wEPA
United States Environmental   Office of Water       EPA-822-R-02-017
Protection Agency       Washington, DC 20460   March 2002
     METHODS FOR EVALUATING WETLAND CONDITION
               #7  Wetlands Classification

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wEPA
United States Environmental   Office of Water         EPA-822-R-02-017
Protection Agency         Washington, DC 20460    March 2002
       METHODS FOR EVALUATING WETLAND CONDITION
                   #7  Wetlands Classification
                        Principal Contributor

                   U.S. Environmental Protection Agency
                         Naomi E. Detenbeck
                         Prepared jointly by:

                  The U.S. Environmental Protection Agency
       Health and Ecological Criteria Division (Office of Science and Technology)

                               and

          Wetlands Division (Office of Wetlands, Oceans, and Watersheds)

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NOTICE

The material in this document has been subjected to U.S. Environmental Protection Agency (EPA)
technical review and has been approved for publication as an EPA document. The information
contained herein is offered to the reader as a review of the "state of the science" concerning wetland
bioassessment and nutrient enrichment and is not intended to be prescriptive guidance or firm advice.
Mention of trade names, products or services does not convey, and should not be interpreted as
conveying official EPAapproval, endorsement, or recommendation.
APPROPRIATE CITATION

U.S. EPA. 2002. Methods for Evaluating Wetland Condition:  Wetlands Classification. Office of
  Water, U.S. Environmental Protection Agency, Washington, DC. EPA-822-R-02-017.

This entire document can be downloaded from the following U.S. EPA websites:

                           http://www.epa.gov/ost/standards

                           http://www.epa.gov/owow/wetlands/bawwg

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                        CONTENTS


FOREWORD	v

LIST OF "METHODS FOR EVALUATING WETLAND
CONDITION" MODULES	vi

SUMMARY	1

PURPOSE	1

INTRODUCTION	1

GOALS OF CLASSIFICATION	2

EXISTING WETLAND CLASSIFICATION SCHEMES 	4

SOURCES OF INFORMATION FOR MAPPING
WETLAND CLASSES	 17

EMPIRICAL CLASSIFICATION METHODS	 19

STATE OF THE SCIENCE	2O

SUGGESTED READINGS	 23

REFERENCES	 24

APPENDIXES	 28

GLOSSARY	 32

                        LIST OF TABLES

TABLE 1:   COMPARISON OF LANDSCAPE AND WETLAND
         CLASSIFICATION SCHEMES	 18

                        LIST OF FIGURES

FIGURE l:  MAP OF OMERNIK AQUATIC ECOREGIONS	5

FIGURE 2:  MAP OF BAILEY ECOREGIONS WITH COASTAL AND
         ESTUARINE PROVINCES	7
                              in

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FIGURE 3:   EXAMPLES OF FIRST FOUR HIERARCHICAL LEVELS OF
          ECOLOGICAL UNITS: DOMAIN, DIVISION, PROVINCE,
          AND SECTION	7

FIGURE 4:   DOMINANT WATER SOURCES TO WETLANDS	8

FIGURE 5:   DOMINANT HYDRODYNAMIC REGIMES FOR
          WETLANDS BASED ON FLOW PATTERN	9

FIGURE 6:   EXAMPLES OF HYDROGEOMORPHIC WETLAND
          CLASSES: A) DEPRESSIONAL WETLAND, B) LACUSTRINE
          FRINGE, C) TIDAL FRINGE, D) RIVERINE WETLAND, E)
          MINERAL FLATS WETLAND, AND F) ORGANIC FLATS WETLAND	 10

FIGURE 7:   INTERACTION WITH BREAK IN SLOPE WITH
          GROUNDWATER INPUTS TO SLOPE WETLANDS	15

FIGURE 8:   A) COWARDIN HIERARCHY OF HABITAT TYPES FOR
          ESTUARINE SYSTEMS, B) PALUSTRINE SYSTEMS	16
                               IV

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                                    FOREWORD

In 1999, the U. S. Environmental Protection Agency (EPA) began work on this series of reports entitled
Methods for Evaluating Wetland Condition. The purpose of these reports is to help States and
Tribes develop methods to evaluate (1) the overall ecological condition of wetlands using biological
assessments and (2) nutrient enrichment of wetlands, which is one of the primary stressors damaging
wetlands in many parts of the country. This information is intended to serve as a starting point for States
and Tribes to eventually establish biological and nutrient water quality criteria specifically refined for
wetland waterbodies.

This purpose was to be accomplished by providing a series of "state of the science" modules concerning
wetland bioassessment as well as the nutrient enrichment of wetlands. The individual module format
was used instead of one large publication to facilitate the addition of other reports as wetland science
progresses and wetlands are further incorporated into water quality programs. Also, this modular
approach allows EPA to revise reports without having to reprint them all. A list of the inaugural set of
20 modules can be found at the end of this section.

This series of reports is the product of a collaborative effort between EPAs Health and Ecological
Criteria Division of the Office of Science and Technology (OST) and the Wetlands Division of the
Office of Wetlands, Oceans and Watersheds (OWOW). The reports were initiated with the support
and oversight of Thomas J. Danielson (OWOW), Amanda K. Parker and Susan K. Jackson (OST),
and seen to completion by Douglas G. Hoskins (OWOW) and Ifeyinwa F. Davis (OST). EPArelied
heavily on the input, recommendations, and energy of three panels of experts, which unfortunately have
too many members to list individually:

     Biological Assessment of Wetlands Workgroup

     New England Biological Assessment of Wetlands Workgroup

     Wetlands Nutrient Criteria Workgroup
More information about biological and nutrient criteria is available at the following EPA website:

                              http ://www. epa. gov/ost/standards


More information about wetland biological assessments is available at the following EPA website:

                          htto ://www.epa. gov/owow/wetlands/bawwg
                                            V

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  LIST OF "METHODS FOR EVALUATING WETLAND
                CONDITION" MODULES

MODULE #	MODULE TITLE	
   1 	INTRODUCTION TO WETLAND BIOLOGICAL ASSESSMENT
   2	INTRODUCTION TO WETLAND NUTRIENT ASSESSMENT
   3	THE STATE OF WETLAND SCIENCE
   4	STUDY DESIGN FOR MONITORING WETLANDS
   5	ADMINISTRATIVE FRAMEWORK FOR THE IMPLEMENTATION OF A
            WETLAND BIOASSESSMENT PROGRAM
   6	DEVELOPING METRICS AND INDEXES OF BIOLOGICAL INTEGRITY
   7	WETLANDS CLASSIFICATION
   8	VOLUNTEERS AND WETLAND BIOMONITORING
   9	DEVELOPING AN INVERTEBRATE INDEX OF BIOLOGICAL
            INTEGRITY FOR WETLANDS
   10	USING VEGETATION TO ASSESS ENVIRONMENTAL CONDITIONS
            IN WETLANDS
   11 	USING ALGAE TO ASSESS ENVIRONMENTAL CONDITIONS IN
            WETLANDS
   12	 USING AMPHIBIANS IN BlOASSESSMENTS OF WETLANDS
   13	BIOLOGICAL ASSESSMENT METHODS FOR BIRDS
   14	WETLAND BIOASSESSMENT CASE STUDIES
   15	BIOASSESSMENT METHODS FOR FISH
   16	VEGETATION-BASED INDICATORS OF WETLAND NUTRIENT
            ENRICHMENT
   17	LAND-USE CHARACTERIZATION FOR NUTRIENT AND SEDIMENT
            RISK ASSESSMENT
   18	 BlOGEOCHEMICAL INDICATORS
   19	NUTRIENT LOAD ESTIMATION
   2O	SUSTAINABLE NUTRIENT LOADING
                           VI

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              SUMMARY

 r I The ultimate goal of classification is to reduce
 J.  variation within classes to enable detection of
differences between reference and impacted con-
dition within classes as cost-effectively as possible,
while minimizing the number of classes for which
reference conditions must be defined.  There are
two different approaches to classification of aquatic
resources, one that is geographically based, and one
that is independent of geography but relies on envi-
ronmental characteristics that determine aquatic
ecosystem status and vulnerability at the region-,
watershed-, or ecosystem-scale. The goal of geo-
graphically based classification schemes is to re-
duce variability based on spatial covariance in cli-
mate and geology, and thus topography, climax veg-
etation, hydrology, and soils. Geographically inde-
pendent or environmentally based schemes include
those derived using watershed characteristics such
as land use and/or land cover, hydrogeomorphol-
ogy, vegetation type, or some combination of these.
It is possible to combine geographically based with
hydrogeomorphic and/or habitat-based ap-
proaches. If an integrated assessment of aquatic
resources within a watershed or region is desired, it
also may be useful to consider intercomparability
of classification schemes for wetlands, lakes, and
riverine systems to promote cost-effective sampling
and ease of interpretation.  In general, very few
definitive tests of alternative classification schemes
for wetlands are available with respect to describ-
ing reference condition for either nutrient criteria or
biocriteria. There are no known studies where ref-
erence conditions for both nutrient criteria and
biocriteria have been assessed simultaneously.
However, evidence from the literature suggests that
in many cases, both geographic factors (e.g., cli-
mate, geologic setting) and landscape setting
(hydrogeomorphic type) are expected to affect both
water quality and biotic communities. Thus, classi-
fication should be viewed as an iterative approach,
involving the initial choice of a framework as an
hypothesis, validation with univariate and multivari-
ate statistical techniques, and subsequent modifica-
tion to create new classes or combine existing
classes.

              PURPOSE

 r I The purpose of this module is to introduce the
 J.  scientific basis for classifying wetlands,
review some common classification schemes, and
discuss their implications for establishing biologi-
cal and nutrient criteria for wetlands.
         INTRODUCTION

 7" Tse of a common scheme across State bound-
 \J aries should facilitate more efficient collabo-
rative efforts in describing reference condition for
biota or water quality and in developing indices of
biological integrity (IBIs) or other indicators (U. S.
EPA  1993, http://www.epa.gov/emap/html/
remap.html). We describe a series of national clas-
sification systems that could be used to provide a
common framework for implementation, and sug-
gest ways in which these classification schemes
could be combined in a hierarchical fashion. Some
regional approaches are also available. Adoption
of any classification scheme must be considered an
iterative process at this point, whereby initial results
of biological or water quality sampling can be used
to test and refine a given system.


  Classes that behave similarly can be combined and
apparent outliers examined for additional sources
of variability that need to be considered. At the
extreme, new classification schemes can be derived
empirically through multivariate analysis. The ulti-
mate goal is to reduce variation within classes to
enable detection of differences between reference
and impacted condition within classes as cost-ef-
fectively as possible, while minimizing the number
of classes for which reference conditions must be
defined. For example, there might be different ex-

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pected conditions with respect to water quality or
biological community composition for wetland
classes in the absence of human impacts, and thus
different criteria might be established for those
classes.  In assessing impacts to wetlands and de-
termining whether restored or created wetlands
were approaching a natural state, it would be most
appropriate to choose a wetland from the same or
targeted class for comparison.


             GOALS OF
        CLASSIFICATION

 rIJ he overall goal of classification is to
 J.  reduce variability within classes caused by dif-
ferences in natural condition related to factors such
as geology, hydrology, and climate. The type of
classification system chosen depends on the par-
ticular scientific, management, or regulatory appli-
cation of interest. For the purposes of criteria de-
velopment, classification is important in refining ex-
pectations for reference condition, or the state of
wetlands in the absence of anthropogenic impacts.

     DEFINITION OF WETLANDS FOR
      CLASSIFICATION PURPOSES

 Wetlands have been included in the definition of
"waters of the United States" since 1975, based on
an interpretation of the Clean Water Act (CWA)
(Natural Resources Defense Council v. Callaway,
524 F.2d 79 (2nd Cir. 1975)). In order to apply
water quality standards to wetlands, wetlands must
be legally included in the scope of States' and
Tribes' water quality standards programs. The U. S.
Environmental Protection Agency (EPA) had re-
quested that States' and Tribes' water quality stan-
dards be modified to include wetlands in the defini-
tion of" State waters" by the end of F Y1993. States
and Tribes could accomplish this by adopting a regu-
latory definition of "State waters" at least as inclu-
sive as the Federal definition of "waters of the U.S."
and adopting an appropriate definition for "wet-
lands" (U.S. EPA 1990a, http://www.epa.gov/
OWOW/wetlands/regs/quality.html). However, the
CWA does not preclude States and Tribes from
adopting a more expansive definition of "waters of
the State" in order to meet the goals of the Act.
Examples of different State approaches can be
found at: http://www.epa.gov/OWOW/wetlands/
partners/links.html#State Agencies.


 One of the most widely accepted definitions of
wetlands was adopted by the U. S. Fish and Wild-
life Service (U.S. FWS) in 1979 (Cowardin et al.
1979, http://www.nwi.fws.gov/classman. html):

   Wetlands are lands transitional between ter-
   restrial and aquatic systems where the water
   table is usually at or near the surface or the
   land is covered by shallow water...  Wetlands
   must have one or more of the following three
   attributes: (1) at least periodically,  the land
   supports predominantly hydrophytes, (2) the
   substrate is predominantly undrainedhydric
   soil, and (3) the  substrate is nonsoil and is
   saturated with water or covered by shallow
   water at some time during the growing sea-
   son of each year.


         REFERENCE CONCEPT

 Under guidance for biocriteria development, ref-
erence conditions "describe the characteristics of
waterbody segments least impaired by human ac-
tivities and are used to define attainable biological
or habitat conditions" (U. S. EPA 1990b).  At least
two general approaches have been defined to es-
tablish reference condition: the site-specific ap-
proach and the  regional approach (U.S. EPA
1990b, http ://www. epa.gov/cei sweb 1 /cei shome/
atlas/bioindicators/). The current approach to de-
veloping water quality criteria for nutrients also
emphasizes identification of expected ranges of nu-
trients by waterbody type and ecoregion for least-
impaired reference conditions (U.S. EPA 1998,
http://www.epa.gov/ost/standards/nutrient.html).
                                            2

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                      BlOCRITERIA-RELATED ISSUES
     Biological criteria are narrative descriptions or numerical values that are used to describe the
     reference condition of aquatic biota inhabiting waters of a designated aquatic life use. They are
     developed by biologists and other natural resource specialists to directly assess the overall
     condition of an aquatic community in surface waters such as streams, rivers, lakes, estuaries,
     and wetlands. Biocriteria have traditionally been developed through comparison of commu-
     nity-level indices describing biological integrity for test sites with index ranges derived for rela-
     tively unimpacted reference sites (U.S. EPA 1990b, http://www.epa.gov/ceiswebl/ceishome/
     atlas/bioindicators/). Reference sites are typically stratified by landscape units such as ecoregions
     to reduce the variation in expected natural biological condition and to facilitate standardization
     of methods. Classification or identification of covariates explaining a significant fraction of
     variation at the waterbody scale also may be necessary. Finally, classification or ranking schemes
     may be necessary to describe gradients of disturbance against which biocriteria can be cali-
     brated.

                        NUTRIENT-RELATED ISSUES
     The Office of Water has established a procedure to implement the Clean Water Action Plan
     through development of regionally-applicable nutrient criteria for each aquatic resource type
     (U. S. EPA 1998b, http ://www. cleanwater. gov/ ) Development of nutrient criteria through com-
     parison to reference conditions requires that the Nation first be stratified to reduce variability in
     expected condition to a reasonable range. (U.S. EPA 1998a, http ://www. epa. gov/ost/stan-
     dards/nutrient.html) For example, it would not be appropriate to set expectations for nutrient
     levels in peatlands receiving primarily precipitation as a water source based on background
     nutrient levels observed in riverine wetlands. Stratification may be necessary both at the land-
     scape level, to take into account natural regional differences in runoff and fertility of soils influ-
     encing background levels  of nutrient inputs, and  at the scale of water-bodies, to take into
     account differences in source water characteristics  and retention time related to sensitivity of
     response. As wetlands water quality criteria are developed for other constituents (e.g., clean
     sediments) regionalization of criteria and related classification issues will be important for these
     as well.
 An alternative definition of the reference concept
has been developed for the hydrogeomorphic as-
sessment (HGM) approach, used to describe ex-
pectations for wetland function  by wetland
hydrogeomorphic type and region. Under the HGM
approach, "(Reference wetlands are actual wetland
sites that represent the range of variability exhibited
by a regional wetland subclass as a result of natural
processes and anthropogenic disturbance. In es-
tablishing reference standards, the geographic area
from which reference wetlands are selected is the
reference domain." For practical purposes, HGM
practitioners define reference standard as: "condi-
tions exhibited by a group of reference wetlands
that correspond to the highest level of functioning
(highest, sustainable level of functioning) across the
suite of functions performed by the regional sub-
class. By definition, the highest level of functional
capacity is assigned a functional capacity index value
of  1.0."  (see  Smith  et al. 1995, http://
www.wes.army.mil/el/wetiands/pdfs/wrpde9.pdf).

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      EXISTING WETLAND
        CLASSIFICATION
             SCHEMES

 rIJ here are two different  approaches  to
 J.  classification of aquatic resources, one that is
geographically based and one that is independent
of geography, but relies on environmental charac-
teristics that determine aquatic ecosystem status and
vulnerability at the region, watershed, or ecosys-
tem scale (Detenbeck et al. 2000). Ecoregions (in-
cluding "nutrient ecoregions") and ecological units
represent  geographically based classification
schemes that have been developed and applied na-
tionwide (Omernik 1987, Keys et al. 1995). The
goal of geographically based classification schemes
is to reduce variability based on spatial covariance
in climate and geology, as well as in topography,
climax vegetation, hydrology, and soils. For some
regions of the country, ecoregions have been re-
fined to explain a finer scale of spatial variation (e.g.,
Omernik and Gallant 1988).  Geographically inde-
pendent or environmentally based schemes include
those derived through watershed characteristics
such as land-use and/or land-cover (Detenbeck et
al., 2000), hydrogeomorphology (Brinson 1993),
vegetation type (Grossman et  al. 1998, http://
consci.tnc.org/library/pubs/class/tocl .html), or some
combination of these (Cowardin et al. 1979). Both
geographically dependent and environmentally
based schemes have been developed for single
scales, and  for a nested hierarchy of scales
(Detenbeck etal. 2000).

        GEOGRAPHICALLY BASED
       CLASSIFICATION SCHEMES

 Regional classification systems were first devel-
oped specifically for the United States by land man-
agement agencies.  The U.S. Department of Agri-
culture (USDA) has described a hierarchical sys-
tem of Land Resource Regions and Major Land
Resource Areas for agricultural management based
mainly on soil characteristics (USDA SCS 1981).
Ecoregions were then refined for USDA and the
U.S. Forest Service based on a hierarchical system
in which each of several environmental variables such
as climate, landform, and potential natural vegeta-
tion were applied to define different levels of classi-
fication (Bailey 1976).  Subsequently, Omernik and
colleagues developed a hierarchical nationwide
ecoregion system to classify streams, using envi-
ronmental features they expected to influence aquatic
resources as  opposed to terrestrial resources
(Hughes and Omernik 1981, Omernik etal. 1982).
The new ecoregion system was based on an over-
lay of "component maps" for land use, potential
natural vegetation, land-surface form, and soils, and
a subjective evaluation of the spatial congruence of
these factors as compared to the hierarchical ap-
proach used by Bailey, which relied only on natural
features (not land use). Omernik has produced a
national map of 76 ecoregions defined at a scale of
1:7,500,000 (Figure 1) (Omernik 1987; http://
water.usgs.gov/GIS/metadata/usgswrd/
ecoregion.html).  More detailed regional maps have
been prepared at a scale of 1:2,500,000 in which
the most "typical" areas within each ecoregion are
defined. Cowardin et al. (1979) have suggested an
amendment to Bailey's ecoregions to  include
coastal and estuarine waters (Figure 2).  In prac-
tice, Omernik's scheme has been more widely used
for  classification of aquatic resources such as
streams, but few examples of applications are avail-
able for wetlands.


  Finally, an attempt has been made to integrate
approaches across Federal agencies to produce
regional boundaries termed ecological units (Keys
etal. 1995). Information has been combined on
climate, landform, geomorphology, geology, soils,
hydrology, potential vegetation, and water to pro-
duce a nested  series of boundaries for the eastern
United States, but different combinations of envi-
ronmental parameters are emphasized at each hier-
archical level  of classification. This scheme was
developed to explain variation in both terrestrial and

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                      41
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            FIGURE l:  MAP OF OMERNIK AQUATIC ECOREGIONS.

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aquatic systems and is consistent with a more com-
prehensive strategy to classify lotic systems down
to the level of stream reaches (Maxwell et al. 1995).
The mapped system for the eastern United States
includes classification at the following levels:

 domain (n=2) > divisions (n=5) > provinces
   (n=14) > sections (n=78) > subsections,

where sections are roughly equivalent to half of an
ecoregion as defined by Omernik (Figure 3).  For
lotic systems, additional spatial detail can be added
by defining watersheds (at the level of landtype
associations), subwatersheds (at the level of
landtypes), valley segments, stream reaches, and
finally channel units (Maxwell etal. 1995). In reality,
all  watersheds are  not  nested neatly  within
subsections, and may cross subsection boundaries.


  Some States and Tribes have chosen to refine the
spatial resolution of Omernik's ecoregional bound-
aries for management of aquatic resources (e.g.,
Region 3 and Florida, http://www.dep.state.fl.us/
water/slerp/bio/sbecoreg.htm). For example, the
State of Florida has defined subecoregions for
streams based on analysis of macroinvertebrate data
from 100 reference sites. Efforts are currently un-
der way to define ecoregions for Florida wetlands
based on variables influencing the water budget (M.
Brown, personal communication). Potential source
geographic information system (GIS) data layers to
support such an effort are described below.


       ENVIRONMENTALLY BASED
       CLASSIFICATION SYSTEMS

Hydrogeomorphic classification system(s)
  Brinson (1993) has defined a hydrogeomorphic
classification system for wetlands, based on geo-
morphic setting, dominant water source (Figure 4),
and dominant hydrodynamics (Figure 5; http://
www.wes.army.mil/el/wetlands/regdoc.html ).
Seven classes have been described: riverine, de-
pressional, slope, mineral soil flats, organic soil flats,
tidal fringe, and lacustrine fringe (Smith et al. 1995).
Depressional systems, as the name implies, are lo-
cated in topographic depressions where surface
water can accumulate (Figure 6a). Depression wet-
lands can be further classified based on presence
of inlets or outlets and primary water source as
closed, open/groundwater, or open/surface water.
Lacustrine fringe wetlands are located along lake
shores where the water elevation of the lake deter-
mines the water table of the adj acent wetland. Great
Lakes coastal wetlands represent one important
region of lacustrine fringe wetlands (Figure 6b).
These coastal systems are strongly influenced by
coastal forming processes, and, as such, have been
further classified by geomorphic type through vari-
ous schemes (Jaworski and Raphael 1979, and oth-
ers summarized in Michigan Natural Features In-
ventory 1997).  These geomorphic  coastal posi-
tions will further influence the predominant  source
of water and degree and type of energy regime (riv-
erine vs. seiche and wave activity).  Tidal fringe
wetlands occupy a similar position relative to ma-
rine coasts and estuaries and where the water level
is influenced by sea level (Figure 6c). Tidal fringe
wetlands can be broken down further based on
salinity into euhaline vs. mixohaline subclasses.
Slope wetlands occur on slopes where groundwa-
ter discharges to the land surface but typically do
not have the capacity for surface water storage (Fig-
ure 7). Riverine wetlands are found in floodplains
and riparian zones associated with stream channels
(Figure 6d). Riverine systems can be broken down
based on watershed position (and thus hydrologic
regime) into tidal, lower perennial, upper perennial,
and nonperennial subclasses. Mineral soil flats are
in areas of low topographic relief (e.g., interfluves,
relic lake bottoms, and large floodplain terraces)
with precipitation as the main source of water (Fig-
ure 6e). In contrast, the topography of organic soil
flats (e.g., peatlands) is controlled by the vertical
accretion of organic matter (Figure 6f). The HGM
classification system is being further refined to the
subclass level for different regions  or states and
classes (Cole et al. 1997, http://www.wes.army.mil/
el/wetiands/regdoc.html).  In addition to the classi-
                                             6

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                                                          I
  FIGURE 2: MAP OF BAILEY ECOREGIONS WITH COASTAL AND ESTUARINE
             PROVINCES, FROM COWARDIN ET AL., 1 979.
               a

           a. Domain
FIGURE 3: EXAMPLES OF FIRST FOUR HIERARCHICAL LEVELS OF ECOLOGICAL
    UNITS: DOMAIN, DIVISION, PROVINCE, AND SECTION, FROM US EPA
                     ENVIRONMENTAL ATLAS.
                             7

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                      PRECIPITATION
        (b)
        :X
J*
                       \
                         GRQUfc
-S
    D WATER
                                  LATERAL
                                   FLOWS
                                      ^^^
FIGURE 4: DOMINANT WATER SOURCES TO WETLANDS, FROM BRINSON 1993.
                          8

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                                      VERTICAL
                                    hLUCTUATIONS
                                  UNIDIRECTIONAL
                                      FLOW
                                    BIDIRECTIONAL
                                       FLOW
FIGURE 5: DOMINANT HYDRODYNAMIC REGIMES FOR WETLANDS BASED ON
             FLOW PATTERN, FROM BRINSON 1 993.
                            9

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   A) DEPRESSIONAL WETLAND
    B) LACUSTRINE FRINGE
   FIGURE 6: EXAMPLES OF HYDROGEOMORPHIC WETLAND CLASSES:
A) DEPRESSIONAL WETLAND, B) LACUSTRINE FRINGE, c) TIDAL FRINGE, D)
RIVERINE WETLAND, E) MINERAL FLATS WETLAND, AND F) ORGANIC FLATS
                         WETLAND.

                            10

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          FIGURE 6 (CONTINUED) (c) TIDAL FRINGE
fication factors described above, the Army Corps
of Engineers (ACE) suggests using parameters such
as the degree of connection between the wetland
and other surface waters (depressional wetlands),
salinity gradients (tidal), degree of slope or channel
gradient (slope and riverine wetlands), position in
the landscape (riverine, slope), and a scaling factor
(stream order, watershed size or floodplain width
for riverine subclasses). In some cases, existing
regional schemes could be used as the basis for
subclass definition (e.g., Stewart and Kantrud 1971,
Golet and Larson 1974, Wharton et al. 1982,
Weakley and Schafale 1991, Keough et al. 1999).
The ACE is currently defining regions for refine-
ment of HGM classes based on factors  such as cli-
mate and geology.


  The HGM classification system has been applied
primarily for a functional assessment strategy termed
the HGM approach (Smith et al.  1995,  http://
www.wes.army.mil/el/wetlands/pdfs/wrpde9.pdf).
However, the same environmental parameters that
influence wetland functions also determine water
regime and background water quality, which in turn
drive wetland habitat structure and community com-
position and the timing of biotic events. Thus, the
HGM classification system can serve as a basis for
partitioning variability in reference trophic status and
biological condition, as well as defining temporal
strategies for sampling.


Habitat-based classification systems
 Wetland habitat types are described very simply
but coarsely by the Circular 39 definitions, ranging
from temporarily flooded systems to ponds (Shaw
and Fredine 1956) (see Appendix A-2). A more
refined hierarchical classification system is available
based on vegetation associations; one system de-
veloped by the Nature Conservancy for terrestrial
vegetation (including some wetland types) has been
adopted as a standard for Federal agencies
(Grossman et al. 1998, http://consci.tnc.org/library/
pubs/class/toc 1 .html). Vegetation associations have
been used to classify Great Lakes coastal wetlands
within coastal geomorphic type (Michigan Natural
Features Inventory 1997).


Cowardin classification system
 The U. S. Fish and Wildlife Service (FWS) classi-
fication system (Cowardin et al. 1979) was devel-
oped as a basis for identifying, classifying, and map-
                                            1  1

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            FIGURE 6 (CONTINUED) (D) RIVERINE WETLAND
ping wetlands, other special aquatic sites, and
deepwater aquatic habitats, and has since been es-
tablished by both Federal and some State agencies
as the official system for wetland inventory and clas-
sification. The Cowardin system combines a num-
ber of approaches incorporating position, hydro-
logic regime and habitat (vegetative) type (Figure
8a,b; http://www.nwi.fws.gov/classman.html).
Wetlands are categorized first by landscape posi-
tion (tidal, riverine, lacustrine, and palustrine), then
by cover type (e.g., open water, submerged aquatic
bed, persistent emergent vegetation, shrub wetlands,
and forested wetlands), and then by hydrologic re-
gime (ranging from saturated or temporarily-flooded
to permanently flooded). Modifiers can then be
added for different salinity or acidity classes, soil
type (organic vs mineral), or disturbance activities
(impoundment, beaver activity, etc.). Thus, the
Cowardin system includes a mixture of geographi-
cally-based factors, proximal forcing functions (hy-
drologic regime, acidity), anthropogenic disturbance
regimes, and vegetative outcomes. In practice, the
Cowardin system can be aggregated by combina-
tion of HGM type and predominant vegetation cover
if digital coverages are available (Ernst et al. 1995).
                                             12

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        FIGURE 6 (CONTINUED) (E) MINERAL FLATS WETLAND
 COMPARISON OF ENVIRONMENTALLY
   BASED CLASSIFICATION SYSTEMS

 The Anderson Level 2 land-cover classification
system, used in classifying cover from satellite im-
agery or aerial photo interpretation, can be de-
scribed as a combination of Cowardin classes (Ap-
pendix A-1) (Anderson etal. 1976). Anderson's
land-cover classification system has been merged
with a modification of Cowardin's system for fresh-
water (Great Lakes) and marine coastal systems as
part of NOAA's Coastal Change Analysis Program
(C-CAP; NOAA 1995,  http://www.csc.noaa.
gov ). Comparisons of Cowardin's classification sys-
tem with other earlier methods can be found in
Cowardin et  al.  (1979;  http://www.nwrc.gov/
diglib.html) (see also Appendix A-2).

 If an integrated assessment of aquatic resources
within a watershed or region is desired, it also may
be useful to consider intercomparability of classifi-
cation schemes for wetlands,  lakes, and riverine
systems to promote cost-effective sampling and ease
of interpretation. The HGM approach could inter-
grade readily with a finer level of classification for
lake type because lentic systems are separated out
as lacustrine fringe or depressional wetlands based
on lake or pond size and influence of water level on
the adjacent wetland.  Lacustrine classification sys-
tems for water quality have included geography (cli-
mate +bedrock characteristics, Gorham et al. 1983)
or hydrologic setting (Winter 1977, Eilers et al.
1983) as factors for categorization.  For Great
Lakes coastal wetlands, McKee et al. (1992) sug-
gest a modification of Cowardin's system, incor-
porating landscape position (system), depth zone
(littoral vs. limnetic subsystems), vegetative or sub-
strate cover (class and subclass), and modifiers of
ecoregions, water level regimes, fish community
structure, geomorphic structure, and human modi-
fication. In contrast, the Michigan Natural Fea-
tures Inventory (1997) categorizes Great Lakes
coastal wetlands by Great Lake, then by nine unique
geomorphic types within lakes, then by vegetative
association.
                                           13

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FIGURE 6 (CONTINUED) (F) ORGANIC FLATS WETLAND
                       14

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           SURFACE
                              SEEPAGE FACE
e,  Seep&gi (ica where
                                flow Inier&acii ihe iarvcf surface
                               SEEPAGE AT  BASE
                        N -
          UNES OF EQUW.  8 o
          HTOMULJC HEAD      '
     b.  Se-epag* In lh* lower a ope puilicn of lh tjreak
FIGURE 7: INTERACTION WITH BREAK IN SLOPE WITH GROUNDWATER INPUTS
            TO SLOPE WETLANDS, FROM BRINSON 1 993.
                             15

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     UPLAND
                ESTU4RWE
                            UPLAND
                        fSTUAKINE
          I
                      nNTHTHI4l.
            IJ
            - '
            & 
            in ft
            O UJ
            K a
E
5s I
Sgl
IM
M  
^ t-
i!
ti
a w
^ -

                                       '
M
P
o LU 
j at T
             o
              s
AQUATIC
aen
ONBOLlOA
BOTTOM
                                 FLOODED
                      U "ItGULA'iLY F LUaUEU
                       iRReaULAftS. v to$iEt
   FIGURE 8: A) COWARDIN HIERARCHY OF HABITAT TYPES FOR
                    ESTUARINE SYSTEMS.
                   .1 TFWPORARIl.v
                   hSfA^^vLtv'F
                   c .--iJMIIPCnM*iWLfl I LV *-Ll.OC-EL
FIGURE 8: B) PALUSTRINE SYSTEMS, FROM COWARDIN ET AL. 1979.
                             16

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 For lotic systems, Brinson et al. (1995) describes
an approach to further classify riverine classes into
subclasses based on watershed position and stream
size/permanence.  This strategy is consistent with
current monitoring efforts to develop stream IBIs,
which typically use stream order as a surrogate for
watershed size in explaining additional background
variation in IBI scores (U.S.  EPA 1996). Amore
detailed classification of stream reach types, based
on hydrogeomorphic character, is described by
Rosgen (1996). This classification scheme has been
predominantly applied to assessments of channel
stability and restoration options, and not to devel-
opment of criteria. The Bureau of Land Manage-
ment has described a cross-walk between riparian
and wetland classification and description proce-
dures (Gephardt et al. 1990); see http://
www.rwrp.umt.edu/Montana.html for a regional
application.


 COMBINATIONS OF GEOGRAPHIC AND
      ENVIRONMENTALLY BASED
             APPROACHES

 It is possible to combine geographically based and
hydrogeomorphic  and/or  habitat-based ap-
proaches. For example, a scheme could be de-
fined that nests Cowardin (Cowardin et al. 1979)
vegetative cover class within HGM class within
ecoregion. Maxwell et al. (1995) have defined a
scheme for linking  geographically based units based
on geoclimatic setting (domains => divisions =>
provinces => sections => subsections) to water-
sheds and subwatersheds  (roughly equivalent to
landtype associations), and thus to riverine systems
composed of valley segments, stream reaches, and
channel units, or to lacustrine systems composed of
lakes, lake depth zones, and lake sites/habitat types.


 Maxwell et al. (1995) also define a series of fun-
damental hydrogeomorphic criteria for classifying
wetlands based on Brinson  (1993) and Winter
(1992), including  physiography (landscape posi-
tion), water source, hydrodynamics, and climate.
The first three are similar to the HGM classification
system, whereas moisture regimes and soil tempera-
ture regimes are generally consistent at the prov-
ince level (see summary tables in Keys et al. 1995).
Finer scale variation in landforms is captured at the
level of sections and below, which in turn will de-
termine the dominance of different hydrogeomorphic
classes of wetlands and associated surface waters
(lakes and rivers).


  Characteristics and relative advantages and dis-
advantages of the different classification systems are
summarized in Table 1.
          SOURCES OF
       INFORMATION FOR
      MAPPING WETLAND
              CLASSES

 7n  order to select  wetlands for sampling,
-/whether in a targeted, random, or random-
stratified design, it is necessary to have a record of
wetland locations to  choose from, preferably
categorized by the classification system of interest.
For some but not all portions of the country,
wetlands have  been  mapped from aerial
photography through the National Wetlands
Inventory (NWI) system maintained by the U.S.
Fish and Wildlife Service.  In other cases, individual
States have developed inventories, or researchers
have developed lists of restricted types wetlands
within a given region, e.g., Great Lakes coastal
wetlands (Herdendorfetal. 1981).

 In order to sample these mapped wetland areas
in a  random fashion  such that the results are
representative for all wetlands, all wetland areas,
or wetlands of a specified type within a region, it is
necessary to have a list of the wetland population,
                                         17

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              TABLE 1: COMPARISON OF LANDSCAPE AND WETLAND
                              CLASSIFICATION SCHEMES
CLASSIFICATION
SCHEME
Bailey=s ecoregions
Omernik ecoregions
Ecological units
(Maxwell a al. 1995)
U.S. ACE
hydrogeomorphic
Classes
Rosgen channel types
Anderson land-cover
classes
Circular 39 classes
National Wetland
Inventory
Vegetation
associations
SCALE
Nationwide
Nationwide
Nationwide
Nationwide at class
level; regionalized
at subclass level
Nationwide
Nationwide
Nationwide
Nationwide
International
HIERARCHICAL?
Yes
No
Yes
Yes - limited
Yes
Yes
No
Yes
Yes
LEVELS OF STRATA
Divisions
Provinces
Sections
Ecoregions
Subecoregions
Provinces
Sections
Subsections
Class
Subclass
Level I
Level II
Level I
Level II
Level III
Class
System
Subsystem
Class
Subclass
Hydrologic modifier
Other modifiers
System
Formation subclass
Formation group
Formation alliance
Association
ADVANTAGES
Only natural attributes
included
Digital maps
Digital maps
Digital maps
Specific for wetlands
Captures differences in
hydrologic regime for
Common basis for land-
use/land-cover mapping
Popular recognition
Digital maps available
(but smallest wetlands
omitted)
Consistency across
terrestrial and aquatic
systems
DISADVANTAGES
Terrestrial basis
Untested for wetlands
No hydrology
Combines land use with natural
attributes
Untested for most wetlands
No hydrology
Greater number of strata and
units than for ecoregions
Untested for wetlands
different regions
Riverine only
Not mapped
Not functionally based
Mixture of criteria used to
distinguish classes
Not mapped
Inconsistencies in mapping water
quality modifiers
Limited consideration of
hydrogeomorphic type
Not functionally based
No digital maps
Taxa specific
POTENTIAL LINKS WITH OTHER
SCHEMES
Could form first strata for any of the
schemes below ecological units
Could form first strata for any of the
schemes below ecological units
Could form first strata for any of the
schemes below ecological units
Ties to classification schemes already
defined within hydrogeomorphic types
Intermediate strata between geographic
and habitat -scale
Intermediate strata between hydro-
geomorphic type and habitat-scale
Cross-walk with NWI system possible
Strata below geographic but contains
mixture of hydrogeomorphic type and
habitat type
Strata below geographic
Hydrogeomorphic class could be
improved by link with HGM system
Could be used as lowest level within
other schemes
preferably with areas attached. A GIS allows one
to automatically produce a list of all wetland
polygons or all wetland polygons by type within a
specified region. Sources of digital information for
mapping and/or classifying wetlands in a GIS are
presented in Appendix B. In areas for which digital
NWI maps do not yet exist, potential wetland areas
can be mapped using GIS tools to predict relative
wetness (e.g., Phillips 1990). It should be noted
that where hydrology has been significantly altered,
e.g., through ditching, tiling, or construction of urban
stormwater systems, areas of potential wetlands will
have been removed already.  Similarly, although
there are no current maps of wetlands by
hydrogeomorphic class, these could be derived
through GIS techniques using a combination of
wetland coverages, hydrography (adjacency to large
lakes and rivers), and digital elevation models to
derive landforms (mineral and organic soil flats) and/
or landscape position (slope and depressional
wetlands; see http://www.geog.le.ac.uk/jwo/
research/LandSerf/index.html for free terrain
analysis software, and example applications of terrain
analysis for identifying landforms  at: http://
www.undersys.com/caseGW.html  , http://
www.ncgia.ucsb.edu/conf/SANTA_FE_CD-
ROM/sf_papers/felsJohn/fels_and_matson.html).
                                           18

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             EMPIRICAL
        CLASSIFICATION

             METHODS

     Classification should be viewed as an
     iterative approach, involving the initial choice
of a framework as a hypothesis, validation with
univariate and multivariate statistical techniques, and
subsequent modification to create new classes or
combine existing classes. Best professional judg-
ment can be used to generate a hypothetical set of
classes, using techniques such as the Delphi ap-
proach to gain consensus  (Linstone  and Turoff
1975). The Delphi approach is a process to ex-
tract the collective intelligence of a group of experts
who may have a wide range of backgrounds, ex-
pertise, and opinions. Responses to the Delphi pro-
cess, either via interviews  or questionnaires, are
anonymous, and must be summarized by a third
party and redistributed back to the group of ex-
perts for reconsideration until a consensus is reached.
The process can be time-intensive, requiring up to
four rounds of questioning to achieve consensus (or
the closest approximation possible). The process is
appropriate when input is needed from a range of
experts, frequent group meetings are not feasible
because of time or cost, or face-to-face communi-
cations may be hindered by the strength of disagree-
ments and/or by the personalities of participants.

 To produce a more  objective framework, it is
possible to sample a suite  of reference wetlands
randomly, and then classify sites based on physical,
chemical, and/or biological characteristics after the
fact through parametric techniques such as cluster
analysis, discriminant function analysis, detrended
canonical correlation analysis (DCCA), and/or non-
parametric techniques such as nonmetric dimen-
sional scaling (NMDS). Cluster analysis is an ex-
ploratory technique that groups similar entities, e.g.,
by community composition, in a hierarchical struc-
ture.  Discriminant function analysis can be used to
obj ectively define those attributes of groups respon-
sible for intergroup differences.  Detrended ca-
nonical correlation analysis is a parametric multi-
variate technique for relating multiple explanatory
variables such as site characteristics to multiple re-
sponse variables such as species abundances, or
metrics within an index of biological integrity. It
corrects for the "arch" effect of regular canonical
correlation analysis (CCA) that results from the
unimodal distribution of species along environmen-
tal gradients.  NMDS is a nonparametric technique
(i.e., does not rely on the normal distribution of un-
derlying data) that can be used to order sites along
gradients based on species composition differences,
then independently determine which environmental
variables significantly covary with community gra-
dients. Although these techniques can be used in
an exploratory fashion, they can also be applied
with a second set of data to confirm an initial classi-
fication scheme:

Option 1:
CHOOSE CLASSES => RANDOMLY
SAMPLE => TEST DATA TO CONFIRM
GROUPINGS

Option 2:
RANDOMLY SAMPLE FULL POPULATION
=> DERIVE CLASSES EMPIRICALLY
FROM SUBSET 1 => TEST VALIDITY OF
CLASSES WITH SUBSET 2.

 Numerous examples of the application of em-
pirical classification schemes for other aquatic eco-
system types can be found in the September 2000
issue of the Journal of the North American
Benthological Society (vol. 19, issue 3). Multi-
variate analysis techniques are available in common
statistical packages such as SAS (SAS Institute
1979), SPSS (Nie et al. 1975), and BMDP (Dixon
1981). In addition, more specialized software ex-
ists that is specifically geared towards the analysis
of biological community data, including CANOCO
(ter Braak and Smilauer 1998), PC-ORD (MJM
                                          19

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Software Design 2000), TWIN-SPAN (Mohler
1991), and others (see http://www.okstate.edu/
artsci/botany/ordinate/software.htm for partial
listing).


          STATE  OF THE
             SCIENCES

 TTery few definitive tests of classification
 V  systems for wetlands monitoring have been
completed, although a number of monitoring strat-
egies have been implemented based on preselected
strata. Monitoring efforts to develop or assess bio-
logical criteria have generally used a combination
of geographic region and hydrogeomorphic class
or subclass (Appendix C). The ability of geographic
or hydrogeomorphic classes to discriminate among
biological community types can be tested a priori
through multivariate analysis. Cole and colleagues
(1997) have measured significant differences in hy-
drologic attributes among riparian wetlands of dif-
ferent HGM subclasses in Pennsylvania, which are
expected to control vegetation type. Subsequent
work on macroinvertebrate communities found simi-
larity among sites within the same HGM subclass.
However, there were important microhabitat dif-
ferences within HGM subclasses, e.g., between soil
and stream habitats in headwater floodplains, Habi-
tats in different HGM subclasses but with similar
hydroperiods (ephemeral pools in riparian depres-
sions  and saturated soils in slope wetlands) were
nearly 50% similar in community composition.
Overall, soil organic matter and site wetness showed
strong relationships with invertebrate community
composition and could probably be used as indices
of similarity across sites (Bennett 1999). Research-
ers with the Michigan Natural Features Inventory
have examined vegetation associations among HGM
subclasses of coastal wetlands within different Great
Lakes using TWINSPAN, a cluster analysis pack-
age (Michigan Natural Features Inventory 1997).
Associations were found to differ by climate re-
gime (N vs. S, roughly at the province level), soil
pH (related to bedrock type), connectivity to the
lake, and degree of human disturbance. Apfelbeck
(1999) classified  Montana wetlands  by
hydrogeomorphic subclass within ecoregion for
development  of IBIs based on diatoms and
macroinvertebrate communities. Multivariate analy-
sis of these communities showed good agreement
overall with preselected classes, although some
classes were indistinguishable for diatoms (ripar-
ian, open lakes, closed basins), whereas others had
to be further subdivided based on extremes of wa-
ter chemistry/source water type (saline, closed ba-
sin-alkaline, closed basin-recharge vs. closed ba-
sin-surface water) or water permanence (ephem-
eral).


  Analysis of vegetative associations has been used
to derive empirical classifications based on factors
such as landscape position, water source, climate,
bedrock, and sediment hydraulic conductivity
(Weakley and Schafale 1991, Nicholson 1995,
Halsey et al. 1997, Michigan Natural Features In-
ventory 1997).  Only one case of classification
based on wetland macroinvertebrate composition
was found. For Australian wetlands, wetland classes
grouped by macroinvertebrate communities were
distinguished by water chemistry extremes (low pH,
high salinity), degree of nutrient enrichment, and
wetland color (Growns et al. 1992).


  In some cases, e.g., northern peatlands, the clas-
sification criteria that are derived on the basis of
vegetation associations are less powerful in discrimi-
nating among nutrient regimes (e.g., Nicholson
1995); this may be particularly true where variation
in vegetation type is related to differences in maj or
ion chemistry and pH. However, controls may dif-
fer regionally. For southern pocosins, short and tall
pocosins differ in seasonal hydrology but not soil
chemistry, whereas pocosins and  swamp forest dif-
fer strongly in soil nutrients  (Bridgham and
Richardson 1993).  For some potential indicators
of nutrient status such as vegetation N:P ratios, in-
dicator thresholds will be consistent across species
(Koerselman andMeuleman 1996), whereas oth-
                                           20

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ers (tissue nutrient concentrations) vary across func-
tional plant groupings with different life history strat-
egies, indicating potential differences in sensitivity
to eutrophication (McJannet et al. 1995).


  Sensitivity to nutrient loading (as evidenced by
differences in nutrient removal efficiency) may also
be related to differences in hydroperiod among
wetlands. Wetland mesocosms exposed to pulse
discharges had higher nutrient removal rates than
those exposed to continuous flow regimes
(Busnardoetal. 1992). Mineralization rates of car-
bon, nitrogen, and phosphorus differ significantly
among soils from northern Minnesota wetlands, re-
lated to an ombrotrophic to minerotrophic gradient
(i.e., degree of groundwater influence) and aera-
tion status. The physical degree of decomposition
of organic matter serves as an integrating variable
that can be used to predict carbon,  nitrogen, and
phosphorus mineralization rates (Bridgham et al.
1998).


  In general, very few definitive tests of alternative
classification schemes for wetlands are available with
respect to describing reference condition for either
nutrient criteria or biocriteria. There are no known
studies where reference conditions for both nutri-
ent criteria and biocriteria have been assessed si-
multaneously. However, evidence from the litera-
ture suggests that in many cases, both geographic
factors (e.g., climate, geologic setting) and land-
scape setting (hydrogeomorphic type) are expected
to affect both water quality and biotic communities.
A hypothetical example of how geographic factors,
landscape setting, and habitat type could be taken
into account in establishing a sampling design is pre-
sented below for the Prairie Pothole Region.


      HYPOTHETICAL CASE STUDY:
       PRAIRIE POTHOLE REGION

  The following example illustrates some of the con-
siderations necessary in designing a classification
strategy for a given region. The resulting classifica-
tion could be used for a variety of purposes, e.g.,
stratification of populations for describing ecologi-
cal condition, choice of reference wetlands against
which to compare impacted or restored sites in lo-
cal assessments, or derivation of nutrient or bio-
logical criteria by wetland class. As this example
illustrates, the strategy employed for a given region
could easily incorporate elements of several differ-
ent classification schemes. For example, a combi-
nation of ecoregions, hydrogeomorphic wetland
classes, Rosgen channel types or water permanence
(NWI hydrology modifier), and NWI cover sys-
tem/class is recommended. In this case, a different
set  of strata is recommended for different
hydrogeomorphic types.  Finally, behavior of dif-
ferent wetland classes can vary depending on the
period of the wet-dry cycle, so that differences in
reference condition should be described over time.
 In  the Prairie  Pothole Region, the  main
hydrogeomorphic wetland types vary by ecoregion
because of the influence of glacial history on the
distribution of landforms. For example, the Glaci-
ated Plains ecoregions contain predominantly de-
pressional wetlands that are differentiated from one
another by hydroperiod related to position in the
landscape and in the groundwater flow path. Wet-
lands high in the landscape typically are fed by snow-
melt or direct precipitation, are groundwater re-
charge sites, and have hydrology that is temporary
or seasonal in nature. Temporary wetlands will typi-
cally have a wet meadow and emergent vegetation
zone, whereas seasonal wetlands may have some
shallow standing water as well as emergent vegeta-
tion and wet meadow zones. Wetlands further down
the landscape gradient will have a longer
hydroperiod and receive more groundwater dis-
charge. Semipermanent wetlands will have the three
habitat zones described above, while permanent
wetlands will be saline due to groundwater inputs
and high evapotranspiration rates and have very little
or no emergent vegetation along the shore (with very
low diversity).
                                           21

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 Macroinvertebrate community structure will be
influenced by both hydroperiod and vegetative struc-
ture. Predator taxa (both large-bodied invertebrates
and tiger salamander larvae) will be more dominant
in systems with longer hydroperiods (e.g., semiper-
manent or permanent wetlands) and should have
an influence on lower trophic level structure as well.
Waterfowl use also differs among wetland basins
with different hydroperiods, although many water-
fowl will use a variety of wetland types over the
course of the season.
 Nutrients in the water column, particularly phos-
phorus, will differ between wet and dry years and
between vegetative zones. During the wet cycle
anoxia may develop, but open-water zones will
experience some diurnal fluctuations in dissolved
oxygen, with the net result that phosphorus released
to the water column is tied up with iron that oxi-
dizes as it diffuses from the sediments. Heavily veg-
etated zones tend to become anoxic throughout the
water column and remain  stagnant throughout the
diurnal cycle. Phosphorus could also be more avail-
able in shallower systems with abundant vegetation
because dissolved organic carbon is higher and may
serve to keep phosphate-iron-humic complexes in
solution. Thus, wetlands may switch from nitrogen
limitation during low to average rainfall years to
phosphorus limitation during wet years.  Thus, ref-
erence trophic status will be a combined function of
water permanence and vegetative cover, both of
which influence redox conditions and nutrient cy-
cling.


 A reasonable sampling design for wetlands in the
Prairie Pothole Region for both water quality and
biological communities would be to first stratify by
ecoregion into Northwestern Glaciated Plains,
Northern Glaciated Plains, and Red River Valley to
take into account differences in landform (and thus
wetland density) and the east-to-west gradient in
precipitation: evapotranspiration ratio.  It is possible
that reference condition would be similar across the
two glaciated plains ecoregions and that the great-
est amount of variation would be explained by dif-
ferences in hydroperiod among wetlands; this could
be assessed after sampling was complete. Within
the Prairie Pothole Region, there are two predomi-
nant hydrogeomorphic wetland classes, depres-
sional wetlands and riverine wetlands. Within the
HGM class of depress!onal wetlands, wetland ba-
sins could be stratified according to hydroperiod
(based onNWI hydrologic modifier), e.g., tempo-
rary vs. seasonal vs. semipermanent vs. permanent.
This could be done in an automated fashion using
NWI maps by selecting basins based on the poly-
gon within the basin, with a hydrologic modifier
denoting the longest hydroperiod. It is possible that
reference condition might be similar enough between
temporary and seasonal wetlands, or between sea-
sonal and semipermanent wetlands, so that these
hydrologic types could be combined, but it is also
likely that the degree of difference would depend
on the status of the wet-dry cycle, so these differ-
ences should be examined empirically over a wet-
dry cycle before combining types. For depress!onal
basins, it is likely that variance in reference condi-
tion would be minimized if sampling were further
stratified (or restricted) by  cover system/class
(palustrine open water vs. palustrine emergent), and
within the palustrine emergent class by the pres-
ence or absence of standing water (shallow emer-
gent vegetation zone vs. wet meadow zone).  The
latter strategy would allow potentially useful com-
parisons to be made across hydrologic types within
vegetative class/zone.


 Within riverine systems of the Prairie Pothole Re-
gion, wetlands can be divided into three NWI sub-
systems: Lower Perennial (with aquatic bed, emer-
gent vegetation, and unconsolidated shore sub-
classes), Upper Perennial (aquatic bed and uncon-
solidated shore), and Intermittent (streambed only).
Reference condition and responses of vegetation in
Lower and Upper Perennial subclasses to hydro-
logic impacts such as dams and withdrawals for ir-
                                            22

-------
rigation can be expected to differ among channel
types. For example, braided and meandering sys-
tems respond differently to climate change and hy-
drologic disturbance (Johnson 1998); thus main
Rosgen channel type could be used as an interme-
diate strata between NWI system and NWI sub-
class.
            SUGGESTED
              READINGS
BrinsonMM. 1993. A Hydrogeomorphic Classification
 for Wetlands. U.S. Army Corps of Engineers, Wash-
 ington, D.C. Wetlands Research Program Technical
 Report WRP-DE-4.
CowardinLM, Carter V, GoletFC, LaRoe ET. 1979.
 Classification of wetlands and deepwater habitats of
 the United States. U.S. Fish & Wildlife Service Pub.
 FWS/OBS-79/31, Washington, DC.

Maxwell JR, Edwards CJ, Jensen ME, Paustian SJ, Parott
 H, Hill DM. 1995. A hierarchical framework of aquatic
 ecological units in North America (Nearctic Zone).
 USD A, Forest Service, Technical Report NC-176.

Mitsch WJ, Gosselink JG 1993. Wetlands, Second
 Edition. VanNostrandReinhold Co., New York.

Omernik JM, Shirazi MA, Hughes RM. 1982. A synoptic
 approach for regionalizing aquatic ecosystems. In: In-
 place resource inventories: principles and practices,
 proceedings of a national workshop. August 9-14,
 1981. Univ. of Maine, Orono, ME. Society of American
 Foresters, pp. 199-218.
                                            23

-------
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                                                 24

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                                                 25

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                                                  26

-------
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 Water Res 13:753-767.
                                                 27

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  APPENDIX A-l. CROSS-WALK BETWEEN ANDERSON AND COWARDIN
CLASSIFICATION SCHEMES PER ROBERT BROOKS (PENNSYLVANIA STATE
 UNIVERSITY). CODING CONSISTENT WITH ANDERSON ET AL. 1976, AND
                  COWARDIN ET AL. 1979.
TYPE
2. Aquatic Cover
1 . Palustrine
1. Open water (< 8ha)
2. Aquatic bed
3. Emergent
4. Scrub/Shrub
1 . Mainly Evergreen
2. Mainly Deciduous
3. Mked
5. Forested
1 . Mainly Evergreen
2. Mainly Deciduous
3. Mked
2. Lacustrine (> 8ha)
1 . Open water
1 . Limnetic
1. Aquatic bed
2. Unconsol=d bottom
2. Littoral
1. Aquatic bed
2. Emergent
3. Unconsolidated bottom/shore
3. Riverine*
1 . Open water
2. Aquatic bed
3. Emergent
4. Unconsolidated bottom
ANDERSON
ETAL. 1976

61x

613
616
617
6182
6181

618
6182
6181

6xx

62x
623
622
63x
633
636
632/635
65x, 66x, 67x
650/660
6x3
6x6
6x2
COWARDIN
ETAL. 1979

p
POW
PAB
PEM
PSS
PF02,3,4,7
PF01,6
PFO#/#
PFO
PF02,3,4,7
PF01,6
PFO#/#
L
LOW
LI
L1AB
L1UB
L2
L2AB
L2EM
L2UB/US
R
ROW
RxAB
RxEM
RxUB/US
* Riverine includes all headwater streams and mainstem rivers, with an associated narrow band of wetland.
4. Estuarine
1 . Open water
1. Subtidal
2. Intertidal
2. Aquatic bed
3. Emergent
4. Scrub/shrub
5. Unconsolidated bottom
5. Marine
1 . Open water
1. Subtidal
2. Intertidal
2. Aquatic bed
3. Rocky shore
4. Unconsolidated bottom/shore
68x, 69x
68x, 69x
68x
69x
683, 691
696
697
682, 695
70x






E
EOW
El
E2
ExAB
ExEM
ExSS
ExUB/US
M
MOW
Ml
M2
MxAB
M2RS
MxUB/US
                          28

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APPENDIX A-2: CROSS-WALK BETWEEN CIRCULAR 39 WETLAND TYPES (SHAW
AND FREDINE 1959) AND COWARDIN CLASSIFICATION SYSTEM, ADAPTED FROM
                     COWARDIN ET AL. 1 979
CIRCULAR 39
WETLAND CLASS
Type 1-Seasonally flooded basins
or flats
Type 2-Inland fresh meadows
Type 3-Inland shallow fresh
marshes
Type 4-Inland deep fresh
marshes
Type 5 - Inland open fresh
water
Type 6 - Shrub swamps
Type 7- Wooded swamps
Type 8 - Bogs
Type 9 - Inland saline flats
Type 10 - Inland saline marshes
Type 11- Inland open saline
water
Type 12 - Coastal shallow fresh
marshes
Type 13 - Coastal deep fresh
marshes
Type 14 -Coastal open fresh
water
Type 15 - Coastal salt flats
Type 16 - Coastal salt meadows
Type 17 - Irregularly flooded
salt marshes
Type 18 - Regularly flooded salt
marshes
Type 19 - Sounds and bays
Type 20 - Mangrove swamps
COWARDIN CLASSIFICATION SYSTEM
CLASSES
Emergent Wetland
Forested Wetland
Emergent Wetland
Emergent Wetland
Emergent Wetland
Aquatic Bed
Aquatic Bed
Unconsolldated Bottom
Scrub-shrub Wetland
Forested Wetland
Scrub-shrub
WetlandForested
WetlandM oss-Hchen
Wetland
Unconsolldated Shore
Emergent Wetland
Unconsolldated Bottom
Emergent Wetland
Emergent Wetland
Aquatic Bed
Unconsolldated Bottom
Unconsolldated Shore
Emergent Wetland
Emergent Wetland
Emergent Wetland
Unconsoll dated
BottomAquatic
BedUnconsoll dated Shore
Scrub-shrub
WetlandForested Wetland
WATER REGIMES
Temporarily Flooded
Intermittently Flooded
Saturated
Semipermanently Flooded
Seasonally Flooded
Permanently Flooded
Intermittently Exposed
Semipermanently Flooded
Permanently Flooded
Intermittently exposed
All Nontldal Regimes except
Permanently Flooded
All Nontldal Regimes except
Permanently Flooded
Saturated
Seasonally flooded
Temporarily flooded
Intermittently Flooded
Semipermanently Flooded
Seasonally Flooded
Permanently Flooded
Intermittently Exposed
Regularly Flooded
Irregularly Flooded
Semipermanently Flooded - tidal
Regularly Flooded
Semipermanently Flooded - tidal
Subtidal
Permanently flooded tidal
Regularly Flooded
Irregularly Flooded
Irregularly Flooded
Irregularly Flooded
Regularly Flooded
Subtidal
Irregularly Exposed
Regularly Flooded
Irregularly Flooded
Irregularly Exposed
Regularly Flooded
Irregularly Flooded
WATER
CHEMISTRY
Fresh
Mixosallne
Fresh
Mixosallne
Fresh
Mixosallne
Fresh
Mixosallne
Fresh
Mixosallne
Fresh
Fresh
Fresh (acid only)
Eusallne
Hypersallne
Eusallne
Eusallne
Mixosallne
Fresh
Mixosallne
Fresh
Mixosallne
Fresh
Hyperhallne
Euhallne
Euhallne
Mixohallne
Euhallne
Mixohallne
Euhallne
Mixohallne
Euhallne
Mixohallne
Hyperhallne
Euhallne
MixohallneFresh
                            29

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APPENDIX B. SOURCES OF GIS COVERAGES AND IMAGERY FOR MAPPING
                AND CLASSIFYING WETLANDS
CATEGORY
SOURCE
WEB SITE
WETLAND AND HYDROGRAPHY COVERAGES
Cowardin et al. (1979)
classification




Great Lakes coastal wetlands
Hydrography (1:100,000)
National Wetland Inventory
Wisconsin Wetland Inventory
Minnesota modified NWI
(contains Circ. 39 classes)
Ohio Wetland Inventory
S. California Coastal Wetlands
Inventory
Herdendorf et al., 1981
USGS - National Hydrography
Dataset (NHD)
http://www.nwi.fws.gov/
http://www.dnr.state.wi.us/org/at/et/geo/guide_2e
/app_g/custodia/wwi_l .htm
http://lucy.lmic.state.mn.us/metadata/nwi.html
http://www.dnr.state.oh.us/odnr/relm/resanalysis/
owidoc.html
http://ceres.ca.gov/wetlands/geo_info/so_cal.html
Ferrenet al., 1996
N/A
http://nhd.usgs.gov/
GENERAL LAND-COVER (INCLUDING WETLANDS)
Aerial photos
Aerial photos
Satellite imagery

Natural Heritage programs
Unclassified satellite imagery
Geographic regions
Ecoregions
Ecological Units
Hydrologic Units
Watershed boundaries
SCS county offices
USGS digital orthophotoquads
(DOQs)
MultiResolution Landscape
Characterization (MRLC)
GAP habitat cover types
Individual States
USGS

EPA (Omernik 1987)
USES (Keyset all 995)
USGS HUCs
Individual States/NRCS

www.terraserver.com
http://edcwww.cr.usgs.gov/programs/lccp/
natllandcover.html
http://www.gap.uidaho.edu/gap/

http://earthexplorer.usgs.gov

http://water.usgs.gov/GIS/metadata/usgswrd/
ecoregion.html

http://water.usgs.gov/GIS/huc.html
http://www.ftw.nrcs.usda.gov/HUC/huc_
download.html
HISTORIC OR POTENTIAL WETLAND COVERAGE
Soils

Surficial geology
Climate
Digital elevation models
(OEMs)
STATSGO
County soil surveys -
SSURGO
USGSState geological surveys
NOAA
USGS National Elevation
Database (NED)
http://water.usgs.gOV/lookup/getspatialPmuidhttp:/
/water.usgs.gov/lookup/getspatial?ussoils
http://www.ftw.nrcs. usda.gov/ssur_data.html
http://water.usgs.gov/lookup/getspatialPofr99-77
_geol75m
http://water.usgs.gov/lookup/getspatial?climate_
divhttp://www.ocs.orst.edu/prism/prism_new.html
http://edcntsl 2. cr.usgs.gov/ ned
                          30

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APPENDIX C. CASE STUDIES APPLYING WETLAND CLASSIFICATION SCHEMES FOR
                   INDICATOR DEVELOPMENT OR STATUS ASSESSMENT
STUDY (LOCATION)
Cole et al., 1997 (PA)
Gernes, 1999 (MN)
Michigan Natural
Features Inventory 1997
(Great Lakes)
Apfelbeck, 1999 (MT)
Fennessey et al.
(OH)http://www.epa.go-
v/owow/wetlands/baww-
g/case/ohl.html
Galatowitsch et al.,
2000 (MN)
Wilcox et al., 2000 (WI,
MI)
Detenbeck, 1994 (MN)
WETLAND TYPE
Riparian wetlands in PA
Riparian wetlands in St.
Croix R. Basin
Great Lakes coastal
wetlands
All wetland types w
standing water in at least
one season
Riparian wetlands
Depressional, riparian,
littoral, and wet
meadows
Great Lakes coastal
wetlands
All wetland types
CLASSIFICATION
CRITERIA
HGM subclasses
HGM subclasses
Great LakeHGM subclasses
Ecoregion
Hydrogeomorphic subclass3
Ecoregions
Hydrogeomorphic classes
Watersheds
Ecoregion sections0
Geomorphic classd
Great Lake
Hydrogeomorphic subclass
Hydrogeomorphic subclass
SUCCESS
Sign, differences in hydrological attributes
among subclasses
Not yet validated
Veg. associations distinguished through
TWINSPAN by climate regime (N v. S), soil
pH, connectivity to lake, and human
disturbance
TWINSPAN, DCCA on diatoms and
macroinvertebrates showed good agreement
overall
No definitive comparisons
No comparisons made across ecoregions or
classes
No test of alternate classification schemes
Sign, differences in nutrient levels
demonstrated by water depth, closed vs.
open basins, confirmed by change following
disturbance
Headwater wetlands, riparian wetlands, open lake wetlands, closed basin wetlands.

Diatom assemblages indistinguishable for riparian, open lakes, and closed basin systems; New classes identified based on water
chemistry and water permanence- ephemeral, saline, closed basin-recharge, closed basin-surface water, closed basin-alkaline.

MWCP 1997, Ecological Classification System for Minnesota.

Defined by combination of landscape position (depression, floodplain, littoral zone, sedge meadows + wet prairies), associated river
size, and associated lake water chemistry (calcareous vs. noncalcareous).
                                                  31

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                                     GLOSSARY
Anderson's classification system A hierarchi-
cal classification system for land-use/land-cover
derived from remote sensing imagery developed by
the U.S. Geological Survey (Anderson etal. 1976).

Channel gradient The slope of the main channel
of a stream, typically expressed in change in eleva-
tion (feet) per mile.

Channel units "Subdivisions of a stream reach
that represent specific habitat and micro-habitat units
that are quite uniform in their morphologic and hy-
draulic properties" (Maxwell et al. 1995)

Classification  The process of assigning units to
categories by similarity of attributes, generally with
a purpose of reducing variation within classes.

Cluster analysis An exploratory multivariate sta-
tistical technique that groups similar entities in an
hierarchical structure.

Delphi approach A means to record best pro-
fessional judgments through a consensus-building
approach.

Depressional wetland A hydrogeomorphic wet-
land type located in topographic depressions where
surface water can accumulate.

Detrended canonical correlation analysis A
multivariate technique for relating multiple explana-
tory variables to multiple response variables (e.g.
species abundances).

Digital elevation models  A grid-based geo-ref-
erenced representation of relative elevation across
a landscape in electronic form.

Discriminant function analysis A multivariate
statistical technique that allows one to determine
what combination of explanatory variables best pre-
dicts the separation among classes of observations.

Ecological units  Mapped units that are delin-
eated based on similarity in climate, landform, geo-
morphology geology, soils, hydrology, potential veg-
etation, and water.
Ecoregion  A geographic unit derived through
comparison of climate, climax vegetation, land-use,
and soils maps.  Several different classification
schemes have been developed, including those by
Omernik 1997 and Bailey 1976.

Emergent vegetation  "Erect, rooted herbaceous
angiosperms that may be temporarily to permanently
flooded at the base but do not tolerate prolonged
inundation of the entire plant; e.g., bulrushes
(Scirpus spp.), saltmarsh cordgrass" (Cowardin et
al. 1979).

Environmentally based classification  In this
chapter, an environmentally based classification
scheme does not rely on geographically based simi-
larities, but classifies units based on their attributes
(e.g., watershed land-cover classes) independent
of geographic adjacency.

Estuarine System "Deepwater tidal habitats and
adj acent tidal wetlands that are usually semienclosed
by land but have open, partly obstructed, or spo-
radic access to the open ocean, and in which ocean
water is at least occasionally diluted by freshwater
runoff from the land." (Cowardin etal. 1979)  The
Coastal Zone Management Act of 1972 includes
estuarine-type coastal wetlands in the Great Lakes
in this definition, but Cowardin's system of classifi-
cation does not.

Euhaline Systems with salinity of 30.0-40 ppt,
derived primarily from  ocean salts.

Floodplain  "The lowland that borders a stream
or river, usually dry  but subject to flooding."
(NDWP Water Words Dictionary, http://
www. state.nv.us/cnr/ndwp/dict- 1/waterwds.htm )

Fringe wetlands  Wetlands that occur along or
near the edge of a large body of water (oceanic or
large lake) such that the water surface elevation of
the wetland is influenced by tides and seiche activ-
ity of the adj acent water body.
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Functional assessment  A process for estimat-
ing the functions or processes occurring in a wet-
land such as nutrient cycling, food chain support,
and water retention.

Geographic information system (GIS) A com-
puterized information system that can input, store,
manipulate, analyze, and display geographically ref-
erenced data to support decision-making processes.
(NDWP Water Words Dictionary)

Geographically based classification  An ap-
proach for delineating units of land based on simi-
larity of adjacent lands with respect to attributes
such as climate, natural potential vegetation, soils,
and landforms.

Geomorphology The origins and changing struc-
ture and form of the earth's land surfaces

Hydraulic conductivity The rate at which water
can move through an aquifer or other permeable
medium (NDWP Water Words Dictionary)

Hydrodynamics Branch of science that deals with
the dynamics of fluids, especially incompressible flu-
ids, in motion (NDWP Water Words Dictionary)

Hydrogeomorphic Land form characterized by
a specific origin, geomorphic setting, water source,
and hydrodynamic (NDWP Water Words Dictio-
nary)

Hydrogeomorphic Assessment Approach  A
process of evaluating wetland functions by com-
paring site profiles with those of reference wetlands
in a similar hydrogeomorphic class.
Hydrography Description and mapping of oceans,
lakes, and rivers. (NDWP Water Words Dictio-
nary)

Interfluve An area of relatively unchannelized
upland between adjacent streams flowing in ap-
proximately the same direction.

Lacustrine  "Includes wetlands and deepwater
habitats with all of the following characteristics: (1)
situated in a topographic depression or a dammed
river channel; (2) lacking trees, persistent emergents,
emergent mosses or lichens with greater than 30%
areal coverage; and (3) total area exceeds 8 ha (20
acres).  Similar wetland and deepwater habitats
totaling less than 8 ha are also included in the Lacus-
trine System if an active wave-formed or bedrock
shoreline feature makes up all or part of the bound-
ary, or if the water depth in the deepest part of the
basin exceeds 2 m (6.6 feet) at low water.. .may be
tidal or nontidal, but ocean-derived salinity is al-
ways less than 0.5%" (Cowardin et al. 1979).

Landform  A discernible natural landscape that
exists as a result of wind, water or geological activ-
ity, such as a plateau, plain, basin, mountain, etc.
(NDWP Water Words Dictionary)

Lentic  Characterized by standing water, e.g.,
ponds and lakes.

Limnetic The open water of a body of fresh wa-
ter.

Littoral Region along the shore of a non-flowing
body of water.

Lotic Characterized by flowing water, e.g., streams
and rivers.

Mesosaline  Waters with salinity of 5 to 18%,
due to land-derived salts.

Mineral soil flats Level wetland landform with
predominantly mineral soils

Mineralization The process of breaking down
organic matter to its inorganic constituents

Minerotrophic  Receiving water inputs from
groundwater, and thus higher in salt content (major
ions) and pHthan ombrotrophic systems.

Mixohaline  Water with salinity of 0.5 to 30%,
due to ocean salts.

Multivariate Type of statistics that relates one or
more independent (explanatory) variables with mul-
tiple dependent (response) variables.

Nonmetric dimensional scaling  Anonparamet-
ric statistical technique for indirect ordination, e.g.,
ordering a series of observations along a gradient
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based on similarity/differences in community com-
position independent of any potential explanatory
variables. Vectors related to potential explanatory
variables can be overlaid on NMDS plots to as-
certain potential environmental relationships with
community gradients.

Nonparametric Referring to a type of statistical
approach that does not rely on the assumption that
data are distributed according to a normal distribu-
tion.

Nutrient ecoregions Level II ecoregions defined
by Omernik according to expected similarity in at-
tributes affecting nutrient supply ( http://
www. epa. gov/O ST/standards/ecomap .html)

Ombrotrophic Receiving water inputs predomi-
nantly from precipitation rather than groundwater.

Organic soil flats  Wetland landforms that are
level, expansive, and comprised of predominantly
organic soil.

Palustrine  "Nontidal wetlands dominated by trees,
shrubs, persistent emergents, emergent mosses or
lichens, and all such wetlands that occur in tidal ar-
eas where salinity due to ocean-derived salts is be-
low 0.5%. It also includes wetlands lacking such
vegetation, but with all of the following four charac-
teristics: (1) area less than 8 ha (20 acres); (2) ac-
tive wave-formed or bedrock shoreline features
lacking; (3) water depth in the deepest part of ba-
sin less than 2 m at low water; and (4) salinity due
to ocean-derived salts less than 0.5%" (Cowardin
etal. 1979).

Peatlands  "A type of wetland in which organic
matter is produced faster than it is decomposed,
resulting in the accumulation of partially decom-
posed vegetative material called Peat. In some mires
peat never accumulates to the point where plants
lose contact with water moving through mineral soil.
Such mires, dominated by grasslike sedges, are
called Fens. In other mires peat becomes so thick
that the surface vegetation is insulated from mineral
soil. These plants depend on precipitation for both
water and nutrients. Such mires, dominated by acid-
forming sphagnum moss, are called Bogs." (NDWP
Water Words Dictionary)

Persistent emergent vegetation  Emergent hy-
drophytes (water-loving plants) that generally re-
main standing until the beginning of the next grow-
ing season, such as cattails or bulrushes.

Physiography  Physical geography

Pocosin  Evergreen shrub bog, found on Atlantic
coastal plain.

Random-stratified  A type of sampling in which
the population is first subdivided into predefined
classes (strata) based on perceived similarities, and
then subsamples are selected randomly (each with
an equal chance of selection) from within each class.

Reference wetlands   Under the Hydrogeo-
morphic Assessment approach, "(Reference wet-
lands are actual wetland sites that represent the range
of variability exhibited by a regional wetland sub-
class as a result of natural processes and anthropo-
genic disturbance." (Smith et al. 1995)

Reference condition Under the EPAs Biocriteria
program, wetland reference condition is defined as
the status of wetland sites either unaltered or least-
impaired by anthropogenic disturbance.

Reference domain Under the Hydrogeomorphic
Assessment approach, the geographic area from
which reference wetlands are selected (Smith et al.
1995)

Riparian  "Pertaining to the banks of a river, stream,
waterway, or other, typically, flowing body of wa-
ter as well as to plant and animal communities along
such bodies of water. This term is also commonly
used for other bodies of water, e.g., ponds, lakes,
etc., although Littoral is the more precise term for
such stationary bodies of water." (NDWP Water
Words Dictionary)

Riverine System   "Includes all  wetlands and
deepwater habitats contained within  a channel, with
two exceptions: (1) wetlands dominated by trees,
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shrubs, persistent emergents, emergent mosses, or
lichens, and (2) habitats with water containing
ocean-derived salts in excess of 0.5%." (Cowardin
etal. 1979)

Riverine wetland A hydrogeomorphic class of
wetlands found in floodplains and riparian zones
associated with stream or river channels.

Site potential  "The highest sustainable functional
capacity that can be achieved in a reasonable pe-
riod of time by a wetland, given disturbance his-
tory, land use, or other ecosystem and landscape
scale factors that influence function." (See http://
www.wes.army.mil/el/wetlands/pdfs/wrpde9.pdn
Slope wetland A wetland typically formed at a
break in slope where groundwater discharges to
the surface. Typically there is no standing water.

Stratification The process of separating a popu-
lation into classes prior to sampling.

Stream reaches  A length of channel which is
uniform in its discharge depth, area,  and slope
(NDWP Water Words Dictionary)

Stream order  A measure of stream size.  First
order streams have no tributaries, while second-
order streams can only be formed by the union of
two first order streams and so on.

Submerged aquatic bed "The Class Aquatic Bed
includes wetlands and deepwater habitats domi-
nated by plants that grow principally on or below
the surface of the water for most of the growing
season in most years." (Cowardin etal. 1979)

Terrace "An old alluvial plain, ordinarily flat or
undulating, bordering a river, lake, or the sea. Stream
terraces are frequently called second bottoms, as
contrasted to flood plains, and are seldom subject
to overflow... Also, a Berm or discontinuous seg-
ments of a berm, in a valley at some height above
the Flood Plain, representing a former abandoned
flood plain of the stream." (NDWP Water Words
Dictionary)

Trophic status Degree of nutrient enrichment of
a water body.
Univariate  Type of statistical analysis involving a
single dependent (response) variable.

Valley segments  "Valley segments stratify the
stream network into major functional components
that define broad similarities in fluvial processes,
sediment transport regimes, and riparian interac-
tions." (Maxwell etal. 1995)

Waters of the United States Waters of the United
States include:

a. All waters that are currently used, were used in
the past, or may be susceptible to use in interstate
or foreign commerce, including all waters that are
subject to the ebb and flow of the tide;

b. All interstate waters, including interstate wet-
lands;

c. All other waters such as interstate lakes, rivers,
streams (including intermittent streams), mudflats,
sandflats, wetlands, sloughs, prairie potholes, wet
meadows, playa lakes, or natural ponds the use,
degradation, or destruction of which would affect
or could affect interstate or foreign commerce in-
cluding any such waters:

1 That are or could be used by interstate or
  foreign travelers for recreational or other
  purposes;
2 From which fish or shellfish are or could be
  taken and sold in interstate or foreign com-
  merce; or
3 That are used or could be used for industrial
  purposes by industries in interstate commerce;

d. All impoundments of waters otherwise defined
as waters of the United States under this definition;

e. Tributaries of waters identified in paragraphs (a)
through (d) of this definition;

f The territorial sea; and

g. Wetlands adj acent to waters (other than waters
that are themselves wetlands) identified in paragraphs
(a) through (f) of this definition.
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Wetland(s) (1) Those areas that are inundated or
saturated by surface or groundwater at a frequency
and duration sufficient to support, and that under
normal circumstances do support, a prevalence of
vegetation typically adapted for life in saturated soil
conditions [EPA, 40 C.ER. 230.3 (t)/USAGE,
33 C.F.R.  328.3 (b)].  (2) Wetlands are lands
transitional between terrestrial and aquatic systems
where the water table is usually at or near the sur-
face or the land is covered by shallow water. For
the purposes of this classification, wetlands must
have one or more of the following three attributes:
(a) at least periodically, the land supports predomi-
nantly hydrophytes, (b) the substrate is predomi-
nantly undrained hydric soil, and (c) the substrate is
nonsoil and is saturated with water or covered by
shallow water at some time during the growing sea-
son of each year (Cowardinetal. 1979). (3) The
term "wetland," except when such term is part of
the term "converted wetland, " means land that (a)
has a predominance of hydric soils, (b) is inundated
or saturated by surface or ground water at a fre-
quency and duration sufficient to support a preva-
lence of hydrophyte vegetation typically adapted
for life in saturated soil conditions, and (c) under
normal circumstances does support a prevalence
of such vegetation. For purposes of this Act and
any other Act, this term shall not include lands in
Alaska identified as having a high potential for agri-
cultural development which have a predominance
of permafrost soils [Food Security Act, 16 U.S. C.
Wetland functions Physical, chemical, or biologi-
cal processes inherent to wetlands. Functions may
or may not be related to wetland "services" or ben-
efits to society.
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