Soil Microbial Community Dynamics Associated with Garlic Mustard Invasions

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Garlic mustard (Alliaria petiolata) is an aggressive invasive plant of temperate forests, and constitutes the single greatest threat to forest health throughout much of the northern US. Garlic mustard produces chemicals within its tissues that are toxic to insects that would normally consume forest plants. This plant has also been found to be toxic to soil bacteria and fungi normally responsible for making nutrients available to other plants. The goal of the study is to examine a particularly aggressive garlic mustard infestation in pine plantations located in Sand Ridge State Forest (IL). The objectives are to identify changes that garlic mustard makes to soil organisms, as well as soil nutrient availability to other plants. Should garlic mustard result in decreases in soil nutrient availability in forest soils, forest productivity could decrease, which would in turn alter harvestable biomass and the amount of carbon that could be stored in forests. The researchers will investigate changes in soil chemistry and microbial communities in response to garlic mustard invasion across a range of forest sites using a combination of lab and field studies including: experimental site manipulations (e.g., additions of garlic mustard or nitrogen); site and experimental plot characterization of general soil chemistry (pH, C, N, cations, P) and microorganisms (biomass, diversity, enzyme activities). These analyses should provide information as to whether garlic mustard alters forest health and suggest changes that will occur to stands as this invasive plant moves into new areas. As garlic mustard is currently invading forests at high rates, infestations that result in reduced nutrient availability in North American forests can lead to serious long-term consequences for forest health. The long-term goal of this project will be to evaluate the impacts of garlic mustard across a broad range of forest soils, and to improve our understanding of the mechanisms by which garlic mustard invades and subsequently acts as an ecological change agent in these forests. All research on this project to date has been a collaborative effort involving Bradley University undergraduate students during the academic year, expanding to include local community college students, local high school students and K-12 educators during the summer, including large numbers of women and members of underrepresented groups in science. Funds acquired through this grant will support continued collaborations among these groups.