Projected increases in rainfall variability resulting from changes in global climate can rapidly reduce productivity and alter the composition of grassland plants, according to scientists funded by the National Science Foundation (NSF). Although the diversity of plant species is increased in this scenario, the most important or dominant grasses were more water-stressed and their growth was reduced. Carbon dioxide release by roots and microbes below ground also was reduced.

Results of the experiment, conducted at NSF's Konza Prairie Long Term Ecological Research (LTER) site, are published in this week's (December 13th) issue of the journal Science.

The biologists, Alan Knapp, Philip Fay, and John Blair and colleagues of Kansas State University, Scott Collins of NSF, and Melinda Smith at the National Center for Ecological Analysis and Synthesis at the University of California, Santa Barbara, found that more extreme swings in rainfall patterns, without any changes in the total amount of rainfall received in a growing season, reduced the biomass of plants but increased the variety of species able to live in a particular experimental plot of land.

"This study is the first to focus on and manipulate climate variability in an intact ecosystem, without altering the average climate," said Quentin Wheeler, director of NSF's division of environmental biology, which funded the research along with the U.S. Department of Agriculture and the U.S. Department of Energy. "Because these responses are similar to those that would occur under drought conditions, the results suggest that increased rainfall variability combined with projected higher temperatures and decreased rainfall amounts, may lead to even greater impacts on ecosystems than previously anticipated."

In this study of how grasslands respond to more variation in rainfall patterns, the scientists hoped to better understand how rapidly and to what extent ecosystems might respond to
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Contact: Cheryl Dybas
cdybas@nsf.gov
703-292-8070
National Science Foundation
12-Dec-2002

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