Abstract

Effects of Garlic Mustard on the Ohio Deciduous Forest

Student: Stefani Schmocker
Faculty Mentor: Laurel Anderson (OWU Department of Botany and Microbiology)

Garlic mustard (Alliaria petiolata) is an invasive herb that has rapidly spread across the eastern North American continent in the last 150 years. Current research suggests that garlic mustard produces chemicals that can hinder the growth of native plant species, impacting plant populations beneath forest canopies. Currently, it is speculated that decomposing tree matter may aid in the growth of garlic mustard by releasing beneficial nutrients to the soil. In this study, we measured individual garlic mustard plants’ largest leaf and proximity to decaying woody matter and statistically compared these measurements to see whether the decomposing matter influences the growth of garlic mustard. We collected soil samples near the decaying tree matter and analyzed the soil for chemicals that can aid in this plant’s development. Additionally, as part of a long-term garlic mustard population data collection, garlic mustard individuals and other understory species were counted in sections of forested land.

Alliaria petiolata is an invasive understory plant introduced to the North American continent during the mid-1800’s from eastern Europe. Since then, this species has infiltrated forest ecosystems across the eastern United States and Canada. Currently, it is not known whether certain soil conditions benefit the growth of garlic mustard. We conducted a study of garlic mustard association with coarse woody debris and surveyed permanent vegetation plots at the Kraus Nature Preserve in Delaware, Ohio. For the coarse woody debris study, 100 first-year A. petiolata individuals were sampled along a fifty meter transect in an area with decaying logs (coarse woody debris). Each plant’s largest leaf length and proximity to the nearest decaying woody debris were measured. Additionally, soil samples were collected within 30 cm of coarse woody debris and in sites with no coarse woody debris within a meter of the soil sample. Soil analyses revealed that soil in the vicinity of the decaying woody debris had significantly greater moisture and organic matter than the debris-absent soils, however there was no significant difference in soil phosphorus levels between the two soil types. Despite the difference in soil conditions, no correlation was found between rosette leaf size and proximity of the rosette to coarse woody debris. As such, more research may be necessary to establish if decaying woody matter impacts A. petiolata growth. In the permanent plot study, individual plant species were counted within 2x2 meter squares in the summer of 2018 and compared to data collected in previous years. Examination of the A. petiolata population counts in each plot revealed a pattern of invasion characterized by a rapid climb at the onset and a steep drop-off in later years. Furthermore, there was found to be a significant positive correlation between the A. petiolata count and the Shannon-Weaver diversity index of the plot, implying that garlic mustard invasion may be associated with higher biodiversity.