From: David A Gabel, ENN
Published April 12, 2012 09:58 AM

Climate Change Effects on Long-Term Plant Growth in Arizona

Climate change around the world is not predicted to be uniform. Most places will get warmer, some will get more rain and others will get less. For areas of Arizona, warmer temperatures are expected to provide a boost in plant growth caused by a longer growing season and more carbon dioxide in the air. However, a new study from Northern Arizona University suggests the contrary. Warming temperatures will cause an initial boost in plant growth, but will quickly diminish over the years. This may lead to significant deterioration in future plant growth.

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Ecologists who took part in the study, subjected four grassland ecosystems to simulated climate change during the 10-year study. The first year witnessed a boost in plant growth, followed by nine years of progressively diminished plant growth until growth actually disappeared.

"The plants and animals around us repeatedly serve up surprises," said Saran Twombly, program director in the National Science Foundation (NSF)'s Division of Environmental Biology, which funded the research. "These results show that we miss these surprises because we don't study natural communities over the right time scales. For plant communities in Arizona, it took researchers 10 years to find that responses of native plant communities to warmer temperatures were the opposite of those predicted."

To simulate climate change, the researchers transplanted four grassland ecosystems from higher to lower elevations, simulating a warmer future environment. They also simulated varying precipitation, some more, less or the same. The elevation changes ranged from the San Francisco Peaks to the Great Basin Desert.

A key finding was the role that the nitrogen cycle played. The warmer climates caused the nitrogen to cycle more quickly. Much of the nitrogen, rather than being available for plants, was washed away by rainfall, or converted to nitrogen gas and released into the atmosphere.

This key finding challenges to the widespread belief that a more rapid nitrogen cycle will benefit plants by increasing their productivity. More nitrogen turnover, in fact, created more nitrogen loss.

This study has been published in the journal Nature Climate Change.

Arizona Ecosystem image via Shutterstock

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