PARENT SESSION
Oral Session #39: Invasions: Effects of invaders -- Aquatic, marsh, riparian. Presiding: C. Kolar.
Wednesday, August 8, 2001. 8:00 AM to 11:45 AM. Madison Ballroom C.
Competitive suppression of an invasive species: competition for nitrogen between Carex hystericina and Phalaris arundinacea.
Perry, Laura1, Rosen, Carl1, Galatowitsch, Susan1, 1
ABSTRACT- Current methods to control invasions by aggressive vegetation involve eradication of existing populations and are effective only in the short-term. Adjusting resource availability to confer a competitive advantage to native vegetation could reduce ecosystem vulnerability to invasion and might more effectively control aggressive vegetation. To evaluate this approach for controlling Phalaris arundinacea L. (reed canary grass) invasion of sedge meadows in restored prairie pothole wetlands, we tested whether Carex hystericina Muhl. can competitively suppress P. arundinacea invasions when nitrogen availability is low. Competition between C. hystericina and P. arundinacea established from seed was examined for 25 weeks in a greenhouse. Nitrogen availability in wetland soil was lowered for the experiment via carbon enrichment. NH4-N was applied at different rates to the nitrogen-depleted soil to create a range of available nitrogen concentrations (30-400 ppm). In soil without carbon added, competition with P. arundinacea reduced C. hystericina biomass by 91%, confirming that P. arundinacea can prevent sedge meadow species establishment in prairie pothole wetland soils. In contrast, in soil with nitrogen availability reduced by carbon enrichment, competition with P. arundinacea reduced C. hystericina biomass by only 32%, whereas competition with C. hystericina reduced P. arundinacea biomass by 82%. C. hystericina dominance over P. arundinacea in carbon-enriched soil suggests that lowering nitrogen availability in restored prairie pothole wetlands may allow sedge meadow species to competitively suppress P. arundinacea invasions.
KEY WORDS: Phalaris arundinacea, invasive species control, wetland restoration, sedge meadows