PARENT SESSION
Wednesday, August 9, 5:00-6:30 pm
Poster Session 19 - Wetland, riparian, and coastal ecology
Exhibit Hall, Ballroom Level, Cook Convention Center
Environmental factors and plant community composition correlate with post-restoration native plant regeneration across two wetland ecosystem types.
Hamingson, Ellen*,1, Jackson, Randall2, 1 Gaylord Nelson Institute for Environmental Studies, Madison, WI, USA2 Department of Agronomy, Madison, WI, USA
ABSTRACT- To develop a system for prioritizing wetlands for low-cost restoration, we investigated factors that correlate with native plant community regeneration when an invasive species is controlled without subsequent revegetation. Study sites consist of wetlands invaded by the perennial grass Phalaris arundinacea. Despite some fairly effective techniques for reducing infestations, sites are frequently re-invaded, leading to the question: Do some sites possess characteristics that would allow native species to recruit into treated areas? Since P. arundinacea establishment is usually light-limited, early success of native species is crucial in longer-term resistance to invasion. Hummock micro-topography may create refugia for native seeds to establish once P. arundinacea is controlled. As invasions progress and result in thatch accumulation, reduced topographic variation may suppress native seed germination even when P. arundinacea is removed. High soil moisture and nitrogen levels have been shown to give P. arundinacea a competitive advantage. Dominant vegetation was characterized; sites were burned, followed by application of a grass-specific herbicide; and soil and seed bank samples, hummock measurements, and post-treatment plant species composition data were collected in 2005 on two Wisconsin farms, containing, respectively, woodland swales and riparian sedge meadows. Analyses of first-year data indicate that soil moisture, maximum hummock height, and pre-treatment invasion status, but not ecosystem type, are significant predictors of post-treatment P. arundinacea cover. Low cover was found only in plots not extensively invaded prior to treatment. Higher cover occurred under conditions of higher gravimetric moisture content and lower hummock surface area and height. Further analyses will investigate whether seed bank composition correlates with post-treatment species composition and P. arundinaceacover. Spatial dependencies differ among groups of explanatory variables, indicating that soil moisture and nitrogen mineralization and hummock micro-topography may track processes that operate at different scales than does spread of the invasive species.
Key words: wetland, plant community dynamics, phalaris arundinacea