The south-west coast of Florida has a continuous band of forested estuarine wetlands, extending from Naples southwards to Cape Sable and covering a total of 60 000 ha. Much of this is located within Everglades National Park (ENP). Three species of mangrove are found: Rhizophora mangle (L.), Avicennia germinans (L.) Stearn and Laguncularia racemosa (L.) Gaertn (Smith et al. 1994). Several large tidal rivers drain the Florida Everglades and enter the Gulf of Mexico (Craighead 1964) within ENP. We established four sites along a tidal gradient in one of these waterways, the Shark River (Fig. 1, Table 1). Tides at these sites are semidiurnal, with depth of inundation varying from 0.75 m at SA to 0.10 m at SD. Site SD is most upstream and during the summer rainy season it may be inundated for periods much longer than a single tidal cycle. We established a fifth site at North Highland Beach (NHB; Fig. 1, Table 1) behind a beach ridge that acts as a barrier from tidal flushing. NHB remains flooded for extended periods of time due to local rainfall (L. M. Romero, T. J. Smith III & J. W. Fourqurean, personal observation). Because of the unique characteristics of NHB with respect to flooding regime, we thought it would allow us to estimate the effects of extended flooding events on wood decomposition.

Climate in this region is characterized by a pattern of alternating wet and dry seasons, and average annual precipitation in Everglades National Park ranges from 1190 to 1570 mm, approximately 60% of which falls from June through September (Duever et al. 1994). Air temperature at our sites ranged from a maximum of 33 °C to a minimum of 8 °C and soil temperature ranged from a maximum of 30 °C to a minimum of 12 °C.

Fig. 1 Position within Florida of the south-west, estuarine coast of Everglades National Park. Four study sites were established along Shark River, with SA near the river mouth, following in alphabetical order to the furthest upstream site (SD). A fifth site was established behind a coastal shell dune at North Highland Beach (NHB). Open water, salt water marsh and mangrove forest habitats are indicated. [larger image]

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Table 1 List of sites in order of decreasing tidal influence. Other characteristics, including location, mean salinity and species composition, are also provided.
Site name	Latitude/longitude	Distance upstream from		Mangrove species present
		Gulf of Mexico (km)	Mean salinity ()
Shark River A (SA)	25°19.38' N/ 81°08.28' W	0.5	36	R. mangle, L. racemosa, A. germinans
Shark River B (SB)	25°21.49' N/ 81°04.43' W	6	23	R. mangle, L. racemosa, A. germinans
Shark River C (SC)	25°22.73' N/ 81°01.84' W	11	3	R. mangle, L. racemosa, A. germinans
Shark River D (SD)	25°24.35' N/ 80°57.49' W	18	3.5	R. mangle, L. racemosa
North Highland Beach (NHB)	25°30.70' N/ 81°12.54' W	NA	25	R. mangle, L. racemosa, A. germinans