University of Massachusetts Amherst, United States
Abstract: There is mounting evidence that climate change interacts with biological invasions to negatively impact native species. However, our knowledge of invasive species’ physiological and population-level responses to climate change remains limited, as does our understanding of concomitant changes in their impacts on native species. We grew seedlings from the model invasive plant Alliaria petiolata (garlic mustard; hereafter GM) under experimental soil temperature and nitrogen conditions in a greenhouse experiment to investigate the trait responses of this species to predicted soil warming and increased nitrogen in New England, where GM is highly invasive. Soil warming (SW), and increased soil nitrogen (N) have also been shown to enhance GM plant productivity in previous studies, but we don’t know if this varies among populations in different environments or how it affects GM’s production of sinigrin, which destroys fungal mutualisms important to native tree seedlings. Seedlings were collected from three sites in Massachusetts that are found along a temperature gradient. Using seedling warming mats and an aqueous nitrogen solution to simulate increased SW + N, the plants were put into one of four treatments: control, SW, N, and SW + N. Plant traits related to growth were measured throughout the duration of the experiment. We found that seedlings treated with increased N and a combination of SW + N were more robust, especially with regards to shoot mass, than those from the control and warming treatments alone. Similarly, leaves of GM seedlings from the N and SW + N treatments were roughly twice as large as those of GM seedlings from the control and warming treatments and the treatment effect was similar for other traits. It appears that seedling responses to treatments were largely driven by N and were consistent across sites, but that there is some variation within and among sites. Because seedling growth is indicative of reproductive success, these findings suggest that increased regional N deposition (also in combination with warming) N may support GM growth and population sizes, potentially enhancing range expansion and negative impacts on native plants.
