Beargrass (Xerophyllum tenax) on the Olympic Peninsula, Washington: Autecology and Population Status

We studied the autecology and population status of beargrass (Xerophyllum tenax (Pursh) Nutt.) on the Olympic Peninsula of Washington State, focusing in the Olympic National Forest (ONF). Objectives were to: (1) define and describe beargrass habitat types in the ONF through an exploratory field study, and (2) determine whether beargrass populations in the ONF have declined where the species was historically present. We found three distinct beargrass habitat types in on the ONF: western low elevation, eastern low elevation, and high elevation habitats. These habitat types significantly differ in elevation, slope, topographic moisture, vegetation cover, successional stage, and litter layer thickness. We suggest environmental conditions of these habitat types may be attributed to the glacial and cultural history of the Olympic Peninsula. Beargrass cover in previously established plots on the southeastern Olympic Peninsula declined over the past 17 years, perhaps due to harvesting for the floral industry and an increase in canopy cover due to the absence of natural and anthropogenic burning. Our methods and findings may apply to other Northwestern species.