Mechanical Measures to Sustain Endangered Grass Species Show Only Short-Term Gain

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An article featured in Castanea tested a mechanical method of limiting the population of shrubs crowding and shading the grass species. By the third season, however, other plant species were also benefiting from the increased light, and flowering of the Tennessee yellow-eyed grass was in decline.

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Cutting back surrounding shrubbery could give the endangered species a chance to reinvigorate--or it could allow other species to flourish instead.

Castanea – The southeastern United States has more than its share of both the nation’s human population and plant species. However, this rich diversity also spawns competition for space, and eight of the southeastern states have large numbers of plant taxa at risk. Finding ways to actively manage these rare plants is essential to conservation strategies.

An example of an imperiled species is Tennessee yellow-eyed grass, known to exist in only 38 locations in Tennessee, Alabama, and Georgia. The flowering wetland plant does not tolerate shade well, and trees and shrubs are encroaching on several of its positions. Cutting back surrounding shrubbery could give the endangered species a chance to reinvigorate—or it could allow other species to flourish instead.

The current issue of the journal Castanea reports results from a 3-year study of a population of Tennessee yellow-eyed grass. Only six of the 38 populations of this grass are at least partially on public land where protective conservation measures can easily be established. The subject of this study was a population of the plant that occurs in an access cloverleaf off I-75 in Georgia.

The current study tested a mechanical method (cutting) of limiting the population of shrubs crowding and shading the grass species. While this native shrub often appears as a companion to Tennessee yellow-eyed grass, in this location, its density was shading and preventing the grass species from flowering.

During the dormant season, woody plants were removed by cutting at their bases. Researchers then noted the effects on several plots of Tennessee yellow-eyed grass. Untreated control plots were also observed. In two plots not known to contain the grass, the shrubbery was removed to determine if dormant rootstock or seedlings might grow in the absence of the shadowing shrubs.

During the first two years after the shrubs were cut, the grass species showed substantially increased flowering as well as visits from bees, flies, and other insects—significant for a species that does not self-pollinate. By the third season, however, other plant species were also benefitting from the increased light, and flowering of the Tennessee yellow-eyed grass was in decline. This study found that, in the long term, the shrubs may actually help the grass by providing a refuge, and that the best management should include a microhabitat of this woody cover and exposed mineral soil.

Full text of the article, “Management of a Population of the Federally Endangered Xyris tennesseensis (Tennessee Yellow-Eyed Grass),” Castanea, Vol. 78, No. 3, September 2013, is now available.

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About Castanea
Castanea is the journal of the Southern Appalachian Botanical Society and publishes articles relating to all aspects of botany in the entire eastern United States and adjoining areas. The Southern Appalachians—the nonglaciated mountainous areas of Alabama, Georgia, South Carolina, North Carolina, Tennessee, Kentucky, Virginia, West Virginia, Maryland, Pennsylvania, and southwestern New York—form an evolutionary center for native plant diversity for the northern temperate regions of the world. The society dates to 1935 and serves all persons interested in the botany of the Southern Appalachian Mountains. The journal encourages submissions of scientific papers dealing with basic research in any field of plant biology, systematics, floristics, ecology, physiology and biochemistry. For more information about the journal or society, please visit: http://www.sabs.appstate.edu.

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Bridget Lamb
Allen Press, Inc.
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