3 September 2007Denver PostKaty Human
if(requestedWidth > 0){ document.getElementById('articleViewerGroup').style.width = requestedWidth + "px"; document.getElementById('articleViewerGroup').style.margin = "0px 0px 10px 10px"; }On eastern Colorado's grassy rangeland, the dominant plant of the future may be one shunned even by the hungriest of cattle: fringed sage.
The unpalatable mint-green shrub increased in bulk by 40 times during climate change experiments conducted by the U.S. Department of Agriculture and Colorado State University, the scientists reported last week.
"It was a minor species at the beginning of the study, but by the end of four years, 10 percent of the aboveground cover was this species," said Jack Morgan, a USDA range scientist in Fort Collins.
"Here's a plant that may be a winner in a greenhouse future," Morgan said.
Grassland covers about 40 percent of Earth's land, Morgan and his colleagues wrote in a paper in the Proceedings of the National Academy of Sciences, and woody shrubs have been moving steadily into most of the planet's grasslands for more than a century.
Scientists have attributed that livestock-unfriendly trend to many things, Morgan said, from the suppression of natural fires to overgrazing, drought and climate change.
"There's some who would debate if carbon dioxide and climate change were a factor," Morgan said. "But that's what our study shows - clearly."
Forty miles northeast of Fort Collins, on Colorado's northeastern plains, Morgan and his colleagues set up clear plastic greenhouses around plots of prairie.
They pumped extra carbon dioxide into some of the greenhouses, left ambient air in others, and followed plant communities in both - and on normal prairie - for four years.
Fringed sage increased its aboveground bulk by 40 times in the greenhouses with extra carbon dioxide, the team found.
"That's a huge response," Morgan said. "I've not seen any plant in the literature that responds as much."
Other studies have shown that plant species react differently to climate change.
In Colorado's mountains, fields of wildflowers gave way to sage during warming experiments.
In a California grassland, species diversity dropped when scientists increased carbon dioxide levels.
On rangeland, the likely continued woody plant encroachment is not just an ecological problem. It's a financial one for ranchers, said Terry Fankhauser, executive vice president of the Arvada-based Colorado Cattlemen's Association.
"We know climate change is inevitable, and we know that means species changes," Fankhauser said.
More shrubs and fewer grasses would not be welcome changes, he said, although Colorado cattlemen have long had to deal with woody invaders.
"It's already a part of everyday ranch management," Fankhauser said. "We have to control those woody species to maintain native vegetation."
Staff writer Katy Human can be reached at 303-954-1910 or [email protected].
