"Marsh hammocks" in coastal salt marshes (and perhaps tidal freshwater marshes)

I have long been interested in tree-islands, small patches of forest surrounded by low stature, often grassy or herbaceous vegetation. These are found all over the world in large areas of nonforested vegetation of several types, but in the SEUS the surroundings are usually wetland, marshes or wet-prairies (the latter term more common in Florida). The “hammocks”** of the Everglades are the best know examples. Flooding stresses (and not rarely, fire stresses) in the surrounding marshes are what is thought to limit tree growth there. The slightly raised site of the tree patch itself ameliorates flooding stresses. The situation with fire is more complex. Salt water has obvious influence as well in the salt marshes.

South Florida is rife with types and numbers of tree-islands but we in the Carolinas have some too, the most important being the beautiful marsh hammocks of the coastal salt marshes. I have little direct experience with these (far more in Florida tree-islands and some in Okefenokee Swamp, GA) but would like to learn more about them. I can tell from aerial photography that some are half-buried coastal dunes, projecting up through the younger marsh mud that has come to surround them in the final slow rise of postglacial sealevel over the past 6000 years or so. These are elongated parallel to the coast and often have the same pine forest as the more typical dunes nearby. Some others, less-elongated and less-oriented, look as if possibly they might have been point bars on large meandering streams that have now meandered away. Other, more rounded, examples are harder to tell or guess at origin. I have heard of, but not yet seen, a study done mostly in NC (and some in SC) where abundant archeological shell debris in mounds were found to form the focuses of many marsh hammocks, to the extent that the carbonate becomes a major ecological soil factor: “calcareous maritime forest” I think is the term I heard used. Archeological sites as focuses for some salt marsh islands is known in upper Gulf coast Florida and New England too, and archeology is an important factor in the development of many Everglades tree-islands. Many rounded Carolina marsh hammocks just seem too big for this to be their main cause, however. That is, some nonhuman agency seems necessary to explain them, and simple dune or point-bar burial may not be able to explain all of them..

Does anyone have some “feet on the ground” experience on marsh hammocks in the Carolinas or Georgia? That is, the isolated true islands (at high tide at least) out in the salt marshes or tidal fresh-water marshes. What were your impressions? What did the soil look like? How high above high tide were they?

Incidentally, there are two divergent though conflicting lines of growing interest in marsh hammocks now. People want to convert them to home sites or unique neighborhoods (accessed by causeway or boat), while this naturally shocks those concerned about their ecological (and scenic) value and about the development effects on them and surrounding marshes.

**In Florida the term “hammock” is used two ways: for a forest patch in the Everglades marshes OR for a type of vegetation (the former, though, commonly is NOT made up by the latter). As a vegetational term it refers to broadleaf evergreen forest, often with some tropical affinities (though “oak hammock” is also used, given liveoaks), while “bayhead” refers to broadleaf evergreen forest of more temperate affinity, typically with aromatic-leaved species present (and ignoring Persea’s tropical relatives). As with much folk or vernacular terminology, it is a bit confusing and non-explicit.