Clay and Holah established eight experimental plots in summer 1994, each of which had a variety of vegetation at the start. Alternating plots were then planted with infected or uninfected fescue seed. After two months, there were stands of fescue in each plot along with many other species. No other treatments were used, such as fertilizer, pesticides or mowing.
After four years, infected plots had become dominated by fescue -- nearly 90 percent of the biomass -- while uninfected plots had more diverse populations of other grasses such as Kentucky bluegrass, with fescue making up less than 60 percent of the biomass.
The total biomass did not differ between infected and uninfected plots, so net productivity was not affected. The fungus could affect the community by several other methods, however.
"The fungus produces toxic alkaloids, which may have altered the feeding patterns of small mammalian herbivores, birds and insects that were abundant in our plots," Clay said. "In addition, infection by the fungus enhances drought tolerance of fescue, and there are often extended periods without rain during summers in southern Indiana. Finally, infected plants are more productive than uninfected plants in the absence of stress. Any or all of these factors may promote the dominance of infected fescue in mixed vegetation."
The results of the study have implications for conservation as well as agriculture, he added, because loss of plant diversity is likely wherever fescue is common and highly infected, not just in areas where it was planted.
"Independent evidence suggests that infection increases in mixtures of plant
species over
time, so that sites with low infection can become highly infected," he
explained. "Seed
transmission of the fungus ensures that it is dispersed with the grass. Given
its widespread
distribution and high infection frequency, tall fescue may threaten th
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Contact: Hal Kibbey
hkibbey@indiana.edu
812-855-0074
Indiana University
5-Oct-1999