Environmental Engineering Reference
In-Depth Information
environmental conditions for wetland condition assessment (Johnston et al.
2007
).
The combination of cluster analysis, NMS ordination, and indicator species
analysis is commonly used to describe and differentiate plant communities in the
wetland literature.
5.4.9 Floristic Quality Assessment Indices
Floristic quality indices (FQAIs) are frequently used to determine the condition of a
wetland based upon the ecological “conservatism” of the plant species (U.S. EPA
2002
). Some plant species are more sensitive to human disturbance and therefore
more conservative in terms of their growth requirements. These species are
indicators of high quality systems. By sampling an area, one can assess its quality
using the plant species scores (i.e., coefficients of conservatism). Species are ranked
with values from one (not conservative) to ten (conservative and highly
ecologically sensitive) by experts. The ranking needs to be done on a regional
basis, because species behave differently in different regions. Therefore, one cannot
apply a FQAI developed in the Upper Midwest to New England wetlands.
Once a wetland has been sampled, various formulas can be used to summarize
the wetland conditions based upon the C of Cs (coefficients of conservatism) of the
plants found there. One commonly used formula is
.
X
N
native
S
l
¼
CC
i
i
¼
Where I
the FQAI for the site, CC
i
is the C of C for species i, and N is the total
number of native species found at the site (Andreas et al.
2004
). A simple mean C of
C(
C
) for all species can also be calculated:
X
S
C
¼
CC
i
N
=
i
Both of these measures rely only on species presence data, which is an advantage in
that it is faster to inventory species presence than abundance. A weighted average
measure can incorporate species abundance, with relativized species abundance as the
weights (see
Exercise 4
). Rooney and Rogers (
2002
) discuss some problems with
FQAI and pose alternative calculations. Matthews et al. (
2009b
) does a thorough
assessment of the performance of different vegetation indicators, including FQAIs,
when tracking wetland restoration trajectories in comparison with reference systems.
They warn that using any single metric to assess wetland restoration success provides
an incomplete picture, that multiple methods should be used, and that there is no
simple metric that adequately assesses restoration success (Matthews et al.
2009b
).