Late Holocene megafires in the diverse Klamath-Siskiyou Ecoregion: a paleoecological analysis of forest resilience

Keywords: paleoecology, paleoenvironmental, forest resilience, megafires, wildfires, palynology, pollen, forest ecology, fire ecology,
Abstract Type: Poster Abstract

Abstract

In 2020 and 2021, megafires accounted for over 62% of area burned in California and Oregon. Megafires are commonly defined as extreme fire events which burn over 100,000 acres. Understanding the response of forest vegetation communities to megafire events is critical to forest conservation in the face of increasing frequency, size, and severity of wildfires in the Western U.S. Fire and forest management goals often emphasize restoring historical conditions; however, baselines often lack a perspective of long-term trends in shifting climate, fire regimes, and vegetation composition. Paleoenvironmental proxies found in lake sediments (e.g., pollen and charcoal) can provide data from thousands of years in the past, allowing for an extended historical account of forest and fire dynamics. Fire is an integral ecological component in the Klamath-Siskiyou Ecoregion (KSE) of Southern Oregon and Northern California; however, the historical prevalence of megafires and their long-term ecological impacts remain relatively unknown. Additionally, the steep west-to-east precipitation gradient of the KSE is hypothesized to contribute to variance in forest resiliency, however, no analysis to date has examined this. This work expands upon previous studies by creating the first fine-scale analysis of individual fire events using pollen and charcoal records from sediment cores along a precipitation gradient and filling a gap in data along the precipitation gradient. This research documents the frequency of and forest resiliency to megafires in the past 2000 years across the west-to-east precipitation gradient, ultimately increasing the understanding of megafire impacts on forest resiliency in the KSE.