Vegetation Classification and Mapping Project Report - USGS

USGS-NPS Vegetation Mapping Program
Colonial National Historical Park
disturbances, and logging. Because of their isolated hydrology and small size, these forested
wetlands are often exempt from protective wetland regulations and much of the habitat
throughout its range is vulnerable to destruction by indirect development impacts such as
siltation, canopy removal, and subsequent nonnative species invasions. Despite considerable
efforts to inventory this community over the years, fewer than 50 patches of this vegetation are
known, covering an aggregate area of perhaps 121 ha (300 ac). In Colonial National Historical
Park, wetlands mapped as Disturbed Seepage Swamp may have once been this association, but
now lack the species composition to confidently classify them as Coastal Plain Calcareous
Seepage Swamp.
Two associations representing non-alluvial, coastal plain depression wetlands are mapped as
small, isolated features in the vicinity of Yorktown Battlefield and together cover 2.0 ha (4.9 ac).
Coastal Plain Depression Wetland (Red Maple - Sweetgum - Willow Oak Type) and Coastal
Plain Depression Wetland (Swamp Tupelo Type) occur as seasonally flooded, deciduous forests
in an otherwise upland landscape. These wetlands have fluctuating, seasonally perched water
tables, and are believed to be sinkhole features that formed through dissolution of underlying
carbonate-rich, shell marl deposits. The marl deposits are too deep to influence soil or water
chemistry of the depressions, which are strongly acidic. Coastal Plain Depression Wetland
(Swamp Tupelo Type) is subject to deeper flooding and has a longer hydroperiod than Coastal
Plain Depression Wetland (Red Maple - Sweetgum - Willow Oak Type). Coastal Plain
depression wetlands are known from the Coastal Plain of Virginia north to New York, and can
range into the eastern edge of the Piedmont in Virginia. Coastal Plain Depression Wetland
(Swamp Tupelo Type) is the less common of the two associations, known only from Virginia
and Delaware. These associations are naturally small in size, occurring in complexes over no
more than 10 ha (25 ac) and, on average, covering much smaller areas. The greatest threat to this
vegetation is incompatible human use of surrounding lands, generally agriculture with
insufficient buffers to protect from pesticide and fertilizer use. Since these associations depend
on intact hydrology, another major threat is altered hydrology from ditching or over-pumping of
groundwater.
Seven upland forest map classes that represent later successional vegetation cover 702.5 ha
(1,736.0 ac) or just over 20% of park land in upland areas that have not been converted to pine
forests or other transitional vegetation. The most common upland forest map class is Mesic
Mixed Hardwood Forest which covers almost 10% (338.2 ha [835.8 ac]) of the park land and is
found on mesic lower slopes and ravines. Some of the forested areas in Colonial National
Historical Park that are mapped as Successional Tuliptree - Loblolly Pine Forest may have been
Mesic Mixed Hardwood Forest prior to canopy removal. Mesic Mixed Hardwood Forest is a
common and widespread community in the Mid-Atlantic Piedmont and Coastal Plain and was
documented in five of the seven parks in this study. Coastal Plain Loblolly Pine - Oak Forest is
the matrix forest of Jamestown Island and the surrounding area, covering 310.7 ha (767.8 ac). It
is found in low-lying areas or sandy interfluves surrounded by tidal wetlands, and is
distinguished by the presence of oaks and coastal shrubs such as as wax myrtle (Morella
cerifera) and swamp bay (Persea palustris). Coastal Plain Loblolly Pine - Oak Forest was only
documented at Colonial National Historical Park and is not in any of the other parks in this
study. It is a middle to late successional forest found over sandy soils in the Coastal Plain of
Virginia and Maryland. It is thought to follow land clearing or cessation of agriculture in nearcoastal
areas.
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