During the spring melt in Western Canada , there are usually one or two areas in fields that take longer to dry than the rest of the land.
In years like 2010, those low-lying areas may stay wet all summer.
While most farmers think of these depressions as a nuisance, Angela Bedard-Haughn, assistant professor in soil science at the University of Saskatchewan, wonders if the soils in these low-lying areas are actually suitable for growing crops.
These natural depressions are known as ephemeral wetlands, said Bedard-Haughn, who grew up on a farm near St. Brieux, Sask., before getting her doctorate at the University of California, Davis.
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The soil in these areas may appear highly fertile, she added, but looks can be misleading.
“In a drier year when you go look at those soils, ‘oh, look at that nice, thick A-Horizon…. That looks like a nice, nutrient rich soil,’ ” she said.
“But what’s less clear is how long those benefits last and how the drainage process affects the longer-term fertility of those soils.”
On the Prairies there are two main types of wetlands.
One is ephemeral, defined as small depressions that usually dry out in the summer or fall.
The other is semi-permanent, or wetlands that are usually full of water, which means kids could skate on its pond in winter if kids still did that sort of thing.
Scientists refer to soils in ephemeral wetlands as gleysolic, an anaerobic soil subjected to long periods of saturation or a high ground water level.
Although tillage, drainage and decades of modern agriculture have altered many of the ephemeral wetlands on the Prairies, the soil under the depressions is distinct from soil in higher elevations in the same field.
Unfortunately, scientists have more or less ignored the soil in ephemeral wetlands, which means there’s a large question mark around the long-term viability of draining these depressions.
In an article she wrote titledPrairie Wetland Soils: Gleysolic and Organic,Bedard-Haughn found a few papers on the effects of drainage on gleysolic soils.
After reviewing the studies, Bedard-Haughn found evidence that draining wetland soils increased leaching, caused binding of soil particles into larger aggregates and reduced the absorption of herbicide, which could potentially contaminate ground water.
In addition, it’s not clear how the bacteria and organisms in the gleysolic soils adjust to drainage.
“In terms of how the microbial community changes over time, how the nutrient cycling changes over time, we don’t have a great handle on that.”
But it’s logical that soils associated with ephemeral wetlands are different, she said, because of the influence of ground water.
“The ground water table is going to be closer to the surface there … and there may be more calcium carbonates or salts coming close to the surface,” said Bedard-Haughn, who was named an outstanding new teacher at the U of S in 2010.
“Your capillary fringe, that zone that’s saturated from the ground water up, might be interacting directly with the surface. So it might influence the chemistry and hydrology, as well as the biology.”
What scientists do know is draining wetlands causes water to leave the land at a faster rate, which causes nutrients to leave the land more rapidly.
“There is a relationship (between) increased drainage and increased fertility moving off the landscape, particularly phosphate,” said Paul Thoroughgood, a Ducks Unlimited agrologist in Regina.
As well, wetlands are known as a tremendous sink for greenhouse gases, Thoroughgood said.
“Restoring some of those drained wetlands might provide ecological value… but also provide (farmers) with some financial rewards through carbon credits.”
Wetlands might be better off as wetlands and could provide an alternative revenue source for farmers, but that water passed under the bridge, or off the fields, many decades ago on the Canadian Prairies.
Approximately 70 percent of wetlands in Canada have already been drained, Thoroughgood said. That number is even higher in the prairie pothole region, where 90 percent of sloughs, marshes and depressions are now dry.
Although restoring wetlands sounds like a simple matter of plugging drains, Bedard-Haughn said it’s much more complicated because no one really knows if restored areas will function as expected.
“We come up against similar issues in the oilsands (restoration). It’s like recreating the ecosystem services that soils naturally perform,” she said.
“Can we take these piles of soil and put them back in layers … and hope it starts doing what it’s supposed to do. Kind of like Frankenstein – put all the pieces together and make it live.”
Despite the ominous Frankenstein reference, Bedard-Haughn remains hopeful that wetlands can be restored in Western Canada, but it will require interdisciplinary re-search and co-operation to find ways to make it happen.
