Postglacial Fire, Vegetation, and Environmental Change in the Sinlahekin Wildlife Area, Okanogan County, Washington (USA)

Historically fire has played a key disturbance role in many ecosystems of the western United States. One of the most affected landscapes is the dry ponderosa pine-dominated forests of eastern Washington. Over the past decade, these forests have experienced a dramatic increase in large, high-severity wildfires, resulting in significant damage to natural resources, property, and habitat. Public land managers are now faced with the increasing challenge of maintaining these fire-dependent ecosystems in tandem with the projected impacts of future climate change. To do this, land managers need to make informed, adaptive decisions based on what it known in terms of historic fire regimes and how ecosystems respond to climate variability, both past and future. However, little is known about the long-term fire history of these dry forests in Washington State. The purpose of this study was to reconstruct the long term fire and vegetation history of Doheney Lake in the Sinlahekin Wildlife Area (SWA), which is located in a dry ponderosa pine forest. A 614 cm-long sediment core was recovered from the site that spanned the past ~12,210 calendar years before present. Macroscopic charcoal and pollen analysis were used to reconstruct the postglacial environmental history of the site. Results show that fire maintained a constant presence on the landscape and has been closely linked to fuel availability, until Euro American settlement (ca. AD 1850). In general, fire activity was highest during late Holocene when climate is thought to have been cool and wet, which may suggest the influence of interannual climate variability and/or the possibility that human ignitions contributed to the fire regime. Fire in the Sinlahekin Wildlife Area will likely continue to be driven by fuel availability and climate, therefore land managers may want to consider expanding their use of fire as a management tool