Prairie Fen Series – Meet our Dynamic Peatland!

Take some time to learn about Southern Michigan’s most underrated ecosystem, the prairie fen! In this three-part series, we will go over what a prairie fen is, how to identify this community by its plant species, and what threats they face. This first post offers a reflection on these globally rare, but locally abundant, biological treasures by comparing them to their more well-known cousin, the bog. We will start the series by looking at the geological events that formed these unique wetlands using photos and stories from Michigan’s largest prairie fen. Stay tuned for two more posts all about our Township’s own prairie fen plant species and its history of being overlooked.

Peatlands: Bogs and Fens

Wetlands have received a lot of hype recently due to their capacity for preserving biodiversity and mitigating climate change. According to the International Peatland Society, the majority of our world’s freshwater wetlands are composed of peatlands. Most peatlands are classified as either fens or bogs. The saturated, anaerobic (no oxygen) soils of these special wetlands do not allow rapid decomposition of plant matter, allowing net accumulation of peat over time. As a result, peatlands are the largest terrestrial storage for carbon, according to the International Union for Conservation of Nature (IUCN).

Although both peatlands are adept at producing incredible biodiversity and carbon storage, they do not receive equal attention. I’ve noticed that even among my science-driven peers, fens are not as well-known as bogs. In undergrad, I was taught more about bogs than fens. Perhaps because bogs are more widely distributed and occur more frequently in Michigan. Or possibly because the highly acidic conditions (low pH) of bogs make them a more singular group, while the fens have several different subtypes. In college, I remember briefly learning that fen wetlands were fed by alkaline (higher pH) calcium and magnesium-rich groundwater, and bogs by rainwater.

Expanding my knowledge of the wondrous prairie fen

In Michigan, the fen group is made up of five natural communities, including prairie fen (check out coastal fen, northern fen, poor fen, and patterned fen if you’d like to learn about the other fens). Prairie fen is appropriately named since it shares many plants found in nearby tallgrass prairies. Prairie fen is found only in the Midwest, thanks to our mighty glaciers.

Map of lower Michigan’s glacier lobes in the most recent glaciation. The Wisconsin glaciation ended around 11,000 years ago. Image is taken from 2015 geomorphic study of the southern Lower Peninsula.

In Michigan, prairie fens primarily occur in the two interlobate regions of the southern Lower Peninsula. We have one interlobate region on the west side of the Lower Peninsula, and other interlobate region called the Jackson Interlobate here in the southeast region. These regions have a complex array of hills and valleys caused by the consolidation and withdrawal of glacier lobes during the Wisconsin glaciation. As noted earlier, all fens are fed by spring water. In the hilly landforms of the Jackson Interlobate, gravity pulls water down through the glacial deposits rich in calcium and magnesium. The alkaline water eventually flows down to the bases of slopes, showing up as spring-fed fens.

A figure displaying fen hydrology from Exploring the Prairie Fen Wetlands of Michigan by MNFI/Michigan State University Extension.

The calcium-rich, alkaline groundwater can be a tough environment for plants. A special set of plants that we call fen “indicator species” tolerate these harsh conditions better than general wetland plants. When we find these plants we know to look closer to see if the surrounding wetland is indeed a prairie fen. Tune into the next blog post in this series to learn more!

Map showing the distribution of prairie fens in Michigan. Circled in red is a cluster of fens that includes those in our township. The northwestern part of Oakland County is where Michigan’s largest prairie fen resides in Springfield Township. Figure from the 2009 Mitchell’s Satyr Habitat Conservation Plan.

My First Fen Visit

No amount of diagrams and reading can prepare someone for what a natural community is like until you are standing in one. I finally had the chance to experience a Michigan fen during the Eastern Massassauga Survey our crew helped with earlier this summer. The survey took place in Michigan’s largest remaining prairie fen in Springfield Township! On the drive there, my unconscious bias predicted the habitat to look similarly isolated and alien as an acidic bog.

I could not have been more naïve. In stark contrast, the landscape was alive and coherent. As I stood unstably on sedge mounds, I could hear what sounded like the thirsty noise of draining a bath. Only in the plants parted could I see where the peculiar sounds were coming from. Calcareous spring water, cold from being locked in the dark earth, ran in rivulets beneath us as we walked. There were also areas where streams flowed on top and through the vegetation. Water and earth weaved in and out of each other; I quickly realized that fens are interlaced with the rest of our sculpted landscape.

This picture depicts the seamless progression from prairie fen to oak forest.

Unlike bogs, which similarly occur in depressions caused by melted glacier ice, prairie fens are not isolated pockets of water. These fens are often part of larger wetland complexes, often occurring on the edges of lakes or along streams. Prairie fen’s plant communities often also morph into surrounding environments like oak barrens and openings, even sharing the same historical need for fire disturbance.

Leaving Springfield’s fen, I rejoiced in the never-ending surprises that come with being a student of the natural world. I had no idea a peatland could feel so energetic. I had been under the impression that all peatlands were as dead as their layers of preserved organic matter.

The next post in this series will dive deeper into the dynamic life that these fens sustain using flora and fauna snapshots from our prairie fen along the paint creek trail. In the meantime, you can check out a previous blog about the Unique Wetland Communities Along the Paint Creek Trail to get some background on the work we do there.

Pitcher Perfect

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Blog post by Heather Herndon, Natural Areas Stewardship Technician

Blog post by Heather Herndon, Natural Areas Stewardship Technician

The nutrient-poor conditions of bogs and fens present a challenging environment for plant growth, so some plants have evolved mechanisms to obtain extra nutrients in interesting ways. The three special plants found in these habitats in Michigan are pitcher plants, bladderworts, and sundews. Carnivorous plants have always been a favorite of mine because of their ability to live in extreme environments and thrive by eating insects! It is also really fun to watch slow motion videos of flies being captured by the infamous Venus flytrap!

Pitcher plant (Sarracenia purpurea) can be found in bogs or fens all over the great state of Michigan, including the bog at Cranberry Lake Park. The highly modified leaves are curved into a pitcher-like shape, thus giving the unique carnivorous plant its name!

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The Pitcher Plant has quite a unique flower!

Pitcher plants in particular attract insects with their brightly colored, highly modified “pitcher” leaves that mimic flowers. Insects crawl down into the leaf and get trapped! Downward pointing hairs and a waxy coating on the inside of leaf prevent the insect from escaping, and enzymes produced by bacteria in the liquid at the bottom on the leaf digest the insect. A “pitcher” perfect ending for the plant, but not so much for the insect!

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Can you see the fine white hairs on the inside of the leaves?

Have you found a carnivorous plant while walking through a fen or bog in your area? If you have, comment below! We would love to see your photos and hear about your experiences with cool carnivorous plants!

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Plant information was gathered from Michigan DNR and NOHLC websites.