Fire Frequency and Subalpine Forest Succession Along a Topographic Gradient in Wyoming

Differences in fire frequency and the rate of secondary succession following fire have had a major effect on the present composition of forest vegetation in a 4500—ha undisturbed watershed in the subalpine zone of the Medicine Bow Mountains, southeastern Wyoming. USA. Periodic fire coupled with slow secondary succession has perpetuated lodgepole pine forest on the upland, while mature Engelmann spruce—subalpine fire forests have developed in sheltered ravines and valley bottoms where fire is less frequent and succession following fire is more rapid and/or more direct. A graphic model is presented showing the relationship between topographic position, fire—free interval, and the occurrence of mature forests dominated by spruce and fire.