279-6 Morphology of Tree Islands in the Arthur R. Marshall Loxahatchee National Wildlife Refuge, Water Conservation Area 1, Southern Florida (USA)

Session: The Current Understanding of the Role of Wetland Hydrology in the Cycling of Elements and other Substances: A Technical Session in Memory of Paul H. Glaser

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Abstract:

Tree islands are slightly elevated fluvial features that occur in many wetland systems.  In the Everglades, tree islands are elevated 0.2 to 1.0 m above surrounding wetlands.  Even this slight relief is sufficient to affect the hydroperiod and chemistry resulting in distinct ecological conditions compared to the adjacent wetlands.  Water Conservation Area 1 (WCA1) is in the northern Everglades in southern Florida.  WCA1 is completely surrounded by dikes and pumping stations.  All surface water inputs and outputs to WCA1 are managed by the South Florida Water Management District (SFWMD).  Many tree islands were shaped by fluvial conditions that predate the current hydrologic controls around WCA1.  The purpose of this study is to use the spatial distribution and morphology of the tree islands to better understand how hydrologic conditions have changed in WCA1.

In this study, over 1,000 tree islands were analyzed in WCA1.  To randomize the sampling of tree islands, 50 1 km² sample sites were identified using the random point tool in GIS.  Tree islands were studied using ortho-photographic imagery.  The location, morphology and direction of long axis of the tree islands were analyzed.  Analyzed morphologic features include relationships between length, width and area, shape and comparison of the shape of tree islands to a lemniscate loop (a streamline form).  Linear regression tree analysis was conducted to evaluate spatial patterns in tree island morphology for statistical significance.

Results indicated that there is spatial variability in the shape of tree islands.  The direction of the long axes of the tree islands shows the movement of surface-water through WCA1.  While the shape of tree islands ranges from circular to streamline, length to width ratios suggest that equilibrium shape of the tree islands is fluvial.  

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-6920

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