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West Virginia State Parks – Naturalist Corner
Some Like it Dry . . . and Hot

Temperatures increase and rainfall diminishes as we move into late August and early September. In the eastern part of the state, these conditions can be exaggerated by a combination of geography and specific weather conditions. The eastern portion of the state is generally drier than the western, and plants that grow there can have a tough time during the hot days of August and September.

As you travel east from the western boundary of the state at the Ohio River, elevations increase from approximately 600 feet to over 4,000 feet at the Allegheny Front. The Allegheny Front is an east-facing escarpment dividing the Allegheny Plateau to the west and the Valley and Ridge Province to the east. Clouds moving east from the Ohio River are forced higher by the land surface, causing moisture to cool and condense, producing rain. This process is known as orographic lifting. Most of the rain occurs along the western edge of the Allegheny Front, producing high average annual rainfalls in this region. The region just east of the front, the Valley and Ridge Geographic Province, is in a "rain shadow"-an area that receives low annual rainfall.

Rainfall records at three locations in the state-Parkersburg, Wood County (on the Ohio River); Pickens, Randolph County (located near the front); and Petersburg, Grant County (in the rain shadow area east of the front)-illustrate this pattern. In 1961, Parkersburg received 45 inches of rain, Pickens 84, and Petersburg 30.

Some plants can tolerate these hot and dry conditions. Deep root systems allow the plant to collect what moisture is present. Some leaves are covered in fine hair or pubescence to reduce moisture loss. A general list of plants that may be found on hot, dry road banks in the rain shadow region may include early goldenrod and fragrant sumac. In some parts of the region, prickly pear cactus may be present.

However, a combination of low rainfall and a particular bedrock geology at certain locations produces some of the harshest growing conditions for plants in the state. Where steep slopes of exposed shale occur on east- or south-facing slopes, a particular habitat develops called a "shale barren." Shale barrens occur on Devonian-aged shales exclusively in the Valley and Ridge Geographic Province.

Very few plants can tolerate conditions on the shale barrens. Daytime temperatures rise well above 100 degrees F, and the constantly shifting shale fragments or "channers" produce unstable soil conditions. These slopes have sparse vegetation with exposed bedrock at the top and loose channery below. It was not until the late 1800s that botanists discovered the unique flora that grew in the shale barrens. They discovered that some plants were endemic, only occurring in these barrens, and realized the importance of this unique habitat.

Shale bindweed
Shale bindweed

Plants that can tolerate the rigorous conditions found in shale barrens include Kate's mountain clover, white-haired leatherflower, mountain pimpernel, shale bindweed, and yellow buckwheat. These plants either are endemic to, or grow mainly in, shale barrens. West Virginia has one endemic plant species that is listed as endangered by the United States Fish and Wildlife Service-shale barren rockcress. Threats to shale barren plant communities include new road construction, foot travel, and invasive plant species.

Our response to rising temperatures of late summer may be to seek the shade of a cool woodland. Plants in the rain shadow must deal with the harsh conditions of their environment on a continuous basis. The West Virginia Natural Heritage Program is monitoring these barrens and working to conserve this unique natural resource within West Virginia. To learn more about the Natural Heritage Program go to http://www.wvdnr.gov/wildlife/wildlife.shtm.

White-haired leatherflower
White-haired leatherflower
White-haired leatherflower
White-haired leatherflower
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