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May 182010
 

From Green Right Now Reports

Photo: James H. Miller, USDA

Photo: James H. Miller, USDA

Here’s one more reason to bemoan the spread of kudzu throughout the southeastern United States: When the ubiquitous “vine that ate the South” isn’t gobbling up landscapes and devastating ecosystems, it also is adding to ozone pollution, a new report says.

In the May 17 online edition of the Proceedings of the National Academy of Sciences, researcher John Hickman and colleagues (who worked together at Stony Brook University) concluded that kudzu is able to fix atmospheric nitrogen at a high rate, potentially altering the nitrogen cycle. Hickman, currently a postdoctoral fellow at the Earth Institute at Columbia University, compared nitrogen cycling and nitrogen oxide fluxes from both invaded and unaffected soils.

“Kudzu had the potential to add a lot of nitrogen to soils, so we expected to see some pretty big impacts on the soils of invaded ecosystems in the United States,” he said. “It turns out that the changes you can’t see in a kudzu invasion are just as dramatic as the ones you can.”

Measurements in Georgia showed that some rates of nitrogen cycling were up to ten times faster in soils where kudzu had invaded. In addition to profound changes in rates of several components of nitrogen cycle, the researchers found that kudzu caused a doubling of emissions of nitric oxide from soils. Along with volatile organic compounds (VOCs), nitric oxide is the key precursor to ozone pollution in the lower atmosphere.

“Air pollution is a risk that hasn’t been considered much in the conversation about invasive species, but it’s something we may have to pay more attention to,” Hickman said.

Though it wasn’t examined in the study, kudzu also emits isoprene, a VOC produced in large quantities by certain plant species, which is involved in reactions with NOx to form ozone.

“In the case of kudzu, you have a plant that is generating NOx from the soil and emitting VOC’s from its leaves—it’s like a living tailpipe,” Hickman said.

“Maybe they’ll start calling kudzu ‘the vine that choked the South.’”