ORAL PRESENTER CO-AUTHOR: Jeffrey Matthews, University of Illinois Urbana-Champaign TITLE: Assessing the competitive abilities of invasive wetland plants under variable light and water availabilities ABSTRACT: Invasive plant species pose substantial risks to wetland ecosystems, resulting in a loss of biodiversity and changes to plant community composition. With an increase in biological invasions, ecosystems are more likely to be simultaneously invaded by multiple nonnative species. In field settings, we observed the invasive Japanese hop (Humulus japonicus) growing over reed canarygrass (Phalaris arundinacea), potentially impacting ecosystems prone to erosion. Additionally, a native analogue to H. japonicus and co-occurring species, burr cucumber (Sicyos angulatus) grew most abundantly in shaded areas. Determining how interactions between species change under different environmental conditions will aid invasive species management. Through a greenhouse experiment, we studied the interactions between the three species under variable environmental conditions. We grew species in monoculture and competition (H. japonicus×P. arundinacea and S. angulatus×P. arundinacea) under two light levels, unshaded or 60% shade, and two water depth levels, with pots submerged in 1 cm or 7 cm of water. All monocultures grew best in low water and unshaded conditions, with significant effects of light and water on total biomass. High water strongly reduced H. japonicus growth, while low light strongly reduced P. arundinacea growth. In competition against P. arundinacea, H. japonicus was a better competitor than S. angulatus, especially in unshaded and low water conditions. However, under both shaded and sun/low water conditions, S. angulatus outcompeted H. japonicus. P. arundinacea was outcompeted by S. angulatus and H. japonicus in shaded conditions. We recommend establishing shade through tree planting to limit P. arundinacea and H. japonicus growth. BIO: Annie Huang is a student pursuing a master’s degree in natural resources and environmental sciences at the University of Illinois Urbana-Champaign, where she is part of the Matthews Lab studying wetland ecology and restoration. Her research examines interactions between invasive wetland plants under variable environmental conditions. She is interested in invasion ecology and the management of invasive species.