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. 1 Author to whom correspondence should be addressed: Dr. Daniela Shebitz. E-mail: [email protected] Introduction Beargrass (Xerophyllum tenax (Pursh.) Nutt.) (Figure 1) is an evergreen, perennial herb in the Melanthiaceae, Liliales (Rudall et al. 2000, Vance et al. 2004) that grows in large, dense clumps or tussocks (Cooke 1997, Higgins et al. 2004). Basal leaves grow densely in a cluster close to the ground, can be up to 60 cm long and 5-10 mm wide at the base, and gradually taper to a narrow and stiff tip (Maule 1959, Henderson et al. 1989). Beargrass reproduces both vegetatively by rhizome, and sexually by seed. Flowering occurs in 5-7 year intervals (Stewart 1994, Munger 2003) and it has been suggested that maximum flowering may be linked to fire (Cooke 1997, Kruckeberg 2003). Vance et al. (2004) found that beargrass flowers are self-incompatible and attract a broad range of pollinators from the insect orders Diptera, Coleoptera, and Hymenoptera. Beargrass inhabits mixed-coniferous forests and meadows in the mountains of west-central California up to northwestern Washington, and from Yellowstone National Park north to southwestern Alberta and southeastern British Columbia (Maule 1959, Higgins et al. 2004). The species’ habitat ranges in elevation from sea level on the Olympic Peninsula to over 2,300 m in the Rocky Mountains (Hitchcock and Cronquist 1973, Stewart 1994, Cooke 1997, Higgins et al. 2004). Beargrass often grows in subalpine meadows or as a dominant understory component of dry, mixed-coniferous forests (Pojar and Mackinnon 1994, Higgins et al, 2004, Kruckeburg 2003), where it occurs in highest densities under canopy openings (Crane 1990). In addition to being a significant component of various ecosystems throughout the northwestern United States, beargrass has cultural and commercial importance in the region (Higgins et al. 2004, Vance et al. 2004). Native Americans of California and the Pacific Northwest (PNW) value beargrass as a fundamental basketry material (Rentz 2003, Vance et al. 2004, Shebitz 2005). Interviews with members of the Quinault and Skokomish Indian Nations on the Olympic Peninsula have revealed concern that commercial harvesters are negatively affecting beargrass populations by not selectively harvesting leaves (Nordquist and Nordquist 1983; Shebitz 2005) Indeed, some floral greens wholesalers consider it to be the highest volume European import of all non-timber forest products (Thomas and Schumann 1993). Between 1999 and 2001,