LUMINESCENCE RECORD OF ENHANCED WILDFIRE INTENSITY: ANALYSIS OF ARCHEOLOGICAL POTTERY AND SOILS IN NEW MEXICO

Fire suppression activities within the dry forests of the western US have led to the increase in tree density and fuel loads, creating uncharacteristically large and intense wildfires that affect the ecosystem recovery, cause property damage, amplify post-fire debris-flow and floods, and increase health risks and mortality to populations near and downwind of fire-prone areas. Climate change and long-term droughts have exasperated this problem by extending the fire-season length and fuel aridity. In consequence, the number and size of wildfire areas have increased. Ponderosa pine-ecosystems are adapted to fire, which maintains ecosystem-function and diversity. However, recent megafires have affected the resilience of these forests.

This study examines the remnant luminescence signals from surface-collected archeological pottery from Ponderosa pine (P. ponderosa) forests in New Mexico to reconstruct past fire-exposure. Optically stimulated luminescence (OSL) measurements of the quartz sand temper within the interior portion of pottery (non-light exposed) provides the time since last exposure to heat, which resets the luminescence signal. The project design includes analysis of pottery samples exposed to cool-season control burns, samples exposed to recent high-intensity fires, and samples from areas that have not been burned in the last 100 years (pre-suppression fire settings). Under natural conditions, it is assumed that ponderosa pine forests would have frequent low-intensity regimes, preventing the accumulation of fuel loads. The luminescence signals in pottery exposed to these frequent low-intensity fires (pre-suppression and control burns) are not expected to be reset, instead the resultant OSL age should reflect the archeological age of the pottery firing during manufacturing. Conversely, if recent wildfires are burning hotter than in the past due to increased fuel loads and aridity, the luminescence signals from pottery are expected to be reset and reflect modern ages. Research results will help test changes in wildfire-regime and provide a window into the effects of forest management policy on fire-regimes and intensity.