PARENT SESSION
Monday, August 7, 5:00-6:30 pm
Poster Session 2 - Invasive species
Exhibit Hall, Ballroom Level, Cook Convention Center
Invasion of Great Lakes coastal wetlands by non-native genotypes of Phragmites australis.
Tulbure, Mirela*,1, Auger, Donald1, Johnston, Carol 1, 1 South Dakota State University, Brookings, South Dakota
ABSTRACT- Phragmites australis has expanded tremendously in wetlands along the Great Lakes coast with the introduction of the M Eurasian genotype. Human-induced manipulations and disturbances across the landscape are believed to play an important role in Phragmites abundance. A survey of 16 Great Lakes coastal wetlands was conducted during the summer of 2005 to examine the effect of very low lake levels during 2000-2004 on Phragmites expansion. These wetlands were previously sampled for vegetation and had Phragmites present during 2001-2003. Significant expansion of Phragmites occurred at 5 of the 16 sites, 4 of them located around Saginaw Bay (Lake Huron) and 1 on Lake Erie. The difference in water level between the long term average and the average during 2002-2004 was 55cm for Lake Huron and 29cm for Lake Erie. These results suggest that Great Lakes coastal wetlands where water level dropped causing the exposure of bottom sediments are more susceptible to Phragmites invasion. PCR/RFLP genetic analysis showed that Phragmites at all 16 sites belonged to the non-native genotype. Ammonia, nitrate and phosphate concentrations in soil water did not differ in Phragmites vs. non-Phragmites stands, suggesting that among site differences might be more important than within site differences. A hierarchical partitioning (HP) analysis was conducted to evaluate the independent influence of 5 main factors (the lake on which a wetland was located, wetland settings, mean water depth at a site, agriculture, and urban development in the watershed) on 2001-2003 and 2005 Phragmites relative abundance. The HP analysis indicated that the urban index had a significant independent influence on the relative cover of Phragmites in both 2001-2003 and 2005 and explained the highest variance in the data.
Key words: invasiveness, Phragmites australis, coastal wetlands