Fire effects on aplant community, soil, and air are not apparent when judged only by surface fire intensity. The fire severity or fire impact can be described by the temperatures reached within the forest floor and the duration of heating experienced in the vegetation, forest floor, and underlying mineral soil. Temporal distributions of temperatures illustrate heat flow in duff and mineral soil in three instrumented plots: two with slash fuel over moist duff and one with litter fuel over dry duff. Fires in the two slash fuel plots produced substantial flame lengths but minimal heating in the underlying mineral soil. In contrast, smoldering combustion in the dry duff plot produced long duration heating with nearly complete duff consumption and lethal temperatures at the mineral soil surface. Moisture content of duff and soil were key variables for determining f i e impact on the forest floor.

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He served 26 years as Project Leader of the Fire Behavior Research Work Unit there. Rothermel has degrees from the University of Washington (B.S. aeronautical engineering, 1953) and Colorado State University (MS. mechanical engineering, 1971). He has published and lectured extensively both in the United States and abroad. His most notable contribution has been the development of a fire spread model that has been used as the basis for the National Fire Danger Rating System and several other systems that require an estimate of fire behavior. Rothermel is working with scientists in Australia and Canada to develop models for the next generation of fire behavior and fire danger systems.ROBERTA A. HARTFORD is a forester at the lntermountain Fire Sciences Laboratory in Missoula, MT. She began working at the Fire Lab in 1968, assisting with studies on the chemical and physical properties of fuels. During the early 1970's she also worked seasonally in fuel inventory and taught high school science. Since 1976 she has remained at the Fire Lab where she has been involved in studies of fuels and fuel bed properties, smoldering combustion, and fire behavior of both laboratory and wi!d!and fires. Recent work includes studies in the use of satellite remote sensing to assess fire potential in wildland vegetation and the use of geographic information systems to document wildfire growth. She has a B.A. degree in zoology from the University of Montana in Missoula and an MS. degree in forestry there. CAROLYN H. CHASE is a mathematician stationed at the lntermountain Fire Sciences Laboratory. She received her B.A. degree in mathematics from the University of Montana in 1969. Chase began working at the Fire Lab in 1978; she is a member of the systems development and application team. Her current work includes integration of geographic information system technology for the next generation of fire danger and fire behavior prediction systems. ACKNOWLEDGMENTSorganizations. Without their support this comprehensive project would not have been possible.