Estimated Smoldering Potential (ESP): a decison support tool for prescribed fire on organic soils in North Carolina

Due to the potential for substantial and prolonged smoke emissions, the smoldering combustion of organic soils and mineral soils with thick organic horizons is an important smoke management concern. At present, tools for evaluating the potential for ground fire are limited. The results of this study provide an alternative tool to estimate the smoldering potential of sustained smoldering in organic soils.

Laboratory burning of organic soil samples from pocosin and pond pine woodland wetlands common on the North Carolina coastal plain was conducted using moisture contents expected during prescribed burning and wildfires. Smoldering of upper horizon root mat soils was sensitive to moisture and mineral content. The estimated smoldering potential decreased as root mat moisture content increased. However, as mineral content increases, the moisture content at which the soil can sustain smoldering increases. The smoldering limits of the deeper muck soils are also inversely related to moisture content but are insensitive to mineral content.

Two operational burns were conducted by the Nature Conservancy and the North Carolina Division of Forest Resources to validate laboratory results. Comparison of laboratory results with the prescribed burning outcomes show the estimated smoldering potential was consistent with measured soil moistures and organic soil consumption.