An in situ investigation of the influence of a controlled burn on the thermophysical properties of a dry soil

Fire can be beneficial or detrimental to soils. If a fire is sufficiently intense soils can suffer irreparable change. This paper examines the possibility that fire can alter soil thermal conductivity and volumetric specific heat capacity of a dry soil. Measurements of soil heat temperatures and heat fluxes were made at several soil depths before, during, and after a controlled surface burn. During the burn the soil was heated to over 400 C at a depth of 0.02 m. At this intensity significant changes in soil chemistry, structure, and nutrient cycling are likely. Using a new soil heat flow model, developed for this study to account for a time lag of about 2.5 hours between the measured soil heat fluxes and the soil temperatures, indicates that the soil thermophysical properties were unchanged by the fire. Estimates of the soil thermophysical properties derived with the new model are in good agreement with laboratory analyses performed on soil samples obtained after the fire. Also presented in this study are some of the first soil heat flux measurements made during a surface fire. Data and analyses of the type discussed in this study should aid modeling studies of the soil thermal pulse associated with fire.