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Arb Notes – Carleton’s Tiny Prairie

The Postage Stamp prairie may be a little bigger than its namesake, but not by much. Carleton’s own remnant prairie fragment overlooks Bell Field and is the only untouched land that the college owns. Postage Stamp’s location on a steep hillside (perhaps one of only three hills on campus!) has protected it since the time of the settlers. Farmers were unable to maneuver their plows on the slope and so left that little patch of prairie undisturbed. The bedrock, Platteville Limestone, is also too close to the surface to support agriculture. The steepness of the slope likely affected this lack of soil accumulation though erosion and decreased soil stability. The outcome? Our little remnant was spared!

Since Postage Stamp’s soil has never been turned over, its historic microbial community and seed bank are intact. This means it can regenerate with native species after experiencing disturbance. When areas surrounding Postage Stamp are cleared of invasive brush, native species grow back in replacement. This doesn’t happen in other areas of the Arb where we have to import native seed.

Postage Stamp is not completely free of human influence. It was likely grazed by cows before Carleton bought it, and even now we manage it extensively. We burn Postage Stamp every few years, use herbicides to treat invading shrubs, and do extensive invasive species weeding. Though human involvement may seem to take away from the untouched aura of our remnant prairie, failure to maintain it would actually allow human influence to have a greater impact on Postage Stamp.

Humans have brought to Minnesota non-native species that don’t have competitors and so can dominate whole plant communities. We also drove bison out of this area long ago and dramatically reduced the frequency of natural fires in the Upper Arb. Both weeding and herbicide use are essential because they prevent non-native species, such as buckthorn, that surround our remnant prairie from taking over.

Postage Stamp Prairie is Carleton’s own connection to natural history; this is a prairie that has always been prairie. Today, we are working to connect Postage Stamp to nearby restored areas. Hopefully, this will help pollinators more easily access the isolated remnant prairie. Postage Stamp’s primary usage is as a cool fact. We generally don’t collect seeds from it because it is so small and could have a hard time maintaining itself if stressed by too much removal. Postage Stamp is one of many small remnant prairies scattered around southern Minnesota. But it’s pretty cool that Carleton has its own half-acre connection to history in the backyard.

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