PARENT SESSION
Poster Session #12: Marine Ecology.
Monday, August 5. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Vegetative and reproductive phenology of fertilized mangroves in a nitrogen-limited ecosystem.

Ewe, Sharon^*,1,2, Lovelock, Catherine², Feller, Ilka², ¹ Smithsonian Marine Station, Fort Pierce, Florida² Smithsonian Environmental Research Center, Edgewater, Maryland

ABSTRACT- The purpose of this research was to compare the vegetative and reproductive growth patterns of fertilized dwarf and transition-zone black mangroves (Avicennia germinans) in central Florida. Within each forest type, individuals (n=9) were either provided nitrogen (N), phosphorus (P) or no nutrients (control) at 30 cm depth approximately one year prior to measurements. Ten branches/tree were tagged. Growth and reproductive changes to each branch above the tag was measured for 12 months. There was a pronounced seasonal leaf and fruit flush. Among treatments, N-fertilized plants showed greatest growth and reproductive responses in both forest types. Nitrogen-fertilized plants had the highest: 1) leaf numbers/branch, 2) rates of branch, leaf and fruit production, and 3) propagule production. These responses were more pronounced in the N-fertilized dwarf compared to transition zone mangroves. Growth and reproductive patterns of control and P-fertilized plants were however not significantly different within or between forest types. High leaf numbers/branch of N-fertilized A. germinans was due to greater leaf retention during the dry season compared to the other treatments. Overall, in this N-limited system, nitrogen enrichment resulted in significant increase of plant biomass and reproductive success for both the dwarf and transition zone mangroves. Phosphorus enrichment however, did not increase plant growth rates or propagule production.

KEY WORDS: Avicennia germinans