Sediment samples suggest how plants would fare in hotter, dr...( CHAMPAIGN Ill. -- Sediment samples dat...)

In the Jan. 13 issue of the Proceedings of the National Academy of Sciences, scientists at the University of Illinois at Urbana-Champaign report that native C4 plants did not fare well during prolonged periods of severe drought that occurred in the middle Holocene (4,000 to 8,000 years ago).

C4 plants, so designated because of their biochemical pathway of photosynthesis, are generally expected to do well in warmer, drier climates driven by rising levels of carbon dioxide. Elevated carbon dioxide concentrations alone should favor C3 plants, which use another photosynthesis pathway. While the middle Holocene had much lower levels of carbon dioxide, the general climate conditions of that time provide a good model for study, said Feng Sheng Hu, a professor in the plant biology and geology departments at Illinois.

The sediment from West Olaf Lake, which contains residue of plant life, indicates that weedy C3 plants such as Ambrosia (ragweed) adapted well during severe-drought episodes because of their ability to exploit very limited amounts of water available during the growing season, said David M. Nelson, lead author of the paper and a doctoral student in ecology and evolutionary biology working with Hu.

The findings suggest that even C4 plants could face disastrous consequences during long periods of drought, despite the fact that they use water more efficiently than C3 plants, Nelson said. Barren areas unsuitable for agriculture may be much more extensive in the Midwest under warmer, drier conditions predicted for the future, he said.

"Previous studies of past grassland change have been hampered by the fact that pollen grains of grasses cannot be separated into species, making it difficult to un
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Contact: Jim Barlow, Life Sciences Editor
jebarlow@staff.uiuc.edu
217-333-5802
University of Illinois at Urbana-Champaign
13-Jan-2004