Tom's Blog

Saturday, September 26, 2009

Visit to Westport Drumlin SNA

Today I joined a group from the Natural Heritage Land Trust on a hike to Westport Drumlin State Natural Area. This is part of an SNA called the Empire Prairies, which comprises three small remnants of what was once the vast (>7000 acres) Empire Prairie, which extended all the way into Columbia County to the north.

The Westport Drumlin SNA contains 15 acres of dry to dry-mesic prairie plus a small bur oak savanna. The prairie contains over 100 dry site species, but is most noted for its substantial population of prairie bush clover (Lespedeza leptostachya), a Federally-threatened and State-endangered species. The photo above shows the group examining a small population of the spectacular downy gentian (Gentiana puberulenta), a colorful gentian which is a late-blooming species.

A drumlin is a geological feature created when the vast Wisconsin continental glacier crossed this area some thousands of years ago. A drumlin has a characteristic tear-drop shape, created as the glacier passed over an area of underlying bedrock. The land rises gently on the upflow side of the drumlin, and drops steeply on the downflow side. The long axis of the drumlin is parallel to the direction of ice flow. Some drumlins are fairly high, but the Westport Drumlin is no more than 100 feet above the surrounding farm land. (Eagle Heights, on the University of Wisconsin-Madison campus, is an excellent example of a much higher drumlin.)

Although the Westport Drumlin is owned by the state, most of the surrounding land, including the access (for which an easement exists) is private land. Because of this, the Natural Heritage Land Trust has become active in acquiring some of this surrounding land. The Trust already owns about 70 acres, and is negotiating to acquire more land.

Although the focus of the trip today was on the prairie vegetation, I was particularly interested in observing the fine bur oak savanna that is present on the lower southeast slope. Although not large, this savanna has a substantial number of large, open-grown bur oaks. Although the savanna is not large enough to have much of a savanna understory flora, the savanna is surrounded by a large patch of prairie grasses, including big and little bluestem and Indian grass.


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