Vegetation at OPC
Herbaceous vegetation in the intertidal and supratidal marshes at OPC
was surveyed in 1991-1992 in 115 1-m2 quadrats at 5-m intervals along
randomly located, 50-m-long belt transects (Figure 1). Percent cover
of herbaceous plants and saplings was determined by counting leaf cover
for each species within each square decimeter of a 1-m2 quadrat (Mueller-Dombois
and Ellenberg 1974). With different layers in the vegetation, total
cover could exceed 100 %. Relative percent cover was calculated by dividing
the percent cover for each species by the total percent cover of all
plants in a quadrat. No trees were observed in or near any of the quadrats.
All vegetation data are reported in Hilgartner (1995), available upon
request. Taxonomy follows Fernald (1970), except Microstegium vimineum
from Hitchcock and Chase (1950) and Phragmites australis from Tiner
and Burke (1995).
One of the major research tasks has been to statistically analyze the
large database of vegetation data to determine the extent to which the
vegetation at Otter Point Creek is organized into distinguishable plant
associations. Using a common multivariate statistical analysis approach,
called cluster analysis, it was possible to determine that there are
9 major groupings of plant species at Otter Point Creek, as shown below.
Seven of the plant associations have a single dominant species together
with several low abundance taxa. For example, the first grouping has
88 % relative cover of Nuphar advena (aka spatterdock).
