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Late Holocene Fire‐climate Dynamics in the Klamath‐siskiyou Ecoregion, Northern California, Usa

Authors: Christy Briles*, University of Colorado - Denver, Shelley Morton, University of Colorado Denver
Topics: Paleoenvironmental Change, Biogeography, Climatology and Meteorology
Keywords: paleoenvironmental history, fire history, lake sediments, northern California, environmental gradients
Session Type: Poster
Presentation File: No File Uploaded

The Klamath-Siskiyou Ecoregion (KSE) is known for its complex topography, mélange of geologies, steep coastal-to inland precipitation gradients, and mixed-severity fire regimes that are thought to maintain high levels of biodiversity. We present a 5000-year paleofire reconstruction using a network of charcoal and pollen records from lake sediment cores to: 1) reconstruct fire activity, biomass burned and fire severity along environmental gradients, and 2) examine how past climate change impacted fire regimes in the KSE. Since high severity fires consume larger trees and biomass in the forest, we examined canopy-understory pollen ratios during fire events to determine fire severity. In addition, charcoal accumulation rates (i.e. biomass burned) for nine KSE sites were divided into four precipitation regimes to examine variations in fire within the KSE and the northwest coast. Results indicate that fire activity was less frequent and more severe at wetter northern and coastal sites, while frequent and less severe at drier southern and inland locations. The region collectively experienced higher fire activity and severity during the Medieval Climate Anomaly when conditions were warmer and drier. These trends were exaggerated at southern and inland sites that received less precipitation than northern and coastal sites. During the Little Ice Age when conditions were cooler and wetter, fewer and less severe fires occurred, especially at northern and coastal sites that receive more precipitation. Current forest and fire conditions are a legacy of the LIA, and future climates will likely result in higher severity more frequent fires.

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