Vegetation Classification and Mapping Project Report - USGS

USGS-NPS Vegetation Mapping Program
Colonial National Historical Park
Depression Wetland (Red Maple - Sweetgum - Willow Oak Type) (CEGL006110), Coastal Plain
Depression Wetland (Swamp Tupelo Type) (CEGL006223), and Non-Riverine Saturated Forest
(CEGL004644). The fourth association, Upland Depression Swamp (CEGL007403) is an
isolated wetland association found in the Piedmont of Virginia and the Carolinas. Compositional
summaries for all three associations found in Colonial National Historical Park are presented in
Appendix H. One example of Coastal Plain Depression Wetland (Red Maple - Sweetgum -
Willow Oak Type) was sampled in Colonial National Historical Park and it is compositionally
representative of the association, but lacks one nominal, swamp doghobble (Leucothoe
racemosa). Coastal Plain Depression Wetland (Swamp Tupelo Type) was not plot sampled in
Colonial National Historical Park. The two plot samples of Non-Riverine Saturated Forest from
the park are compositionally representative of the association, containing all but one of the
nominal species and all of the most-constant species. The plots in Colonial National Historical
Park lack coastal sweetpepperbush (Clethra alnifolia), but have higher than average species
richness (51 and 62 species per 400 m 2 ). Coastal Plain Depression Wetland (Red Maple -
Sweetgum - Willow Oak Type) was also documented in Fredericksburg and Spotsylvania
National Military Park. Coastal Plain Depression Wetland (Swamp Tupelo Type) was only
documented in Colonial National Historical Park. Non-Riverine Saturated Forest occurs in four
of the seven national parks included in this study. All four of the nonriverine forest associations
recognized in this analysis are uncommon to rare in the mid-Atlantic region and three are
globally rare (Appendix D).
Classification of 129 tidal herbaceous marsh plots is illustrated in Appendix G, Figure G26. The
dendrogram shows eight distinct compositional groups that correspond to eight tidal marsh
associations. The ordination of the tidal herbaceous plots does not show a clear separation of
associations along the three ordination axes (Appendix G, Figure G27). The eight associations
were grouped into three units used to map tidal herbaceous marshes (see next section of report);
Tidal Freshwater Marsh, Tidal Oligohaline Marsh, and Tidal Mesohaline and Polyhaline Marsh.
Figure G28 illustrates how these three groups separate along all three ordination axes.
Environmental relationships were not explored due to a lack of environmental data for the
majority of the tidal herbaceous plot samples. All eight associations illustrated in the
dendrogram (Appendix G, Figure G26) are found at Colonial National Historical Park, and ten
quantitative plot samples from the park were included in the regional analysis. Compositional
summaries for the eight associations are presented in Appendix H, Tables H14 - H21. These
eight tidal marsh associations are considered common in the mid-Atlantic region, but have not
yet been assigned conservation ranks. Four of the associations are also found at George
Washington Birthplace National Monument, while the other four were only documented at
Colonial National Historical Park in this study (Appendix D).
Figure G29 in Appendix G illustrates the classification of 94 tidal forest and shrubland plot
samples. The groups segregate on axis one of the two-dimensional ordination (Figure G30)
which represents 72% of the variance in the compositional data (Table 10). Environmental
relationships were not explored due to lack of environmental data for the tidal forest and
shrubland plot samples. Three of the four associations classified in this group are present at
Colonial National Historical Park, Salt Scrub (CEGL003921), Tidal Shrub Swamp (Wax Myrtle
Type) (CEGL004656), and Tidal Bald Cypress Forest / Woodland (CEGL004654). A
compositional summary of each association is presented in Appendix H, Tables H22-H24. The
fourth association, Tidal Shrub Swamp (Iva Type) was identified only from George Washington
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