Global changes exacerbate threats from yellow starthistle (Centaurea solstitialis L.).
Dukes, Jeffrey*,1, Loarie, Scott2, Field, Christopher3, 1 Department of Biology, Boston, MA, USA2 Nicholas School of the Environment and Earth Sciences, Durham, NC, USA3 Department of Global Ecology, Stanford, CA, USA
ABSTRACT- Global environmental changes will alter interactions among plant species, sometimes favoring invasive weeds. We examined how multiple global changes affect the success of Centaurea solstitialis L. (yellow starthistle), often considered California's worst weed. We introduced seeds of this invasive species to the grassland plots of the Jasper Ridge Global Change Experiment, in the San Francisco Bay Area. Centaurea shoot biomass increased by over 600% in response to elevated CO2, and by over 200% in response to increased nitrate deposition, but did not respond to modest warming, increased winter precipitation, or fire. Centaurea's unusually strong responses to CO2 and nitrate far outpaced those of the resident plants in the community, suggesting that ongoing global changes will act to increase the weed's prevalence in western North America.
Key words: invasive species, carbon dioxide, community ecology, species interactions
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