Monday, November 5, 2007 - 10:30 AM
95-5

Ecological Engineering by Invasive Plants: the Role of Microbes.

Sherri Morris, Leah Barth, Dan Dreger, Ken Kitchell, Heather Milligan, Daniel O'Keefe, Sam Fan, and Kelly McConnaughay. Biology Department, Bradley University, 1501 West Bradley Ave., Peoria, IL 61625

Previous studies have determined that introduced plant species can alter microbial community dynamics. This studied evaluated the impacts of a severe infestation of an invasive species, Alliaria petiolata, on microbial community dynamics in a forest soil. We sampled areas of infestation vs. non-infestation within a sand prairie pine plantation in central Illinois using several techniques to evaluate microbial community structure and function. In situ and laboratory incubations of showed increased CO2 efflux for soils collected from garlic mustard infested sites. Laboratory incubations of soils collected from non-infested sites showed increased CO2 efflux when soils were amended with garlic mustard tissues or with mustard seed meal (chemically similar to garlic mustard). In a separate study, soils from infested or non-infested sites were exposed to 12 different carbon/nitrogen treatments over 20 days. This resulted in a 2-fold increase in the output of CO2 for infested soils treated with glucose and a nitrogen source. Nitrogen mineralization rates were evaluated using thirty-two day incubations. There was a significant increase in nitrogen turnover in infested soils. Microbial community dynamics were further evaluated by inoculating soil slurries on non-selective nutrient agar plates and nitrogen free selective agar plates. Direct counts of colonies on non-selective plates revealed an almost ten-fold increase in bacteria for infested soils. These studies suggest that Alliaria petiolata infestations shift microbial community structure by increasing the population of free-living nitrogen fixing bacteria. As garlic mustard is currently invading forests at high rates there is a concern that changes in microbial community structure will alter nutrient availability or competitive dynamics of aboveground biomass and alter nutrient dynamics of North American forests.