Conceptual ecological models for the Long Island pitch pine barrens: implications for managing rare plant communities

Fire dependent pitch pine (Pinus rigida Mill.) and scrub oak (Quercus ilicifolia Wang.) barrens are found on coarse-textured, droughty soils in the northeastern United States. These communities are globablly rare and, in many areas, dependent on active management to sustain them. We used historic and recent aerial photographs of the Central Pine Barrens in New York to develop transition matrices and trajectories of vegetation change. A vegetation map for 1990 provided pre-burn cover type information for a 1,200 ha area burned by an extremely severe wildfire in August 1995. Geographic information system analyses, a fire-history study, post-wildfire research and existing literature provided additional information for development of three conceptual models that describe our understanding of vegetation change in response to fire and land clearing. A simulation model was then used to predict the amount of each cover type in 2046. The reasonableness of the prediction was assessed based on our understanding of pine barrens vegetation dynamics. In 1938, following a period of frequent, intense wildfires of the region, 90 % of vegetation in the study area was open canopy barrens (including dwarf pine plains, pitch pine–scrub oak woodland, heath, pine–heath woodland, and scrub oak shrubland). Between 1938 and 1994, wildfires decreased in size, the average area burned per year generally declined, and there were no fires in 70 % of the study area. As a result, barrens decreased to 45 % of study area vegetation. In August 1995, an unusually severe summer wildfire converted 810 ha of woodland and forest into scrub oak shrubland, and increased barrens to 60 % of study are