Disturbance is an ecological process fundamental to population dynamics across animal and plant taxa. While disturbance can kill individuals, it can also enhance habitat quality, augment fecundity and lead to population growth. Understanding demographic responses of focal populations, how survivorship of different life stages and fecundity respond to the initial disturbance event and to habitat quality in the years that follow, is critical to predicting the effects of natural disturbances and management actions alike. In this study we do two things. First, we investigate the demographic and behavioral responses of the endangered Fender’s blue butterfly to fire. Second, we build on demographic matrix models to construct a spatially implicit model to investigate how disturbance influences population growth rate and to compare the impact of alternative disturbance regimes on long-term population dynamics.
Results/Conclusions
As expected, fire had costs and benefits. Fire killed overwintering larvae but resulted in higher egg counts for two years after the burn, as well as higher larval survival. All three movement parameters (move length, turning angle and move time) were substantially influenced by presence of lupine, but not by fire history. Our models demonstrate that a strategy of only burning habitat that is at least 3 years since burn produces the highest population growth rates for Fender’s blue and that it is optimal to burn as much of this successional stage as possible. While this strategy is always better than randomly burning without respect to fire history, in the latter case, the optimal strategy is to burn ~1/3 of the habitat.