Vegetation Classification and Mapping Project Report - USGS
Vegetation Classification and Mapping Project Report - USGS
Vegetation Classification and Mapping Project Report - USGS
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<strong>USGS</strong>-NPS <strong>Vegetation</strong> <strong>Mapping</strong> Program<br />
Colonial National Historical Park<br />
contain Magnolia virginiana (sweetbay) <strong>and</strong> recruitment of the overstory trees. The shrub layer<br />
varies from open to dense. <strong>and</strong> most characteristically contains Clethra alnifolia (coastal<br />
sweetpepperbush), Leucothoe racemosa (swamp doghobble), Ilex verticillata (common<br />
winterberry), Vaccinium corymbosum (highbush blueberry), Vaccinium fuscatum (black<br />
highbush blueberry), Vaccinium formosum (southern blueberry), Viburnum dentatum (southern<br />
arrowwood), Rhododendron viscosum (swamp azalea), <strong>and</strong> Viburnum nudum var. nudum<br />
(possumhaw). The herb layer is also highly variable. Some st<strong>and</strong>s have a rather sparse<br />
herbaceous flora, with scattered colonies <strong>and</strong> individuals of Woodwardia areolata (netted<br />
chainfern), Osmunda cinnamomea (cinnamon fern), Osmunda regalis var. spectabilis (royal<br />
fern), Woodwardia virginica (Virginia chainfern), Saururus cernuus (lizard's tail), <strong>and</strong> various<br />
sedges. Others have a relatively dense graminoid-dominated herb layer with variable patchdominance<br />
by Chasmanthium laxum (slender woodoats), Carex debilis var. debilis (white edge<br />
sedge), Carex intumescens (greater bladder sedge), Carex seorsa (weak stellate sedge), Carex<br />
lonchocarpa (southern long sedge), <strong>and</strong> more rarely, Carex bullata (button sedge) or Carex<br />
striata var. brevis (Walter's sedge). Many st<strong>and</strong>s of this association have been degraded by<br />
cutting or ditching, <strong>and</strong> extensive areas of suitable habitat have been lost to agriculture,<br />
hydrologic alterations, <strong>and</strong> conversion of hardwood forests to silvicultural pine plantations.<br />
Environmental Description: This association occurs on extensive, flat Coastal Plain terraces<br />
<strong>and</strong> very wide, ancient floodplains that are no longer subject to alluvial processes. Its hydrology<br />
is seasonally to nearly permanently saturated, with occasional ponding or groundwater<br />
sheetflows, <strong>and</strong> is maintained by a high water table rather than riverine or estuarine flooding.<br />
Shallow channels <strong>and</strong> streams are sometimes evident, <strong>and</strong> hummock <strong>and</strong> hollow<br />
microtopography may be present. On the Eastern Shore of Virginia (Accomack County), it is<br />
found in isolated <strong>and</strong> extensive but shallow upl<strong>and</strong> depressions. The st<strong>and</strong>s here cover many<br />
hectares <strong>and</strong> occur in slight depressions with drainage impeded by an impermeable clay layer<br />
about half a meter below the soil surface. The habitat apparently has a seasonally high water<br />
table but ponds water only intermittently or for short periods (G. Fleming pers. comm.). Surficial<br />
soils occupied by this forest are extremely acidic <strong>and</strong> infertile silt or silty-clay loams.<br />
<strong>Vegetation</strong> Description: The overstory of relatively undisturbed examples contain variable<br />
mixtures of hydrophytic oaks, most commonly Quercus phellos (willow oak), Quercus pagoda<br />
(cherrybark oak), <strong>and</strong> Quercus michauxii (swamp chestnut oak). Associated canopy species<br />
varying from site to site can include Quercus alba (white oak), Quercus palustris (pin oak),<br />
Quercus lyrata (overcup oak), Liquidambar styraciflua (sweetgum), Acer rubrum (red maple),<br />
Pinus taeda (loblolly pine), Nyssa sylvatica (blackgum), <strong>and</strong> Fraxinus pennsylvanica (green<br />
ash). Liquidambar styraciflua (sweetgum), Acer rubrum (red maple), <strong>and</strong> Pinus taeda (loblolly<br />
pine) are often abundant in st<strong>and</strong>s disturbed by cutting. The subcanopy layers are usually<br />
dominated by Ilex opaca var. opaca (American holly) <strong>and</strong> also contain Magnolia virginiana<br />
(sweetbay) <strong>and</strong> recruitment of the overstory trees. The shrub layer varies from open to dense, <strong>and</strong><br />
most characteristically contains Clethra alnifolia (coastal sweetpepperbush), Leucothoe<br />
racemosa (swamp doghobble), Ilex verticillata (common winterberry), Vaccinium corymbosum<br />
(highbush blueberry), Vaccinium fuscatum (black highbush blueberry), Vaccinium formosum<br />
(southern blueberry), Viburnum dentatum (southern arrowwood), Rhododendron viscosum<br />
(swamp azalea), <strong>and</strong> Viburnum nudum var. nudum (possumhaw). The herb layer is also highly<br />
variable. Some st<strong>and</strong>s have a rather sparse herbaceous flora, with scattered colonies <strong>and</strong><br />
individuals of Woodwardia areolata (netted chainfern), Osmunda cinnamomea (cinnamon fern),<br />
Osmunda regalis var. spectabilis (royal fern), Woodwardia virginica (Virginia chainfern),<br />
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