[californiadisasters] Heightened air pollution increases fire risks

High nitrogen levels near L.A. are detrimental to native shrubs, study shows

Thousand Oaks Acorn
2014-01-30 / Community

Initial results from experiments conducted in the Santa Monica Mountains indicate that high levels of nitrogen may adversely impact native plants and also increase the risk of wildfire.

The preliminary results are from the first year of a threeyear study undertaken by Dr. Edith B. Allen of UC Riverside, Drs. Andrzej Bytnerowicz and Mark Fenn of the U.S. Forest Service, and Dr. Irina Irvine, restoration ecologist for Santa Monica Mountains National Recreation Area.

Researchers measured atmospheric nitrogen deposition levels at 10 sites throughout the Santa Monica Mountains from Newbury Park to Los Angeles and found significantly higher pollution levels in the L.A. end.

At the two sites with the best air quality, they added various levels of nitrogen into experimental plots of coastal sage scrub to simulate pollution levels found throughout the mountains.

Higher levels of nitrogen led to a decline in native shrub seedlings and an increase in nonnative grasses. Other studies in Australia and California have demonstrated a link between nonnative grasses, also known as “flashy fuels,” and larger and more frequent wildfires.

“No one will be surprised to learn that our data shows increased air pollution on the eastern end of the mountains, closer to Los Angeles,” said Irvine. “What’s more intriguing about this study is learning how high nitrogen levels affect native vegetation and what that might mean for fire risk in such a fireprone region.”

Funded by the National Park Service’s Air Resources Division, the $100,000 study will help scientists better determine the “critical load” when vegetation shifts, causing alterations to the structure and functionality of ecosystems.

Coastal sage scrub once covered much of coastal California and is now an endangered habitat type, primarily due to development.

Generally attributed to vehicle emissions in the Santa Monica Mountains, nitrogen deposition is the air pollution from industry, agriculture and transportation that settles out of the atmosphere and onto the Earth’s surface.

Source: http://www.toacorn.com/news/2014-01-30/Community/Heightened_air_pollution_increases_fire_risks.html

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