On the Complexity of Catchment-Scale Temperature Response to Land Disturbance by Wildfire and Post-Fire Salvage Logging in the Rocky Mountains

The Lost Creek wildfire severely burned 210 km² of forest on the eastern slopes of the Rocky Mountains in 2003. Seven headwater catchments with varying levels of disturbance (burned, post-fire salvage logged, and unburned) were instrumented as part of the Southern Rockies Watershed Project to measure stream flow, stream temperature, and meteorological conditions. From 2004 to 2010 mean annual stream temperature (T_s) was elevated 0.8 to 2.1°C in the burned and post-fire salvage logged streams compared to the unburned streams. Mean daily maximum T_s was 1.0 to 3.0°C warmer and mean daily minimum T_s was 0.9 to 2.8°C warmer in the burned and post-fire salvage logged streams compared to the unburned catchments. The effects of wildfire on the thermal regime of the burned catchments were persistent and trend analysis showed no apparent recovery during the study period. Temporal patterns of T_s were strongly associated with seasonal variability of surface and groundwater interactions and air temperature. Advective heat fluxes between groundwater and surface water were likely the dominant controls on T_s, though the strength of these advective controls varied among catchments, highlighting the importance of simultaneous catchment-scale and process-focused research to better elucidate the physical drivers influencing T_s response to disturbance.