Vegetation Classification and Mapping Project Report - USGS

USGS-NPS Vegetation Mapping Program
Colonial National Historical Park
Problems with the field keys were addressed by modifying the keys to better help the user make
distinctions between similar vegetation types. Descriptions of map classes were modified, where
needed, to include comments about similar vegetation classes or seasonal constraints on
vegetation identification. Polygons that could be confidently reclassified using accuracy
assessment data were reattributed in the final version of the map and minor refinements to the
map were made using information collected during accuracy assessment.
The following revisions were made to the vegetation map:
• The ecotonal area between two polygons mapped as Coastal Plain / Piedmont Small-
Stream Floodplain Forest and Coastal Plain / Piedmont Floodplain Swamp Forest (Green
Ash – Red Maple Type) was edited to better reflect what was observed on the ground.
• Two polygons initially mapped as Coastal Plain / Piedmont Floodplain Swamp Forest
(Green Ash – Red Maple Type) were reclassified as Non-Riverine Saturated Forest based
on accuracy assessment data and the landscape position.
• Three polygons initially mapped as Coastal Plain Loblolly Pine - Oak Forest were
reclassified as Successional Tuliptree – Loblolly Pine Forest.
• A 0.6 hectare inclusion of Tidal Bald Cypress Forest / Woodland was split out of a
polygon initially mapped as Coastal Plain Loblolly Pine - Oak Forest.
• Three polygons initially mapped as Mesic Mixed Hardwood Forest were reclassified as
Acidic Oak – Hickory Forest, Piedmont / Coastal Plain Oak - Beech / Heath Forest, and
Successional Tuliptree - Loblolly Pine Forest.
• The boundary between a polygon mapped as Mesic Mixed Hardwood Forest and the
adjacent Coastal Plain / Piedmont Small-Stream Floodplain Forest was refined to better
reflect what was observed on the ground.
• One polygon initially mapped as Non-Riverine Saturated Forest was reclassified to
Successional Tuliptree - Loblolly Pine Forest.
• One polygon initially mapped as Salt Scrub was reclassified to Coastal Plain Loblolly
Pine - Oak Forest .
• A 1.2 ha inclusion of Tidal Oligohaline Marsh was split out of a polygon initially mapped
as Coastal Plain Loblolly Pine - Oak Forest .
• A portion of the single polygon mapped as Successional Tree-of-Heaven Forest was
remapped to split out an area of Sucessional Tuliptree – Loblolly Pine Forest.
• Seven polygons initially mapped as Tidal Oligohaline Marsh were reclassified to the map
class Tidal Mesohaline and Polyhaline Marsh.
• A new polygon of Coastal Plain Dry Calcareous Forest encountered during accuracy
assessment, in transit between sampling points, was split out of an area initially mapped
as Mesic Mixed Hardwood Forest.
A second contingency matrix was constructed using the revised vegetation map as reference
data. The final contingency matrix based on the revised vegetation map is presented in Table 13.
The Kappa Index for the final vegetation map was 83.8% ± 4.7%, with an overall accuracy of
84.7%. Errors of omission in the final vegetation map equal or exceed 80% for all but five map
classes: Coastal Plain Loblolly Pine – Oak Forest (76%), Coastal Plain Mesic Calcareous
Ravine Forest (25%), Successional Black Walnut Forest (75%), Successional
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