PARENT SESSION
Oral Session # 15: Wetland Ecology I: The Everglades and Southern Wetlands.
Presiding: J Chick
Tuesday, August 5. 8:00 AM to 11:30 AM, SITCC Meeting Room 101.
Effects of Simulated Hydrologic Regimes on Twelve Tree Species of Everglades Tree Islands.
Jones, David*,1, Ross, Michael 1, Hwang, Bernice1, Walters, Joshua1, Oberbauer, Steven1, Jayachandran, Krish1, 1 Florida International University, Miami, Florida
ABSTRACT- The responses of tree species to environmental gradients within Everglades tree islands have rarely been tested under controlled conditions. We describe the response of 12 tree species to three realistic hydrologic regimes that were applied while holding other variables (e.g., light, nutrients) constant. Seven species (Annona glabra, Chrysobalanus icaco, Ilex cassine, Magnolia virginiana, Myrica cerifera, Persea borbonia, Salix caroliniana) were characteristic of Shark Slough (Everglades National Park, Florida) bayhead and bayhead swamp forests, while five (Bursera simaruba, Coccoloba diversifolia, Eugenia axillaris, Mastichodendron foetidissimum, Simarouba glauca) were common in hardwood hammocks (uplands) in the region. Recently emerged seedlings of all species were collected from Everglades tree islands in May-June 2001 and raised in a shadehouse. The experimental design was randomized complete block, with 36 species x treatment combinations represented twice in each of four pools (blocks). Water levels in the pools were managed to mimic variation among weekly means of water depths at a known marsh location. Treatments representing hardwood hammock, bayhead, and bayhead swamp hydrologic regimes were maintained in each pool at the appropriate relative heights. Commencing in April 2002, plant structural and physiological responses were monitored at one to six week intervals for 24 weeks. Upland species showed signs of both morphological and physiological stress from inundation between weeks 6 and 12. Some species typically found in bayhead and bayhead swamp sites appeared to be better adapted to rising water levels than others. Our data suggested that Annona, Magnolia, Myrica, and Salix responded most positively to flooding, while Chrysobalanus, Ilex, and Persea were less flood-tolerant. The arrangement of species according to their response to the flooding treatment roughly paralleled their spatial distribution in the marsh landscape. Such experimental work may allow us to isolate the mechanism and timing of morphological and physiological responses in tree species, possibly permitting early warning of flooding stress in tree islands and modification of water distribution that may benefit natural resources management in the Everglades.
Key words: Everglades National Park, tree islands, flooding responses, wetland ecology