Collaborative SGER: Dispersal and Local Population Dynamics Following Large-Scale Fire

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Gurevitch0107406Data from population responses to recent Florida wildfires offer the possibility of extending andtesting demographic models we have been developing for pitch pines in a new system. The investigators propose to acquire these data, parameterize and test models on the interaction between dispersal and local population dynamics in longleaf and slash pine in Florida flatwoods. A similar opportunity is not expected to be available until, at least, the next major La Nina event. The terrestrial ecosystems of Florida and adjacent regions of the Southeastern US are strongly fire-dependent. Fire in Florida occurs frequently because rainfall is strongly seasonal. The intensity and extent of these fires varies greatly among years, largely as a result of the El Nino - Southern Oscillation. During La Nina years, Florida often experiences unusually strong spring droughts. Fires can thus be more intense and of greater spatial extent. The drought of Spring 2000 was the most extreme ever recorded, and consequently the fire season involved fires of very great spatial extent and intensity. The 1999-2000 La Nina, which caused the severe spring drought, appears to be over; all climate models are now predicting normal rainfall for the ensuing years. Thus, there is a time -critical aspect to data acquisition.In particular, a number of large-scale fires occurred in pine flatwoods. In much of this type of habitat - which covers much of peninsular Florida -- pine stands are naturally fragmented. What motivates this proposal as an SGER is the spatial extent of the Spring 2000 fires and this natural fragmentation. Jointly, these factors permit study the spatial component of recruitment with unusually high resolution. Because fires of this kind will not recur for many years, there is a time-critical component to this request.This research involves demography in disturbance-prone populations. The models and data have been developed in the context of pitch pines in the pine barrens of Long Island, NY. One question of particular importance is how much spatial data is needed? A principal result is that populations are expected to undergo substantial shifts from dynamics dominated by local demography to dynamics dominated by inter-stand dispersal, as the scale of disturbance increases.