Tidal Bald Cypress Forests and Woodlands
Coniferous or mixed swamp forests and woodlands dominated by bald cypress (Taxodium distichum) are known only from the upper tidal reaches of rivers in Maryland, southeastern Virginia and North Carolina. Examples are documented in Virginia from the lunar-tidal Dragon Swamp / Piankatank River (Gloucester, King and Queen, and Middlesex Counties), Chickahominy River (Charles City, James City, and New Kent Counties), and James River (Isle of Wight and Surry Counties); and the wind-tidal Northwest and North Landing Rivers (City of Chesapeake and Virginia Beach). At some sites, these communities occur in ecotones between tidal marshes and non-tidal backswamps or uplands.
In lunar-tidal stands, bald cypress (Taxodium distichum) dominates an open to very open overstory, with or without hardwood associates such as swamp tupelo (Nyssa biflora), water tupelo (Nyssa aquatica), and green ash (Fraxinus pennsylvanica). Stand structure and canopy cover range from closed forest to very open woodland. Shrub and herb layers are variable but generally contain a mixture of species characteristic of both marshes and swamps. Some well-developed tidal bald cypress forests appear floristically similar to palustrine Bald Cypress-Tupelo Swamps. Other stands have a nearly monospecific herb dominance by shoreline sedge (Carex hyalinolepis). In a unique, possibly fire-influenced, savanna-like stand on the Northwest River, the herbaceous dominants, in rough seasonal order, are silvery sedge (Carex canescens var. disjuncta), spikerushes (Eleocharis fallax and Eleocharis rostellata), rattlesnake-master (Eryngium aquaticum var.aquaticum), and wild rice (Zizania aquatica var. aquatica).
A distinctive, mixed tidal swamp forest in extreme southeastern Virginia is subject to irregular wind-tidal flooding. As currently defined, this community type appears to be a globally rare endemic of the Embayed Region of southeastern Virginia and northeastern North Carolina; similar communities, however, occur occasionally further north on the irregularly flooded edges of lunar-tidal systems. In Virginia, stands occur primarily along the North Landing and Northwest Rivers (Cities of Virginia Beach and Chesapeake), estuarine tributaries of Currituck Sound. Although these systems are no longer influenced by lunar tides because of inlet closures, they are subject to wind-driven currents that produce as much as 1 m (3 ft) of variation in water levels and contribute to a salinity regime that fluctuates between completely fresh and about 5 ppt. This forest borders the wind-tidal marshes along the lower portions of the two rivers, extending well upstream of the limit of marshes in narrowing channel-side belts. It appears to represent a long-term seral stage in succession from marsh to swamp forest. Habitats have a pronounced hummock-and-hollow microtopography, with an average flooding depth 40 cm (16 in) above the hollow bottoms. Soils are coarse, fibric peats that appear indistinguishable from adjacent marsh peats. Bald cypress (Taxodium distichum), swamp tupelo (Nyssa biflora), and loblolly pine (Pinus taeda) are the dominant overstory trees in variable combinations. Spanish-moss (Tillandsia usneoides) is locally abundant, festooning the trees in some stands. Sweetbay magnolia (Magnolia virginiana) and red bay (Persea palustris) are scattered understory trees, while wax myrtle (Morella cerifera) dominates the shrub layer. The herb layer is diverse, containing species characteristic of both marshes and swamps, but royal fern (Osmunda spectabilis) often dominates.
The environmental dynamics, compositional variation, and state-wide distribution of Tidal Bald Cypress Forests and Woodlands are not well known and need intensive study.
Reference: Fleming and Moorhead (1998).
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Tidal bald cypress woodland with overwhelming herb-layer dominance by clones of shoreline sedge (Carex hyalinolepis). Along College Run near its confluence with the James River, Surry County (Chippokes Plantation State Park). Photo © Gary P. Fleming.
Tidally inundated bald cypress (Taxodium distichum) forest along the Chickahominy River at Wilcox Neck, Charles City County. Photo: Tom Rawinski / © DCR Natural Heritage. Tidal bald cypress forest along the James River near Swanns Point, Surry County. Floating and submersed aquatics such as common duckweed (Lemna minor) and common hornwort (Ceratophyllum demersum) dominate the herbaceous flora. Photo: Gary P. Fleming / © DCR Natural Heritage.
Wind-tidally inundated Estuarine Fringe Swamp Forest with overstory dominance by bald cypress (Taxodium distichum) and swamp tupelo (Nyssa biflora), and herb-layer patch-dominance by shoreline sedge (Carex hyalinolepis). Along Milldam Creek near its confluence with the North Landing River, City of Virginia Beach. Photo: Gary P. Fleming / © DCR Natural Heritage.