A Regional Synthesis of Post-Glacial Fire History in the Eastern Cascades, Washington, Using Macroscopic Charcoal Analysis

Keywords: Macroscopic Charcoal Analysis, Pacific Northwest, Historical Fire Activity, CharAnalysis
Abstract Type: Poster Abstract

Abstract

The recent rise in severe wildfires in the Pacific Northwest has created a sense of urgency to better understand future wildfire risk. To put current activity into a broader temporal context, a more in-depth look at long-term fire histories from frequently burned areas is needed. The goal of this study was to use seven previously developed macroscopic charcoal-based fire history records from the eastern Cascades of Washington (USA) to test the ability of the CharAnalysis statistical program to decompose the charcoal records and to calculate fire frequency and other measures of fire activity. The sites included span a range of elevations and ecozones in the eastern Cascades, and a variety of user-selected parameters were tested including widow width and smoothing functions. Our results indicate that CharAnalysis is an inappropriate analysis tool for many of the charcoal records from the eastern Cascades. This is likely because several of the sites tend to experience frequent, low-severity fire regimes that make it difficult for the program to adequately distinguish between the “peak” and “background” charcoal components. We found that inadequate decomposition of these records leads to an underestimation of the amount of fire events that occurred at these sites, in particular during the late Holocene when charcoal accumulation rates were highest. While we are not the first to recognize that CharAnalysis is an inappropriate statistical tool for some fire records, we argue there is still valuable information to be gained from testing a variety of user-defined parameters and visually analyzing the output data.