Vegetation Classification and Mapping Project Report - USGS

USGS-NPS Vegetation Mapping Program
Colonial National Historical Park
Tidal Mesohaline and Polyhaline Marsh covers 42.7 ha (105.6 ac) in the park and is found as
small pocket marshes along the York River from Ringfield / King Creek to Yorktown Creek and
in the vicinity of College Creek / Kingsmill. This tidal vegetation is characterized by plants
associated with mesohaline or polyhaline conditions, where salt concentrations are between 5
and 18 ppt or 18 to 30 ppt, respectively. Tidal Mesohaline and Polyhaline Marsh can be one of
two associations, but were combined into one map class since they cannot be mapped separately
based on photo signatures. Tidal Mesohaline and Polyhaline Marsh (Low Salt Marsh) is the
more common of the two associations and is distinguished by the dominance of smooth
cordgrass (Spartina alterniflora) occurring with species indicative of mesohaline conditions such
as saltmeadow cordgrass (Spartina patens) and inland saltgrass (Distichlis spicata). Tidal
Mesohaline and Polyhaline Marsh (Transitional Marsh) is distinguished by the dominance of
smooth cordgrass (Spartina alterniflora) occurring with species indicative of more oligohaline or
freshwater conditions such as big cordgrass (Spartina cynosuroides), green arrow arum
(Peltandra virginica), and annual wildrice (Zizania aquatica var. aquatica). Little is known
about the conservation status of these associations. They have been documented from Virgina,
Maryland, and Delaware.
Tidal Bald Cypress Forest / Woodland (12.0 ha [29.6 ac]) is found along the James River at
Swanns Point with small, disturbed examples mapped at Jamestown Island. This forest forms a
fringe between open tidal water and tidal marsh, and can occur along the riverfront or on
protected shorelines. This globally rare association occupies very specialized habitats in
Maryland and Virginia. Salt Scrub (5.5 ha [13.6 ac]) occurs as small, linear patches along the
York River north of Yorktown, and along the James River in the vicinity of Kingsmill. This
sandy, tidal shrubland is often found in a complex with tidal herbaceous vegetation. Salt Scrub
is a common coastal association found from South Carolina to Massachusetts. Tidal Shrub
Swamp (Wax Myrtle Type) covers only 4.2 ha (10.4 ac) in the park and is found in small patches
in the vicinity of Yorktown, along Colonial Parkway, Ringfield / King Creek, and at College
Creek / Kingsmill. These dense shrublands occur adjacent to tidal marshes and are dominated by
the shrub wax myrtle (Morella cerifera) in association with narrowleaf cattail (Typha
angustifolia). Tidal Shrub Swamp (Wax Myrtle Type) is known from North Carolina, Virginia,
and Maryland.
Nontidal forested wetlands include six map classes that cover 171.9 ha (424.7 ac) in the park.
Coastal Plain / Piedmont Small-Stream Floodplain Forest (65.9 ha [162.9 ac]) and Coastal Plain /
Piedmont Floodplain Swamp Forest (Green Ash - Red Maple Type) (30.9 ha [76.4 ac]) are found
on the floodplains of small streams in the park. The majority of Coastal Plain / Piedmont Small-
Stream Floodplain Forest is mapped in Yorktown Battlefield where it is found along Baptist Run
and Great Run over deep, sandy alluvial soils that are subject to occasional, brief flooding,
typically once or twice a year. Small areas classed as Coastal Plain / Piedmont Small-Stream
Floodplain Forest are also found along Colonial Parkway, just north of Jones Millpond. Coastal
Plain / Piedmont Small-Stream Floodplain Forest is characterized by species adapted to welldrained
alluvial soils such as tuliptree (Liriodendron tulipifera), American sycamore (Platanus
occidentalis), New York fern (Thelypteris noveboracensis), Christmas fern (Polystichum
acrostichoides), and nodding fescue (Festuca subverticillata). The deep, moist, well drained
soils of Coastal Plain / Piedmont Small-Stream Floodplain Forest are highly susceptible to
nonnative species invasion, and thus it is important not to site trails and roads in the active
floodplain and to mitigate impacts from surrounding development. Coastal Plain / Piedmont
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