Vegetation Classification and Mapping Project Report - USGS

USGS-NPS Vegetation Mapping Program
Colonial National Historical Park
herbaceous vegetation and 400 m 2 plots were used to sample forested vegetation. The
configuration of the plot was flexible (e.g. 20 x 20 m, 16 x 25m, 13.33 x 30 m, 10 x 40 m) to
accommodate special site conditions and vegetation pattern. If a forest had particularly large
diameter trees or a diverse canopy composition, a 1000 m 2 plot (20 x 50m) was used to fully
capture tree species composition.
Within each plot, the percent cover of each vascular plant taxon was visually estimated as a
vertical projection of above-ground biomass onto the full plot area and assigned to one of nine
numerical cover classes (Table 2). In addition to this total cover value, cover was estimated for
each species in the following height/lifeform classes:
herb (field) layer (all herbaceous plants, woody plants 1 to 6 m
tree layer, >6 to 10 m
tree layer, >10 to 20 m
tree layer, >20 to 35 m
tree layer, >35 m
The overall cover of mosses, lichens, and liverworts was estimated, but the individual cover of
non-vascular taxa was not estimated. The cover of vines climbing into the canopy or subcanopy
was recorded in the maximum height stratum attained by the plant. Vascular plants thought to be
characteristic of the sampled community, but located outside the plot, were recorded
parenthetically if visible from the boundary, and assigned a cover class of 1.
Additional vegetation information collected included the estimated height and total vegetative
coverage of each stratum, the leaf type and leaf phenology of each stratum, and the
physiognomic class represented by the stand. The maximum canopy height was measured using
a clinometer.
Table 2. Cover-class scores used in field sampling and data analysis.
Area of Coverage
Cover Class Percent Cover Range for a 400 m 2 Cover Class
plot Percent Cover Midpoint
1