PARENT SESSION
Poster Session # 17: Aquatic Systems.

Thursday, August 7 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Seed germination and growth of four wetland tree species in response to environmental factors in tree islands of northern Shark Slough, Everglades National Park.

Reed, David^*,1, ¹ Florida International University, Miami, Florida

ABSTRACT- Seedling dynamics are the initial filter in the establishment of tree species in wetland forests. Patterns of seedling establishment of dominant species can be attributed to key environmental variables including light and hydrology. The vegetative communities within Everglades tree islands known as Bayheads and Bayhead Swamps are continuously inundated for parts of the year and are delineated by heterogeneous canopies and microtopographic features, creating correlate variable light and hydrologic environments. Hydrology is further affected by seasonal oscillations in water level in Everglades National Park (ENP), allowing for temporary drainage of soils during spring. This may cause seedling emergence to be a function of the timing of seed germination. Likewise, microtopographic highs along the elevation gradients within these communities provide temporary refugia from rising water levels and prolonged drainage. Life history and physiology of four dominant wetland tree species: pond apple (Annona glabra), cocoplum (Chrysobalanus icaco), sweetbay (Magnolia virginiana), and wax myrtle (Myrica cerifera) with regard to variable shade and flood conditions were explored. Field experiments quantified elevation, hydrology, and light environments, while monitoring recent germinant density and growth in three tree islands of northern Shark Slough, ENP. The physiological and morphological responses of early juveniles to variable light and flood conditions were assayed in shadehouse experiments, including three light and three flood treatments. Preliminary data show seasonal trends in seedling density and species diversity. A. glabra dominates the wetter sites all year, and both sites during winter months. C. icaco appears ubiquitously, but at lower densities, while M. virginiana and M. cerifera often appear at higher elevations and in the spring and summer months when overall densities increase. Synthesis of these and site hydrologic data allows for prediction of early juvenile species composition and density, and may further predict community response to long-term changes in hydropattern.

Key words: seedling establishment, hydrology, Everglades, tree islands