Vegetation Classification and Mapping Project Report - USGS

USGS-NPS Vegetation Mapping Program
Colonial National Historical Park
The classification of 93 oak / heath forest sample plots is illustrated in Figures G1-G2 of
Appendix G. Plot samples cluster into two compositionally distinct groups in both the
dendrogram and the three-dimensional ordination (Appendix G, Figures G1 and G2). The two
associations, Coastal Plain Mixed Oak / Heath Forest (CEGL006269) and Piedmont / Low
Elevation Mixed Oak / Heath Forest (CEGL008521) separate along axis three of the ordination
diagram. There were no environmental variables that were significantly correlated with the
ordination axes. The single oak / heath sample plot from Colonial National Historical Park is
classified as Piedmont / Low Elevation Mixed Oak / Heath Forest (CEGL008521).
Environmental variables from plot samples classified as Piedmont / Low Elevation Mixed Oak /
Heath Forest (CEGL008521) are summarized in Appendix F. A compositional summary based
on 75 sample plots of this association is presented in Appendix H, Table H1. The plot sample
from Colonial National Historical Park is fairly typical of the association, both compositionally
and environmentally. The Colonial National Historical Park plot sample contained most of the
constant species, but lacked common serviceberry (Amelanchier arborea), striped prince's pine
(Chimaphila maculata), scarlet oak (Quercus coccinea), and sassafras (Sassafras albidum).
Instead of pignut hickory (Carya glabra) or mockernut hickory (Carya alba), the Colonial
National Historical Park example had sand hickory (Carya pallida). Piedmont / Low Elevation
Mixed Oak / Heath Forest is found in three of the seven national parks included in this study
(Appendix D).
Figures G3 and G4 of Appendix G illustrate the classification of 25 plots of pine - oak forest into
two compositionally distinct groups. Coastal Plain Loblolly Pine - Oak Forest (CEGL004766)
was classified from eight plot samples from Colonial National Historical Park. Eastern White
Pine – Hardwood Forest (CEGL008539) is an association found primarily in the Piedmont and
mountains, which was documented at Fredericksburg and Spotsylvania National Military Park.
The two associations separate along axis 1 of the two-dimensional ordination, which represents
60% of the variance in the data (Table 10). Although there were no significant environmental
variables separating the associations in analysis, samples of Coastal Plain Loblolly Pine - Oak
Forest occurred on flat topography over very infertile soils, while samples of Eastern White Pine
– Hardwood Forest were found on moderately steep to steep rocky slopes with slightly more
fertile soils (Appendix F). 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 (Appendix D).
Classification results for the mesic acidic forest group are presented in Appendix G, Figures G5­
G7. Plot samples cluster into two compositionally distinct groups in both the dendrogram and
the three-dimensional ordination (Appendix G, Figures G5 and G6). Axis three of the joint plot
(Appendix G, Figure G7) is highly correlated with joint plot vectors representing pH, and the soil
cations calcium, magnesium, manganese, and iron. The two associations classified within the
mesic acidic forests group are Mesic Mixed Hardwood Forest (CEGL006075) and Piedmont /
Coastal Plain Oak – Beech / Heath Forest (CEGL006919). Although both associations can occur
in the same landscape, Piedmont / Coastal Plain Oak – Beech / Heath Forest is found on steeper,
more exposed slopes with less fertile soils than Mesic Mixed Hardwood Forest. A summary of
environmental variables for the two associations is presented in Appendix F. Both associations
occur at Colonial National Historical Park. Two plot samples from the park represent Piedmont /
Coastal Plain Oak – Beech / Heath Forest and three represent Mesic Mixed Hardwood Forest. A
compositional summary for 26 sample plots of Piedmont / Coastal Plain Oak – Beech / Heath
Forest is presented in Appendix H, Table H4 and a compositional summary for 170 sample plots
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