Friday, September 12, 2008

How Might Climate Change Affect Native Grasslands?

Ten miles west of Cheyenne, carbon-dioxide levels are nearly twice as high as they are in the city.

Well, at least in some test plots at the High Plains Grasslands Research Station.

Thirty plots of native grasslands are part of an experiment to determine how local prairies could react to climate change. The results could shape congressional policy decisions, as well as rangeland management in the Rocky Mountain region.

Wyoming's semi-arid landscape also is a good place to start, since grasslands cover more than 40 percent of the Earth's surface.

"What makes it tricky is that weather and climate, by nature, are variable," said project leader and plant physiologist Dr. Jack Morgan from the U.S. Department of Agriculture. "You look out at this field, and there are probably 100 different plant species. To predict which ones will be the winners and losers is difficult."

Experts know that the environment changes when a rancher puts cattle out to graze. What they don't know is how climate change will impact the animals' preferred meals or the invasive weeds that share the same space. Wyoming and southern New Mexico share similar precipitation levels, but dissimilar temperatures shape the scenery within each state.

"Ranchers stock grasslands according to how much forage is available when," he added.

Ecologists, plant physiologists and soil scientists at the High Plains Grasslands Research Station are comparing the effects of elevated levels of carbon dioxide, temperature and rainfall on spring and summer plant species. Morgan said the 2 -year-old project is a collaborative effort between the USDA, the University of Wyoming and Colorado State University.

Rings of pipe corral each site above ground, while a thin layer of plastic carves through the soil two feet down. Some of the rings "hiss" with the constant release of carbon dioxide. Infrared heaters hang over other locations to simulate a planet that is a few degrees hotter than it is today.

He said cool-season plants like western wheatgrass seem to thrive with additional carbon dioxide. But warm-season species such as the blue gramma are better at adapting to the extra heat. The challenge for scientists is to determine the overall result of the combination of factors.

Morgan said the experiment is only one of a handful worldwide that evaluates more than one feature of climate change. Part of the reason is time. It takes several years to accumulate solid data. Another problem is the cost. He said it takes $250,000 each year to run the carbon dioxide and heating equipment.

High-tech cameras also are used to gauge the topsoil and root system changes under each scenario, said Dan LeCain, site field manager and plant physiologist with the USDA. He added that 80 percent of a grasslands ecosystem is located underground, making root depth an important factor to consider.

But if Wyoming's researchers know the impacts of climate change on one grasslands environment, they will have a pretty good idea how global warming could impact similar ecosystems across the globe, he said.

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