasslands I manage) with abundant forbs, and what’s good for prairie coreopsis et. al. appears to be good for Canada thistle, at least in southwest Minnesota. Prescribed burning in spring tends to release thistle from suppression underneath grass thatch, and we invariably have more flowering thistle after the burn. Grazing can create bare patches as well. Pocket gopher mounds and even badger dens are places I see thistle invade in reconstructions, and I wouldn’t want to eliminate those species even if we could. In general Canada thistle is much less of a problem on dry mesic to dry soils, so I tend to use heavier forb rates and species diversity there, and accentuate the seeding rate of forbs resistant to the prevalent thistle herbicides (but not the the exclusion of other species) on mesic soils. And in truth the best way I have found of dealing with thistle infestations is the hear no evil, see no evil philosophy. Thistle is primarily a social problem, not a biological one in my area, and if no one reports them on a particular unit, they tend not to get sprayed. The funny thing is that thistle doesn’t appear any more prevalent there than in the areas we aggressively control it.
FYI, the toad hibernation phenomena I was talking about is much larger scale than the occassional mammal burrow. Toads will hibernate in large groups disturbing huge patches of soil. This activity elevates the soil into vast mounds. Biologist were puzzled by the large mounds colonized by disturbance adapted plant species. The answer was later found to be huge numbers of toads hibernating together.
I work for the Conservation Corps of Minnesota and I worked with these guys last year collecting native seed. It was a great time and they were having us focus on hard to find/rare species. It would of been great to be present for the workshop there in South Dakota.
I think parasitic plants may be helpful, possibly even against Canada thistle, particularly in seedling stage. Pedicularis canadensis is a species that goes in every prairie seed mix I sow here, and it is effective not only at reducing the “thuggishness” of certain aggressive natives, but also some exotic, including (Oh joy of joys!) sericea lespedeza. Meanwhile, some of the rarer and harder to establish natives are apparently resistant to its parasitism, including gentians, lead plant, and Carex spp. (the unsung graminoids of prairie restoration, and of which I always try to incorporate as much seed as possible when doing prairie plantings at my work site). Similar results with lousewort have been observed up by some of our colleagues in Wisconsin (at that other Madison) and in central Illinois.
Jeff’s question and your response alleviated some of my concern, “yes, they’re planning to incorporate grazing into their long-term management”. One of my main concerns with restorations and value to grassland wildlife is that there has to be some means to control vegetation height and density to benefit the majority of wildlife that we hope will use it. Prairie-chickens, sharptailed grouse, upland sandpipers, grasshopper sparrows, and waterfowl didn’t evolve with 5-6 tall prairie vegetation. The vegetation was either grazed or recovering from having been grazed and, thus, limited in height and density. Also the sod was old and Nature didn’t expend a lot of energy producing seed stalks, thus more vegetative than reproductive. Generally, the exotic grasses and legumes used for dense nesting cover don’t get so tall that grassland wildlife won’t use them but not so restorations. Some means must be employed to controlling height and density. Grazing, as you know, is the most efficient method, high-clipping is another, and species selection yet another. The latter may be done by using high proportions of mid-grasses, e.g. little bluestem, and limiting or omitting big bluestem, indiangrass, and other tall species but the taller grasses will eventually show up especially if the restorations are burned. High-clipping must be done after nesting to avoid nests and broods and, of course is expensive and takes time, equipment and staff.
Restorationists must remember that where early settlers described prairie grass as high as a man on horseback was neither the time or place where abundant grouse or ducks were produced.
High grass makes excellent winter cover for upland game. Pheasants love to congergate in CRP if heavy hunting pressure has not driven them away. Blue-wing Teal also nest in tall prairie grasses a considerable distance from water.
The highest population of prairie chickens in Illinois occurred when there was still a good mix of farm land and tall grass prairie. I think a mix of habitats is important, but other factors are also having an impact. For example, the introduced pheasant has been shown to destroy the nests of prairie chickens. It is believed this is a significant factor hampering their recovery. Another factor is coyotes have moved into our area from further West. They love to eat our Canada goose eggs. I’m sure duck eggs are an even easier meal for them. In the Chicago Area coyote predatation on Canada goose eggs is actually considered to be a positive. People do not like huge flocks of Canada geese deficating on their sidewalks, lawns, and in there waterways.
Maybe if you had some Wolves to chase away the coyotes and other small mammalian predators you would have more game birds?
Research by Ducks Unlimited in the Dakotas found that duck nesting success was actually higher where coyotes are the dominant predator, as they suppress the populations of mid sized carnivores, especially fox.
My bad actually the research was done by the Northern Prairie Science center, now a division of the United State Geologic Survey and they are based in North Dakota.
Mr. Coyote … “Yummy, eggs!”
Widespread Canada thistle populations in prairie plantings tells me something is out of balance. Canada thistle is an agricaultural weed and will be present for a few years in new prairie plantings, in time it will found only in isolated populations. Planting diversity is important, don’t forget the Asters, Sunflowers and Goldenrods.
I would hestitate to rely on herbicides as part of my new prairie management strategy, we have been spraying for thistle since the introducton of 2-4D and we still have thistle. A diverse and robust seeding is the answer to vigor and weed control, I have been chemical free for 15 years and harvest noxious weed free seed from my grassland every year.
I have seen excellent results from the selective application of herbicides. Herbicides are the most effective and economical way of controling the outbreaks of many invasive species. Herbicide seem to be the only feasible way to eliminate patches of Reed Canary Grass. Herbicides are also necessary for the removal and control of woody species. I could not imagine trying to control common buckthorn without applying herbicide to cut stumps.
Being near that “other” Madison, wood betony certainly gets my vote. My biggest problem with this plant is not being able to get enough seed. Once wood betony gets a foot hood in the tall grasses, we have been successful in introducing small conservative forbs among the wood betony colonies.
Canada thistle can be a problem for us in rich soils and especially planted prairies that are abundant in showy forbs but short on grasses. As James M. mentioned, obedient plant is an excellent competitor with Canada thistle (and goldenrods and asters) in rich mesic soils. The clones grow very tight together so I doubt there is enough ground space for little ducks to navigate?
I am not a big fan of Milestone as it causes too much collateral damage (via soil into neighboring plant roots) for my taste, but it is the most effective chemical that I have used to date on Canada thistle.
Good luck to the Dakota folks with their native plantings. I hope they share their findings. Thanks to all for the great discussion.
So far, we have little Canada thistle here in Missouri. Except for teasel, we have few other thistle problems since introductiong of the two thistle weevils. I don’t know if they use Canada thistle. Has anyone tried wicking Canada thistle? We’ve had great success controlling sumac by wicking using either of the two herbicides labeled for it–Tordon 22K or glyphosate. Wicking requires a height difference between target and non-target plants which may require some manipulation. Dr. Walt Fick, KSU, is even experimenting with wicking old world bluestem by grazing or mowing everything down, then wicking the more rapidly growing owb. Grassworks, Inc., has used a similar technique for sericea lespedeza but with a much lower glyphosate solution.
As for prairie-chickens using tallgrass prairie, yes, I know Illinois once had hundreds of thousands of prairie-chickens but once I saw Ron Westemeier’s data on the sanctuaries in Illinois, I understood how. Ron shows no gpc use in unmowed or ungrazed native grasses or native remnants. There were few gpc in the tallgrass prairie between bison and Amerindian extirpation until arrival of EuroAmerican settlers. The explosion after settlment has always been misinterpreted to have been due to introduction of grain but grain had nothing to do with it. It was grazing of the prairie, which I think was patch-burn grazing by default, that made it usable for nesting and brood rearing by gpc again. Yes, I know the exotic pheasants like tall, native grasses but this introduced bird isn’t bothered by cover taller than its head.
Jef is also right, coyotes do help control more efficient nest predators such as foxes.
Thanks for explaining why Prairie Chickens were common in Illinois from after settlement until ~1950. I keep trying to get some grazing in our local prairie restorations, but no one seems interested.
The information Jeff presented also taught me knew things. I still just wonder how wolves would effect the dynamic.
Great discussion. For the study with NDSU, we are utilizing the following publication to help select forbs in the same functional group as Canada thistle – Levang-Brilz, N. and Biondini, M. 2002. Growth rate, root development and uptake of 55 plant species from the Great Plains grasslands, U.S.A. Plant Ecology 165: 117-144.