Speaker: Rebecca Mostow, NSF Graduate Fellow, Department of Integrative Biology, Oregon State University

Topic: Like watching grass grow: Impacts of a newly-discovered ecosystem-engineering hybrid beachgrass on plant species interactions and dune building potential on the U.S. Pacific Northwest coast.

The two dominant beachgrasses of the U.S. Pacific Northwest, Ammophila arenaria (European beachgrass) and A. breviligulata (American beachgrass), build tall stable dunes that increase coastal protection but decrease habitat for some native animal and plant species. For decades, these intentionally planted but invasive grasses have presented complex tradeoffs to land managers trying to balance conservation and coastal protection. It was recently discovered that these two nonnative grasses are hybridizing on the Oregon and Washington coast. In 2020, a Markham-funded common garden experiment was installed at HMSC to investigate the potential for competition between these two species and their interspecific hybrid. Results from the experiment show that the hybrid beachgrass can grow at higher stem densities than either parent grass (a trait important for dune building potential) and that the hybrid negatively impacts both parent grasses when grown in competition. Understanding the impact of this novel hybrid beachgrass is imperative in a system where changes in dominant beachgrass may impact dune shape, coastal protection, and biodiversity conservation.