Four general post fire successional pathways leading to a climax Engelmann spruce (Picea engelmannii Parry) subalpine fire (Abies lasiocarpa [Hook] Nutt.) forest operate on the T.W. Daniel Experimental Forest in northern Utah. Depending on the successional pathway followed, reestablishment of the prefire climax will take 200 to 400 years or more due to a rarity of extreme burning conditions. During the long period between catastrophic stand-replacing fires, a variety of other natural disturbances contribute to the varying structure and composition of vegetation and the fuel mosaic in intermountain subalpine spruce-fir forests. Disturbances may range from chronic and small scale to acute and catastrophic, resulting in a broad range of vegetative responses. In addition to crown fires, other major abiotic disturbances (I.E. landslides, mudflows, severe soil erosion, snow avalanche) and biotic disturbances (i.e. disease and insect outbreaks) control the availability of sites for the initiation of new stands of accelerated growth of understory plants and subcanopy trees. Understanding the role of natural disturbance in forest ecosystems is key to managing long-return interval fire regimes. This paper explains how the disturbance regime operating in a given landscape influences vegetative dynamics and fuel mosaics and how the state of the vegetation in turn influences these natural disturbance agents. Managers must recognize biotic and abiotic agents of disturbance and their interactions to fully understand fire regimes and the effects of fire suppression and prescribed fire
