This land Tennessee: A lone prairie

Natural History, Sept, 1997 by Robert H. Mohlenbrock

The term prairie readily conjures up an image of the cast seas of tall, short or mixed grasses that historically occupied the heartland of the United States. But tongues of grassland also penetrated parts of Wisconsin, Michigan, Illinois,Indiana, and Ohio. Botanist Edward N. Transeau coined the term prairie peninsula for such tongues, small patches of which persist even within the eastern deciduous forest (see Buffalo Beats, Ohio" Natural History, December 1991). Having lived all my life in southern Illinois, I have long been familiar with such prairie remnants, but I learned only two years ago that a tall-grass prairie may have existed in parts of Tennessee. A remnant, called Mary Prairie (after a member of the family that formerly owned the land), lies in the outskirts of Manchester, some sixty miles southeast of Nashville.

Surveyors who made their way through Tennessee and Kentucky in the early 1800s recorded finding a number of barrens"' or treeless areas. One by one these habitats have been erased, mostly through agricultural practices and urbanization. In addition, because fires were suppressed, some small patches of prairie undoubtedly turned into forest. May Prairie survived undisturbed, however. Visiting it on July 4, 1947, botanist Aaron J. Sharp and his colleagues from the University of Tennessee recorded that the prairie covered about forty acres. In addition to tall-grass prairie species, they identified many plants rare for the region but commonly found on the Atlantic and Gulf coastal plains or elsewhere in the southeast.

In 1975 the state of Tennessee purchased an eighty-two-acre parcel and designated it a State Natural Area, and in 1981 the federal government registered it as a National Natural Landmark. At purchase the property consisted of five acres of good prairie, fifteen acres of degraded prairie (overrun by small trees and shrubs), and sixty-two acres of surrounding forest, to be used as a buffer zone. From aerial photographs taken years earlier, it was possible to identify twenty additional acres of the forest that had been prairie half a century ago. Tennessee's Division of Natural Heritage is taking steps to convert the degraded and forested sections back to pure prairie through a management plan that includes prescribed burning.

Tennessee ecologists Brian Bowen and Milo Pyne offer an explanation of how May Prairie came to exist in a region dominated by forest. The soil in this region -- a rather high, flat zone called the Eastern Highland Rim, just west of the Cumberland Plateau -- consists of clay overlain by a thick mantle of wind-blown particles, called loess, deposited at the end of the last ice age, about 12,000 years ago. The clay, which can become saturated in the winter, is not very favorable for the roots of trees, while the mantle of loess is ideal for the more shallow-rooted prairie species. Nevertheless, the area might have become forested long ago had it not been for an especially hot and dry climatic episode between about 8,000 and 4,000 years ago. This enabled prairie species to invade areas that became too dry for trees. A prairie peninsula may have extended into parts of Tennessee at this time, but fossil evidence shows that May Prairie itself remained covered by forest until about 6,000 years ago.

When the climate became cooler and wetter, forest reclaimed the land. May Prairie and other prairie remnants in Tennessee might have been swallowed up had it not been for the presence of Native American peoples, who apparently burned them periodically in an effort to maintain better hunting grounds for bison, elk, and deer.

Tall-grass prairie species include big bluestem, little bluestem, Indian grass, and switch-grass, some of which attain heights of twelve feet by late autumn. Mixed in among these grasses is an array of prairie wildflowers: Indian paintbrush, wild blue false indigo, Kansas gay-feather, tall tickseed sunflower, prairie brown-eyed Susan, closed gentian, purple gerardia, smooth prairie phlox, false dragonhead, narrow-leaved mountain mint, woolly prairie sunflower, rattlesnake-master, green milkweed, capitate bush clover, and several kinds of asters and goldenrods. Most of these bloom from late spring and summer into autumn, while others, such as birdfoot violet, yellow star-grass, and bird's-eye bluet, bloom as early as April.

The low and shrubby prairie pussy willow is scattered throughout the prairie, while in one area at the edge is a huge stand of the yellow, sunflowerlike southern prairie dock, one of Tennessee's threatened species. Where moisture accumulates in shallow depressions, typical flowers are perfoliate boneset, joe-pye weed, New England aster, grass-leaved goldenrod, monkey flower, blue lobelia, and water hemlock.

Coastal plain plants include the very showy false asphodel and death camas of the lily family, Canby's lobelia, Nuttall's milkwort, narrow-leaved bush clover, white-scaled boneset, a sundew, and an assortment of grasses and sedges. Snowy orchis, southern yellow orchis, and other wild orchids have been recorded.