Effect of Burn Severity on Dissolved Organic Carbon After the Roblar Fire in San Diego, Californi

Wildfires are a common in Mediterranean ecosystems such as southern Californian. The natural occurrence of wildfires can impact the water quality of the disturbed watersheds. When wildfires release large quantities of organic carbon into the environment, dissolved organic carbon (DOC) is transported to surface water through soil infiltration, leaching, and surface runoff. In this research, samples were collected after the 2016 Roblar in Camp Pendleton, San Diego, California, leached in the laboratory to simulate post-fire runoff, and analyzed to establish a relationship between wildfire burn severity (unburned, low, moderate, moderate-high, and high) and DOC (Phase I). The results established that DOC is correlated with burn severity (R2 = 0.56) and DOC concentration in low burn severity areas is less than the high. The burn severity areas classified under Coastal sage---chaparral shrub demonstrated higher concentration of DOC due to the fire regime of the vegetation. The significance of the Phase I results are the implications behind the role of vegetation and how it impacts burn severity and DOC.;Phase II investigated whether controlled, laboratory scale burning replication studies can be used to experimentally model and represent wildfire processes observed in the field. Soil samples were burned under laboratory conditions under varying temperatures to simulate wildfire conditions and leached in the laboratory. Results suggest that a decrease in DOC concentration was strongly correlated with an increase in temperature class for burn duration of 10 ( R2 = 0.84), 15 (R2 = 0.94), and 20 minutes (R2 = 0.95). The results support that elevated DOC concentration resulted from incomplete combustion processes at lower temperatures; as the temperature increased, the combustion process transitioned from partial combustion to complete, and DOC concentration reduced as a result. Phase I average DOC concentration increased from the low burn severity condition to the high, but for Phase II, it exhibited the opposite trend. The inverse relationship suggests that Phase II results do not mimic the results from the Roblar Fire. The implications of the comparison study are significant because it highlights that replication comparison studies can better model a wildfire by taking into account variability in the field.