A Prairie in the Swamp

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Published on: Jun. 2, 2004

Last revision: Nov. 16, 2010

Southeast Missouri receives more rain than any other part of the state, but it also harbors the rarest of dry habitats--sand prairies. These unique prairies are a major link to geologic history and are a major influence on the cultural history of the region.

Missouri's sand prairies are dry islands in a land of swamps. To understand how they came to be, you have to look back through Missouri's geologic history. Much of Missouri's lowlands were once inundated by a shallow gulf. The Ohio River emptied into that gulf, dumping large volumes of sand.

When the glaciers that inched across North America melted, they released enormous volumes of water that flowed down what is now the Mississippi River and its tributaries. The relentless current eroded sand plains that had long before been deposited by the Ohio River. When the super floods receded, only two long sandy ridges remained.

One of these sand ridges is called the Sikeston Sand Ridge. It runs north and south from Benton Hills to the town of New Madrid. Interstate 55 runs along this ridge. The other ridge, named for Malden, Missouri, begins south of Crowley's Ridge and runs down through Malden into Arkansas.

Factors influencing dry conditions include elevation, heat and fire. Because they are 10 to 20 feet above the surrounding land, the sand ridges allow water to rapidly percolate down into the ground water. Although the sand is mixed with some soil particles, it drains much faster than surrounding soils. This draining enhances dry conditions favorable for prairie formation. Heat, provided by sunlight, also dries sand ridges.

Fast drainage and evaporation make sand ridges a challenging environment where only drought-tolerant plants can survive.

Periodic fires also help shape sand prairies. These fires remove dead leaf litter and color the soil black. Darkened sand heats up faster and stays warm longer than lightcolored sand. Fires also improve growing conditions by removing dead grass and wildflower leaves and releasing the nutrients from dead plants into the sand. This process would take months and even years under passive decomposition.

Historically, fire burned the sand prairies every five to eight years, killing sprouting oak trees such as blackjack or post oaks.

Another challenging factor facing sand prairie life is rapid heating and cooling. Just like deserts, sand prairies heat and cool quickly. These rapid and dramatic temperature changes can make life impossible for plants not adapted to these

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