Scientists have long known that forests sometimes act as "carbon sinks," absorbing more of the greenhouse gas carbon dioxide than they release. Now, a team of researchers has identified a mechanism through which grasslands appear to demonstrate the same property.

The research findings, published in the Jan. 11 issue of the journal Nature, may have important implications as scientists and policy-makers around the world debate ways to lower levels of atmospheric carbon dioxide, believed to be a major contributor to the greenhouse effect and global climate change.

The lead author of the paper is Dr. Shuijin Hu, assistant professor of plant pathology at North Carolina State University. The project leaders are Dr. F. Stuart Chapin III, formerly at the University of California, Berkeley, and now at the University of Alaska; Dr. Christopher B. Field of the Carnegie Institution of Washington; and Dr. Harold A. Mooney of Stanford University.

Hu explains that other scientists have proposed that grasslands can act as carbon sinks when atmospheric carbon dioxide is elevated. The research described in the Nature paper, however, identified a mechanism through which grassland soils can sequester carbon, and, in fact, found a trend toward increased soil carbon under elevated carbon dioxide conditions.

"Our data indicate that soil microbes quickly respond to changes in carbon and nitrogen availability and may play critical roles in determining the potential of grasslands and other terrestrial ecosystems, too to act as a carbon sink," Hu said.

Carbon sequestration occurs in an ecosystem when the amount of carbon dioxide absorbed by growing plants is greater than the amount of the gas released by decomposing plant material.

The results are from a five-year study conducted at an annual grassland on Stanford University's Jasper Ridge Biological Preserve in central California. Between 1992 and 1997, the researchers maintained two sets of open-top chambers a
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Contact: Dr. Shuijin Hu
shuijin_hu@ncsu.edu
919-515-2097
North Carolina State University
9-Jan-2001