A lake sediment–based paleoecological reconstruction of late Holocene fire history and vegetation change in Great Basin National Park, Nevada, USA

Abstract

Analyses of macroscopic charcoal, sediment geochemistry (%C, %N, C/N, δ13C, δ15N), and fossil pollen were conducted on a sediment core recovered from Stella Lake, Nevada, establishing a 2000 year record of fire history and vegetation change for the Great Basin. Charcoal accumulation rates (CHAR) indicate that fire activity, which was minimal from the beginning of the first millennium to AD 750, increased slightly at the onset of the Medieval Climate Anomaly (MCA). Observed changes in catchment vegetation were driven by hydroclimate variability during the early MCA. Two notable increases in CHAR, which occurred during the Little Ice Age (LIA), were identified as major fire events within the catchment. Increased C/N, enriched δ15N, and depleted δ13C values correspond with these events, providing additional evidence for the occurrence of catchment-scale fire events during the late fifteenth and late sixteenth centuries. Shifts in the vegetation community composition and structure accompanied these fires, with Pinus and Picea decreasing in relative abundance and Poaceae increasing in relative abundance following the fire events. During the LIA, the vegetation change and lacustrine geochemical response was most directly influenced by the occurrence of catchment-scale fires, not regional hydroclimate.

A Link Between Hydroclimate Variability and Biomass Burning During the Last Millennium in the Interior Pacific Northwest

“…ENSO and the PDO have also influenced fire synchroneity in the eastern Cascades over the past several centuries, with severe fire years associated with El Niño/PDO + conditions (Heyerdahl et al., 2008). The amplitude of interannual and multidecadal climate variability has also been hypothesized to drive biomass burning, as wet periods generate fine fuels that subsequently burn during dry periods (Cooper et al., 2021; Walsh et al., 2015). A lack of multi‐proxy sedimentary reconstructions which are sensitive to both hydroclimate and fire activity at sub‐decadal timescales hinder a comprehensive understanding of the relationship between climate variability and biomass burning.…”