The Authors 



Research Summary 



Stephen F. Amo is a research forester in the 

 Prescribed Fire and Fire Effects research work unit 

 at the Intermountain Fire Sciences Laboratory in 

 Missoula, MT. He received a B.S. degree in forestry 

 from Washington State University and M.S. and 

 Ph.D. degrees from the University of Montana. He 

 has studied various aspects of forest ecology since 

 1963, including ecological site classifications, forest 

 succession, fire history, fire effects, and the develop- 

 ment of strategies for prescribed fire. 



Joe H. Scott is a consultant forester specializing 

 in treatments for stands in the suburban wildland 

 interface. He helped develop and implement this 

 study as a forestry technician for the Prescribed Fire 

 and Fire Effects research work unit at the Intermoun- 

 tain Fire Sciences Laboratory in Missoula, MT. He 

 received a B.S. degree in forest and resource manage- 

 ment fi-om the University of California at Berkeley, 

 and is a graduate student in forestry at the Univer- 

 sity of Montana. 



Michael G. Hartwell is a forestry technician for 

 the Prescribed Fire and Fire Effects research work 

 unit at the Intermoimtain Fire Sciences Laboratory 

 in Missoula, MT. He received a B.S. degree in natural 

 resource sciences from Washington State University 

 and is a graduate student at the University of Mon- 

 tana studying present and past forest structures at 

 the landscape scale. 



Trees on nine 100 by 100 m plots in old growth pon- 

 derosa pine/Douglas-fir stands in western Montana 

 were aged and mapped. Fire history since the early 

 1600's was determined for each plot fi'om fire scar 

 cross-sections. Six of seven sample plots on the Bit- 

 terroot and Lolo National Forests had a nearly all- 

 aged structure among the overstory ponderosa pine; 

 trees commonly ranged up to 500 years of age. TTiese 

 plots were on steep slopes, and prior to 1900 had ex- 

 perienced nonlethal underbums at mean intervals 

 of 13 to 50 years. 



Plots on the Flathead National Forest were on gen- 

 tle topography in a moist glacial valley. They had 

 even-aged structures supporting primarily ponderosa 

 pine and western larch. Pre- 1900 fire history was 

 characterized by patchy stand-replacing events (fire 

 and perhaps bark beetle epidemics) at intervals of 

 150 to 400 or more years with intervening underbums 

 at mean intervals of 20 to 30 years. 



All stands had developed an understory of Douglas- 

 fir in recent decades. Only the two plots that expe- 

 rienced natural fires in this century (1919 and 1953) 

 had a major proportion of vigorous, yotmg ponderosa 

 pine. Our data suggest that understory fires were in- 

 fluential in maintaining ponderosa pine dominance in 

 a variety of stand age structures. We conclude that, 

 in many stands, the effects of fire exclusion during 

 this century preclude use of fire alone to recreate 

 historic structures. 



About the cover: Old growth serai ponderosa pine stand on a Douglas-fir habitat type 

 (dry site) at Lick Creek, Bitterroot National Forest, southwest of Hamilton, MT. Scene 

 is in 1909 immediately before partial cutting. Gruell and others found an average fire 

 interval of 7 years between 1600 and 1900, and the last fire was about 1895. U.S. Forest 

 Service photo by W. J. Lubken. 



The use of trade or firm names in this publication is for reader information and does 

 not imply endorsement by the U.S. Department of Agriculture of any product or service. 



Intermountain Research Station 

 324 25th Street 

 Ogden, UT 84401 



