From the Summary...'Historically, fires have repeatedly burned nearly every square foot of northern Rocky Mountain forests. Fire damage was especially severe during the 75 years following 1860, and much of this was due to promiscuous burning by whites. Prior to 1940, fire was second only to precipitation as the major factor shaping the character of forests in this region. Unlike the frequent periodic ground fires reported in other parts of the United States, fires in the northern Rocky Mountains generally were catastrophic causing heavy damage to the burned stand. As a result, forest stands tend to be even-aged. Very limited areas of ponderosa pine and Douglas-fir ecosystems have burned periodically without destroying all the forest stand. Tree species vary greatly in resistance to fire; however, severe fires largely erase differences in resistance. Scattered old trees of fire resistant species--western larch, ponderosa pine, and Douglas-fir--have been able to survive fires in all of the ecosystems in which they occur. The major ecological effect of fire has been disruption of forest succession. As a result, seral species have been favored and climax forests are of limited extent. Certain species, including western larch, lodgepole pine, and western white pine, largely owe their present occurrence in the region to past fires.'