The historical role and current restoration applications of fire in maintaining beargrass (Xerophyllum tenax (Pursh) Nutt.) habitat on the Olympic Peninsula, Washington State
AbstractThesis (Ph. D.)--University of Washington, 2006.
This dissertation combined ethnobotanical, historical ecological, exploratory, and experimental studies to research beargrass (Xerophyllum tenax (Pursh) Nutt.) population status, historic habitat distribution, and restoration potential using prescribed burning. Ethnographic interviews with Skokomish, Quinault, and Quileute Tribal Members revealed that many beargrass gathering areas in the Olympic Peninsula lowlands were maintained through anthropogenic burning prior to European settlement and that beargrass is declining in those sites. Through the exploratory study, beargrass in the Olympic National Forest was found to occur in three habitat types: western low elevation, eastern low elevation, and high elevation. A significant decline in beargrass abundance was found in the eastern low elevation populations.The historical ecology study documented the past existence of beargrass savannas on the southeastern Olympic Peninsula. This former ecosystem owed its character to frequent anthropogenic burning prior to European settlement. Experimental studies were taken to understand fire's effects on beargrass seed germination, seedling establishment, flowering rates, vegetative reproduction, and growth. Results indicated that fire may be effectively used to manage beargrass in the Olympic Peninsula lowlands. On the southeastern Peninsula, high-severity fire led to significant increases in seedling establishment within a year after the fire and an increase in beargrass vegetative reproduction and flowering rates after two years. Manually clearing areas of vegetation and coarse woody debris on the southeastern Peninsula resulted in an increase in beargrass shoots after one year whereas low-severity fires did not result in a significant increase in beargrass shoot production. High-severity fires proved to be more effective than low-severity burns or manually clearing plots at recruiting beargrass seedlings. A greenhouse experiment found western low elevation beargrass seed germination rates significantly increase when seeds are exposed to smoke-water prior to undergoing cold stratification.The scope of this work was neither limited to beargrass nor to the methods described. The studies were based on the premise that indigenous knowledge and land management are inextricably linked to the history and biodiversity of the landscape. As such, this research serves as a case study to other ecologists interested in incorporating indigenous management into their work.