The Future of Tidal Wetlands 403

stress (chlorosis), and eventually the forest is overtaken by halophytic species—salt marsh transgression. An inventory of wet-lands in Maryland reported the occurrence of “estuarine forests,” former loblolly pine forests now subjected to tidal flooding and harboring an understory of halophytic (salt-tolerant) species (Tiner and Burke 1995). Examples of this phenomenon are common on the Delmarva Peninsula, espe-cially on Maryland’s Lower Eastern Shore along Chesapeake Bay ( Dorchester and Somerset Counties). The presence of dead trees or stumps in salt and brackish marshes elsewhere provides ample evidence of this phenomenon along the Atlantic Coast (e.g., spruce in Maine and Atlantic Canada, white pine in New Hampshire, red cedar in Mas-sachusetts, Atlantic white cedar in New Jersey, loblolly pine in Maryland and North Carolina, and cabbage palm in South Caro-lina and Florida; see Figure 12.9). Along the New Jersey coast, swamp and lowland for-ests along brackish marshes are changing—trees are dying and the canopy is opening,

providing opportunities for light-loving herbs ( Figure 12.11). Common reed, seaside goldenrod (Solidago sempervirens), annual salt marsh fleabane (Pluchea odorata), and groundsel-bush (Baccharis halimifolia) are among the first halophytic species to colonize these sites. In South Carolina, pine–oak–gum forest vegetation (Pinus–Quercus–Nyssa) was replaced by a succession of marsh species: high-tide bush (Iva frutescens), black needlerush ( Juncus roemerianus), sea ox-eye (Borrichia frutescens), glasswort (Salicor-nia), short form of smooth cordgrass, and finally by medium-height smooth cordgrass (Gardner et al. 1992). In the Florida Keys, rising sea level has increased local ground-water levels and soil salinity resulting in the death of lowland slash pine (Pinus elliottii) forests ( Ross et al. 1994). On Florida’s west coast, cabbage palm forests (Sabal palmetto) are retreating as sea level rises and being replaced by salt marsh (Williams et al. 1999a). Exposure to salt was identified as the major cause preventing tree regenera-tion, which then allowed salt marsh plants

Figure 12.11. As lowland forest trees die from increased salinity and, in some cases, increased flooding and soil saturation, the canopy opens creating conditions for coloni-zation by herbs such as common reed (Phragmites australis).