Regional Wildfire Inferred From Micro-Charcoal Over Past 15,000 years in Southern Colorado USA.

Abstract:

Climate and land use change are altering wildfire frequency and severity. In combination with increasing precipitation extremes, landslides and debris flows are increasing. Short historical records hinder our understanding of regional wildfire baselines and thus future risk assessment. To establish a baseline for the San Juan Mountains, southern Colorado, we reconstruct a timeline of regional wildfires over the past 15,000 years from Crater Lake sediment cores. A heavy liquid separation technique is used to float micro-charcoal (<180 µm) from the remaining sediment spiked with a known count of Lycopodium spores. The charcoal particles are counted and a charcoal concentration is calculated. This technique is used to capture the regional rather than local wildfire signal. The wildfire pattern from Crater Lake is compared to previously reconstructed climate data as well as existing extra-local wildfire records. Our initial results corroborate with a previous study on the same lake for the period of overlap. Both suggest that the charcoal concentration decreased into the present with particularly low concentrations in the 16th century CE. This decrease in wildfire is potentially due to change in climatic conditions, and human involvement into the present.