Temperatures at varying depths in mineral soil deserve comment at this point. The degree of direct heat in mineral soil is dependent primarily on the depletion and moisture-content profile of the organic layer (Shearer1975, 1976). For example, during prescribed fires in red pine (Pinus resinosa Ait.) and eastern white pine (P.trobus L.) stands, Van Wagner (1970b) found very little increase in temperature within mineral soil when 1.3 cm or more of the organic mantle remained unburned.