Garlic Mustard, Alliaria petiolata, is a herbaceous species that was introduced to North America in the mid 19th century, from Europe. Many environmental NGOs and government agencies list it as being one of the most invasive plant species of forest understories. The presence of garlic mustard in forests is often correlated with reduced native species richness. The negative ecological impacts of this biennial forest herb that have been reported from greenhouse experiments, include suppression of native plant species richness, and native tree mycorrhizae. Garlic mustard synthesizes secondary compounds known as glucosinolates, which may cause allelopathy, thus providing a mechanism for suppressing other plant species.
A long-term data set (1995-2009) was compiled from previous undergraduate and graduate student studies of forest plots in two parks in southern Ontario, in which the presence and density of garlic mustard and other plant species was scored. These were Point Pelee National Park and Rondeau Provincial Park, two peninsulas on the north shore of Lake Erie. We report on the long-term trends in which an initially expanding garlic mustard population (1995) declined in terms of its presence and density, when white-tailed deer popuations were reduced, allowing increased forest regeneration to occur.
Future collaborations with Kristina Stinson’s group are planned, aimed at exploring the local mechanisms that have may be operating, to result in garlic mustard declines in these parks.