PS 62-72 - Responses of native and introduced plant species to sucrose addition in Puget lowland prairies

Thursday, August 11, 2011
Exhibit Hall 3, Austin Convention Center
H. Elizabeth Kirkpatrick, Biology, University of Puget Sound, Tacoma, WA and Kaitlin C. Lubetkin, Environmental Systems, Univeristy of California at Merced, Merced, CA

Nitrogen enrichment has often been demonstrated to enhance the success of introduced plant species at the expense of native species. In the south Puget lowland prairies of Washington State, invasion by Scotch broom (Cytisus scoparius), a nitrogen-fixing legume, is associated with elevated soil nitrogen levels. The higher soil nitrogen levels have been associated with secondary invasion of the prairies by numerous non-native species, particularly pasture grasses that can interfere with native plant seedling establishment. Numerous studies have shown the potential for carbon addition to immobilize soil nitrogen and reduce the success of introduced species relative to native species. Over four years, we compared the available soil nitrate, native and introduced species cover, and the success of native species transplants between sugar-treated (1000 g C m-2) and control plots on two Puget lowland prairies. 


Sugar treatment initially immobilized nitrate and reduced cover of introduced species compared to that on control plots, but these effects dissipated within two years. Moreover, after four years, cover of introduced species had rebounded to become higher in sugar-treated than in control plots. However, one-year survival of native species transplants was higher and their harvested biomass marginally greater in sugar-treated than control plots, suggesting that, where sugar treatment is feasible, combining sugar with the establishment of a high density of native species might limit the potential for introduced species to rebound.

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