Geoscience Reference
In-Depth Information
Term
Definition(s)
Wetland
Transitional land between terrestrial and aquatic ecosystems where the water table
is usually at or near the surface, land that is covered by shallow water, or an area
that supports hydrophytes, hydric soil, or shallow water at some time during the
growing season (after Cowardin et al., 1979)
Target plant species
Phragmites australis
or
Typha
spp. (per Voss, 1972; Voss, 1985)
Nontarget plant species
Any herbaceous vegetation other than target plant species
Vegetation stand
A relatively homogeneous area of target plant species with a minimum approximate
size of 0.8 ha
Edge of vegetation stand
Transition point where the percentage canopy cover ratio of target:nontarget species
is 50:50
Table 18.2 Nonspectral Data Parameters Collected (
) along Vegetation Sampling Transects
at Pointe Mouillee
Parameter Description
1.0 m
quadrat
3.0 m
quadrat
2
2
Number of live target species stems
Number of senescent target species stems
Number of flowering target species stems
Water depth
Litter depth
Mean stem diameter (
n
= 5)
Percentage cover live target species in canopy
Percentage cover senescent target species in canopy
Percentage cover live nontarget species in canopy
Percentage cover senescent nontarget species in canopy
Percentage cover live nontarget species in understory
Percentage cover senescent nontarget species in understory
Percentage cover senescent target species in understory (i.e.,
senescent material that is not litter)
Percentage cover exposed moist soil
Percentage cover exposed dry soil
Percentage cover litter
Percentage cover water
General dominant substrate type (i.e., sand, silt, or clay)
Distance to woody shrubs or trees within 15 m
Direction to woody shrubs or trees within 15 m
Total canopy cover (area) of woody shrubs
a low infeasibility value. Pixels with a high matched filter result and high infeasibility were “false
positive” pixels that did not match the
Phragmites
target.
18.3.2
Field Reference Data Collection
To minimize ambiguous site identifications, specific definitions of wetland features were pro-
vided to field investigators (Table 18.1). Vegetation was sampled on August 7-8, 2001, to provide
training data for the semiautomated vegetation mapping (Table 18.2) and subsequent accuracy
assessment effort. Prior to field deployment, aerial photographs were used along with on-site
assessments to locate six large stands of vegetation at the site. They included (1) two stands of
and (3) two nontarget vegetation stands for comparison to
the target species (Figure 18.2). Digital video of each vegetation stand was recorded to fully
characterize the site for reference during image processing and accuracy assessment. Additional
field data used to support accuracy assessment efforts included vegetation stand sketches, notes of
the general location and shape of the vegetation stand, notes of landmarks that might be recognizable
in the imagery, and miscellaneous site characterization information.
Phragmites,
(2) two stands of
Typha,
