|3/11/2016 9:55:00 AM|
60 years of change in Wisconsin's prairie remnants
by Doug Hansmann
Southwestern Wisconsin's Driftless Region gets its very name from the ancient heritage of its soil. And as Amy Alstad, the Blue Mounds Area Project (BMAP) outreach ecologist told an audience last Thursday evening, that soil was essential for the prairies that once blanketed the region.
Aided by a favorable climate, the tallgrass prairie that was so common to the south and west in Illinois, Iowa and Minnesota took hold in our hilly countryside. But along with this essential combination of soil and climate, prairies must have one more element to flourish - they need to be forged in fire.
Alstad spoke to an audience at the fourth and final BMAP Winter Conservation Conversation about her work to document the changes in the remnant patches of prairie that still exist throughout our area today.
"Many of you know me because of the work I do wearing my BMAP ecologist hat, but it is the work that I'm doing wearing my UW-Madison graduate student hat that I'll be talking about tonight," said Alstad.
As a graduate student, she is continuing in the footsteps of a man who was a giant in her field of study.
"John Curtis was a big deal," sa id Alstad. "His book 'The Vegetation of Wisconsin' was described in 1959 as one of the single most important contributions to the field of plant ecology in the 20th century."
Born and educated in Wisconsin, Curtis was lured away to teach at the University of Pennsylvania in 1940. But in a turn of events almost unheard of today, he left his Ivy League position to return to UW-Madison.
"It was rumored at the time," said Alstad, "that he came back because of the ecological restoration projects that were just beginning at the UW-Madison Arboretum."
Curtis and his students produced an extremely well documented record of the kinds of plants found at over 2,000 stands of vegetation around the state, representing 38 different plant communities, and according to Alstad, the prairie community personally interested Curtis most of all.
"Wisconsin is unique. There are states that have some historical records but not with as many sites or as long a time span."
"Already at this time around 1950, almost all of the prairies of Wisconsin had been lost. The sites Curtis chose to sample included pioneer-era cemeteries, railroad rights-of-way and protected land destined to become state natural areas or parks, as well as roadsides and private land," said Alstad.
The Driftless Area was well represented in Curtis' original survey along with other sites in south-central and southeastern Wisconsin.
In the summers of 1987 and 1988 Mark Leach revisited a number of Curtis' prairie sites to repeat a survey of the plant communities, and in 2012, Alstad followed up with her own re-survey. Their results show a pattern of declining prairie quality.
While the total number of species found at a particular site hasn't changed noticeably, there are a lot more non-native and woody plants today.
"On average, about 40% of the species found today are non-natives," said Alstad. "We're seeing a big jump in these exotic species."
What those non-natives are replacing are often the native prairie specialists. High quality plants found only in the best prairie remnants, like the wood lily or the white or purple prairie clover, are now less common.
"These plants are indicators of a good prairie that I was really excited to find," said Alstad.
When Alstad looks at the loss of high quality plants and the increase in invasive species, she sees far more change in the later 1987 - 2012 time window since Leach did his survey than in the earlier 1950 - 1987 time window.
"The pace of change of losing those nice native prairie specialists and gaining exotic and woody species has really picked up."
Not content with only documenting the changes in the plant community, Alstad is also asking why these changes are happening. Looking at the earlier time window before 1987, wetter prairies suffered the most loss, but this doesn't seem to be true more recently.
"Soil moisture matters early on, but no longer matters much," said Alstad.
The story changes when the sizes of prairie remnants are compared. While the earlier time window does not show a difference in species loss based on remnant size, since 1987 "bigger prairies are losing native species at a much slower rate," said Alstad, "so patch area matters a lot."
Prairie burning is also a key piece of the puzzle. As April approaches, the sight and smell of smoke rising from blackened prairie remnants will once again be common around the region.
"Frequent fire helps maintain the quality of these plant communities," said Alstad.
While fire is an important management tool, Alstad commented, "I am not advocating that every single prairie gets burned edge to edge every single year. Land managers are aware that there is a lot more than just plants out there in a prairie. While plants may be a highly visible part, insects are also important. Still, I'm leery of too many caveats on using fire. Fire needs to be part of the toolkit."
The Black Earth Rettenmund Prairie State Natural Area has had a particularly high rate of fires in its history, and it has a much slower than average rate of extinction. It is also a site that has benefited from having "a core remnant area and then prairie restoration around that core, so the prairie is actually bigger now than it was when Curtis surveyed," said Alstad. Looking at this kind of connectivity is part of her ongoing research.
So what is the future of our remnant prairies in the Driftless Area? Positioned as we are on the northeastern edge of the historic tallgrass prairie, Alstad speculated about whether a warmer climate might allow the prairie to march more firmly into Wisconsin.
"I think there is good evidence to suggest that a warming climate is going to favor prairie habitat. The problem is I don't think this is going to override some of the other factors. The patches are so small and isolated. If you've got one tiny little prairie here, and one tiny little prairie there, are species going to be able to track that climate change? We don't really know."
Alstad hopes her research motivates people to recognize and protect our remaining prairie remnants.
"Reclaiming or restoring sites is a really good thing. Grassroots efforts can run the gamut from somebody in the middle of a dense urban area planting a few native plants in the backyard to attract pollinators, all the way to maintaining a large, high-quality site like Scuppernong prairie in Jefferson County."
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