Kate, BallantineGary, GillisHoopes, MarthaGerbi, Elizabeth2025-07-082025-07-082025-07-08https://hdl.handle.net/10166/6755ABSTRACT Climate change effects throughout the globe cause increased ecosystem disturbance risk from invasive species. Common St. John’s Wort (Hypericum perforatum) is a forb native to Europe, Western Asia, and North Africa, and considered an invasive weed in the northwestern United States. H. perforatum is present in New England, but appears to be non-invasive. Climate change is highly affecting New England temperatures and precipitation variability, which could have a species-dependent effect on invasives, either facilitating or discouraging invasion. As climate change alters New England climate and ecosystems, the shift in conditions could facilitate H. perforatum growth, possibly spurring invasion in New England. This research examines changes in temperature and water availability on H. perforatum both alone and combined with competition and disturbance. Water availability was the most important factor in H. perforatum germination in this study. Increased temperature facilitated germination when combined with consistent water availability but inhibited germination when combined with variable watering. Disturbance and competition both led to low germination and survival rates although a combination of consistent water and heat increased both. The current climate conditions in New England appear favorable for H. perforatum invasion, but non-climate factors likely best explain the current lack of H. perforatum invasion.en-USEcologyThesispublic