COS 32-1
Alternative life history responses to fire: Demographic resistance vs. resilience in the Brazilian cerrado
Tuesday, August 12, 2014: 8:00 AM
Bataglieri, Sheraton Hotel
Carol Horvitz, University of Miami
Shripad Tuljapurkar, Department of Biology, Stanford University, Stanford, CA
Background/Question/Methods Natural populations employ different strategies for persisting in disturbed environments. Given prevalent disturbance in both natural and managed settings, it is important to understand life history adaptations that mediate population persistence and species coexistence in variable environments.
How do we distinguish strategies for persisting under frequent fire disturbance? What can we learn about disturbance-adaptation from the responses of populations to frequent burning?
We examine demographic data on five sympatric woody plant species growing in the Brazilian cerradoand analyze demographic responses to fire frequency as indicators of life-history adaptations to frequent fire disturbance. We apply Markov chain theory to investigate how fire frequency affects life expectancy and age schedules of development, and we use these responses to as demographic diagnostics to characterize species as either ‘demographically resistant’ or ‘demographically resilient’ with respect to fire disturbance.
Results/Conclusions
‘Demographically resistant’ species are those that are strongly influenced by fire and must reach a threshold size to escape fire-induced mortality. ‘Demographically resilient’ species are those that are relatively insensitive to fire in terms of mortality and rebound after fire by taking advantage of the transient opportunities afforded by nutrient releases and reduced competition during early succession post-fire. The former succeed by retaining biomass and the latter succeed by renewing it.
Species vary in how their longevity and developmental rates respond to increasing frequency of disturbance. Life expectancy of resistant species is strongly influenced by fire frequency; these species rely on vegetative reproduction or very high seed production for persistence. Life expectancy and developmental rates of resilient species are relatively indifferent to fire frequency and because they are under less pressure to escape fire-induced mortality, they may allocate more resources to reproduction during early-succession. Such inter-specific variation in life history is predictive of population structure, species persistence and community composition under distinct disturbance scenarios. We suggest that the distinction between demographically resistant and demographically resilient among Brazilian cerrado species may be generalizable as two distinct modes of persistence in the face of disturbance.
