CLIMATE, FUEL, AND FIRE IN THE GREAT BASIN: MID- TO LATE-HOLOCENE PERSPECTIVES FROM BLUE LAKE, NV

The semi-arid Great Basin of the American West is highly sensitive to future environmental change; even small shifts in temperature and precipitation patterns may have outsized effects on ecological and agricultural systems alike. Long, continuous sedimentary reconstructions of environmental change from the Great Basin are relatively rare, as few permanent lakes exist in the region. Here, we present high-resolution elemental composition and charcoal data from Blue Lake, in the Pine Forest Range of northern Nevada to improve our understanding the coevolution of climate and fire ecology over the past 7000 years. XRF and sedimentology data suggests the lake became deeper since the middle Holocene, consistent with other proxy reconstructions from the Great Basin derived from tree-rings, cave deposits, and pollen spectra. Significant correlations between the XRF record and a bristlecone pine-derived temperature reconstruction suggest warming climate was a major control on water balance. Charcoal reconstructions indicate fires became more commonplace as climate became wetter, indicating fuel availability was a primary control on biomass burning in this semi-arid region. Charcoal morphologies show that woody biomass burning (from tree species, rather than grasses and herbs) was extremely limited prior to 5000 years BP, only becoming a prominent feature of the record after regional water balance became sufficient to sustain widespread tree cover. These results suggest future warming will have a negative impact on precipitation-evaporation balance. While this will make fire activity more probable and more intense in the near-term, long-term ecological impacts of anthropogenic climate change may induce a shift towards a higher-frequency, lower-severity fire regime.