The five-year grant, which begins Oct. 1, is the largest study of its kind ever attempted, said principal investigator Edith Allen, a professor in the UCR Department of Botany and Plant Sciences. She will lead a team of UC Riverside and UC Berkeley researchers who will monitor weed growth in the state, and make appropriate recommendations. Weeds are important because they out-compete native species and they can contribute to the spread of wildfires.
"Nitrogen deposition occurs at high levels in southern California, and is fertilizing our wildlands," Allen said. "While growers and gardeners may appreciate this free fertilizer, it promotes the growth of weedy species in our forests, shrublands, deserts and grasslands. The invasion of weeds is a huge problem for maintenance of our fragile biodiversity, which is already impacted by development."
Allen says that most of the nitrogen is the result of automobile emissions. Some of this is converted to nitrate or nitric acid, the form of nitrogen (known as N) that is used by plants as fertilizer.
"California has been subject to weed invasions since the arrival of the first European settlers, but the southern California coastal sage scrub and deserts have been experiencing weed invasions primarily in the last 40 years, since the level of nitrogen deposition has increased," Allen said. "Some of these weeds have been present for the past 100 years, but they are just now becoming dense, and they are replacing native vegetation."
The weeds are primarily from the Mediterranean region, and include annual grasses and flowering plants such as stork's bill and mustard. The grasses are problematic, Allen said, because they form a fine fuel that can help carry fire during the dry season, more so than any of the sta
Contact: Kris Lovekin
University of California - Riverside