This interview has been lightly edited for clarity.
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Scott Hall:
It's the Tuesday morning show, and we tell stories of Northern Minnesota through music, conversation, and events. We're starting a new series looking at the history of our local forests, and today I'm delighted to welcome John Almendinger back to our studios. John is a forest ecologist for many years with the DNR. Hi John. Thanks for coming in.
John Almendinger:
You're welcome.
Scott Hall:
John, are you retired?
John Almendinger:
Yes. <laugh>.
Scott Hall:
Are you doing any work related to DNR these days?
John Almendinger:
I'm on what they call a post-retirement option, and I'm trying to finish up a project that's 30 years old. Over 30, I guess. We started at university in 1980. I'm just trying to make sure the DNR actually gets something out of this project, and maybe bring it to some kind of conclusion. So, I'm working on a map of historic vegetation in the state.
Scott Hall:
Yeah. And that's what a forest ecologist is knowledgeable about. We're glad you could be here. We also have Mark Jacobs, a retired land commissioner and forester on from Aitkin. Mark's joining us. Hi Mark. Welcome back.
Mark Jacobs:
Good morning.
Scott Hall:
And John Latimer is on the line, you guys, so he may have a dumb question for you. <laugh>. Hi, John.
John Latimer:
Hey, good morning, guys. Glad to be a part of this.
Scott Hall:
Hey, I think this is an exciting discussion because you guys have agreed to select how glaciers created the forest we have in Northern Minnesota. And we're talking thousands of thousands of years [that] we're gonna try to condense into 15 minutes, right?
John Almendinger:
No sweat.
Scott Hall:
<laugh>. So we have diverse forests in our area. We have bogs, marshes, and fans. And John, you work up in the bog project. So, John Almendinger, why don't we start with you? Describe how you would describe our forest here in Northern Minnesota.
John Almendinger:
Oh, lots of different kinds.
Scott Hall:
Okay.
John Almendinger:
52 to be exact, according to us, 52 in the state. But, to get to the topic of the day, Mark had asked me to address three kinds that people see a lot here in the listening area: pine forests, mesic hardwood forests (sugar bushes, sugar maple, basswood trees, stuff like that,) and our peatland forests. There are other kinds, like floodplain forests that occur along the Mississippi, Minnesota River, and Cloquet River around here. And other vegetation types too: there are prairies, there are wetlands, fens, open bogs, other kinds of vegetation. But glaciers had a lot to do with it.
Scott Hall:
What did the glaciers do?
John Almendinger:
The glaciers created virtually the entire land surface of the state. And at one point or time, glaciers affected probably almost every square inch of the state.
Scott Hall:
And they, they left behind what?
John Almendinger:
The surface. The material that forms the surface in the soils of the state.
Scott Hall:
Including the ups and downs as well as the materials.
John Almendinger:
They did several things. They determined the kinds of rocks that you would find in the state. They were forming lobes of glaciers that affected the state. Some came from the Lake Superior Basin, some came from the Hudson Bay lowlands. Some came from directly north of us across the Canadian Shield, where there's almost no carbonates in the rocks, so it's very acidic kinds of rock deposits. Then others came from the lowlands in Manitoba, which are very chock-full of limestone and other kinds of rocks. So, the kinds of rocks that you find are quite different, and the processes by which the glaciers deposit these rocks are quite different. And with regard to the surface topography, whether it's hills or plains or things like that. And the amount of mixing that you see in the soil. So some soils, for example, if the ice deposited the materials rather directly, you can get everything from car-sized boulders to clay particles.
Scott Hall:
You were talking a lot about rocks, though. Did soils come after the glaciers, or were some soils dragged in here by the glaciers? Oh,
John Almendinger:
One thing to mention is everybody says, “Oh, glaciers: 10,000 years ago.” Yeah, no. The Pleistocene epoch, which is a geologic epoch, lasted 2 million years.
Scott Hall:
You were there too.
John Almendinger:
Yeah, exactly.
Scott Hall:
And John Latimer!
John Almendinger:
Latimer was there with me. Yeah.
John Latimer:
<laugh>, I was there first! <laugh>
John Almendinger:
I said almost every square inch [because] we had a patch in southeastern Minnesota that wasn't very much affected by the last series of glaciation. So, we had a few small places that might not have been covered by ice in this last one, but basically, it set the scene. [The glaciers] set topography, the drainage patterns where rivers are determined, where our lakes are. So it controlled the topography, the kinds of rocks you find, the drainage you find, and that had everything to do with what kinds of plants and trees can grow there. So, that's set the scene.
The way to sort of think about it is, if you look at this official geology map of the state, it's like a big mosaic. The tiles of the mosaic range in size from 50 acres up to 5,000 acres. It's a mosaic of different size tiles. And what we've found over the years is since Minnesota's been ice-free, the vegetation within those mosaic tiles is fairly consistent. In other words, it's fairly uniform across those tiles. Now, it's totally naive to think that when the glaciers left, that was it: the glaciers made these forests. Nuh uh, no. For two reasons: One is the climate has not been consistent. Minnesota's climate's been changing since we were ice-free from the glaciers. So, we've undergone a lot of climate change since. So, it doesn't mean that the glaciers made pine forest habitat right off the bat, and it's always been a pine forest. There are a few places where that's happened, like at Basswood Lake and Lake of the Clouds up in the Boundary Waters where it hasn't changed hardly at all.
And there are places down along the Iowa border and out along the Dakotas where it was prairie right after the glaciers, and it has been prairie since. But in between those two spots, there's been a lot of vegetational change because there's a steep climatic gradient between Southwestern and Northeastern Minnesota. So, things have changed a lot. And the other reason that there has been a lot of change. It's naive to think that geologic processes haven't just quit when glaciers had their way with Minnesota: there's still erosion, there's still movement of materials. Rivers are still down-cutting, they're draining sediment and depositing terraces along the rivers. So, there's modern deposits as well. There are sand dunes, there's been movement of particles as fine as silt-sized particles that have been blown onto other land forms. So, some of the soil surfaces are modern (meaning since the glaciers were here).
Scott Hall:
So your point is, it's always a work in progress.
John Almendinger:
It is, but the basic tapestry, the mosaic that was set in place, was basically the result of glaciers.
Scott Hall:
Now, Mark Jacobs, you've probably walked every square foot of forests in Aitkin County over the last 30 or 40 years. As you're listening to John talk, what are you thinking about?
Mark Jacobs:
Well, Even where I live over by Savannah Portage State Park in the St. Louis moraines, you've got big ridges with hardwoods on them, and there's a silt cap on top of these big ridges. Now, when I normally think of silt, I think of sedimentation from flooding. But how does that silt get up on top of those high ridges?
John Almendinger:
Okay. You asked me about mesic hardwood forests: Maple trees, basswood trees, ironwood trees, stuff like that. That's one where they're growing on a surface that was only indirectly built. Okay. It's hilly. Hardwood forest needs several things. One is they can't burn. They have to be protected [from] fire. They're in hills where fires don't carry very easily. They're also in places that historically were oak forest. The oak forest helped leach the soils and develop an impermeable layer at depth, which means that it could perch water. And it turns out the spring snow melt saturates these soils to the surface every spring. So, they were saturated, and they tended not to ever have spring fires.
And to answer Mark's question, these hills are downwind of a big ablation basin where Lake Winnie now occurs. It's part of the Rosy Lake Plain. And when that lake receded, the strong winds built a dunefield, meaning that the sand particles fell out first. So, there are sand dunes from Tamarac Point in Lake Winnie all the way to the Leech River. So, the dunes were built, and it kept pushing the Leech River farther south. So that's all sand. The finer particles, which is loamy, drapes over the tops of the moraines that were built by a stagnant moving glacier. And he's talking about the St. Louis Marines, which were also built by a stagnant moving glacier. The finer particles, the pure silt, which is slightly smaller size yet, blew all the way to Aitkin County, where Mark is seeing the mesic hardwood forest that he has. So the basic structure was built by a glacier, but the icing on top of the cake was put there by wind, so it's very uniform. There's not a stone in the top of it. It's very amenable to the growth of mesic hardwood forest, which is what Mark is talking about.
John Latimer:
Would this be similar to what we in Itasca County experienced down in the Sugar Hills region?
John Almendinger:
Yes. Identical. Same deflation basin, same source. Only, the particle sizes get bigger and bigger as you approach dunefield.
Scott Hall:
What does deflation mean?
John Almendinger:
Oh. Once all that sediment from the Rosy Lake Plain was exposed, the wind was picking those particles up and depositing them. Most of this probably happened at the end of glaciation. If you think about a glacier, you've got a mile-high hunk of ice, which is as high as Pikes' Peak, and the winds are very strong. It's cold on the top of a glacier. Cold wind sinks, and forms what they call adiomatic gravitational winds. And they come off the glacier, and they're very strong, and they can pick up loose sediment once this lake basin drained.
John Latimer:
Okay. If, for example, I had actually been there (I got there just a little bit too late,) would it have been a super dusty kind of sandstorm sort of thing? Or would this have been intermittent?
John Almendinger:
<laugh> I lied. I wasn't there. <laugh> Yeah. I think it would've been pretty dusty at certain times.
John Latimer:
There would've been no vegetation to speak of.
John Almendinger:
Not to start with, yes. Eventually, they stabilized. And during the mid-Holocene, when it got very warm and dry, there was some reactivity around 8,000 years ago. We know because there's some organic materials that are buried between lenses of this. Either the sand at the high banks on Winnie and other places. There's some buried organics.
Mark Jacobs:
I'm kind of sandwiched in between two former glacial lakes. Could you talk a little about those?
John Almendinger:
Yeah. If we wanna talk about carbon, one of the biggest carbon sinks in the world are the peatlands that occur at high altitudes in both North America and especially Russia. That's sort of what makes Minnesota unique in the lower 48 states and Canada. When the glaciers were here, all that meltwater had to go someplace. The glaciers got hung up on the Mesabi range. They were having a hard time getting over that big hump, which is the iron range. And the meltwater had to go somewhere. And glaciers, believe it or not, are big enough and heavy enough to depress the surface of the earth like you were pushing on a balloon or something. So, the water pools at the front of the glacier, and the north shore of the proglacial lake is the ice itself. And the south shore is wherever there's a height of land south of the glacier. And in this case, he's talking about glacial lake Upham, which is almost right up against the Mesabi range and the ice itself. And glacial Lake Aitkin. It basically was all one lake. There's a narrow spot at Hay Lake about midway, maybe that's where Mark's house is. But anyway, there was a big glacial lake there, and the big river came through about here in Grand Rapids and Goodland: it formed a huge delta out there. So, a lot of sediment was coming that way. And it all gets sorted out: it was sandy around the edges of the lake. Silt and clay fell out towards the center of the lake. If several things happened, that wouldn't eventually drain, because when the ice melted the land tipped back up about 20 meters, I believe.
So, you can follow the beach lines. the land relaxed as the weight of the ice came off the earth, and basically poured it out like you'd pour water out of a saucer. And it was exposed sediment. Again, we have a lot of sand dunes around the Cow Horn Lakes here in Grand Rapids. And some of that was also moved by the wind. But, basically ,it was a big spot and it was the lowest in the land. The Mississippi River goes right through the spot. It was very low and very wet. For some time, it was basically marshes and prairies. But it was always wet. And that's the key. This has nothing to do with glacial land surface: it has to do with the land surface that developed starting about 5-6 thousand years ago in spots and starting at 4,000 years ago in other spots. It's wet. And the reason organics accumulated is there's no oxygen. By comparison, air is 21% oxygen, that's 21 parts per hundred. In water. It's like eight parts per million. So, organic matter accumulates, and then you get a perfect environment for mosses to grow. Mosses don't have roots like vascular plants, so it's a great spot to be a moss. And once sphagnum mosses start to invade places like this, they have the ability to grow vertically, raise the water table up above the land surface itself, and spread out horizontally. And all of this happened in the Glacial Lake Upham and Aitkin basins. Once they isolated from the groundwater, the environment was organic, always wet, and very nitrogen-poor. Basically, it isolated itself, raised itself up above the regional water table, and it's perfect habitat for tamarac and spruce trees. And these are huge carbon sinks. That's how we ended up with all these extensive Tamarac in the glacial lake basins. Glacial Lake Aggasiz, which we also have here in Minnesota, was the biggest freshwater lake ever to occur in the world, probably.
These are big sinks for carbon, and they are in peril to due to climate change. And Mark might want to take that topic up as an independent topic someday. Right now, they're in trouble, and they're exuding methane quite a bit. They're burning up in places. We have, (I'm going to guess: by now, I don't know the numbers for sure) around 600,000, 700,000 acres of standing dead Tamarac in Minnesota now. Hmm. Uh, they are very vulnerable to climate change. And this is a big concern. But that's pretty much the history of how we got these Tamarac and spruce bogs. And I think John's study at SPRUCE is gonna start telling us the same story. He might know more about methane emissions than I do.
Scott Hall:
Well, we're out of time. I think I could probably go on a while about the forests created by what the glaciers left behind, but we'll leave it there for today. Um, Mark Jacobs, thanks for calling our attention to John Almendinger on this topic. And I'm sure there's more we can cover in it, but thank you.
John Almendinger:
Yeah. Well, thanks for having us.
Scott Hall:
Great to see you. Yep. John Latimer, you hang in there, buddy. We'll talk to you soon.
John Latimer:
Thanks, John. Thanks, Mark. I could have stayed on the phone and talked to you guys for all day and just been fascinated.
Scott Hall:
Well, I was a little worried about that <laugh> <laugh> cause we've gotta move on!
