Identifying suitable areas for the reestablishment of Pinus elliottii var. densa on previously farmed lands in the Hole-in-the-Donut restoration, Everglades National Park

Within Everglades National Park is the largest remaining tract of pine rockland in the United States, a subtropical vegetation community that has been classified as globally imperiled community. Aerial interpretation of 1940's photos revealed that approximately 15% of the Hole-in-the-Donut, or HID, was comprised of pine rockland before the lands were rockplowed and farmed. Agricultural practices in the HID altered soil properties such that 2,670 ha of fallow fields became invaded by woody vegetation, primarily the non-native Schinus terebinthifolius. Following removal of the disturbed soil to limestone bedrock, Pinus elliottii var. densa (South Florida slash pine) regenerated adjacent to undisturbed pine rockland; however, reestablishment was limited by distance from seed source and elevation via hydrology. Therefore, the central hypothesis of this project was that South Florida slash pine germination and short-term survival was attributable to surface elevation, hydroperiod, and microsite soil differences; with hydroperiod being the primary controlling site characteristic in the Hole-in-the-Donut. In order to promote slash pine occurrence in areas far removed from seed source the objectives of this research were to (1) characterize the site with historical aerial photographic interpretation (1940's) and current soil analyses, (2) test the effects of hydroperiod on South Florida slash pine using a mesocosm experiment modeled on field observations in order to determine suitable Pinus elliottii var. densa areas post-scraping for Schinus, and (3) monitor the growth and survival of planted and seeded Pinus elliottii var. densa in the HID by elevation treatment.;Indirect relationships were discovered for soils, as depth, total carbon, and total nitrogen increased as elevation decreased, and pH increased with an increase in elevation. There were observable differences in hydroperiod over the 2007 and 2008 rainy seasons; however, the lowest elevation supported a hydroperiod typical of marl prairie wetland that was unsuitable for South Florida slash pine. A mesocosm that simulated the high, low, and midpoint of HID elevation ranges and hydroperiods for South Florida slash pine reestablishment revealed that partially flooded pines had higher growth and biomass after one growing season. Nitrogen and C:N tissue levels were similar to Pinus elliottii var. densa tissue samples in the Everglades, and this research demonstrated that this subspecies has apparently adapted to survive with lower phosphorus levels than Pinus elliottii var. elliottii. Suitable areas for slash pine in HID were identified as areas that were inundated for five weeks or less during the rainy season, while marginal areas were flooded for a total duration of five to ten weeks. Pines planted in the HID had significantly greater height and root collar diameter growth when compared to seeded pines of the same age. It appeared that the survival of South Florida slash pine across the higher elevation ranges was similar to the historical occurrence of Pinus elliottii var. densa that existed in the Hole-in-the-Donut prior to farming, despite lower elevations associated with the restoration process. Overall, site characterization in conjunction with pine growth and survival under flooded conditions will guide the restoration of South Florida slash pine in the Hole-in-the-Donut and throughout South Florida.