Forest Service Southern Research Station ecologist Barry Clinton (Coweeta Hydrologic Laboratory)--with fellow researchers from Clemson University and the University of North Carolina-Chapel Hill--tested the effects of fallen chestnut leaves on five tree species that historically competed with the American chestnut before chestnut blight destroyed almost all of the great trees.

"American chestnut reached its greatest size and stand density in the southern Appalachians, where it may have taken up almost 50 percent of the forest canopy," said Clinton. "Chestnut's dominance has traditionally been attributed to its rapid growth rate, resistance to rot and fire, and ability to thrive on poor soil. Our experiments show that allelopathy may also have contributed to its dominance."

Allelopathy is the secretion by plants of chemicals that inhibit the growth or reproduction of competing plant species. Black walnut is a prime example of allelopathy: the tree produces the chemical Juglone, which suppresses the growth of trees, shrubs, and other vegetation. Other allelopathic trees include sycamore, eucalyptus, and hackberry.

Clinton and his fellow researchers tested the effects of an extract made from the leaves of young American chestnut trees on the seeds of red maple, eastern white pine, eastern hemlock, yellow-poplar, and the native shrub rosebay rhododendron. Under controlled laboratory conditions, the researchers found that the extracts inhibited the germination of eastern hemlock and rosebay rhododendron. Eastern hemlock is a major species along the mountain streams of the Southern Appalachians. Rosebay rhododendron has become the dominant shrub on moist sites, where it interferes with hardwood r
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Contact: Barry Clinton
bclinton@fs.fed.us
828-524-2128
Southern Research Station - USDA Forest Service
10-Oct-2002