Response of Vegetation to Hydroclimate Variability and Wildfire during the late Holocene in the Mountains of the central Great Basin, Nevada, USA.

Abstract:

Analyses of macroscopic charcoal, sediment geochemistry (%C, %N, C/N, δ¹³C, δ¹⁵N) and biotic remains (chironomids, pollen) were conducted on a lake sediment core to establish a 2000-year record of temperature, fire history and vegetation change in a sub-alpine catchment located in the Snake Range, NV. This study documents that: changes in catchment vegetation occurred during the late 1^st millennium corresponding to hydroclimate changes at the onset of the Medieval Climate Anomaly (MCA); two severe, catchment-scale fires occurred during the late 15^th and 16^th centuries; and the sub-alpine forest has not yet recovered to its pre-fire forest composition and structure, following these Little Ice Age (LIA) fire events. In addition, this study suggests that the change in the chironomid assemblage observed during the LIA, which previously was inferred to reflect the influence of depressed July air temperatures, was likely driven by changes in the aquatic ecosystem following the catchment-scale fire events. Importantly, the results of this study indicate that that the most severe fires of the late Holocene occurred during the LIA, regionally characterized to be a time of cooler temperatures and variable hydroclimate. The combined effects of drought and increased variability in precipitation regime likely contributed to the occurrence of these LIA fire events. Continued research into the complex relationship between wildfire and vegetation community composition and recovery will assist in the design of effective wildfire management plans for montane regions in the Great Basin.