Menges, E.S. , Marks, P.L. .
Fire and Flood: Why are South-central Florida Seasonal Ponds Treeless?
While seasonal ponds in the scrub landscape of the Lake Wales Ridge in south-central Florida are favorable for establishment of small south Florida slash pines (Pinus-elliottii var. densa), few seasonal ponds have mature trees. We studied the demography of slash pines in relation to water level and fire for a decade from 1992-2001 in four seasonal ponds, two with long hydroperiods and two with short hydroperiods. Seasonal ponds were favorable for pine growth (0.1-0.6 m increase in height annually) and annual survival (survival generally over 80% in years without fires). Wetter ponds had lower relative growth rates but higher absolute growth rates. Most recruitment (appearance of seedlings in a “grass stage”) occurred in drier ponds. Growth from grass-stage plants to 1 meter took about seven years. Flooding episodes occurred in 40-80% of years (by site) and lasted 3-11 months. Mortality decreased with plant height in all years and increased with flooding intensity in 3 of 9 years. Flood-induced mortality was concentrated in small pines < 1 m tall. Growth rates were unaffected by flooding. A low-intensity prescribed fire in 1999 in one population dominated by grass-stage plants created 72% mortality. In 2001, a large, intense wildfire burned through two seasonal ponds when they were dry, causing nearly 100% mortality of south Florida slash pines. Although South Florida slash pine can survive short-term flooding and moderately intense fire, both flooding and fire can exclude trees from many seasonal ponds. Fire was a stronger force during our study. Seasonal ponds in south-central Florida are usually treeless not because conditions are generally unfavorable for growth and establishment of south Florida slash pines, but because episodic flooding and fire cause massive mortality of seedling and sapling pines.
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1 - Archbold Biological Station, Plant Ecology Lab, P.O. Box 2057, Lake Placid, Florida, 33862, USA
2 - Cornell University, Ecology and Evolutionary Biology, Corson Hall, Ithaca, NY, 14853, USA
south Florida slash pine
Lake Wales Ridge.
Presentation Type: Oral Paper:Papers for Sections
Location: Boulevard A/Hilton
Date: Wednesday, July 11th, 2007
Time: 8:00 AM