Schoennagel, T. 2002. The influence of fire interval and climate on successional patterns in Yellowstone National Park. PhD Dissertation, University of Wisconsin, Madison.

Fire regimes are fundamental processes governing the pattern and dynamics of forested landscapes.  I examined successional responses to variation in interval between stand-replacing fires throughout the subalpine plateaus of Yellowstone National Park.  I sampled 12-year old stands that burned in 1988, but which varied in the timing of the previous fire, to determine the influence of fire interval on regeneration patterns of lodgepole pine and understory plant communities.  I also sampled spatial and temporal variation in serotiny, a variable trait in lodgepole pine that significantly affects propagule abundance following fires.  Fire interval influences patterns of initial postfire succession when the abundance of propagules varies with stand age.  Postfire lodgepole pine densities varied with fire interval, spatial and temporal patterns of serotiny, and soil fertility.  Fire interval effects on understory communities were less pronounced, but varied by functional group and elevation.  Environmental variation in elevation and soil fertility influences tree density and understory cover postfire.  This promotes asymmetry in competitive advantage within the regeneration niche, contributing to qualitatively different successional outcomes following fire.  I also explored how climatically altered fire regimes may affect broad-scale successional patterns in a modeling context.  Altered fire regimes significantly influence landscape age distributions; however, aggregate landscape structure may be insensitive to plausible shifts in fire regimes across the subalpine plateaus of Yellowstone National Park over the next century.  Density responses to fire regimes are a function of (1) mean fire interval relative to peaks in propagule abundance, (2) mean stand age of the landscape relative to self-thinning rates, and (3) the distribution of serotiny across the landscape.  Adaptive responses not represented in the model may expand serotiny to higher elevations with more frequent fire, increasing stand densities across the Yellowstone landscape over time.