United States
Environmental Protection
Agency
Assessment of Wetland Ecosystem
Condition across Landscape Regions:
A Multi-metric Approach
Part B. Ecological Integrity Assessment
Protocols for Rapid Field Methods (L2)
EPA/600/R-12/021b
June 2012
www.epa.gov
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EPA/600/R-12/021b
June 2012
www.epa.gov
Assessment of Wetland Ecosystem Condition across
Landscape Regions: A Multi-metric Approach
Part B. Ecological Integrity Assessment Protocols for
Rapid Field Methods (L2)
Don Faber-Langendoen1, Joe Rocchio2, Steve Thomas3, Mike Kost3, Cloyce Hedge4, Bill Nichols5,
Kathleen Strakosch Walz6, Gwen Kittel1, Shannon Menard1, Jim Drake1, and Esteban Muldavin7
^atureServe, Conservation Science Division, 4600 N. Fairfax Dr., 7th floor, Arlington, VA 22203
2 Washington Dept. of Natural Resources, Natural Heritage Program, Olympia WA 98504
3 Michigan Natural Features Inventory, Michigan State University-Extension, P.O. Box 30444,
Lansing, Ml 48909
4 Indiana Natural Heritage Program, Division of Nature Preserves, Department of Natural Resources.
402 West Washington, Rm. W267, Indianapolis, IN 46204
5 NH Natural Heritage Bureau, Division of Forests & Lands - DRED, PO Box 1856,172 Pembroke Road
Concord, NH 03302
6 Natural Heritage Program, NJDEP MC 501-04, Office of Natural Lands Management. 501 E. State
Street, 4th Floor. Trenton, NJ 08625
7 Natural Heritage Program, New Mexico Division, Museum of Southwestern Biology, Department of
Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM 87131
Notice: Although this work was reviewed by EPA and approved for publication, it may not
necessarily reflect official Agency policy. Mention of trade names and commercial
products does not constitute endorsement or recommendation for use.
U.S. Environmental Protection Agency
Office of Research and Development
Washington, DC 20460
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Notice
The United States Environmental Protection Agency (EPA) through its Office of
Research and Development funded and managed the research described here via a
grant (#R-83377501). It has been reviewed by the EPA and approved for publication.
Mention of trade names or commercial products does not constitute endorsement
or recommendation by EPA for use.
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Foreword
EPA's Environmental Monitoring and Assessment Program (EMAP) is a research program to
develop the tools necessary to monitor and assess the status and trends of national ecological
resources over broad spatial and temporal scales. Regional EMAP (REMAP) is a partnership
between the EPA Regional Offices and EPA's Office of Research and Development (ORD), with
the goal of building state and tribal capacity for using statistically valid monitoring data for
reporting on the condition of their aquatic resources. ORD works with the Regional Offices to
provide funds for projects meeting EMAP criteria that are of importance to the needs within
the region. In the REMAP 2007 funding announcement, one of the identified priority focus
areas was the "Development and testing of protocols and/or the monitoring and assessment
of wetlands in the Region 5 states using a stratified, statistically-valid sample survey design that
will allow extrapolation of wetland conditions throughout ecological regions of the Midwest".
Under a competitive process, a Cooperative Agreement (R-83377501) was awarded to
NatureServe for the proposal they submitted to this focus area. .
This report describes the results of NatureServe's project "Assessment of Wetland Ecosystem
Conditions across Landscape Regions - a Multi-metric Approach". The project was conducted
in partnership with the Natural Heritage programs of Indiana and Michigan, and included
assessment of ~360 wetland sites in those two states. Main elements of the project include
examining the suitability of existing spatial datasets and classification systems as the basis for
sampling design, developing and assessing metrics for various aspects of wetland condition, and
synthesizing the results into an ecological integrity scoring system.
Anett Trebitz (Mid-Continent Ecology Division, Duluth MN), was the EPA Project Officer,
providing administrative oversight and technical input and reviews. Other individuals at EPA
who provided input or reviews included Sue Elston (Region 5, Chicago IL), Peter Jackson (Region
5, Chicago IL), Mike Scozzafava (Office of Wetlands, Washington DC), and Rich Sumner
(Regional liaison for the National Wetlands Program, Corvallis OR). Jo Thompson (REMAP
Coordinator, Mid-Continent Ecology Division, Duluth MN) facilitated the funding announcement
and selection process and David Ack (Grants Management Division, Washington DC) was the
grant specialist for the project.
EPA's Mid-Continent Ecology Division is publishing this report to make these findings more
widely available, given their potential significance for EPA's new National Wetlands Condition
Assessment, as well as for state or tribal agencies involved in assessments of their wetland
resources.
Carl Richards,
Director,
EPA, Office of Research and Development, Mid-Continent Ecology Division
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This document is the 2nd of a two part publication.
PART A:
Faber-Langendoen, D., C. Hedge, M. Kost, S. Thomas, L. Smart, R. Smyth, J. Drake, and S.
Menard. 2012a. Assessment of wetland ecosystem condition across landscape regions: A
multi-metric approach. Part A. Ecological Integrity Assessment overview and field study in
Michigan and Indiana. EPA/600/R-12/021a. U.S. Environmental Protection Agency Office of
Research and Development, Washington, DC.
PART B (this publication):
Faber-Langendoen, D., J. Rocchio, S. Thomas, M. Kost, C. Hedge, B. Nichols, K. Walz, G. Kittel, S.
Menard, J. Drake, and E. Muldavin. 2012b. Assessment of wetland ecosystem condition
across landscape regions: A multi-metric approach. Part B. Ecological Integrity Assessment
protocols for rapid field methods (12). EPA/600/R-12/021b. U.S. Environmental Protection
Agency Office of Research and Development, Washington, DC.
Here, in part B of this publication, we are publishing the latest version (version 3.0) of our Ecological
Integrity Assessment. See Faber-Langendoen et al. (2012a, Appendix C) for a summary of the various
versions. This is an improved version that reflects the results of our Michigan and Indiana study, and has
been upgraded for both style and content. The authors of this publication include not only the co-
investigators of the Michigan and Indiana study, but also the authors that contributed in substantial
ways to the protocols.
IV
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ACKNOWLEDGEMENTS
Developing the overall NatureServe methodology for ecological integrity assessments has been
a team effort over many years. The protocols presented here were developed through a series
of studies, as summarized by Faber-Langendoen et al. (2008, 2011), and through more recent
collaboration with Kathleen Walz on a New Jersey wetland assessment (Walz and Domber
2011). These protocols, in turn, drew from NatureServe's Ecological Integrity Assessment
Working Group between 2004 and 2007. Members consisted of NatureServe and Network
member program staff, including Don Faber-Langendoen and Pat Comer (co-chairs), and David
Braun, Elizabeth Byers, John Christy, Greg Kudray, Gwen Kittel, Shannon Menard, Esteban
Muldavin, Milo Pyne, Carl Nordman, Joe Rocchio, Mike Schafale, Lesley Sneddon, and Linda
Vance. The overall framework for the methodology has been summarized by Unnasch et al.
(2009).
Many aspects of the protocols presented here were funded through Cooperative Agreement
No. RM-83377501 awarded by the U.S. Environmental Protection Agency (EPA). Although EPA
made comments and suggestions on the document, the views expressed are those of
NatureServe. EPA does not endorse any products or commercial services mentioned in this
publication. We are grateful for support from staff of the EPA, including the project
management provided by Anett Trebitz, and ongoing support from Rich Sumner and Mike
Scozzafava for their support, and for peer review comments from Rich Sumner, Peter Jackson,
and Sue Elston.
We thank Kristin Snow and Mary Harkness for their critical database support for the protocols
provided here. They helped design and implement the Ecological Observations database, which
houses all information collected using this methodology. In turn, that database can be linked to
NatureServe's Biotics databases used by Natural Heritage Programs, who track the many high
quality wetlands found across the country.
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TABLE OF CONTENTS
NOTICE //
FOREWORD ///
ACKNOWLEDGEMENTS V
INTRODUCTION 1
INTRODUCTION TO ECOLOGICAL INTEGRITY ASSESSMENT METHODS 1
* Conceptual Model for Assessing Integrity of Ecosystems 2
• Major Factors: Landscape Context, Size, and Condition 2
• Indicators at Multiple Scales 3
• Rating Ecological Integrity 5
LEVEL 2 ECOLOGICAL INTEGRITY ASSESSMENT METHOD 6
• Level 2 Metrics 6
• Level 2 Stressor Checklist 6
• Assessment Area (AA) 7
• Field Methods Guidance 8
WETLAND CLASSIFICATION AND LEVEL 2 ASSESSMENTS 8
VARIATIONS ON THE LEVEL 2 ASSESSMENT 9
• More Rapid vs. Less Rapid 9
• Assessing Ecosystem Services and Functions 11
OVERVIEW OF WETLAND METRICS 12
• Main Metrics 12
• Supplemental Metrics 14
• Metric Description Format 15
PROTOCOLS FOR ECOLOGICAL INTEGRITY METRICS 16
LANDSCAPE 16
* 1. Landscape Connectivity 16
• 2. Land Use Index 21
BUFFER 25
• 3. Buffer Index 25
SIZE 31
• 4. Absolute Patch Size 31
• 5. Relative Patch Size 35
VEGETATION 37
* 6. Vegetation Structure 37
• 7. Woody Regeneration 43
• 8. Native Plant Species Cover 45
• 9. Invasive Plant Species Cover 47
• 10. Vegetation Composition 49
HYDROLOGY 52
vi
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• 11. Water Source 52
• 12. Hydroperiod 56
• 13. Hydrologic Connectivity 61
SOIL /SUBSTRATE 65
• 14. Physical Patch Types 65
• 15. Soil Surface Condition 67
STRESSOR CHECKLIST 70
GUIDELINES FOR COMPLETING THE STRESSOR CHECKLIST 70
STRESSOR CHECKLIST FORM 72
GUIDANCE ON COMPLETING THE STRESSOR CHECKLIST FORM 75
REFERENCES 78
APPENDIX 1. TEMPLATE FOR METRICS PROTOCOLS 86
APPENDIX 2. FIELD METHODS 87
* Introduction 87
• Defining the Assessment Area 87
• Guidelines for Field Methods for Ecological Integrity Assessments 88
APPENDIX3. VEGETATION PLOTS 93
• Plot Size and Design 93
• Plot Data 94
APPENDIX 4. DESCRIPTIONS OF MAJOR WETLAND FORMATIONS IN THE USNVC. 97
APPENDIX 5. DESCRIPTIONS OF HYDROGEOMORPHIC CLASSES 101
VII
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INTRODUCTION
Introduction to Ecological Integrity Assessment Methods
Building on the related concepts of biological integrity and ecological health, ecological integrity
is a broad and useful endpoint for ecological assessment and reporting (Harwell et al. 1999).
Ecological integrity assessments can be defined as "an assessment of the degree to which,
under current conditions, an occurrence of an ecosystem matches reference conditions for
structure, composition, and function, operating within the bounds of natural or historic
disturbance regimes, and is of exemplary size" (adapted from Lindenmayer and Franklin 2002,
Parrish et al. 2003). "Integrity" is the quality of being unimpaired, sound, or complete. To have
integrity, an ecosystem should be relatively unimpaired across a range of characteristics and
spatial and temporal scales. This broad definition can serve as a guide to developing
assessment methods, steering us through the related assessment methods for ecological
functions and ecosystem services (Jacobs et al. 2010, USFWS 2010).
Our Ecological Integrity Assessment (EIA) method builds on the work of other rapid assessment
methods. Methods prior to 2006 are reviewed by Fennessy et al. (2007); more recent methods
include the California Rapid Assessment Method or CRAM (Collins et al. 2006, 2007) and USA
RAM 2011). Our approach provides a national and international approach that is
comprehensive for all wetlands and it is based on ecological integrity concepts, which can be
effectively assessed using a suite of rapid assessment metrics, structured around our general
ecological model. Although some of our metrics require greater expertise than others, all
attributes have at least two metrics that can be evaluated in a relatively straightforward
manner, allowing for wide applicability. This wetland EIA is also one part of a larger suite of
ElAs for forests, grasslands, etc., that NatureServe and the Natural Heritage Network are
developing, and which are being developed for multiple levels of assessment, from remote
sensing based (Level 1) assessments to intensive field-based methods (Level 3) (see Faber-
Langendoen et al. 2012; http://wwwl.dnr.wa.gov/nhp/refdesk/communities/eia list.html).
Together, they allow us to assess the entire set of ecosystems across landscapes and
watersheds. The EIA methods can also be integrated with a watershed approach to provide an
integrated "wetland and watershed" perspective on conservation and restoration goals (Kittel
and Faber-Langendoen 2011).
Here, we briefly summarize the overall approach to the development of ElAs, with a focus on
Level 2 EIA methods (often referred to as rapid assessment methods or RAMs), but our main
purpose is to provide the current metric protocols for Level 2 ElAs of wetlands. A companion
document provides a full overview of the EIA method along with a field study in Indiana and
Michigan based on the method (Faber-Langendoen et al. 2012). A previous version of that
study (Faber-Langendoen et al. 2011) contains the original metric protocols.
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• Conceptual Model for Assessing Integrity of Ecosystems
Identifying the ecological attributes that need to be assessed involves building a conceptual
ecological model of ecological integrity. This model rests on the knowledge of a wetland or
upland system, its setting, and similar or associated systems. The result is a set of hypotheses
about how the system functions, its defining characteristics and dynamics, and critical
environmental conditions and disturbance regimes that may act as drivers of these
characteristics and dynamics. These hypotheses both guide management and monitoring, and
highlight gaps in knowledge that require additional investigations (Unnasch et al. 2009).
We use a conceptual ecological model that provides a general set of ecological factors common
to all terrestrial systems, and then encourage identification of individual key ecological
attributes for individual system types. The model also provides a means to correlate stressors
or agents of change to the ecological factors (Noon 2003). The terms come from a variety of
models available in the literature (e.g., Harwell et al. 1999, Parrish et al. 2003), and our own
work (Faber-Langendoen 2009, Faber-Langendoen et al. 2011).
• Major Factors: Landscape Context, Size, and Condition
The major components of the model include three primary factors (landscape context, size, and
(on-site) condition, subdivided by six major ecological factors of landscape, buffer, size,
vegetation, hydrology, and soils. Together these are the components that capture the
structure, composition, and processes of a system (Figure 1.1). Other major attributes, such as
algae, birds, amphibians, and macroinvertebrates, can also be assessed where resources, time,
and field sampling design permit. The model can be refined, as needed, based on increasing
specificity of ecosystem types, as described by various wetland classifications (e.g., U.S.
National Vegetation Classification [FGDC 2008], system classifications from Natural Heritage
Programs, National Wetland Inventory [Cowardin et al. 1979], or Hydrogeomorphic
classification[Smith et al. 1995]). The model can also be expanded to include more specific key
ecological attributes of individual wetland types (e.g., the vegetation factor can be refined into
"plant assemblage composition" and "vegetation structure" attributes to ensure that metrics
address each of these attributes (Parrish et al. 2003, Unnasch et al. 2009).
The model is fairly intuitive, but a key component is that, to describe how a system "works,"
one must include both the "inner workings" (condition) and the "outer workings" (landscape
context). A third primary factor, the size of an ecosystem patch or occurrence, helps to
characterize patterns of diversity, area-dependent species, and resistance to stressors.
Addressing all of these characteristics and processes will contribute not only to understanding
the current levels of ecological integrity but to the resilience of the ecosystem in the face of
climate change and other global causes of stress.
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Figure 1.1. Example of a conceptual model for Ecological Integrity Assessments of Terrestrial
Systems. The three primary factors (landscape context, size, and (on-site) condition) and six major
ecological factors (landscape, buffer, size, vegetation, hydrology, and soils of ecological integrity
are shown for wetlands and uplands. The model can be expanded to include additional measures
of biotic Integrity, such as birds, amphibians, macroinvertebrates, or algae.
LANDSCAPE
CONTEXT
Metric 1
Metric 2
Metric 3
ECOLOGICAL
INTEGRITY
• Indicators at Multiple Scales
The selection of specific indicators, or metrics, to assess ecological integrity can be executed at
three levels of intensity depending on the purpose and design of the data collection effort (Brooks
et al. 2004, Tiner 2004, U.S. EPA 2006). This "3-level approach" to assessments allows the flexibility
to develop data for many sites that cannot readily be visited or intensively studied, permits more
widespread assessment, while still allowing for detailed monitoring data at selected sites.
To ensure that the 3-level approach is consistent across levels in how ecological integrity is
assessed, a standard framework or conceptual model for choosing metrics should be used, as
described above (Figure 1.1). Using this model, metrics are identified that address the three
primary factors (landscape context, size, and condition), and six major ecological factors
(landscape, buffer, size, vegetation, soils and hydrology).
Level 1 Remote Assessments rely on Geographic Information Systems (GIS) and remote sensing
data to obtain information about landscape condition and stressors in and around an
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occurrence. They can also help assess the distribution and abundance of ecological types in the
landscape or watershed. Level 2 Rapid Assessments use relatively simple field metrics for
collecting data on specific occurrences, and will often require considerable professional
judgment. Our approach emphasizes a condition-based rapid assessment, supplemented by
information on stressors that may be affecting condition. Level 3 Intensive Assessments
require more rigorous, field-based methods that provide higher-resolution information on the
wetland occurring within an assessment area, often employing quantitative plot-based
assessment procedures coupled with a sampling design. Calculations of calibrated indices, such
as a vegetation or aquatic based Index of Biological Integrity (IBI), or a Floristic Quality Index
(FQI) may also be used (Mack and Kentula2010). This 3-level approach to assessments,
summarized in Table 1.1, allows for the flexibility of developing data on many occurrences that
cannot readily be visited or intensively studied as well as those for which detailed information is
desirable. When coupled with standardized procedures for defining occurrences across the
landscape, it encourages a widespread application of ecological integrity assessments based on
a reasonable and cost-effective approach for programmatic or project needs.
Table 1.1. Summary of 3-level approach to conducting ecological integrity assessments
(adapted from Brooks et al. 2004, U.S. EPA 2006).
Level 1 - Remote Assessment
Level 2 - Rapid Assessment
Level 3 - Intensive Assessment
General description:
Imagery or GIS based assessment of
landscapes
General description:
Rapid site integrity assessment
General description:
Quantitative site integrity assessment
Evaluates:
Integrity of both on and off-site conditions
around individual sites/occurrences
using
• Indicators within occurrences that
are visible with remote sensing data
• Indicators in the surrounding
landscape / watershed
Evaluates:
Integrity of individual areas/occurrences
using relatively simple field indicators
• Very rapid assessment (narrative)
• Rapid assessment (standard
metrics)
• Hybrid assessments (rapid +
vegetation plot)
Evaluates:
Integrity of individual areas/occurrences
using relatively detailed quantitative field
indicators
• Choice of metrics may vary,
depending on whether they are
applied for assessment or
monitoring, or both
Based on:
• GIS and remote sensing data
• Layers typically include:
- Land cover, land use, other
ecological types
• Stressor metrics (e.g., roads and
land use)
Based on:
• On-site condition metrics (e.g.,
vegetation, hydrology, and soils)
• Stressor metrics (e.g., ditching, road
crossings, and pollutant inputs)
Based on:
• On-site condition metrics (e.g.,
vegetation, hydrology, and soils)
• Indicators that have been calibrated
to measure responses of the
ecological system to disturbances
(e.g., indices of biotic or ecological
integrity)
Potential uses:
• Identifies priority sites
• Identifies status and trends of
acreages across the landscape
• Identifies condition of ecological
types across the landscape
• Informs targeted restoration and
monitoring
Potential uses:
• Relatively inexpensive field
observations across many sites
• Informs monitoring for
implementation of restoration,
mitigation, or management projects
• Landscape / watershed planning
• General conservation and
management planning
Potential uses:
• Detailed field observations, with
repeatable measurements, and
statistical sampling design
• Identifies status and trends of
specific occurrences or indicators
• Informs monitoring for restoration,
mitigation, and management
projects
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The 3-level approach is intended to provide increasing accuracy of ecological integrity
assessment, recognizing that not all conservation and management decisions need equal levels
of accuracy. We discuss all three levels in detail in Faber-Langendoen et al. (2012). Here, we
focus on Level 2 rapid assessments.
• Rating Ecological Integrity
The choice of individual indicators and their contribution to overall assessments of ecological
integrity depends on having a conceptual understanding of integrity. Earlier we stated that
ecological integrity assessments can be defined as "an assessment of the degree to which,
under current conditions, an occurrence of an ecosystem matches reference conditions for
structure, composition, and function, operating within the bounds of natural or historic
disturbance regimes, and is of exemplary size." We can expand that definition by providing a
narrative set of guidelines on the kinds of structural, compositional, and ecological functions (or
processes) that are core to the assessment. Using a scorecard approach (where A = excellent
integrity and D = poor integrity), we can define an A-rated example as an...
"...Occurrence believed to be, across the range of a type, among the highest quality
examples with respect to key ecological attributes functioning within the bounds of
natural disturbance regimes. Characteristics include 1) the landscape context contains
natural habitats that are essentially unfragmented (reflective of intact ecological
processes) and with little to no stressors; 2) the size is very large or much larger than the
minimum dynamic area; 3) vegetation structure and composition, soil status, and
hydrological function are well within natural ranges of variation, exotics (non-natives)
are essentially absent or have negligible negative impact; and 4) a comprehensive set of
key plant and animal indicators are present." (Faber-Langendoen et al. 2012).
A full set of definitions for A - D ratings is provided in Faber-Langendoen et al. (2012). These
ratings help guide the recognition of reference wetlands, from reference standards (A-ranked
wetlands) to degraded (D-ranked wetlands). Assignment of a rating presumes that a particular
type is still recognizable at some level as "the type," despite varying levels of degradation. At
some point, a degraded type will "cross the line" (or be "transformed," sensu SER 2004) into a
separate, typically semi-natural or cultural type. In some state-and-transition models, these
examples may be treated as shifts to an "alternative state." As a matter of practicality, the
current ecosystem under transformed conditions is considered lost. Using a scorecard
approach requires working with a set of diagnostic classification criteria, based on composition,
structure, and habitat (see "Wetland Classification and Level 2 Assessments" below) to
distinguish "transformed" ecosystem states from degraded conditions of a particular ecosystem
type.
A scorecard approach depends on a consistent scaling of the indicators or metrics, such that
their ratings are comparable with respect to levels of integrity. It is then reasonable to
summarize the metric ratings and roll them into aggregate scores, including an overall Index of
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Ecological Integrity, based on a weight of evidence approach (Linkov et al. 2009). Details of the
scorecard are provided in Faber-Langendoen et al. (2012).
LEVEL 2 ECOLOGICAL INTEGRITY ASSESSMENT METHOD
• Level 2 Metrics
The intent of ecological integrity based rapid assessment methods (RAMs) is to evaluate the
complex ecological condition of a selected ecosystem using a specific set of observable field
indicators, and to express the relative integrity of a particular occurrence in a manner that
informs decision-making, whether for restoration, mitigation, conservation planning, or other
ecosystem management goals (Stein et al. 2009). These Level 2 assessments are structured
tools combining scientific understanding of ecosystem structure, composition, and processes
with best professional judgment in a consistent, systematic, and repeatable manner (Sutula et
al. 2006).
Metrics that are chosen should provide information on the integrity or sustainability of the major
ecological factors and their relationship to associated stressors (this is sometimes described as the
metrics showing a "stressor-dose response" to changes in stressor levels). Sensitivity analyses can
be conducted to ensure that metrics are informative (e.g., by assessing how metrics respond to a
gradient of stressor levels) (Rocchio 2007; Lemly and Rocchio 2009, Jacobs et al. 2010; Faber-
Langendoen et al. 2011, 2012).
Level 2 assessments rely primarily on relatively rapid (ca. 2-4 hours) field-based site visits, but this
may vary, depending on the purposes of the assessment. They provide the opportunity to do
direct, ground based surveys of ecosystem occurrences. RAMs are widely available for wetlands
because of the need for mitigation and restoration tools, and they are used by many state wetland
programs (Fennessy et al. 2007). Typically three to five metrics are identified for each of the
ecological factors, with each metric designed to assess a major ecological factor or attribute.
• Level 2 Stressor Checklist
Stressor checklist can be useful as additional information when evaluating the ecological
integrity of an occurrence (Sutula et al. 2006). Typically, they are an aid to further
understanding the factors that affect the overall condition of the wetland. The term "stressor"
is defined as "the proximate (human) activities or processes that have caused, are causing, or
may cause the destruction, degradation, and/or impairment of biodiversity and natural
processes" (from Salafsky et al. 2008). Here we restrict our focus to those stressors that have
caused, or are causing impacts whenever the effects of the stressors are evident (we exclude
potential future threats). For example, a direct stressor may be recent tree removal or mowing.
Less recent mowing or tree removal would be included only if the effect of those stressors is
still currently evident (e.g., old tree stumps). The term is synonymous with "direct threats" as
defined by Salafsky et al. (2008) or with "stressors" as used by the U.S. EPA (Young and Sanzone
2002).
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Stressors may be characterized in terms of scope and severity (Master et al. 2012). Scope is
defined as the proportion of the occurrence of an ecosystem that is currently affected by the
stressor, including stressors that may have occurred in the past, but the effect is still currently
evident (e.g., past logging that has removed all large trees from a stand, resulting in a current
small tree structure). Within the scope (as defined spatially and temporally in assessing the
scope of the stressor), severity is the level of damage to the ecosystem from the stressor,
based on existing evidence (using a 10 year window).. Severity is typically assessed by known
or inferred degree of degradation or decline in integrity to specific major ecological attributes,
such as the buffer, vegetation, soils, and hydrology.
Standardized checklists of stressors have been developed for a variety of rapid assessment
methods (Collins et al. 2006, Faber-Langendoen 2009, Faber-Langendoen et al. 2011). They can
be used to create field-based versions of stressor indices. For example, the Human Stressor
Index of Rocchio (2007) integrates stressor scores for hydrology, soils, and buffer.
• Assessment Area (AA)
The protocols for ElAs are conducted within an Assessment Area (AA), defined by a wetland
type with relatively broadly homogeneous biotic and abiotic composition and structure (see
"Wetland Classification and Level 2 Assessments" below), and in the buffer and surrounding
landscape. These assessment areas can be defined as points, polygons, or patches. A point-
based approach typically defines a relatively small area (e.g., 0.5 ha) around a point, within and
around which the assessment is conducted. A polygon approach defines a specific ecosystem
area that is delineated (using vector or raster methods) to create a mapped area. Pixel (or
raster) based approaches, such as from satellites, are perhaps intermediate between points and
polygons. Pixels are often smoothed into larger "patches," these patches can be assigned to
ecosystem types, and analyses can be performed on these patches. Or these patches can be
further aggregated into clusters (e.g., using separation distances between patches, comparable
to clustering polygons or patches or as "bounded patches," where a larger landscape or
watershed boundary is used, and all patches of the same ecosystem type within that boundary
are included as part of the assessment area). The "bounded patch" approach is currently being
used by NatureServe to conduct ecological integrity assessments in western U.S. ecoregions
(NatureServe 2012, in prep).
For Level 2 assessments, AAs are typically placed within a patch or cluster of patches of a
wetland type. As these patches get larger in area, at some point they will exceed the area that
is reasonable to survey as part of a rapid assessment. We recommend that Level 2 assessments
should be limited to areas less than 20 ha. If the wetland patch or series of patches is larger,
and the goal is to establish a rating for the patch or series of patches, then a decision will need
to be made as to whether the ratings within the AA can be extrapolated to the larger patch or
whether multiple AAs are needed.
The choice of AA affects the area included in the surrounding buffer and landscape assessment
(Table 2). With a small, fixed area (e.g., 50 m radius AA), and fixed distances from the AA edge,
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the buffer area being assessed is 6 ha, and the supporting landscape is 67 ha. With a variable
AA, and the same fixed distances from the AA edge, the area of the buffer and landscape
assessed depends on the size and shape of AA polygon that is being surveyed (as stated above,
we recommend a maximum size of 20 ha for the AA, in order to keep the field work
reasonable). Potential variation in total area assessed is between 92 and 330 ha (Table 1.2).
See "Landscape Connectivity" metric for more details.
Table 1.2. Fixed point versus Variable Polygon Assessment Areas (AA) and the changing area
of buffer, core and supporting landscape. Minimum AA size is 0.5 ha (5000 m2); maximum
size is 20 ha (200,000 m2).
METRIC & DISTANCE
AA and METRIC
Assessment
Area (ha)
Buffer
Core Landscape
Supporting
Landscape
Total
Distance
From Outer
Edge Of AA
0-100 m
100-250 m
250-500 m
TOTAL AREA = AA + Buffer +
Core & Supporting Landscape
FIXED (Point)
AA AREA
FIXED AA
(e.g. 40 m
radius circle)
0.5 ha
6 ha
20 ha
65 ha
92 ha
VARIABLE (Polygon) AA AREA
Compact
Circular
(e.g. 40m to
252m radius)
0.5 -20 ha
6 - 19 ha
20 -40 ha
65 -98 ha
92 -178 ha
Narrow
Rectangular
(e.g. 10 x 500m to
100 x 2000m)
0.5 -20 ha
14 - 46 ha
36 - 84 ha
100 - 180 ha
152 -330 ha
Irregular
(see Figure
2.1)
0.5 -20 ha
shape
dependent
shape
dependent
shape
dependent
92-330 ha
• Field Methods Guidance
Field methods for applying ecological integrity assessments vary, depending on the purpose of
the assessment. We provide general guidance on field methods in Appendix 2.
Wetland Classification and Level 2 Assessments
The success of developing indicators of wetland ecological integrity depends on an
understanding of the structure, composition, and processes that govern the wide variety of
wetland systems. Ecological classifications can be helpful tools in categorizing this variety.
These classifications help wetland managers to better understand natural variability within and
among types so that differences between occurrences with good integrity and poor integrity
can be more clearly recognized.
We integrate three main classifications into our Level 2 assessments:
-------
• U.S. National Vegetation Classification (NVC) (FGDC 2008, Faber-Langendoen et al.
2009a, Jennings et al. 2009).
• National Wetlands Inventory (NWI) (Cowardin et al. 1979).
• Hydrogeomorphic (HGM) classification (Smith et al. 1995).
A summary of these classifications is provided in Faber-Langendoen et al. (2008, 2011, 2012).
Our goal is to apply the classification categories to the degree that they are needed for
improving the rapid assessment of ecological integrity. For some metrics (e.g., Invasive Plant
Species Cover), we do not require any wetland classification information - the same metric is
used for all wetland types. For others, such as Vegetation Structure and Hydrologic
Connectivity, the metric varies depending on the wetland type, either by NVC Formation/NWI
Class or by HGM class (Table 1.3). The NVC Formation level is similar to the NWI Class level, but
the formations incorporate key wetland ecological factors reflected in the vegetation. HGM
defines classes based on hydrology and geomorphology. Thus it adds an important dimension
to the other classifications, but doesn't integrate vegetation with the abiotic factors. A brief
description of NVC Formation categories is provided in Appendix 4 and HGM classes in
Appendix 5.
Variations on the Level 2 Assessment
• More Rapid vs. Less Rapid
We have described what may be called the "Level 2 - standard method." It is worth noting
several variants of the Level 2 EIA assessment methods may appeal to different needs. First,
there is the "very rapid method," in which, the attributes themselves serve as the general
indicators, and field crews complete a structured narrative evaluation of those attributes. This
approach has been widely used by the Natural Heritage Network, beginning with the work of
White (1978) in Illinois. In this approach, field crews may record observations on the
vegetation, soils, and hydrology, and then rate the on-site condition against a general narrative
of grades. For example:
Grade A: Relatively stable or undisturbed communities. — Ideally, a Grade A community has a structure
and composition that has reached stability and does not show the effects of disturbance by humans.
However, this grade does include a range of conditions: the community may be gradually changing, or it
may have been lightly disturbed. Examples: (1) old growth, ungrazed forest, (2) prairie with undisturbed
soil and natural plant species composition, (3) wetland with unpolluted water, unaltered water level, and
natural vegetation (White 1978, Appendix 22).
While not preferred, it has been a valuable approach for professional ecologists, well-
experienced in the range of variation in wetland conditions and degradation, and who need to
provide rapid evaluations of many sites. But because it is based on professional judgment, the
ratings should be well-documented.
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Table 1.3. The inter-relationships among three main wetland classifications: NVC, NWI, and HGM.
NVC-NWI-HGM Wetland Classification Crosswalk Table*
Hydrogeomorphic Classification
Vegetation Classification RIVERINE DEPRESSION SLOPE* MINERAL ORGANIC SOIL ESTUARINE LACUSTRINE
SOIL FLATS FLATS FRINGE2 FRINGE
NVC FORMATION4
FLOODED & SWAMP
FOREST (Tropical,
Temperate, Boreal)
MANGROVE
FRESHWATER MARSH,
WET MEADOW &
SHRUBLAND (Tropical,
Temperate, Boreal)
SALT MARSH
BOG & PEN(Tropical,
Temperate, Boreal)
AQUATIC VEGETATION
(Freshwater, Saltwater)
NWI CLASS
Forested (FO)
Scrub-Shrub (SS)
Emergent (EM)
Scrub-Shrub (SS)
Emergent (EM)
Moss-Lichen (ML)
Aquatic Bed (AB)
Palustrine:
Riverine
PFO
-
PSS
PEM
-
-
~
R1AB
Palustrine
PFO
-
PSS
PEM
PEM3
PML, PEM, PSS
PAB
Palustrine
PFO
-
PSS
PEM
-
-
PML, PEM,
PSS
-
Palustrine
PFO
-
PSS
PEM
-
-
-
-
Palustrine
PFO
-
PSS
PEM
-
-
PML, PEM, PSS
-
Estuarine:
Intertidal;
Riverine
E2FO
E2FO
R1SS
R1EM
E2SS
E2EM
~
E2AB
Lacustrine:
Littoral
PFO
-
PSS
PEM
-
-
~
L2AB
* NVC = National Vegetation Classification (FGDC 2008, Faber-Langendoen et al. 2009, Jennings et al. 2009)
* NWI = National Wetland Inventory (Cowardin et al. 1979)
* HGM = Hydrogeomorphic Classification (Smith et al. 1995, NRCS 2008)
Includes groundwater slope/riverine or "sliverine" wetlands (e.g., streamside fens/savannas) and freshwater wetlands on the coast with some tidal influence (e.g., sea level
fens)
Includes salt, brackish, oligohaline, and freshwater tidal wetlands
Inland haline marsh
NWI - NVC classification crosswalk details may differ with respect to strata (e.g., NWI tree cover cutoff for PFO is 30% whereas NVC tree cover is 10%; NWI treats sapling stages
as Scrub-Shrub whereas in NVC they are treated as part of the Flooded & Swamp Forest)
10
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A second variant may be referred to as the "enhanced rapid method," in which more
quantitatively based Level 2 metrics or a few select level 3 indicators, are added to a Level 2
assessment, because it is important for the goals of the project to better understand some key
attributes. A common addition is that of a vegetation plot, or some type of standardized plant
species list for an occurrence, referred to as a level 2.5 assessment by Nichols and Faber-
Langendoen (2012). The plot may be set up and data collected more or less rapidly (see
Appendix 3 for information on vegetation plot sampling). These data can provide sufficient
composition information for Level 3 VIBIs or FQIs, or more detailed information on vegetation
structure (e.g., old growth or coarse woody debris ratings in forests). As long as the added
metrics are guided by the overall conceptual model, there should be little difficulty in producing
comparable results to other RAMs.
• Assessing Ecosystem Services and Functions
Assessing ecosystem services addresses aspects of wetlands that address human needs (the
term "functional assessment" has also been used, but functions can refer broadly to ecological
functions in general or to those ecosystem functions that address specific human needs).
Ecosystem services include 1) surface water detention, 2) streamflow maintenance, 3) nutrient
transformation, 4) sediment and particulate retention, 5) carbon sequestration, 6) shoreline
stabilization, 7) coastal storm surge detention, 8) provision of various fish and bird and other
animal habitats, etc. To assess these services requires additional models and metrics not
discussed here, such as using various landscape, landform and hydrologic attributes in
conjunction with HGM classes to predict levels of various ecosystem services (see Tiner 2003,
Faber-Langendoen et al. 2008, USFWS 2010). The metrics overlap to some degree with that of
the EIA method. We caution that a wetland may be in excellent condition but may not be rated
highly for any given ecosystem service. Conversely, a wetland in poor ecological condition may
still provide valuable ecosystem services. For example, floodplain forests with high ecological
integrity have a range in capacity for providing flood control services; these forests could also
be modified to increase those services, but depending on the modification, this may or may not
maintain their level of integrity.
11
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OVERVIEW OF WETLAND METRICS
• Main Metrics
The standard set of rapid assessment metrics for wetlands is provided in Table 1.4.
NatureServe, working especially with EPA and state partners, developed these indicators as
part of a standard Level 2 Ecological Integrity Assessment method for all wetlands in the U.S.
(Faber-Langendoen et al. 2008, Faber-Langendoen 2009). Some metrics have variants for
certain ecosystem types (using NVC Formations and Macrogroups) or hydrogeomorphic types
(using HGM classes).. Variants are described in the "Protocols" section. Eight of the metrics (1,
3, 5, 8, 9, 11, and 13 and 16) could be considered "basic" metrics; that is, they are based on
readily accessible and repeatable office and field information. Other metrics require greater
levels of information or expertise to apply. See next section for supplemental metrics. Our
approach is straightforward: for each metric, we list the kinds of classification units, either NVC
Formation or HGM class, that are needed to more accurately assess wetland condition (Table
1.5). This is a work in progress and some metric variants require further testing and refinement.
12
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Table 1.4. The standard set of wetland metrics based on the conceptual model of ecological
integrity (see Figure 1.1). Eight metrics have variants based on particular wetland types (NVC
Formation or groupings of HGM Classes) (e.g., tidal vs. non-tidal and riverine vs. non-riverine).
Additional details on the metric variants are provided in Table 1.5.
RANK FACTOR
LANDSCAPE
CONTEXT
SIZE
CONDITION
ECOLOGICAL
FACTOR
LANDSCAPE
BUFFER
SIZE
VEGETATION
HYDROLOGY
SOIL
METRIC NAME
1. Connectivity (Core,
Supporting)
2. Land Use Index (Core,
Supporting)
3. Buffer Index
Percent of AA Having Buffer
Average Buffer Width
Buffer Condition
4. Relative Patch Size (ha)
5. Absolute Patch Size (ha)
6. Vegetation Structure
7. Woody Regeneration
8. Native Plant Species Cover
9. Invasive Plant Species Cover
10. Vegetation Composition
11. Water Source
12. Hydroperiod
13. Hydrologic Connectivity
14. Physical Patch Types
15. Soil Condition
METRIC
VARIANTS
Y
Y2
(Y)1
(Y)2
Y
Y
Y
Y
METRIC: NVC
or HGM
NVC
NVC
NVC
HGM
HGM
HGM
NVC
HGM & NVC
Metric is specific to a wetland type (e.g., metric 3 is only used for tidal wetlands), but has no actual
variants.
2
Metric currently has no variants, but is best applied when wetlands are classified at more specific
levels (e.g., assessing alterations to vegetation composition is improved using NatureServe System
or NVC Group types, rather than at the higher NVC Formation level.
13
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Table 1.5. Metric Variants Based on HGM and NVC Classification.
NVC-based Variants
METRIC
Metric Variant by NVC
Formation Type
FLOODED & SWAMP
FOREST
MANGROVE
FRESHWATER MARSH,
WET MEADOW &
SHRUBLAND
SALT MARSH
BOG & FEN
AQUATIC VEGETATION
VEGETATION
7. Vegetation
Structure
vl
v3
VEGETATION
8. Woody
Regeneration
vl
VEGETATION
11. Vegetation
Composition
vl*
SOILS
15. Physical
Patch Types
vl
v3
SOILS
16. Soil
Surface
Condition
vl
vl
* Metric can be refined at the Macrogroup or Group level of the NVC, or using Ecological Systems.
HGM-based Variants
METRIC
Metric Variant by HGM Class
Estuarine (Tidal)
Riverine) Non-tidal)
Organic Soil Flats, Mineral Soil
Flats
Other HGM (Depression,
Lacustrine, Slope)
HYDROLOGY
12. Water Source
vl
v2
-
v3
HYDROLOGY
13. Hydroperiod
vl
v2
v3
v4
HYDROLOGY
14. Hydrologic
Connectivity
vl
v2
v3
v4
• Supplemental Metrics
Although the EIA L2 method covers the basic metrics needed to assess ecological condition,
supplemental metrics may be developed for particular wetland types or systems in a
specific study, state or region. Customizing the EIA with additional metrics is encouraged as
long as the core metrics are not replaced. In addition, it is very important to consider the
weighting of the supplemental metrics in the ecological integrity assessment ratings.
For example, using a Floristic Quality Index developed for a particular state or region may
be needed to supplement the Level 2 vegetation metric data for wetland mitigation
evaluation. While FQI is normally a Level 3 metric, it can be used to augment Level 2
assessments (Rocchio 2007, Lemly et al. 2011). Another example is a supplemental metric
for landscape connectivity to evaluate the barriers to landward migration (BLM) of tidal
marshes (Jacobs et al. 2010). This connectivity metric would serve to evaluate the ability of
a tidal marsh to move inland in the face of sea level rise.
14
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• Metric Description Format
All metrics are described using a standard format (see Text Box below). A full explanation of
the template is provided in Appendix A.
Text Box. Template for Metric Description
Metric Name:
Definition:
Background:
Metric Type:
Tier:
Rationale for Selection of the Variable:
Measurement Protocol:
Metric Rating:
Metric Rating
EXCELLENT (A)
GOOD (B)
FAIR(C)
POOR(D)
Metric Name & Wetland Type(s) to which it applies
Metric Rating Description
Metric Rating Description
Metric Rating Description
Metric Rating Description
Data for Metric Rating:
Scaling Rationale:
Confidence that reasonable logic and/or data support the metric:
15
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PROTOCOLS FOR ECOLOGICAL INTEGRITY METRICS
LANDSCAPE
• 1. Landscape Connectivity
Definition: A measure of connectivity assessed using the percent of natural habitat in the
surrounding landscape beyond the 100 m buffer, based on an additional 150 m width for
the core landscape and an additional 250 m width for the supporting landscape.
Background: This metric addresses the broader landscape beyond the immediate buffer. It
addresses ecological dynamics and species that depend on the larger landscape.
Metric Type: Condition.
Tier: 1 (remote sensing).
Rationale for Selection of the Variable: The intensity of human activity in the landscape
often has a proportionate impact on the ecological processes of natural systems. The
percentage of cultural land use (e.g., agricultural and developed urban/suburban patches)
within the surrounding landscape provides an indirect estimate of connectivity among
natural ecological systems. Landscapes that retain more connectivity among patches of
otherwise isolated wetlands, and therefore have higher levels of connectivity, are assumed
to be more likely to maintain populations of various species that inhabit the natural patch.
Studies have shown that lack of landscape connectivity reduces pollination and seed
dispersal, animal movements, ecological processes, and ultimately genetic diversity
(Lindenmayer and Fischer 2006).
The integrity of the landscape context of wetlands can be important to certain biota.
Amphibians and reptiles are especially sensitive to the matrix of habitats surrounding a
wetland because they spend the majority of their lives foraging, resting, and hibernating in
the adjacent terrestrial habitat (Semlitsch 1998). Upland habitats immediately surrounding
wetlands serve as important dispersal corridors and are also used as foraging and
aestivation areas for many amphibian species (Semlitsch 1998). Total unaltered area
around the wetland also seems to be an important landscape component in the
maintenance of wetland fauna. Guerry and Hunter (2002) found that wood frogs, green
frogs, eastern newts, spotted salamanders, and salamanders of the blue-spotted/Jefferson's
complex (Ambystoma laterale/A.jeffersonianum) were more likely to occupy ponds in
unaltered landscapes (i.e., intact forested areas).
16
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In riverine habitats, the floodplain landscape typically comprises a continuous corridor of
intact natural vegetation along the stream channel and floodplain. These corridors allow
uninterrupted movement of animals to up- and down-stream portions of the riparian zone
as well as access to adjacent uplands (Gregory et al. 1991). These corridors also allow for
unimpeded movement of surface and overbank flow, which are critical for the distribution
of sediments and nutrients as well as recharging local alluvial aquifers. Fragmentation of
the riverine corridor can occur as a result of human alterations such as roads, power and
pipeline corridors, agriculture activities, and urban/industrial development.
Tests of the Landscape Connectivity metric in conjunction with the Land Use Index metric
found a high level of correlation (redundancy), suggesting that perhaps both are not needed
(Faber-Langendoen et al. 2011). Landscape Connectivity is a simpler metric to apply.
However, the tests were done in a fairly homogeneous region of land uses, and further tests
should be conducted across a wider range of land use types.
This metric is sufficient for both Level 1 and many Level 2 assessments, where it is not
practical to conduct field surveys in the surrounding landscape. But this metric could be
refined by incorporating the idea that some cultural land use types having greater or less
degrees of connectivity to natural ecosystems.
Measurement Protocol: The Landscape Connectivity metric is measured by estimating
connectivity based on a fixed distance from the edge of the buffer that surrounds the
assessment area (AA) (see "Buffer Index," where buffer width is set at 100 m from edge of
AA). The core landscape area is set at 100-250 m and the supporting landscape from 250-
500 m. The metric is fairly simple, treating the landscape in a binary fashion: all land cover
categories are assigned to either a natural or cultural category (see Mclntyre and Hobbs
1999). The assessment should be completed in the office using remote sensing imagery,
such as aerial photographs or satellite imagery, then, where feasible, verified in the field, at
readily accessible points.
The metric could be measured by defining the landscape area based on the watershed or
catchment landscape area, rather than the more general landscape area used here, which
could include areas outside the watershed. Testing is needed to determine how sensitive
the ratings may be to this approach.
17
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Metric Rating:
Table 1.1. Landscape Connectivity Metric Rating.
Metric Rating
EXCELLENT (A)
GOOD(B)
FAIR(C)
POOR(D)
Landscape Connectivity: ALL WETLANDS
Intact: Embedded in 90-100% natural habitat around AA.
Variegated: Embedded in 60-90% natural habitat.
Fragmented: Embedded in 20-60% natural habitat.
Relictual: Embedded in <20% natural habitat.
Data for Metric Rating: See Mclntyre and Hobbs (1999); also see Faber-Langendoen et al.
(2011) for an evaluation of the discriminatory power of this metric based on an assessment
of 277 wetlands in Michigan and Indiana. Lemly and Rocchio (2009) tested user variability
and the performance of this metric in relation to a Level 3 EIA (e.g., vegetation index of
biotic integrity).
Scaling Rationale: Less fragmentation increases connectivity between natural ecological
systems and thus allow for natural exchange of species, nutrients, and water. The
categorical ratings are based on Mclntyre and Hobbs (1999). Their scaling rationale is
summarized in Table 1.2.
Table 1.2. Landscape Connectivity Scaling Rationale.
Metric Rating
EXCELLENT
GOOD
FAIR
POOR
Landscape Connectivity: Scaling Rationale
Connectivity is expected to be high; remaining natural habitat is in good
condition (low modification); and a mosaic with gradients.
Connectivity is generally high, but lower for species sensitive to habitat
modification; remaining natural habitat with low to high modification and
a mosaic that may have both gradients and abrupt boundaries.
Connectivity is generally low, but varies with mobility of species and
arrangement on landscape; remaining natural habitat with low to high
modifications and gradients shortened.
Connectivity is essentially absent; remaining natural habitat generally
highly modified and generally uniform.
In addition, the Heinz Center (2002) used <10% non-forest as a measure of unfragmented
forest (core = 100%; interior=90-99%), and between 10-40% as "connected" forest. The
data on which these breakpoints were established needs to be investigated, and depends
on whether the forest patches are expected to occur in relatively continuous blocks or
18
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naturally occurred in patches (e.g., in prairie or steppe landscapes). The Heinz Center is also
investigating the use of a fragmentation index that takes into account roads that occur
within the surrounding landscape (Cavender-Bares, pers. comm. 2005).
Confidence that reasonable logic and/or data support the metric: Medium/High.
19
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Example:
JUS
Leaend
Assessment Area
100m buffer
250m core landscape
500m supporting landscape
0 100, 200 5 0 Meters ,
• - .^t- JP i*
250m core landscape
500m supporting landscape
Natural Vegetation
Non-Natural Vegetation
Water
Figure 1.1. Landscape Connectivity evaluation based on percent natural vegetation. A) Raw
imagery and B) interpreted natural vegetation versus cultural land cover, with concentric
rings for buffer (100 m radius), core landscape (100 - 250 m radius) and supporting
landscape (250-500 m radius). The percent natural vegetation within the core and the
supporting landscapes determines the Landscape Connectivity rating. In this example, the
Core Landscape has an B rating, and the Supporting Landscape has a C rating (see Table 1.1)
20
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• 2. Land Use Index
Definition: This metric measures the intensity of human dominated land uses in the
surrounding landscape beyond the 100 m buffer, based on an additional 150 m with for the
core landscape and an additional 250 m width for the supporting landscape.
Background: This metric is one aspect of the landscape context of specific stands or
polygons of ecosystems and is based on Hauer et al. (2002) and Mack (2006)..
Metric Type: Stressor
Tier: 1 (remote sensing).
Rationale for Selection of the Variable: The intensity of human activity in the landscape has
a proportionate impact on the ecological processes of natural ecosystems. Assessing land
use incorporates both the aspect of "habitat destruction" and "habitat modification" (sensu
Mclntyre and Hobbs 1999), at least for the non-natural habitats. That is, in addition to the
effect of converting natural habitat to agricultural, urban and other land use modifications,
there is the additional aspect of the intensity of that land use. Human land uses often
directly or indirectly alter many natural ecological processes.
Tests of this metric in conjunction with the Landscape Connectivity metric found a high level
of correlation (redundancy), suggesting that perhaps both are not needed (Faber-
Langendoen et al. 2011). Landscape Connectivity is a simpler metric to apply. However, the
tests were done in a fairly homogeneous region of land uses, and further tests should be
conducted across a wider range of land use types.
Measurement Protocol: The Land Use Index metric is measured by documenting the
surrounding land use(s) within the core and supporting landscape areas. The assessment
should be completed in the office using remote sensing imagery, such as aerial photographs
or satellite imagery, then, where feasible, verified in the field, using roads or transects to
verify land use categories. Ideally, both field data as well as remote sensing tools are used
to identify an accurate percent of each land use within the landscape area, but remote
sensing data alone can be used.
The metric could be measured by defining the landscape area based on the watershed or
catchment landscape area, rather than the more general landscape area used here, which
could include areas outside the watershed. Testing is needed to determine how sensitive
the ratings may be to this approach.
To calculate a Total Land Use Score, estimate the percent of each Land Use type and then
assign the corresponding coefficient (Table 2.1) into the following equation:
Sub-land use score = I LU x PC/100
21
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LU = Land Use Score for Land Use Type
PC = % of adjacent area in Land Use Type
Do this for each land use separately within 100 - 250 m core landscape area, and the 250 -
500 m supporting landscape area, then sum Sub-Land Use Score to arrive at a Total Land
Use Score for both Core Landscape and Supporting Landscape. For example, if 30% of the
Core Landscape area was under moderate grazing (0.3 * 0.6 = 0.18), 10% composed of
unpaved roads (0.1 * 0.1 = 0.01), and 60% was a natural area (e.g., no human land use) (1.0
* 0.6 = 0.6), the Total Core Landscape Land Use Score = 0.79 (0.18 + 0.01 + 0.60). The score
can then be rated using Table 2.2 (i.e., C or Fair) and combined with the Supporting
Landscape Score (with core weighted 2x that of supporting) (Table2.1).
22
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Table 2.1. Current Land Use and Corresponding Land Use Coefficients, modified from
Table 21 in Hauer et al. (2002).
Surrounding Land Use Index:
Worksheet : Land Use Categories
Paved roads/ parking lots
Domestic, commercial, or publicly developed
buildings and facilities (non-vegetated)
Gravel pit / quarry / open pit / strip mining
Unpaved roads (e.g., driveway, tractor trail, 4-
wheel drive roads)
Agriculture (tilled crop production)
Intensively developed vegetation (golf courses,
lawns, etc.)
Vegetation conversion (chaining, cabling, roto-
chopping, clearcut)
Intense recreation (ATV use / camping / popular
fishing spot, etc.)
Military training areas (armor, mechanized)
Heavy grazing by livestock on pastures or native
rangeland
Agriculture /permanent crop (vineyard, orchard,
nursery, hayed pasture, etc.)
Logging or tree removal (50-75% of trees >50 cm
dbh removed)
Commercial tree plantations / holiday tree farms
Recent old fields and other disturbed fallow lands
dominated by ruderal and exotic species
Moderate grazing of native grassland
Moderate recreation (high-use trail)
Mature old fields and other fallow lands with
natural composition
Selective logging or tree removal (<50% of trees
>50 cm dbh removed)
Light grazing or haying of native rangeland
Light recreation (low-use trail)
Natural area / land managed for native vegetation
Coefficient
0.00
0.00
0.00
0.10
0.20
0.20
0.30
0.40
0.40
0.40
0.40
0.50
0.50
0.50
0.60
0.70
0.70
0.80
0.90
0.90
1.00
A >95%, B = 80-94%, C = 40 -79%, D = <40% Total
Land Use Score
Total Land Use Rating
Core Landscape
%Area
-
Score
Supporting L.
%Area
-
Score
Combined Land Use Index Score (Core score x 2) +
(Supporting score x 1) / 3)
Combined Land Use Index Rating
-
23
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Example:
Current Land Use
0 = Developed
0.4 - Agriculture
i 0.5 = Cleared Forest
1.0 = Natural
Figure 2.1. Application of land use coefficients to assess the Land Use Index metric in the
core and supporting landscapes (Nichols and Faber-Langendoen 2012). In this example,
buffer is shown as 50 m (our standard EIA buffer is 100 m). The percent area of each land
use is recorded in Table 2.1.
Metric Rating:
Table 2.2. Land Use Index Metric Rating.
Metric Rating
EXCELLENT (A)
GOOD(B)
FAIR(C)
POOR(D)
Land Use Index: ALL WETLANDS
Average Land Use Score = 1.0-0.95
Average Land Use Score = 0.80-0.95
Average Land Use Score = 0.4-0.80
Average Land Use Score = <0.4
Data for Metric Rating: The coefficients were assigned according to best scientific judgment
regarding each land use's potential impact, and evaluation of tables provided by Hauer et al.
(2002) and Mack (2006). See also Faber-Langendoen et al. (2011) for an evaluation of the
discriminatory power of this metric based on an assessment of 277 wetlands in Michigan
and Indiana. Lemly and Rocchio (2009) tested user variability and the performance of a
variant of this metric in relation to a Level 3 EIA (e.g., vegetation index of biotic integrity).
Scaling Rationale: Land uses have differing degrees of potential impact on ecological
patterns and processes. Some land uses have minimal impact, such as simply altering the
integrity of native vegetation (e.g., recreation and low intensity grazing), while other
24
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activities (e.g., hay production and agriculture) may replace native vegetation with non-
native or cultural vegetation yet still provide potential cover for species movement.
Intensive land uses (e.g., urban development, roads, and mining) may completely destroy
vegetation and drastically alter ecological processes (Hauer et al. 2002, Mack 2006).
Confidence that reasonable logic and/or data support the metric: Medium.
BUFFER
• 3. Buffer Index
Definition: A measure of the overall area and condition of the buffer immediately
surrounding the assessment area (100 m radius), using 3 sub-metrics: (a) Percent of AA
Having Buffer, (b) Average Buffer Width, and (c) Buffer Condition. Wetland buffers are
vegetated, natural areas that surround a wetland.
Background: The buffer of wetlands is important to biotic and abiotic aspects of the
wetland. The Environmental Law Institute (2008) has also recently reviewed the critical role
of buffers for wetlands. We use a somewhat narrowly defined 100 m buffer, but add a
surrounding landscape assessment that extend up to 400 m from the buffer edge (see Table
2 above, and the "Landscape Connectivity" and "Land Use Index" metrics). Here we apply
the buffer metric to the assessment area, which may be a subset of the entire wetland
polygon, if the AA is restricted to a certain size. An assessment of the buffer around the
entire wetland may produce a different rating.
Metric Type: Condition.
Tier: 1 (remote sensing) or 2 (rapid field measure).
Rationale for Selection of the Variable: The Environmental Law Institute (2008) summarizes
extensive data on the rationale for the role of buffers in maintaining ecological integrity of
wetlands. Many studies have looked at specific effects of buffers on water quality, birds
and other attributes of ecosystems. For example, Semlitsch (1998) monitored terrestrial
migrations for six Ambystomid salamander species and found that buffers were critical to
permitting their passage into uplands. They found that buffer areas 164 m from wetland
edges were needed to encompass 95% of population forays.
Measurement Protocol: Metric is adapted from Collins et al. (2006) and USA RAM (2011).
3a. Buffer Metric: Percent of AA Having Buffer
Estimate the length of the AA perimeter contiguous with a natural buffer. Use a 5 m
minimum buffer width and length. Perimeter includes open water (see Table 3.1).
25
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Table 3.1. Guidelines for identifying wetland buffers and breaks in buffers (adapted from
Collins etal. 2006, Table 3.3).
Examples of Land Covers Included
in Buffers
Examples of Land Covers
Excluded from Buffers
Examples of Land Covers
Crossing and Breaking
Buffers
Natural upland habitats and plant
communities; open water*; dirt
roads not hazardous to wildlife;
vegetated levees; rough meadows
or greenbelts; swales and ditches;
foot trails; horse trails; bike trails;
pastures subject to open range
grazing pressure; dry-land farming
areas; non-intensive plantations')";
Conservation Reserve Program
pastures
Parking lots; commercial and
private developments; gravel
or paved roads or very active
roadways and bike trails;
intensive agriculture;
intensive plantations')";
orchards; vineyards;
railroads; pastures subject to
heavy grazing pressure (e.g.,
horse paddock, feedlot, or
turkey ranch); lawns; sports
fields; traditional golf
courses
Large paved roads (two
lanes or larger); residential
areas; bridges; culverts;
paved creek fords; railroads;
sound walls; fences that
interfere with movements
of water, sediment, or
wildlife species that are
critical to the overall
functions of the wetland
*0pen Water: Open water adjacent to the wetland site, such as a lake, large river, or
lagoon, is excluded from the buffer by some wetland protocols because the water quality or
water disturbance regimes (natural waves vs. boat traffic waves) may or may not be in good
condition (e.g., Collins et al. 2006). Here we include open water as part of the buffer, and
handle the condition of the open water using the Buffer Condition sub-metric (3c).
tPlantations: These include plantations, in which the overstory is allowed to mature and
may regain some native component, and in which the understory of saplings, shrubs, and
herbs are native or naturalized species and not strongly manipulated, i.e., they are not
"row-crop tree plantings" with little to no vegetation in the understory, typical of intensive
plantations.
26
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Map Legend:
BUFFER (100 ml
^AA WITHOUT BUFFER
AA (40 m radius)
I I Wetland Boundary
H AA CENTER
250
300 Meters
Hfc-
Figure 3.1. Example of calculation for Percent of AA Having Buffer. The wetland
boundary is marked by a thin green line. The assessment area (AA) is shown by the inner
circle; yellow indicates portions of the AA perimeter that adjoin a buffer land cover (i.e.,
buffer of at least 5 m width and 5 m in extent). The red indicates that part of AA perimeter
lacking a buffer. In this case, about 86% of the AA perimeter has buffer.
3b. Buffer Metric: Average Buffer Width
Assessment Protocol:
1. Determine the areas considered to be buffer.
2. Draw eight straight lines from the edge of the AA out through the buffer area at regular
intervals in the portions of perimeter that are considered buffer (see Figure 3.2 below).
Drawing the lines on the printed map makes verification and Quality Assurance procedures
easier.
3. Measure the buffer width.
4. Assign a metric score based on the average buffer width.
27
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Table 3.2. Measuring Average Buffer Width. See Figure 3.2.
Line
1
2
3
4
5
6
7
8
Average Buffer
Width (m)
Buffer Width (m)
(max = 100 m)
63
0
0
100
100
100
100
100
70
Map Legend;
BUFFER £100 m)
WITHOUT BUFFER
AA(4D m radius)
AA CENTER
A/NO BUFFER LINES
BUFFER LINES
Wetland Boundary
300 Meters
J
Figure 3.2. Example of Average Buffer Width calculation. The wetland boundary is marked
by a thin green line; the AA circular perimeter is yellow; the 100 m buffer assessment area
around the AA is dark blue, and the eight transect lines are assessed for the buffer width.
The blue segment of each transect indicates buffer is present and the purple segment
indicates non-buffer land use. For example, transect 1 (north) has 63 m of buffer (see Table
3.2). An additional level of evaluation may be completed by having field crews walk the
four cardinal direction lines to assess buffer condition, if logistically feasible.
28
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There is also value in adjusting the rating of upslope buffer width based on degree of slope.
Slope can be estimated in the field or using imagery. The following adjustment should be
used for buffers upslope of the AA (Environmental Law Institute 2008, based on data from
Island County, Washington).
Table 3.3. Adjusting Rating of Upslope Buffer.
Slope Gradient
5-14%
15-40%
>40%
Additional Buffer Width Multiplier
1.3
1.4
1.5
3c. Buffer Metric: Buffer Condition
Estimate the overall condition of vegetation cover within that part of the perimeter that has
a buffer. That is, if buffer length is only 30% of the perimeter, then assess condition within
that 30%. Condition is based on cover of native vegetation, disruption to soils, signs of
reduced water quality, amount of trash or refuse, and intensity of human visitation or
recreation, including from foot or boat traffic. The evaluation can be made by scanning an
aerial photograph in the office, followed by ground-truthing, as needed, the eight lines
shown in Figure 3.2.
Metric Rating:
Table 3.4. Buffer Index Metric Rating.
Buffer Sub-metrics: ALL WETLANDS
Sub-metric
Ratings
EXCELLENT
(A)
VERY
GOOD (A-)
a. Percent of
AA having
Buffer
Buffer is 90 -
100% of AA
Buffer is >75 -
89% of AA
b. Average Buffer
Width (m)
Average buffer
width is >95 m,
adjusted for slope.
Average buffer
width is 75 -94 m,
after adjusting for
slope.
c. Buffer Condition
Buffer is characterized by abundant (>95%)
cover of native vegetation, with intact soils,
no evidence of loss in water quality and little
or no trash or refuse.
Buffer is characterized by substantial (75-
95%) cover of native vegetation, intact or
moderately disrupted soils, minor evidence of
loss in water quality, moderate or lesser
amounts of trash or refuse, and minor
intensity of human visitation or recreation.
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GOOD(B)
Buffer is 50
75% of AA
Average buffer
width is 50 -74 m,
after adjusting for
slope.
Buffer is characterized by a moderate (50-
75%) cover of native vegetation, and either
moderate or extensive soil disruption,
moderate to extensive evidence of loss in
water quality, moderate or greater amounts
of trash or refuse, and moderate intensity of
human visitation or recreation.
FAIR(C)
Buffer is 25-
49% of AA
Average buffer
width is 25-49 m,
after adjusting for
slope.
Buffer is characterized by a low (25- 50%)
cover of native vegetation, barren ground
and highly compacted or otherwise disrupted
soils, strong evidence of loss in water quality,
with moderate or greater amounts of trash or
refuse, and moderate or greater intensity of
human visitation or recreation.
POOR(D)
Buffer is
<25% of AA
Average buffer
width is <25 m,
after adjusting for
slope.
Very low (<25%) cover of native plants,
dominant (>75%) cover of non-native plants,
extensive barren ground and highly
compacted or otherwise disrupted soils,
moderate - great amounts of trash, moderate
or greater intensity of human visitation or
recreation, OR no buffer at all.
Buffer Index
The buffer index is adapted from Collins et al. (2006). The index integrates the three sub-
metrics, but the Buffer Condition is given half the weight of the Percent of AA with Buffer
and the Average Buffer Width, as its influence on overall on-site condition is not as strong
as the other two. First convert the letter scores to numeric values (e.g., A = 4, A- = 3.5, B =
3, C = 2, D = 1). Then proceed as follows:
1. Percent of AA with Buffer + Average Buffer Width / 2= Average Buffer Score
2. Average Buffer Score + (Average Buffer Condition X 0.5) / 1.5 = Buffer Index
The merit of integrating the submetrics is that they are closely related, and the overall index
puts the metric on a comparable level of distinctiveness with other metrics. See Table 3.5
for the ratings for the Buffer Index Metric.
Table 3.5. Example of a Buffer Index Metric Rating.
Metric Rating
EXCELLENT (A)
GOOD(B)
FAIR(C)
POOR(D)
Buffer Index: ALL WETLANDS
3.5-4.0
2.5-3.5
1.5-2.5
1-1.5
30
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Data for Metric Rating: See Environmental Law Institute (2008); also see Faber-Langendoen
et al. (2011) for an evaluation of the discriminatory power of this metric based on an
assessment of 277 wetlands in Michigan and Indiana. Lemly and Rocchio (2009) tested user
variability and the performance of a variant of this metric in relation to a Level 3 EIA (e.g.,
vegetation index of biotic integrity).
Scaling Rationale: There is abundant evidence on the value of even narrow buffers between 5
and 25 m (Environmental Law Institute 2008); thus the rating for the "Percent of AA Having
Buffer" is extended to have an A-E rating. More generally, setting buffer widths is based on
assessing edge effects. The edge effect width of 100 m is based in part on data from Kennedy
et al. (2003), who reviewed edge effects for both plants and animals. They recommend a buffer
up to 230-300 m as a precautionary threshold. A buffer width of 100 m is also a widely used
minimum threshold (e.g., USA RAM). Here we work with 100 m as the "inner buffer" distance,
but separately assess the surrounding landscape (core landscape up to 250 m, and supporting
landscape to 500 m) (see the "Landscape Connectivity" and "Land Use Index" metrics).
Confidence that reasonable logic and/or data support the metric: Medium/High.
SIZE
• 4. Absolute Patch Size1
Definition: A measure of the current absolute size (ha) of the entire wetland type polygon
or patch. The metric is assessed with respect to expected patch sizes for the type across its
range.
Background: This metric is one aspect of the size of specific occurrences of a wetland type.
The metric rating is taken from NatureServe's Ecological Integrity Assessment Working
Group (Faber-Langendoen et al. 2008). Assessors are sometimes hesitant of using absolute
size as part of an EIA out of concern that a small, high quality example will be down-ranked
unnecessarily. We address these concerns to a degree by providing a pattern-type scale, so
that types that typically occur as small patches (seepage fens) can use a different rating
than types that may occur over large, extensive areas (e.g., marshes or boreal bogs/fens).
Size is also more accurately assessed at finer scales of classification (e.g., Systems or
Groups). Then, for example, Midwest fens are compared separately from boreal fens.
Metric Type: Condition.
31
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Tier: 1 (remote sensing); 2 (rapid field measure).
Rationale for Selection of the Variable: The role of absolute size in assessing integrity is
complex. First, higher ratings for size may not always indicate increased integrity. For some
types absolute size can vary widely for entirely natural reasons (e.g., a forest type may have
very large occurrences on rolling landscapes, and be restricted in other landscapes to small
occurrences on north slopes or ravines).
Second, size overlaps with landscape context as a metric, depending on the scale of the
wetland type. Size and landscape context both address spatial aspects of an occurrence.
Very large sized, matrix occurrences essentially define the landscape context. Standards for
establishing the size metric ratings sometimes can be confounded with criteria for
Landscape Context. For example, the use of Minimum Dynamic Area (MDA) as the basis for
the Size criteria is misleading, at least at the system or natural community level, because
MDA is really assessing the landscape area within which an occurrence is embedded and on
which it depends for its persistence (Leroux et al. 2007). MDA is typically applied to types at
very broad classification scales (e.g., northern hardwood and boreal forest landscapes).
Nonetheless, size can be an important aspect of integrity. For some types, diversity of
animals or plants may be higher in larger occurrences than in small occurrences that are
otherwise similar. For occurrences in mosaics, the larger occurrences often have more
micro-habitat features. Larger wetlands are more resistant to hydrologic stressors; larger
uplands more resistant to invasion by exotics, since they buffer their own interior portions.
Thus size can serve as a readily measured proxy for some ecological processes and the
diversity of interdependent assemblages of plants and animals.
Note that NatureServe's methodology for evaluation patches or polygons (the "Element
Occurrence Rank") integrates integrity and conservation values, so with respect to size,
larger occurrences are generally presumed to be more value for conservation purposes, as
they provide a better representation of the type being conserved. We keep the Size metrics
separate within a Primary "Size Rank Factor" so that users can readily determine the role of
these metrics in the overall EIA scores. Some consideration had been given to combining
size metrics with a broader "landscape context and size rank factor," so that interactions
between size and landscape context could be dealt with first, before considering their joint
interaction with condition. Users focused strictly on ecological integrity may find this an
appealing option.
Measurement Protocol: The choice of patch type for the particular wetland being assessed
is an important first step (see Table 4.1), and should be based on knowledge of the typical
sizes of mid to broad scale ecological types (Formations, Groups, Systems) found in
excellent sites. Knowledgeable ecologists in the state or region should be consulted.
Ecological System and Group types have all been assigned to a pattern type, so if the site is
classified to Ecological System or Group, that information can be readily attained
(www.natureserve.org/explorer).
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Table 4.1. Definitions of various patch types that characterize the spatial patterning of
ecosystems (ecological community and system types) (Comer et al. 2003).
PATCH TYPE
Matrix
Large Patch
Small Patch
Linear
DEFINITION
Ecosystems that form extensive and contiguous cover, occur on the most extensive
land/arms, and typically have wide ecological tolerances. Disturbance patches
typically occupy a relatively small percentage (e.g., <5%) of the total occurrence.
In undisturbed conditions, typical occurrences range in size from 2,000-
10,000 ha (100 km2) or more.
Ecosystems that form large areas of interrupted cover and typically have
narrower ranges of ecological tolerances than matrix types. Individual
disturbance events tend to occupy patches that can encompass a large proportion
of the overall occurrence (e.g., >20%). Given common disturbance dynamics,
these types may tend to shift somewhat in location within large landscapes over
time spans of several hundred years. In undisturbed conditions, typical
occurrences range from 50-2,000 ha.
Ecosystems that form small, discrete areas ofvegetation cover, typically limited in
distribution by localized environmental features. In undisturbed conditions,
typical occurrences range from 1-50 ha.
Ecosystems that occur as linear strips. They are often ecotonal between
terrestrial and aquatic ecosystems. In undisturbed conditions, typical
occurrences range in linear distance from 0.5-100 km.
Absolute Size can be measured in CIS using aerial photographs, orthophoto quads, National
Wetland Inventory maps, or other data layers. Size can also be estimated in the field using
7.5 minute topographic quads, NFS Vegetation Mapping maps, National Wetland Inventory
maps, or a global positioning system. Wetland boundaries are not delineated using
jurisdictional methods (U.S. Army Corps of Engineers 1987); rather, they are delineated by
ecological guidelines for delineating the boundaries of the wetland type, based on the
International Vegetation Classification, equivalent National Vegetation Classifications,
National Wetland Inventory, or other wetland classifications.
Metric Rating:
Two metric ratings may be used. One is based on an absolute patch size rating, in the context
of the typical patch type of the wetland (Table 4.2). The other is a comparative rating, based on
the known distribution of wetland sizes for a wetland type (Table 4.3). If information on both
ratings is available, then the rating that generates the higher rating is used.
33
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Table 4.2. Absolute Patch Size Metric Rating: Area by Patch Type. General guidelines for
assessing patch size of wetlands. A determination first needs to be made as to the typical
spatial pattern type of the wetland type in the ecoregions or across its entire range.
Metric Rating
EXCELLENT
(A)
GOOD (B)
FAIR(C)
POOR(D)
Absolute Size Metric (hectares): ALL WETLANDS, BY PATTERN TYPE
MATRIX LARGE PATCH SMALL PATCH LINEAR
Matrix (ha)
>25,000
500-25,000
50-500
<50
Very
Large
Patch (ha)
>500
100-500
20 -100
<20
Large
Patch
(ha)
>125
25-125
5-25
<5
Medium-
Small
Patch (ha)
>50
10-50
2-10
<2
Small
Patch (ha)
>10
2-10
0.5-2
0.5
Very Small
Patch (ha)
>2
0.5-2
0.1-0.5
0.1
Linear
(length in
km)
>5 km
1-5 km
0.1- 1km
<0.1 km
OR
Metric Rating
Spatial
Pattern Type
EXCELLENT
(A)
GOOD (B)
FAIR(C)
POOR(D)
Absolute Size Metric (acres): ALL WETLANDS, BY PATTERN TYPE
MATRIX LARGE PATCH SMALL PATCH LINEAR
Matrix (ac)
>6,000
1,250-6,000
125 - 1,250
<125
Very
Large
Patch (ac)
>1,250
250-
1,250
50 - 250
<50
Large
Patch
(ac)
>300
60-300
12-60
<12
Medium-
Small
Patch (ac)
>125
25 - 125
5-25
<5
Small
patch (ac)
>25
5-25
1-5
1
Very
Small
Patch (ac)
>5
1-5
0.25-1.25
0.25
Linear (mi)
>3 mi
0.6-3 mi
0.06-0.6 mi
<0.06 mi
Table 4.3. Absolute Patch Size Metric Rating: Comparative.
Metric Rating
Absolute Patch Size: ALL WETLANDS
EXCELLENT (A)
Patch size is very large compared to other examples of the same type (i.e.,
top 10% based on known and historic occurrences; most area-sensitive
indicator species very abundant within occurrence).
GOOD(B)
Patch size is large compared to other examples of the same type (i.e.,
within 10-30% based on known and historic occurrences; many area-
sensitive indicator species moderately abundant within occurrence).
FAIR(C)
Patch size is medium to small compared to other examples of the same
type, (i.e., within 30-70% of known or historic sizes; some area-sensitive
indicator species are able to sustain a minimally viable population; many
characteristic species are of low abundance but present).
POOR(D)
Patch size is small to very small; occurrence too small to sustain full
diversity and function of the type (e.g., smallest 30% of known or historic
occurrences; both key area-sensitive indicator species and characteristic
species are sparse to absent).
34
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Data for Metric Rating: See Faber-Langendoen et al. (2011) for an evaluation of the
discriminatory power of this metric based on an assessment of 277 wetlands in Michigan
and Indiana. Lemly and Rocchio (2009) tested user variability and the performance of this
metric in relation to a Level 3 EIA (e.g., vegetation index of biotic integrity).
Scaling Rationale: Scaling criteria are based on the NatureServe Ecological Integrity
Assessment Working Group (Faber-Langendoen et al. 2008). Our scaling has been informed
by considerations of spatial pattern types, but no general guidelines have yet been
established to assess wetland patch size. Tables 4.2 and 4.3 provide some standard
guidance.
Confidence that reasonable logic and/or data support the metric: Medium.
• 5. Relative Patch Size
Definition: A measure of the current size of the wetland (in hectares) divided by the historic
wetland size (within most recent period of intensive settlement or 200 years), multiplied by
100.
Background: This metric is one aspect of the size of specific occurrences of a wetland type.
The metric rating is adapted from Rondeau (2001) and Faber-Langendoen et al. (2008),
where it is referred to as "Patch Size Condition."
Metric Type: Condition.
Tier: 1 (remote sensing); 2 (rapid field measure).
Rationale for Selection of the Variable: Relative size is an indication of the amount of the
wetland change caused by human-induced disturbances. It provides information that
allows the user to calibrate the current size to the historic area of the wetland. For
example, if a wetland has a current size of 1 hectare but the historic size was 2 hectares,
this indicates that half (50%) of the original wetland was lost or severely degraded.
Complicating the use of this metric is that in some cases, wetland size increases due to
human disturbances.
Measurement Protocol: Relative size can be measured in CIS using aerial photographs,
orthophoto quads, National Wetland Inventory maps, or other data layers. Field
assessments of current size may be required since it can be difficult to discern the historic
area of the wetland from remote sensing data. However, use of old aerial photographs may
also be very helpful, as they may show the historic extent of a wetland.
Relative size can also be estimated in the field using 7.5 minute topographic quads, NFS
Vegetation maps, National Wetland Inventory maps, or a global positioning system.
35
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Wetland boundaries are not delineated using jurisdictional methods (U.S. Army Corps of
Engineers 1987); rather, they are delineated by ecological guidelines for delineating the
boundaries of the wetland type, based on a standard wetland classification.
The definition of the "historic" timeframe will vary by region, but generally refers to the
intensive Euro-American settlement that began in the 1600s in the eastern United States
and extended westward into the 1800s. If the historic time frame is unclear, use a
minimum of a 50 year time period, long enough to ensure that the effects of wetland loss
are well-established, and the wetland has essentially adjusted to the changes in size.
Metric Rating:
Table 5.1. Relative Patch Size Metric Rating:
Metric Rating
EXCELLENT (A)
GOOD(B)
FAIR(C)
POOR(D)
Relative Patch Size: ALL WETLANDS
Occurrence is at, or only minimally reduced (<5%) from its full original,
natural extent, and has not been artificially reduced in size. See note
below for interpretation of "reduction."
Occurrence is only modestly reduced (5-20%) from its original natural
extent. See note below for interpretation of "reduction."
Occurrence is substantially reduced (20-50%) from its original, natural
extent. See note below for interpretation of "reduction."
Occurrence is heavily reduced (>50%) from its original, natural extent
See note below for interpretation of "reduction." .
*Note: Reduction in size for metric ratings A-D can include conversion or disturbance (e.g., changes
in hydrology due to roads, impoundments, development, human-induced drainage; or changes
caused by recent cutting). Assigning a metric rating depends on the degree of reduction.
Data for Metric Rating: See Faber-Langendoen et al. (2011) for an evaluation of the
discriminatory power of this metric based on an assessment of 277 wetlands in Michigan
and Indiana. Lemly and Rocchio (2009) tested user variability and the performance of this
metric in relation to a Level 3 EIA (e.g., vegetation index of biotic integrity).
Scaling Rationale: Scaling criteria are based on Rondeau (2001), NatureServe Ecological
Integrity Assessment Working Group (2008) and best scientific judgment.
Confidence that reasonable logic and/or data support the metric: Medium.
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VEGETATION
For various aspects of the vegetation metrics, we rely on variants based on NVC Formations
(see also Table 5 above).
Table 6.1. Metric Variants (v) for Vegetation and Soils by NVC Formation.
METRIC
Metric Variant by NVC
Formation Type
FLOODED & SWAMP
FOREST
MANGROVE
FRESHWATER MARSH,
WET MEADOW &
SHRUBLAND
SALT MARSH
BOG & FEN
AQUATIC VEGETATION
VEGETATION
6. Vegetation
Structure
vl
v3
VEGETATION
7. Woody
Regeneration
vl
VEGETATION
10. Vegetation
Composition
vl*
SOILS
14. Physical
Patch Types
vl
v3
SOILS
15. Soil
Surface
Condition
vl
vl
* Metric can be refined at the Macrogroup or Group level of the NVC, or using Ecological
Systems.
• 6. Vegetation Structure
Definition: An assessment of the overall structural complexity of the vegetation layers and
growth forms, including presence of multiple strata, age and structural complexity of
canopy layer, and evidence of the effects of disease or mortality on structure.
Background: This metric has been drafted by NatureServe's Ecological Integrity Assessment
Working Group (Faber-Langendoen et al.2008).
Metric Type: Condition.
Tier: 2 (rapid field measure).
Rationale for Selection of the Variable: In wetlands, vegetation structure can have an
important controlling effect on composition and processes. The patch structure is an
important reflection of vegetation dynamics and for creating heterogeneity within the
community. Plants strongly influence the quantity, quality, and spatial distribution of water
and sediment within wetlands. For example, vascular plants entrap suspended sediment
and contribute organic matter to the sedimentary layers. Plants reduce wave energy and
decrease the velocity of water flowing through wetlands, potentially reducing flooding or
erosion further down in a watershed. Vascular and non-vascular plants and large patches of
macro algae function as habitat for wetland wildlife (Collins et al. 2006, Rocchio 2007).
37
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The patch structure is often homogenized by disturbance such as logging of wetland forests,
soil compaction, or heavy grazing by livestock and geese in fresh and salt marshes. In
general, beaver-caused disturbances are treated as part of the range of variability expected
within minimally-disturbed stands. Impacts from beavers can affect almost all wetland
types, but they are most commonly associated with wetlands along streams and ponds
Beaver dams create impoundments that typically kill woody plants and drastically alter
structure, species composition, and hydrology. These natural disturbances generally occur
in cycles that span decades. As the beaver deplete their woody food supply they abandon
dam maintenance and move to other suitable habitat. Eventually, when the dam fails, and
the beaver pond drains, the resulting wet mud flats are quickly colonized by annuals, then
herbaceous perennials, and finally woody plants after several years. Without further
disturbance over subsequent decades, succession will progress toward a more mature
natural community. Wetland communities that are commonly associated with drainages
used by beaver include aquatic beds, emergent marshes, wet meadows, shrub thickets, and
forested wetlands, but peatlands in drainages are influenced by beaver activity as well
(Tiner 1998, Thompson and Sorenson 2000). The cycle of natural disturbances caused by
beaver can be difficult to interpret, because beaver were heavily trapped and eliminated
from large parts of the landscape in the 19th century, then subsequently reintroduced. Thus
the watersheds and landscapes may still be recovering from the absence of beaver.
Measurement Protocol: This metric consists of evaluating the horizontal and vertical
structure of the vegetation relative to the reference condition of structural heterogeneity of
the dominant growth forms. The protocol is a visual evaluation of variation in overall
structure (e.g., age, size, and density), overall canopy cover, frequency of canopy gaps with
regeneration, and number of different age/size patches represented. A field form should be
used, as shown in Table 7.1, which describes structure using either strata or growth forms
(Jennings et al. 2009). For the strata method, list all major strata - tree, shrub, herb, non-
vascular, floating, submerged - then estimate strata cover and cover of dominant (>5%
cover), characteristic, and exotic species. For the growth form method, list major growth
forms - tree (subdivided into overstory and regeneration), shrub (subdivided by tall and
medium/low), herb, non-vascular, floating, submerged, epiphyte, and liana -then estimate
strata cover and cover of dominant (>5%), characteristic, and exotic species. The prevailing
height of a stratum or growth form is used to determine its height class. For example,
although the tree canopy may vary from 10 to 30 m, the prevailing height may be 25 m. For
particular field applications, it can be helpful for field crews to create a standard list of vine
/ liana species, or even tree species.
38
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Table 6.1. An example of a vegetation structure/growth form vertical profile.
VEGETATION GROWTH FORM PROFILE
Cover scale: 0, 1-4%, then +5% (10, 15, 20, etc.)
Growth forms / strata
Tm. Mature (tall) Tree
(>5m)
Ts. Sapling (medium) Tree
(2-5 m)
Te. Seedling (small) Tree
(<2m)
S1. Tall Shrub
(>2m)
S2. Short/ Dwarf-shrub
(<2m)
HI Herbaceous
A1. Floating-leaved Aquatic
A2. Submerged Aquatic
N. Non-vascular - Moss
- Lichen
-Algae
V. Vine /Liana
Cover
(%)
Ht(m)
To
nearest 5
m.
X
X
X
X
X
VEGETATION SPECIES PROFILE BY GROWTH FORM
Dominant Species: List all species and their absolute cover if >5%
cover, to + 5% (e.g., 10% = 5-14 etc.). List all exotic spp. <5% cover.
Optional: List other characteristic native spp. <5% (1-4%, <1% =T).
e.g., Acerrubrum- 15%
39
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Table 6.2. Example of a vegetation structure spatial profile description.
VEGETATION PROFILE
Structural Stage: Estimate the % aerial cover of all trees in each structural stage to nearest 10%. Evaluate only the
top canopy layer (i.e. view canopy from above, but canopy might be sapling layer). Total should add to 100%. [dbh
ranges - eastern N.A. temperate]
_% woody stages absent or seedlings (i.e. stems < 2m)
_% Sapling: stems < 10 cm (< 4") dbh
_%Large: stems 30—50 cm (12-20") dbh
_ %Very Large: stems >50 cm (20") dbh
. %Pole: stems 10-30 cm (4 - 12") dbh
Field survey method for estimating structure may be either 1) qualitative data where the
observers walks the entire AA and make notes on vegetation strata, their cover, and exotic
species, using tables such as shown in Table 6.1 or 6.2 above or2) quantitative data, where a
fixed area is surveyed, using either plots or transects. The plot or transect is typically a
"rapid" plot, but a single intensive plot can also be taken (Appendix 3).
Metric Rating:
Metric ratings can be assigned using Table 6.3 based on variants by NVC Formation class.
The metric can be further improved by using a mid-scale classification unit, such as
Ecological System or NVC Group.
Table 6.3. Vegetation Structure Metric Rating: Variants are provided in six separate tables
by NVC Vegetation Formation (VI: Flooded & Swamp Forest, V2: Mangrove, V3: Freshwater
Marsh, Wet Meadow & Shrubland, V4: Salt Marsh, V5: Bog & Fen, and V6: Aquatic
Vegetation.
Metric Rating
EXCELLENT (A)
GOOD (B)
FAIR (C)
POOR (D)
VI: Vegetation Structure Variant: FLOODED & SWAMP FOREST
FLOODED & SWAMP FOREST: Canopy a mosaic of small patches of different
ages or sizes, including old trees and canopy gaps containing regeneration, AND
number of live stems of medium size (30-50 cm / 12-20"dbh) and large size (>50
cm / >20" dbh) well within expected range.
FLOODED & SWAMP FOREST: Canopy largely heterogeneous in age or size, but
with some gaps containing regeneration or some variation in tree sizes, AND
number of live stems of medium and large size within or very near expected
range.
FLOODED & SWAMP FOREST: Canopy somewhat homogeneous in age or size,
AND number of live stems of medium and large size below but moderately near
expected range.
FLOODED & SWAMP FOREST: Canopy very homogeneous, in size or age OR
number of live stems of medium and large size well below expected range.
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Metric Rating
EXCELLENT (A)
GOOD (B)
FAIR (C)
POOR (D)
1/2: Vegetation Structure Variant: MANGROVE: [metric variant under
development]
MANGROVE: Canopy heterogeneous, with patches of different ages or sizes,
including old trees and young saplings. No evidence of human impacts.
MANGROVE: Canopy largely heterogeneous in age or size, but with some gaps
containing regeneration or some variation in tree sizes. Negative human
impacts to structure (such as cutting) are minor.
MANGROVE: Canopy somewhat homogeneous in age or size. Negative human
impacts to structure (such as cutting) are moderate.
MANGROVE: Canopy very homogeneous, in size or age. Negative human
impacts to structure (such as cutting) are major.
Metric Rating
EXCELLENT (A)
GOOD (B)
FAIR (C)
POOR (D)
1/3: Vegetation Structure Variant: FRESHWATER MARSH, WET MEADOW &
SHRUBLAND [metric variant under development]
FRESHWATER MARSH, WET MEADOW & SHRUBLAND: Vegetation structure is
at or near minimally disturbed natural conditions. Little to no structural
indicators of degradation evident.
FRESHWATER MARSH, WET MEADOW & SHRUBLAND: Vegetation structure
shows minor alterations from minimally altered from minimally disturbed
natural conditions. Structural indicators of degradation are minor (e.g. levels of
grazing, mowing).
FRESHWATER MARSH, WET MEADOW & SHRUBLAND: Vegetation structure is
moderately altered from minimally disturbed natural conditions. Structural
indicators of degradation are moderate (e.g. levels of grazing, mowing).
FRESHWATER MARSH, WET MEADOW & SHRUBLAND: Vegetation structure is
greatly altered from minimally disturbed natural conditions. Structural
indicators of degradation are strong (e.g. levels of grazing, mowing).
Metric Rating
EXCELLENT (A)
GOOD (B)
FAIR (C)
POOR (D)
1/4: Vegetation Structure Variant: SALT MARSH (salt/brackish marsh &
shrubland) [Metric variant under development]
SALT MARSH: Vegetation structure is at or near minimally disturbed natural
conditions. Little to no structural indicators of degradation evident.
SALT MARSH: Vegetation structure shows minor alterations from minimally
disturbed natural conditions. Structural indicators of degradation are minor.
SALT MARSH: Vegetation structure is moderately altered from minimally
disturbed natural conditions. Structural indicators of degradation are moderate.
SALT MARSH: Vegetation structure is greatly altered from minimally disturbed
natural conditions. Structural indicators of degradation are strong.
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Metric Rating
1/5: Vegetation Structure Variant: BOG & FEN
EXCELLENT (A)
BOG & FEN: Peatland is supporting structure with little to no evident influence
of negative anthropogenic factors. Some very wet peatlands may not have any
woody vegetation or only scattered stunted individuals. Woody vegetation
mortality is due to natural factors. The site meets near minimally disturbed
condition.
GOOD (B)
BOG & FEN: Generally, peatland structure has only minor negative
anthropogenic influences present or the site is still recovering from major past
human disturbances. Mortality or degradation due to grazing, limited timber
harvesting or other anthropogenic factors may be present although not
widespread. The site can be expected to meet minimally disturbed condition in
the near future if negative influences do not continue.
FAIR (C)
BOG & FEN: Peatland structure has been moderately influenced by negative
anthropogenic factors. Expected structural classes are not present. Human
factors may have diminished the condition for woody vegetation. The site will
recover to minimally disturbed condition only with the removal of degrading
influences and moderate recovery times.
POOR (D)
BOG & FEN: Expected peatland structure is absent or much degraded due to
anthropogenic factors. Woody regeneration is minimal and existing structure is
in poor condition, unnaturally sparse, or depauperate. Recovery to minimally
disturbed condition is questionable without restoration or will take many
decades.
Metric Rating
EXCELLENT (A)
GOOD (B)
FAIR (C)
POOR (D)
V6: Vegetation Structure Variant: AQUATIC VEGETATION [Metric variant under
development]
AQUATIC VEGETATION: Vegetation structure is at or near minimally disturbed
natural conditions. No structural indicators of degradation evident.
AQUATIC VEGETATION: Vegetation structure shows minor alterations from
minimally disturbed natural conditions. Structural indicators of degradation are
minor.
AQUATIC VEGETATION: Vegetation structure is moderately altered from
minimally disturbed natural conditions. Structural indicators of degradation are
moderate.
AQUATIC VEGETATION: Vegetation structure is greatly altered from minimally
disturbed natural conditions. Structural indicators of degradation are strong.
Data for Metric Rating: See Faber-Langendoen et al. (2011) for an evaluation of the
discriminatory power of this metric based on an assessment of 277 wetlands in Michigan
and Indiana.
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Scaling Rationale: This metric has been scaled based on scientific judgment of
NatureServe's Ecological Integrity Assessment Working Group (Faber-Langendoen et al.
2008) and survey work in Michigan and Indiana wetlands (Faber-Langendoen et al. 2012).
The metric is scaled based on the similarity between the observed vegetation structure and
what is expected based on reference (or minimally disturbed natural) conditions. Reference
conditions reflect the accumulated experience of field ecologists, studies from sites where
natural processes are intact, regional surveys and historic sources. The basis for assigning
the ratings should be documented on the field forms.
Assessing structure is challenging in herbaceous and shrub wetlands, e.g., freshwater
marshes vary in their complexity. Some marshes are structurally simple, such as the
Everglades sawgrass types, or freshwater bulrush marshes. Others may have combinations
of high, medium, or low structure. For example, in peatlands in the western U.S., some
woody species (e.g., Spiraea douglasii, Myrica gale, and Pinus contorta) may expand rapidly
in degraded examples caused by hydrologic change, nutrient loading, and fire suppression
(J. Christy pers. comm. 2008), and increased woody structure means increased degradation.
Thus, down-rating based on simplicity of structure, per se, should be avoided.
Confidence that reasonable logic and/or data support the metric: Medium.
• 7. Woody Regeneration
Definition An assessment of tree regeneration.
Background: This metric was developed by NatureServe and Natural Heritage Program staff,
and applied in a study in Michigan and Indiana (Faber-Langendoen et al. 2012). It combines
both structural and compositional information, in that regeneration abundance is assessed
with respect to native tree and shrub species.
Metric Type: Condition.
Tier: 2 (rapid field measure).
Rationale for Selection of the Variable: The tree regeneration and shrub layers provide
independent information on the structural characteristics, ecological processes, and
stressors (such as herbivore browsers) found at the site, and indicate potential future
canopy composition. We rely on a qualitative evaluation for our rapid assessment, which
may only detect substantial degradation. We recognize that a more rigorous approach is
often necessary to accurately assess this metric (e.g., Tierney et al. 2009).
Measurement Protocol: This metric consists of evaluating the tree regeneration layer (tree
seedlings less than 1.3 m tall and saplings 1.3+ m tall and up to 10 cm dbh), and/or the
shrub regeneration layer. The protocol is a visual evaluation of abundance of tree seedlings
and saplings and/or younger shrub growth. Information on this metric can be gained from
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tables that describe composition using strata or growth forms (Jennings et al. 2009) (see
"Vegetation Structure" metric, Table 6.1). For the growth form method, list major growth
forms - tree (subdivided into overstory and regeneration), shrub (subdivided by tall and
medium/low), herb, non-vascular, floating, submerged, epiphyte, and liana -then estimate
strata cover and cover of dominant (>5%), characteristic, and exotic species.
The field survey method for estimating woody regeneration may be either a (1) Site Survey
(semi-quantitative) method where the observers walk the entire AA, and make notes on
vegetation strata, their cover, and native vs. exotic species or (2) Quantitative Plot Data,
where a fixed area is surveyed, using either plots or transects. The plot or transect is
typically a "rapid" plot, but a single intensive plot can also be taken (Appendix 3).
Metric Rating:
Table 7.1. Woody Regeneration Metric Rating. The metric is typically applied in forested
wetlands, but can be used for shrublands or any other wetland with woody vegetation.
Metric Rating
EXCELLENT (A)
GOOD(B)
FAIR(C)
POOR(D)
Woody Regeneration: ALL WETLANDS (except for Aquatic
Vegetation)
Native tree saplings and/or seedlings or shrubs common to the type
present in expected amounts and diversity; obvious regeneration.
Native tree saplings and/or seedlings or shrubs common to the type
present but less amounts and diversity than expected.
Native tree saplings and/or seedling or shrubs common to the type present
but low amounts and diversity; little regeneration.
No, or essentially no regeneration of native woody species common
type.
to the
Data for Metric Rating: See Faber-Langendoen et al. (2011) for an evaluation of the
discriminatory power of this metric based on an assessment of 277 wetlands in Michigan
and Indiana. Lemly and Rocchio (2009) tested user variability and the performance of a
variant of this metric in relation to a Level 3 EIA (e.g., vegetation index of biotic integrity).
Scaling Rationale: The metric is scaled based on field judgments of expected natural
regeneration within the AA, and evidence of heavy browsing or grazing of the woody layers.
The metric also addresses situations where native diversity of the tree regeneration layer or
shrub layer is reduced through anthropogenic disturbance or increased native herbivory.
Confidence that reasonable logic and/or data support the metric: Medium.
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• 8. Native Plant Species Cover
Definition: A measure of the relative percent cover of all plant species in the AA that are
native to the region. The metric is typically calculated by estimating total absolute cover of
all vegetation (summing total cover by major strata), subtracting total exotic species cover,
and expressing the total native species cover as a percentage of the total vegetative cover.
Background: This metric has been developed by NatureServe's Ecological Integrity
Assessment Working Group (Faber-Langendoen et al. 2008). To a certain degree this metric
is the converse of the "Invasive Plant Species Cover." However, the Native Plant Species
Cover metric only includes native species, whereas the Invasive Plant Species Cover metric
includes both native and exotic species that are considered to be invasives to the ecosystem
understudy (e.g., Typha angustifolia in Midwestern and Northeastern U.S. marshes).
Testing in the Midwest showed the two metrics to be moderately strongly correlated
(Faber-Langendoen et al. 2011) and it may be reasonable to combine these two metrics into
a single Index.
Metric Type: Condition.
Tier: 2 (rapid field measure).
Rationale for Selection of the Variable: Native species dominate an ecosystem when it has
excellent ecological integrity. This metric is a measure of the degree to which native
ecosystems have been altered by human disturbance. With increasing human disturbance,
non-native species increase and can dominate a system.
Measurement Protocol: This metric consists of evaluating the exotic and native species
composition of the vegetation. The protocol is a visual evaluation of native vs. exotic
species cover. A field form should be used that describes species composition by strata or
growth forms (Jennings et al. 2009) (see Table 6.1. for the Vegetation Structure metric).
Field survey method for estimating structure may be either a (1) Site Survey (semi-
quantitative) method where the observers walk the AA and make notes on vegetation
strata, their cover, and the cover of native vs. exotics or (2) Quantitative Plot Data, where a
fixed area is surveyed, using either plots or transects. The plot or transect is typically a
"rapid" plot, but a single intensive plot can also be taken (see Appendix 3).
The metric can be calculated in three ways (Table 6.1 can be used to record the information
needed for all three way):
1. Where species cover is available by growth form or strata:
First estimate the total cover of the vegetation, across strata and growth forms (e.g.,
cover of the tree, shrub, herb, and non-vascular growth forms are combined, thus
the total could easily exceed 100%), then estimating the total cover of each of the
exotic species, by growth form or strata. Divide the total vegetation cover by the
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total exotics cover, multiply by 100, and subtract from 1. This method can be used
when all species, or only dominant species, are listed.
2. Where species cover is available only as total cover:
If cover is recorded for each species, but not by strata or growth form (e.g., tree
species cover combines cover across sapling and tree layer), then sum the cover
across all species, and divide it by the sum of the cover across all exotic species,
multiply by 100, and subtract from 1. This method can be used when all species, or
only dominant species, are listed.
3. Where species cover is only available for exotic species, and total cover is
available:
Where a complete or dominant species list and cover is not available, but total cover
or total cover by growth form or strata is available, and exotic species cover is
available, then sum the total cover, and divide it by the sum of the cover across all
exotic species, multiply by 100, and subtract from 1. This third option is less
accurate than the first two, but allows field crews with less botanical skills to apply
the metric.
Metric Rating:
Table 8.1. Native Plant Species Cover Metric Rating.
Metric Rating
EXCELLENT (A)
VERY GOOD (A-)
GOOD(B)
FAIR(C)
POOR(D)
Native Plant Species Cover: ALL WETLANDS
>99% relative cover of native plant species.
95-99% relative cover of native plant species
85-95% relative cover of native plant species.
60-85% relative cover of native plant species.
<60% relative cover of native plant species.
Data for Metric Rating: See Faber-Langendoen et al. (2011) for an evaluation of the
discriminatory power of this metric based on an assessment of 277 wetlands in Michigan
and Indiana. Lemly and Rocchio (2009) tested user variability and the performance of this
metric in relation to a Level 3 EIA (e.g., vegetation index of biotic integrity).
Scaling Rationale: The criteria are based on best scientific judgment and the extensive
knowledge of native and introduced floras across the country. These criteria need further
validation. Scaling of this metric using native vs. exotic species richness rather than cover is
an alternative approach (Miller et al. 2006).
Confidence that reasonable logic and/or data support the metric: High.
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• 9. Invasive Plant Species Cover
Definition: The percent cover of a selected set of exotic (or more rarely native) species that
are considered invasive to the ecosystem being evaluated. An invasive species is defined as
"a species that is non-native to the ecosystem under consideration and whose introduction
causes or is likely to cause ...environmental harm..." (Executive Presidential Order 1999,
Richardson et al. 2000).
Background: This metric has been drafted by NatureServe's Ecological Integrity Assessment
Working Group (Faber-Langendoen et al. 2008), based in part on work by Tierney et al.
2008) and Miller et al. (2006). This metric is a counterpart to "Native Plant Species Cover,"
but "Invasive Plant Species Cover" includes all invasives, whether exotic or not. That is, this
metric includes plants native to a region that may be invasive in a particular ecosystem (e.g.,
Phalaris arundinacea and Typha angustifolia in the Northeastern U.S.), so it is not a direct
mirror of the previous metric.
The definition of invasive used here is related to the perceived impact that invasives have
on ecosystem condition, or what Richardson et al. (2000) refer to as "transformers". They
distinguish invasives (Naturalized plants that produce reproductive offspring, often in very
large numbers, at considerable distances from parent plants and thus have the potential to
spread over a considerable area) from "transformers" (A subset of invasive plants that
change the character, condition, form, or nature of ecosystems over a substantial area
relative to the extent of that ecosystem). Although our definition is essentially equal to that
of "transformers" in that we are concerned with those naturalized plants that cause
ecological impacts, we retain the term "invasive" as the more widely used term. Our use of
the term also equates to "harmful non-indigenous plants" of Snyder and Kaufman (2004):
"Invasive species that are capable of invading natural plant communities where they
displace indigenous species, contribute to species extinctions, alter the community
structure, and may ultimately disrupt the function of ecosystem processes."
Invasives are distinguished from "increasers," which are native species present in an
ecosystem that respond favorably to increasing human stressors. For example, Dennstaedia
punctilobula, a native fern in northeastern U.S. northern hardwoods forests, responds
favorably to heavy deer browse (de la Cretaz and Kelty 2006).
Metric Type: Stressor/Condition.
Tier: 2 (rapid field measure).
Rationale for Selection of the Variable: As viable populations of invasive plants become
established in novel habitats, they can have a number of ecological impacts including loss of
habitat; loss of native biodiversity; decreased nutrition for herbivores; competitive
dominance; overgrowth and shading; resource depletion; and alteration of biomass, energy
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cycling, productivity, and nutrient cycling (Dukes and Mooney 1999). Invasive plant species
can also affect hydrologic function and balance, making water scarce for native species.
Measurement Protocol: A comprehensive list of invasive species should be established for
any given project, in order to make the application of the metric as consistent as possible.
Examples of wetland invasive plant species in different regions of the United States are
listed below, but these are for illustration only:
Northeast: purple loosestrife (Lythrum salicaria), reed canary grass (Phalaris arundinacea),
Japanese knotweed (Polygonum cuspidatum), water chestnut (Trapanatans), flowering rush
(Butomus umbellatus), yellow iris (Iris pseudacorus), Chinese tallow tree (Triadica sebifera),
Chinese privet (Ligustrum sinense), and exotic biotype of giant reed (Phragmites australis).
Narrow-leaf and white cattail (Typha angustifolia and T. x glauca [= T. latifolia x T.
angustifolia]) are also an increasing problem.
Southeast: water hyacinth (Eichhornia crassipes).
Midwest: reed canary grass (Phalaris arundinacea), purple loosestrife (Lythrum salicaria),
and giant reed (Phragmites australis).
West: reed canary grass (Phalaris arundinacea), purple loosestrife (Lythrum salicaria),
parrotfeather (Myriophyllum aquaticum), cordgrasses (Spartina alterniflora, S. anglica, S.
densiflora, and S. patens), hydrilla (Hydrilla verticillata), Brazilian waterweed (Egeria densa),
and Eurasian water-milfoil (Myriophyllum spicatum).
This metric consists of evaluating the percent cover of invasive plant species. The protocol is
a visual evaluation of invasive plant species cover. A field form should be used that
describes species composition using either strata or growth forms (Jennings et al. 2009) (see
Table 6.1, Vegetation Structure metric). The cover of those species identified as non-native
invasives and native plant increasers is summed to produce the total cover of invasive plant
species.
Field survey method for estimating structure may be either a (1) Site Survey (semi-
quantitative) method where the observers walk the entire occurrence, or assessment area
within the occurrence, and make notes on vegetation strata, their cover and the cover of
native vs. exotics or (2) Quantitative Plot Data, where a fixed area is surveyed, using either
plots or transects. The plot or transect is typically a "rapid" plot, but a single intensive plot
can also be taken (see Appendix 3).
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Metric Rating:
Table 9.1. Invasive Plant Species Cover Metric Rating. A specific list of invasive
(transformer) species should be provided with this metric.
Metric Rating
EXCELLENT (A)
VERY GOOD (A-)
GOOD(B)
FAIR(C)
POOR(D)
Invasive Exotic Plant Species Cover: ALL WETLANDS
Invasive plant species absent or cover is very low (<1% absolute cover).
Invasive plant species present but sporadic (1-3 % cover).
Invasive plant species somewhat abundant (4-10% cover).
Invasive plant species abundant (10-30% cover).
Invasive plant species very abundant (>30% cover).
Data for Metric Rating: See Faber-Langendoen et al. (2011) for an evaluation of the
discriminatory power of this metric based on an assessment of 277 wetlands in Michigan
and Indiana.
Scaling Rationale: Establishment of invasives at a site can be followed by rapid increases,
with the potential for exponentially increasing levels of abundance and effects on other
species and ecological processes (Rejmanek et al. 2005, Figure 6.12). Thus the metric is
scaled to be sensitive to relatively small levels of invasive cover (e.g., 1-3% cover receives an
"A-" rating).
Confidence that reasonable logic and/or data support the metric: Medium/High.
• 10. Vegetation Composition
Definition: An assessment of the overall species composition and diversity, including by
layer, and evidence of species specific diseases or mortality.
Background: This metric has been drafted by NatureServe's Ecological Integrity Assessment
Working Group (Faber-Langendoen et al. 2008).
Metric Type: Condition.
Tier: 2 (rapid field measure).
Rationale for Selection of the Variable: Trees, shrubs, herbs, and alga play an important
role in providing wildlife habitat, and they are the most readily surveyed aspect of wetland
biodiversity. Vegetation is also the single, largest component of net primary productivity.
The integrity of ecosystems is optimized when a characteristic native flora dominates the
plant community, and suitable habitat exists for multiple animal species. Much of the
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natural microbial, invertebrate, and vertebrate species of wetlands respond to overall
vegetation composition. Vegetation composition also reflects the interactions between
plants and physical processes, especially hydrology. A change in vegetation composition, as
a result of invasive and exotic plant invasions for example, can have cascading effects on
system form, structure, and function (Collins et al. 2006, Rocchio 2007).
We use overall composition, emphasizing key diagnostic species typical of a wetland type,
rather than species diversity or richness (which is also more typically a Level 3 metric). This
metric can be thought of as a rapid version of a Level 3 Floristic Quality Index (FQI) or Index
of Biotic Integrity (VIBI), requiring experienced ecological judgment in the field in
combination with good vegetation descriptions of the wetland type being evaluated (Mack
and Kentula (2010).
Measurement Protocol: This metric consists of evaluating the species composition of the
vegetation. The protocol is a visual evaluation of variation in overall composition. This
metric requires the ability to recognize the major-dominant aquatic, wetland, and riparian
plants species of each layer or stratum. When a field team lacks the necessary botanical
expertise, voucher specimens will need to be collected using standard plant presses and site
documentation. This can greatly increase the time required to complete an assessment.
A field form should be used that describes composition using either strata or growth forms
(Jennings et al. 2009) (see "Vegetation Structure" metric, Table 6.1). For the strata method,
list all major strata - tree, shrub, herb, non-vascular, floating, submerged - then estimate
strata cover and cover of dominant (>5% cover), characteristic, and exotic species. For
the growth form method, list major growth forms - tree (subdivided into overstory and
regeneration), shrub (subdivided by tall and medium/low), herb, non-vascular, floating,
submerged, epiphyte, and liana - then estimate strata cover and cover of dominant (>5%),
characteristic, and exotic species.
The metric refers to species which are diagnostic, increaser, or ruderal. Diagnostic species,
or the characteristic combination of species, are typically native plant species whose
relative constancy or abundance differentiates one type from another, including character
species (strongly restricted to a type), differential species (higher constancy or abundance in
a type as compared to others), constant species (typically found in a type, whether or not
restricted), and dominant species (high abundance or cover) (FGDC 2008). Together these
species also indicate certain ecological conditions, typically that of minimally disturbed
sites. Information on diagnostic species for USNVC types is available for the USNVC Group
level and below (alliance and association), and many state Natural Heritage Programs
maintain natural community classifications where lists of diagnostic species are provided
(see "Wetland Classification" above).
Increaser species are native species in the wetland whose dominance is indicative of
degrading ecological conditions, such as heavy grazing or browse pressure (Daubenmire
1968), but where sites typically do not have substantial soil profile disturbances. For
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example, Dennstaedia punctilobula, a native fern in northeastern U.S. northern hardwood
forests, responds favorably to heavy deer browse (de la Cretaz and Kelty 2006). Degrading
conditions that lead to presence of invasives species are treated in the "Invasive Plant
Species Cover" metric. Ruderal species are either native or exotic species whose presence
or dominance is indicative of disturbed soils, such as disturbances caused by grading,
plowing, or vehicular ruts; that is, they are especially dominant native increasers or invasive
exotic species on heavily disturbed sites, and where strongly dominant, they may cause a
wetland to be "transformed" to a different type (e.g., a native sedge meadow type could be
transformed to a reed canary grass type). Guidance on typical "increaser" species is helpful
for field crews, but needs to be developed in the context of diagnostic species that are
specific to the wetlands being evaluated.
Field survey method for estimating vegetation composition may be either a (1) Site Survey
(semi-quantitative) method where the observers walk the AA, and make notes on
vegetation strata, their cover, and native vs. exotic species or (2) Quantitative Plot Data,
where a fixed area is surveyed, using either plots or transects. The plot or transect is
typically a "rapid" plot, but a single intensive plot can also be taken (see Appendix 3).
Metric Rating
Table 10.1. Vegetation Composition Metric Ratings. See text ("Measurement Protocol")
for definitions of diagnostic, increaser, and ruderal species terms.
Metric Rating
Vegetation Composition: ALL WETLANDS
EXCELLENT (A)
Vegetation composition minimally to not disturbed:
i) Typical range of native diagnostic species present, including those native
species sensitive to anthropogenic degradation, AND
ii) Native species indicative of anthropogenic disturbance (i.e., increasers,
weedy or ruderal species) absent to minor.
GOOD(B)
Vegetation composition with minor disturbed conditions:
i) Some native diagnostic species absent or substantially reduced in
abundance, AND
ii) Some native species indicative of anthropogenic disturbance (increasers,
weedy or ruderal species) are present but minor in abundance.
FAIR(C)
Vegetation composition with moderately disturbed conditions:
i) Many native diagnostic species absent or substantially reduced in
abundance, AND
ii) Species are still largely native and characteristic of the type, but they also
include increasers, weedy or ruderal species.
POOR(D)
Vegetation composition with severely disturbed conditions:
i) Most or all native diagnostic species absent, a few may remain in very low
abundance, OR
ii) Native species from entire strata may be absent or species are dominated by
ruderal ("weedy") species, or comprised of planted stands of non-
characteristic species, or unnaturally dominated by single species.
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Data for Metric Rating: See Faber-Langendoen et al. (2011) for an evaluation of the
discriminatory power of this metric based on an assessment of 277 wetlands in Michigan
and Indiana.
Scaling Rationale: The metric is scaled based on the similarity between the described
species composition of the vegetation and what is expected based on reference condition.
Reference conditions reflect the accumulated experience of field ecologists (as recorded in
detailed wetland type descriptions - see "Wetland Classification" section above), studies
from sites where natural processes are intact, regional surveys and historic sources.).
Confidence that reasonable logic and/or data support the metric: Medium/High.
HYDROLOGY
For various aspects of the hydrology metrics, we have benefitted from the work of the Ohio
Rapid Assessment Method (Mack 2001) and California Rapid Assessment Method (Collins et
al. 2006).
Table 11.0 Hydrology Metric Variants by HGM Class.
METRIC HYDROLOGY HYDROLOGY HYDROLOGY
Metric Variant by Hydrogeomorphic Class
Estuarine Fringe (Tidal)
Riverine) Non-tidal)
Organic Soil Flats, Mineral Soil Flats
Other HGM (Depression, Lacustrine, Slope)
12. Water Source
VI
V2
V3
V4
13. Hydroperiod
VI
V2
V3
14. Hydrologic Connectivity
VI
V2
V3
• 11. Water Source
Definition: An assessment of the extent, duration, and frequency of saturated or ponded
conditions within a wetland, as affected by the kinds of direct inputs of water into, or any
diversions of water away from, the wetland.
Background: Water Sources encompass the forms, or places, of direct inputs of water to the
AA as well as any unnatural diversions of water from the AA. Diversions are considered a
water source because they affect the ability of the AA to function as a source of water for
other habitats while also directly affecting the hydrology of the AA. The metric is adapted
from Collins et al. (2006), but the variants are modified for national and international
application, and the role of wetland plant indicators is de-emphasized (their role is assessed
by the Vegetation Composition metric). Collins et al. (2006) state:
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"A water source is direct if it supplies water mainly to the AA, rather than to areas
through which the water must flow to reach the AA. Natural, direct sources include
rainfall, ground water discharge, and flooding of the AA due to high tides or naturally
high riverine flows. Examples of unnatural, direct sources include storm drains that
empty directly into the AA or into an immediately adjacent area. For seeps and springs
that occur at the toe of an earthen dam, the reservoir behind the dam is an unnatural,
direct water source. Indirect sources that should not be considered in this metric
include large regional dams or urban storm drain systems that do not drain directly into
the AA but that have systemic, ubiquitous effects on broad geographic areas of which
the AA is a small part. For example, the salinity regime of an estuarine wetland near
Napa is affected by dams in the Sierra Nevada, but these effects are not direct. But the
same wetland is directly affected by the nearby discharge from the Napa sewage
treatment facility. Engineered hydrological controls, such as tide gates, weirs,
flashboards, grade control structures, check dams, etc., can serve to demarcate the
boundary of an AA..., but they are not considered water sources."
Metric Type: Condition.
Tier: 2 (rapid field measure).
Rationale for Selection of the Variable: Natural inflows of water to a wetland are important
to its ability to persist as a wetland. The flow of water into a wetland also affects sediment
processes and the physical structure/geometry of the wetland (Collins et al. 2006).
Measurement Protocol: This metric can be assessed initially in the office using available
imagery, and then revised based on the field visit. The metric focuses on direct sources of
tidal and non-tidal water, comparing the natural sources to unnatural sources. Permanent
or semi-permanent features that affect water source at the overall watershed or regional
level should not be considered in the evaluation of this metric (Collins et al. 2006).
The office assessment can work outward from the AA, to include landscape indicators of
unnatural water sources, such as adjacent intensive development or irrigated agriculture,
nearby wastewater treatment plants, and nearby reservoirs. These indicators identified in
the office can then be checked in the field.
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Metric Rating:
Table 11.1. Water Source Metric Rating. Separate metric ratings are provided for Estuarine Fringe
(Tidal), Riverine (Non-tidal), Organic and Mineral Soil Flats,, and Other HGM - (Depression,
Lacustrine, Slope).
Metric Rating
EXCELLENT (A)
GOOD(B)
FAIR(C)
POOR(D)
VI: Water Source: ESTUARINE FRINGE (Tidal) Wetlands
Tidal water source is natural with no artificial alterations to natural salinity. Non-
tidal source (alluvial) is natural; no indication of direct artificial water sources
(e.g., land use in the local drainage area of the site is primarily open space or low
density, passive uses. Lacks point source discharges into or adjacent to the site.
Tidal water source is mostly natural with minor alterations to natural salinity.
Non-tidal source is mostly natural, but site directly receives occasional or small
continuous amounts of inflow from anthropogenic sources (indicators include
<20% of core landscape is agricultural or developed land, storm drains etc.)
Tidal water source is somewhat impacted by human activity. Non-tidal source is
primarily urban runoff, direct irrigation, pumped water, artificially impounded
water, or other artificial hydrology (indicators include >20% of core landscape is
agricultural or developed land, major point sources of discharge, etc.).
Tidal water source is substantially impacted by human activity. Non-tidal water
flow has been substantially diminished by human activity.
Metric Rating
1/2: Water Source variant: RIVERINE (Non-tidal) Wetlands
EXCELLENT (A)
Water source is natural, site hydrology is dominated by precipitation,
groundwater, and natural runoff from an adjacent freshwater body. System may
naturally lack water at times, such as in the growing season. There is no
indication of direct artificial water sources. Land use in the local drainage area of
the site is primarily open space or low density, passive uses. Lacks point source
discharges into or adjacent to the site.
GOOD(B)
Water source is mostly natural, but site directly receives occasional or small
amounts of inflow from anthropogenic sources. Indications of anthropogenic
input include developed land or agricultural land (<20%) in the immediate
drainage area of the site, or the presence of small storm drains or other local
discharges emptying into the site, road runoff, or the presence of scattered
homes along the wetland that probably have septic systems. No large point
sources discharge into or adjacent to the site.
FAIR(C)
Water source contains a large component of urban runoff, direct irrigation,
pumped water, artificially impounded water, or other artificial hydrology.
Indications of substantial artificial hydrology include >20% developed or
agricultural land adjacent to the site, and the presence of major point sources
that discharge into or adjacent to the site.
POOR(D)
Water flow exists but has been substantially diminished by known
impoundments or diversions of water or other withdrawals directly from the
site, its encompassing wetland, or from areas adjacent to the site or its wetland,
OR water source has been severely altered to the point where it no longer
supports much vegetation (e.g., flashy runoff from impervious surfaces).
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Metric Rating
1/3: Water Source variant: ORGANIC SOIL FLATS, MINERAL SOIL FLATS
EXCELLENT (A)
Water source is natural, and site hydrology is dominated by precipitation. There
is no indication of direct artificial water sources. Land use in the local drainage
area of the site is primarily open space or low density, passive uses. Lacks point
source discharges into or adjacent to the site.
GOOD(B)
Water source is mostly natural, but site directly receives occasional or small
amounts of inflow from anthropogenic sources, or is ditched, causing peatland
to dry out more quickly. Indications of anthropogenic input include developed
land or agricultural land (<20%) in the immediate drainage area of the site; or
the presence of small storm drains, ditches, or other local discharges emptying
into the site; road runoff; or the presence of scattered homes along the wetland
that probably have septic systems. No large point sources discharge into or
adjacent to the site.
FAIR(C)
Water source is moderately impacted by increased inputs into the peatland,
artificially impounded water, or other artificial hydrology. Indications of
substantial artificial hydrology include >20% developed or agricultural land
adjacent to the site, and the presence of major point sources that discharge into
or adjacent to the site.
POOR(D)
Water source is substantially impacted by impoundments or diversions of water
or other input into or withdrawals directly from the site, its encompassing
wetland, or from areas adjacent to the site or its wetland.
Metric Rating
1/4: Water Source variant: OTHER HGM (DEPRESSION, LACUSTRINE, SLOPE)
EXCELLENT (A)
Water source is natural: site hydrology is dominated by precipitation,
groundwater, natural runoff from an adjacent freshwater body, or the system
naturally lacks water in some periods. There is no indication of direct artificial
water sources. Land use in the local drainage area of the site is primarily open
space or low density, passive uses. Lacks point source discharges into or
adjacent to the site.
GOOD(B)
Water source is mostly natural, but site directly receives occasional or small
amounts of inflow from anthropogenic sources. Indications of anthropogenic
input include developed land or agricultural land (<20%) in the immediate
drainage area of the site, or the presence of small storm drains or other local
discharges emptying into the site, road runoff, or the presence of scattered
homes along the wetland that probably have septic systems. No large point
sources discharge into or adjacent to the site.
FAIR(C)
Water source is primarily urban runoff, direct irrigation, pumped water,
artificially impounded water, or other artificial hydrology. Indications of
substantial artificial hydrology include >20% developed or agricultural land
adjacent to the site, and the presence of major point sources that discharge into
or adjacent to the site.
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POOR(D)
Water source exists but has been substantially diminished by known
impoundments or diversions of water or other withdrawals directly from the
site, its encompassing wetland, or from areas adjacent to the site or its wetland,
OR water sources has been severely altered to the point where they no longer
support much vegetation (e.g., flashy runoff from impervious surfaces).
Data for Metric Rating: See Faber-Langendoen et al. (2011) for an evaluation of the
discriminatory power of this metric based on an assessment of 277 wetlands in Michigan
and Indiana.
Scaling Rationale: Metric ratings are adapted from Collins et al. (2006).
Confidence that reasonable logic and/or data support the metric: Medium/High.
• 12. Hydroperiod
Definition: An assessment of the characteristic frequency and duration of inundation or
saturation of a wetland during a typical year.
Background: Metric is adapted from Collins et al. (2006), and modified to include other
hydroperiod variants outside of California. Hydroperiod integrates the inflows and outflows
of water and varies by major wetland types (Mitsch and Gosselink 2000). For tidal
wetlands, there are many hydroperiod cycles that correspond to different periodicities in
the orbital relationships among the earth, moon, and sun, creating a variety of tidal
patterns at semi-daily, daily, semi-weekly, monthly, seasonal, and annual timeframes. For
non-tidal wetlands, with fluctuating hydroperiods such as depressional, lacustrine, riverine,
and mineral flats wetlands, cycles are governed by seasonal or annual patterns of rainfall
and temperature. For non-tidal wetlands with more stable, saturated hydroperiods, such as
groundwater-fed slope wetlands, these seasonal patterns are often over-ridden by
groundwater flows. Lagoons can be episodically subjected to tidal inundation, but may
otherwise have similar hydroperiods to lacustrine systems (Collins et al. 2006).
Metric Type: Condition.
Tier: 2 (rapid field measure).
Rationale for Selection of the Variable: For all non-riverine wetlands, hydroperiod is the
dominant aspect of hydrology. Hydroperiod, or the pattern and balance of inflows and
outflows, is a major determinant of wetland functions. The patterns of import, storage, and
export of sediment and other water-borne materials are functions of the hydroperiod. In
most wetlands, plant recruitment and maintenance are dependent on hydroperiod. The
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interactions of hydro period and topography are major determinants of the distribution and
abundance of native wetland plants and animals (Mitsch and Gosselink 2000).
For riverine wetlands, hydroperiod is assessed through the patterns of water flow
associated with rainfall, snowmelt, dams, and long term weather patterns, i.e. the flow
regime (Poff et al. 1997). The natural flow regime of a river can be characterized in terms of
the magnitude, frequency, duration, and timing of extreme high flows and low flows (Poff et
al. 1997, 2007). Flow regime has an important impact on sediment movement and sinuosity
of the stream and river.
Measurement Protocol: This metric evaluates recent changes in the hydroperiod, and the
degree to which these changes affect the structure and composition of the wetland plant
community. Common indicators are presented for the different wetland classes. This
metric focuses on changes that have occurred in the last 20-30 years.
A basic understanding of the natural hydrology or channel dynamics of the type wetland
being evaluated is needed to apply this metric. For example, high gradient riparian areas in
mountainous areas have very different dynamics from those in flat coastal plains, especially
in terms of aggradation or degradation (Poff et al. 1997).
Measurement Protocols for Tidal Wetlands (Estuarine)
Collins et al. (2006) describe the hydroperiod of estuaries:
"The volume of water that flows into and from an estuarine wetland due to the
changing stage of the tide is termed the "tidal prism". This volume of water consists of
inputs from both tidal (i.e., marine) and non-tidal (e.g., fluvial or upland) sources. The
timing, duration, and frequency of inundation of the wetland by these waters is termed
the tidal hydroperiod. Under natural conditions, increases in tidal prism result in
increases in sedimentation, such that increases in hydroperiod do not persist. For
example, estuarine marshes tend to build upward in quasi-equilibrium with sea level
rise. A decrease in tidal prism usually results in a decrease in hydroperiod. In lagoons,
freshwater inputs are substantial and tidal prisms are altered by barriers to tidal inputs,
which may occasionally be breached by occasional winds driving overwash across the
tidal barrier or by seepage through the tidal barrier, etc."
Collins et al. (2006) provide indicators of alterations to the estuarine hydroperiod (i.e., a
change in the tidal prism):
• Changes in the relative abundance of plants indicative of either high or low marsh.
• A preponderance of shrink cracks or dried pannes is indicative of decreased
hydroperiod.
• Inadequate tidal flushing may be indicated by algal blooms or by encroachment of
freshwater vegetation.
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• Dikes, levees, ponds, ditches, and tide control structures are indicators of an altered
hydroperiod resulting from management for flood control, salt production,
waterfowl hunting, boating, etc.
Measurement Protocols for Non-Tidal Wetlands
Riverine (non-tidal): To score this metric, visually survey the AA for field indicators of
aggradation or degradation (listed in Table 12.1). After reviewing the entire AA and
comparing the conditions to those described in the table, determine whether the AA is in
equilibrium, aggrading, or degrading, then assign a metric rating. Groundwater-fed
wetlands in a riverine context are treated with non-riverine (e.g., New Jersey's
groundwater-fed riverine pine barrens). See Collins et al. (2006) for additional guidance.
Table 12.1. Suggested field indicators for evaluating the Hydroperiod Metric for Riverine
Wetlands (adapted from Collins et. al. 2006, Table 4.8).
Condition
Field Indicators
Indicators of
Channel
Equilibrium
The channel (or multiple channels in braided systems) has a well-
defined usual high water line, or bankfull stage that is clearly
indicated by an obvious floodplain, topographic bench that
represents an abrupt change in the cross-sectional profile of the
channel throughout most of the site.
The usual high water line or bankfull stage corresponds to the
lower limit of riparian vascular vegetation.
The channel contains embedded woody debris of the size and
amount consistent with what is available in the riparian area.
There is little or no active undercutting or burial of riparian
vegetation.
Indicators of
Active
Degradation
Portions of the channel are characterized by deeply undercut
banks with exposed living roots of trees or shrubs. There are
abundant bank slides or slumps, or the banks are uniformly
scoured and unvegetated.
Riparian vegetation may be declining in stature or vigor, and/or
riparian trees and shrubs may be falling into the channel.
The channel bed lacks any fine-grained sediment.
Recently active flow pathways appear to have coalesced into one
channel (i.e., a previously braided system is no longer braided).
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Indicators of
Active
Aggradation
The channel through the site lacks a well-defined usual high
water line.
There is an active floodplain with fresh splays of sediment
covering older soils or recent vegetation.
There are partially buried tree trunks or shrubs.
Cobbles and/or coarse gravels have recently been deposited on
the floodplain.
There are partially buried, or sediment-choked, culverts.
Non-Riverine (non-tidal): Assessment of the hydroperiod for all non-riverine wetlands
should be initiated with an office-based review of diversions or augmentations of flows or
alteration of saturated conditions to the wetland. Field indicators for altered hydroperiod
include pumps, spring boxes, ditches, hoses and pipes, encroachment of terrestrial
vegetation, excessive exotic vegetation along the perimeter of the wetland, and desiccation
during periods of the year when comparable wetlands are typically inundated or saturated
(Table 12.2).
Table 12.2. Suggested field indicators for evaluating the Hydroperiod Metric for Non-
Riverine, Non-tidal Freshwater Wetlands (adapted from Collins et. al. 2006, Table 4.8).
Condition
Field Indicators
Upstream spring boxes, diversions, impoundments, pumps,
ditching, or draining from the wetland.
Evidence of aquatic wildlife mortality.
Encroachment of terrestrial vegetation.
Stress or mortality of hydrophytes.
Compressed or reduced plant zonation.
Organic soils occurring well above contemporary water tables.
Reduced Extent and
Duration of Inundation
or Saturation
Berms, dikes, or other water control features that increase
duration of ponding (e.g., pumps).
Diversions, ditching, or draining into the wetland.
Late-season vitality of annual vegetation.
Recently drowned riparian or terrestrial vegetation.
Extensive fine-grain deposits on the wetland margins.
Increased Extent and
Duration of Inundation
or Saturation
Organic Soil Flats. Bog and Poor Fen: Bogs (and poor fens) have a very stable, saturated
hydroperiod, or a much damped cycle of saturation and partial drying. Because drying is
limited to the upper layers of peat, bogs are rarely subject to fires, which can burn woody
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vegetation and upper peat layers when they do occur. The hydroperiod can be altered by
ditches, which further increase drying of the peat layer, or by increased runoff into the
system, which if weakly minerotrophic (and not truly ombrotrophic), as occurs in poor fens,
can lead to nutrient enrichment.
Metric Rating:
Table 12.3. Hydroperiod Metric Rating. Separate metric ratings are provided for Estuarine
Fringe (Tidal), Riverine (Non-Tidal), Organic and Mineral Soil Flats, other HGM (Depression,
Lacustrine, Slope) variants.
Metric Rating
VI: Hydroperiod variant: ESTUARINE FRINGE (Tidal)
EXCELLENT (A)
Area is subject to the full tidal prism, with two daily tidal minima and
maxima. Lagoons: Area subject to natural inter-annual tidal fluctuations (range
may be severely muted or vary seasonally), and is episodically fully tidal by
natural breaching due to either fluvial flooding or storm surge.
GOOD(B)
Area is subject to reduced, or muted, tidal prism, although two daily minima and
maxima are observed. Lagoons: Area is subject to full tidal range more often than
would be expected under natural circumstances, because of artificial breaching of
the tidal barrier.
FAIR(C)
Area is subject to muted tidal prism, with tidal fluctuations evident only in
relation to extreme daily highs or spring tides. Lagoons: Area is subject to full
tidal range less often than would be expected under natural circumstances due to
management of the breach to prevent its opening.
POOR(D)
Area is subject to muted tidal prism, plus there is inadequate drainage, such that
the marsh tends to remain flooded during low tide. Lagoons: Area appears to
have no episodes of full tidal exchange.
Metric Rating
EXCELLENT (A)
GOOD(B)
FAIR(C)
POOR(D)
1/2; Hydroperiod variant: RIVERINE (Non-tidal)
Most of the channel/riparian zone is characterized by equilibrium conditions, with
no evidence of severe aggradation or degradation (based on the field indicators
listed in Table 12.1).
Most of the channel/riparian zone is characterized by some aggradation or
degradation, none of which is severe, and the channel seems to be approaching
an equilibrium form (based on the field indicators listed in Table 12.1).
Most of the channel/riparian zone is characterized by severe aggradation or
degradation (based on the field indicators listed in Table 12.1).
Most of the channel is concrete or artificially hardened (see field indicators in
Table 12.1).
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Metric Rating
EXCELLENT (A)
GOOD(B)
FAIR(C)
POOR(D)
1/3: Hydroperiod variant: ORGANIC SOIL FLATS, MINERAL SOIL FLATS
Stable, saturated hydrology, or naturally damped cycles of saturation and partial
drying.
Minor altered inflows or drawdown/drying (e.g., ditching).
Moderately altered by increased runoff, or drawdown and drying (e.g., ditching).
Substantially altered by increased inflow from runoff, or significant drawdown
and drying (e.g., ditching).
Metric Rating
EXCELLENT (A)
GOOD(B)
FAIR(C)
POOR(D)
1/4; Hydroperiod variant: OTHER HGM (DEPRESSION, LACUSTRINE, SLOPE)
Natural patterns associated with inundation - drawdown, saturation, and
seepage discharge.
Some alteration to the natural patterns associated with inundation - drawdown,
saturation, and seepage discharge.
Moderate alteration to the natural patterns associated with inundation -
drawdown, saturation, and seepage discharge.
Significant alteration to the natural patterns associated with inundation -
drawdown, saturation, and seepage discharge.
Data for Metric Rating: See Faber-Langendoen et al. (2011) for an evaluation of the
discriminatory power of this metric based on an assessment of 277 wetlands in Michigan
and Indiana.
Scaling Rationale: Metric ratings are adapted from Collins et al. (2006), except for Bog
&Poor Fen, were drafted by the NatureServe Ecological Integrity Assessment Working
Group (Faber-Langendoen et al. 2008).
Confidence that reasonable logic and/or data support the metric: Medium/High.
• 13. Hydrologic Connectivity
Definition: An assessment of the ability of the water to flow into or out of the wetland, or
to inundate adjacent areas.
Background: Metric is adapted from Collins et al. (2006, CRAM manual 4.0), with additional
metric variants added.
Metric Type: Condition.
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Tier: 1 (remote sensing); 2 (rapid field measure).
Rationale for Selection of the Variable: Hydrologic connectivity between wetlands and
adjacent uplands supports key ecologic processes, such as the exchange of water, sediment,
nutrients, and organic carbon. Connectivity of both surface and subsurface hydrologic
connections, including connections with shallow aquifers and hyporheic zones (zones
beneath and alongside stream beds, where surface water and groundwaterjnix), is a
challenging and often poorly understood aspect of connectivity. Many animal species, such
as amphibians, depend on the connectivity between streams and their floodplains, or ponds
and surrounding habitats (Poff et al. 1997, Amoros and Bornette 2002).
The number of junctions in tidal channels (Adamus 2005; 2006, Appendix A, code 54A)
provides a measure of the number of branches in typically dendritic networks of channels in
tidal marsh, and provides an indication of existing tidal connectivity or potential
connectivity at proposed restoration sites. Occurrences are determined by channels visible
in 1:24,000 aerial photographs. Tidal channel sinuosity can be quantified, but more work is
needed to determine whether general metrics of sinuosity can be established. Time
elapsed since restoration of tidal circulation and extent of restoration (Adamus 2005, 2006)
provides a measure of rate and extent of sediment accretion.
Measurement Protocol:
Scoring of this metric is based solely on field indicators (see Collins et al. 2006). No office
work is required. The metric is assessed in the field by observing signs of alteration to
overbank flooding, channel migration, channel incision, and geomorphic modifications
present within the assessment area.
For riverine wetlands and riparian habitats, Hydrologic Connectivity is assessed in part
based on the degree of alteration of flooding regimes (e.g., channel entrenchment).
Entrenchment varies naturally with channel confinement. Channels in steep canyons
naturally tend to be confined, and tend to have small entrenchment ratios indicating less
hydrologic connectivity. Assessments of hydrologic connectivity based on entrenchment
must therefore be adjusted for channel confinement based on the geomorphic setting of
the riverine wetlands. Prevention of river flooding by human-created levees and dikes are
other ways in which changes to hydrological connectivity can be assessed (Collins et al.
2006). Natural levees may form as part of river dynamics, and may be breached during
natural flooding events, also altering connectivity. Their form is distinctive enough from
human-created levees, helping to minimize misidentification.
We do not present an "isolated wetland" variant, as it is difficult to verify this category in
the field. Depressional wetlands often have outlets, as well as subsurface connectivity.
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Metric Rating:
Table 13.1. Hydrologic Connectivity Metric Rating. Separate Estuarine Fringe (Tidal),
Riverine (Non-Tidal), Organic and Mineral Soil Flats), Other HGM (Depression, Lacustrine,
Slope) variants are provided.
Metric Rating
VI: Hydrologic Connectivity variant: ESTUARINE FRINGE (Tidal)
EXCELLENT (A)
Tidal channel sinuosity reflects natural processes; absence of channelization.
Marsh receives unimpeded tidal flooding. Total absence of tide gates, flaps, dikes
culverts, or human-made channels.
GOOD(B)
Tidal channel sinuosity minimally altered: marsh receives essentially unimpeded
tidal flooding, with few tidal channels blocked by dikes or tide gates, and human-
made channels are few. Culvert, if present, is of large diameter and does not
significantly change tidal flow, as evidenced by similar vegetation on either side of
the culvert.
FAIR(C)
Tidal channel sinuosity moderately altered: marsh channels are frequently
blocked by dikes or tide gates. Tidal flooding is somewhat impeded by small
culvert size, as evidenced in obvious differences in vegetation on either side of
the culvert.
POOR(D)
Tidal channel sinuosity extensively altered: tidal channels are extensively blocked
by dikes and tide gates; evidence of extensive human channelization. Tidal
flooding is totally or almost totally impeded by tidal gates or obstructed culverts.
Metric Rating
EXCELLENT (A)
GOOD(B)
FAIR(C)
POOR(D)
1/2; Hydrologic Connectivity variant: RIVERINE (Non-tidal)
Completely connected to floodplain (backwater sloughs and channels). No
geomorphic modifications made to contemporary floodplain.
Minimally disconnected from floodplain. Up to 25% of stream banks are affected.
Moderately disconnected from floodplain due to multiple geomorphic
modifications (e.g., dikes, tide gates, and elevated culverts); 25-75% of stream
banks are affected.
Extensively disconnected from floodplain; >75% of stream banks are affected.
Metric Rating
EXCELLENT (A)
GOOD(B)
FAIR(C)
POOR(D)
V3: Hydrologic Connectivity variant: ORGANIC SOIL FLATS, MINERAL SOIL
FLATS
No or very little direct connectivity to groundwater. Precipitation
or only source.
Minor hydrological connectivity, as caused by human activity (e.g.
is the dominant
, ditching).
Moderate connectivity caused by human activity (e.g., ditching).
Substantial to full connectivity caused by human activity.
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Metric Rating
1/4; Hydrologic Connectivity variant: OTHER HGM (DEPRESSION,
LACUSTRINE, SLOPE)
EXCELLENT (A)
No unnatural obstructions to lateral or vertical movement of ground or surface
water, or if perched water table then impermeable soil layer (fragipan or duripan)
intact. Rising water in the site has unrestricted access to adjacent upland,
without levees, excessively high banks, artificial barriers, or other obstructions to
the lateral movement of flood flows.
GOOD(B)
Minor restrictions to the lateral or vertical movement of ground or surface waters
by unnatural features, such as levees or excessively high banks. Less than 25% of
the site is restricted by barriers to drainage. If perched then impermeable soil
layer partly disturbed (e.g., from drilling or blasting). Restrictions may be
intermittent along the site, or the restrictions may occur only along one bank or
shore. Flood flows may exceed the obstructions, but drainage back to the
wetland is incomplete due to impoundment.
FAIR(C)
Moderate restrictions to the lateral or vertical movement of ground or surface
waters by unnatural features, such as levees or excessively high banks. Between
25-75% of the site is restricted by barriers to drainage. If perched then
impermeable soil layer moderately disturbed (e.g., by drilling or blasting). Flood
flows may exceed the obstructions, but drainage back to the wetland is
incomplete due to impoundment.
POOR(D)
Essentially no hydrologic connection to adjacent wetlands or uplands. Most or all
water stages are contained within artificial banks, levees, sea walls, or
comparable features. Greater than 75% of wetland is restricted by barriers to
drainage. If perched then impermeable soil layer strongly disturbed.
Data for Metric Rating: See Faber-Langendoen et al. (2011) for an evaluation of the
discriminatory power of this metric based on an assessment of 277 wetlands in Michigan
and Indiana. Lemly and Rocchio (2009) tested user variability and the performance of a
variant of this metric in relation to a Level 3 EIA (e.g., vegetation index of biotic integrity).
Scaling Rationale: Metric ratings are adapted from Collins et al. (2006), except for Bog &
Poor Fen. Use of a "wide salinity gradient and connectivity" metric could be helpful in
assessing the hydrologic connectivity of mangroves, and it could be applicable to many
estuaries. But it does not apply to salt marsh lagoons on the U.S. west coast that may have
restricted tidal access in summer and restricted salinity gradients, so a lagoon variants may
need to be addressed at lower levels of classification, such as NVC Group or Ecological
System, where Atlantic or Pacific salt marshes are treated as separate types (J. Christy pers.
comm. 2008).
Confidence that reasonable logic and/or data support the metric: Medium/High.
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SOIL / SUBSTRATE
• 14. Physical Patch Types
Definition: A checklist of the number of different physical surfaces or features that may
provide habitat for species.
Background: This metric is adapted from Collins et al. (2006), but has been rescaled by
NatureServe's Ecological Integrity Assessment Working Group to emphasize condition
rather than functional complexity (Faber-Langendoen et al. 2008).
Metric Type: Condition.
Tier: 2 (rapid field measure).
Rationale for Selection of the Variable: The rationale for this variable as used by Collins et
al. (2006) emphasizes the connection between increasing physical complexity and
increasing ecological functions, beneficial uses, as well as overall condition. Here we revise
the metric to primarily emphasize condition. For each wetland class, there are visible
patches of physical structure that typically occur at multiple points along the hydrologic
gradient. But not all patch types will occur in all wetland types. Therefore, the rating is
based on the percent of total expected patch types fora given wetland class at a site.
Measurement Protocol: Prior to fieldwork, the imagery of the site should be reviewed to
survey the major physical features or patch types present. The office work must be field-
checked using a descriptive list of patch types, as summarized in the Physical Patch Type
Worksheet below (Table 14.1), by noting the presence/absence of patch types expected for
a particular example of a given wetland type, and calculating the percentage of expected
patch types actually found at the site.
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Table 14.1. Physical Patch Type Worksheet.
FLOODED & SWAMP FOREST
Open water - Oxbows /
Backwater channels / Pools /
Tributaries
Seeps / Springs - onsite or
adjacent
Depositional orerosional
features, e.g., point bar, flats,
bare ground, undercut banks
Debris jams / Woody debris
on-site or in adjacent channel
Tip up mounds/ Pits
Beaver dams/ Canals
Terraces
Natural levees
Upland pockets in floodplain
or swamp
Plant hummocks and hollows
Animal mounds and burrows
MANGROVE
Open water (tidal)
Non-vegetated flats or bare
ground
Topographic gradient
Marl levee
Prop roots, drop roots,
pneumatophores, aerial
rootlets, viviparous propagules
Intertidal barnacle or oyster
colonies
Fiddler crab burrows
OTHER:
FS1
FS2
FS3
FS4
FS5
FS6
FS7
FS8
FS9
FS10
FS11
Ml
M2
M3
M4
M5
M6
M7
FRESHWATER MARSH, WET
MEADOW & SHRUBLAND
Open water - ponds or lakes
Open water- pools
Open water- streams
Seeps / Springs: adjacent or
onsite
Non-vegetated areas (e.g.,
Bare ground / Mudflat / Sand)
Beaver dams/ Canals
Debris jams / Woody debris
Topographic gradient
Swale topography
Plant hummocks/ Hollows
Animal mounds and burrows
SALT MARSH
Natural tidal creeks/Creeklets
Pannes or Pools
Mudflats /Sandflats
Deposition or erosional
features e.g., sand or mud
fans, edge sloughing, intertidal
rocky shore
Topographic and/or Salinity
gradient
Detrital mats
Intertidal mussel colonies
Fiddler crab burrows
Ml
M2
M3
M4
M5
M6
M7
MS
M9
M10
Mil
SMI
SM2
SMS
SM4
SMS
SM6
SM7
SMS
BOG& FEN
Open water margin - Moats /
Laggs
Inlet /Outlet Stream (fens)
Rivulets
Springs / Seeps / Shallow open
water (fen)
Moss / Aquatic hollows / Bog
pools
Floating mats
Beaver dams / Canals
Peat flats (bog) /Marl flats
(fens)
Flarks/ Strings
Plant hummocks/ Hollows
Animal mounds and burrows
AQUATIC VEGETATION
Shallow open water (<2 m
deep)
Non-vegetated flats or bare
ground
Woody debris
Boulders, rocks, or bedrock
Topographic gradient
BF1
BF2
BF3
BF4
BF5
BF6
BF7
BF8
BF9
BF10
BF11
AVI
AV2
AV3
AV4
AV5
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Metric Rating:
Table 14.2. Physical Patch Type Metric Rating.
Metric Rating
EXCELLENT (A)
GOOD(B)
FAIR(C)
POOR(D)
Physical Patch Types: ALL WETLAND TYPES
Expected physical patch types for a particular example of wetland type
are present (see worksheet for examples).
One or two of the expected physical patch types are lacking (give
evidence).
Several of the expected physical patch types are lacking (give
evidence).
Most or the entire expected physical patch types are lacking (give
evidence).
Data for Metric Rating: See table from Collins et al. (2006, Physical Patch Type Worksheet).
Refinement is ongoing as we apply this to a variety of wetlands. Also see Faber-Langendoen
et al. (2011) for an evaluation of the discriminatory power of this metric based on an
assessment of 277 wetlands in Michigan and Indiana. Lemly and Rocchio (2009) tested user
variability and the performance of a variant of this metric in relation to a Level 3 EIA (e.g.,
vegetation index of biotic integrity).
Scaling Rationale: Scaling rationale focuses more on a characteristic set of physical patch
types, appropriate to the site rather than a presumption that more physical patch types are
better than fewer patch types. But assessing a characteristic set of patch types may not be
a particularly sensitive metric (Faber-Langendoen et al. 2011). Further testing is needed.
Confidence that reasonable logic and/or data support the metric: Low.
• 15. Soil Surface Condition
Definition: An indirect measure of soil condition based on stressors that increase the
potential for erosion or sedimentation of the soils, assessed by evaluating intensity of
human impacts to soils on the site.
Background: This metric is partly based on a metric developed by Mack (2001) and the
NatureServe Ecological Integrity Working Group (Faber-Langendoen et al. 2008). This
metric has also been called "Substrate / Soil Disturbance."
Metric Type: Condition/Stressor.
Tier: 2 (rapid field measure).
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Rationale for Selection of the Variable: Soils are a key feature of wetlands, providing the
medium in which plants grow and storing filtrate water. Assessment of soils is challenging
for rapid assessments; surface condition is the most visible aspect that can be assessed.
The attributes for this metric describe surface conditions that affect a site's biological and
physical characteristics and functions (Page-Dumroese et al. 2000, 2009a).
Measurement Protocol: Prior to fieldwork, aerial photography of the site can be reviewed
to determine if any soil alterations have occurred, but the primary assessment is based on
field observations of the AA.
Metric Rating:
Table 15.1. Soil Surface Metric Rating. Separate variants are provided by NVC Formation
for all freshwater wetlands (non-tidal) including Flooded & Swamp Forest, Freshwater
Marsh, Wet Meadow & Shrubland, Bog & Fen, Aquatic Vegetation versus estuarine
wetlands (tidal) including Mangrove and Salt Marsh.
Metric Rating
VI: Soil Surface Condition variant: ALL FRESHWATER NON-TIDAL
WETLANDS (FLOODED & SWAMP FOREST, FRESHWATER MARSH, WET
MEADOW & SHRUBLAND, BOG & FEN, AQUATIC VEGETATION)
EXCELLENT (A)
Bare soil areas are limited to naturally caused disturbances such as flood
deposition or game trails.
GOOD(B)
Small amounts of bare soil areas due to human causes are present but the
extent and impact is minimal. The depth of disturbance is limited to only
several centimeters (a few inches) and does not show evidence of ponding,
channeling water, or effects of boat traffic. Any disturbance is likely to recover
within a few years after the disturbance is removed.
FAIR(C)
Moderate amounts of bare soil areas due to human causes. Soil trampling by
livestock can cause 5-10 centimeters (several inches) of soil disturbance. Off-
road-vehicles or other machinery may have left some shallow ruts or erosion.
Damage is not excessive and the site will recover to potential with the removal
of degrading human influences and moderate recovery times.
POOR(D)
Bare soil areas substantial and contribute to altered hydrology or other long-
lasting impacts. Deep ruts from Off-road-vehicles or machinery may be
present, or livestock soil trampling and/or trails are widespread. Water will be
channeled or ponded. The site will not recover without restoration and/or
long recovery times.
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Metric Rating
EXCELLENT (A)
GOOD (B)
FAIR (C)
POOR (D)
1/2: So/7 Surface Condition variant: ESTUARINE WETLANDS (MANGROVE, SALT
MARSH, and tidal variants of FRESHWATER MARSH, WET MEADOW &
SHRUBLAND)
Excluding mud flats, bare soils are limited to salt pannes.
Limited exposure of bare soils caused by erosion of marsh and channel banks
due to excavation by marine traffic.
Frequent exposure of bare soils caused by erosion of marsh and channel banks
due to excavation by marine traffic.
Extensive bare soils caused by erosion of marsh and channel banks due to
excavation by marine traffic.
Data for Metric Rating: See Faber-Langendoen et al. (2011) for an evaluation of the
discriminatory power of this metric based on an assessment of 277 wetlands in Michigan
and Indiana. Also see Page-Dumroese et al. (2009b) for a summary of data for forests.
Scaling Rationale: Page-Dumroese et al. (2009a) summarize how increasing levels of soil
impacts in forests lead to changes in hydrology and other ecological processes.
Confidence that reasonable logic and/or data support the metric: Medium/High.
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STRESSOR CHECKLIST
GUIDELINES FOR COMPLETING THE STRESSOR CHECKLIST
Definition: A stressor is an anthropogenic perturbation within the AA or surrounding
landscape that can negatively affect the condition and function of the wetland.
Background: The term "stressor" is defined as "the proximate (human) activities or
processes that have caused, are causing, or may cause the destruction, degradation, and/or
impairment of biodiversity and natural processes" (from Salafsky et al. 2008). Here we
restrict our focus to those stressors that have caused or are causing impacts, whenever the
effects of the stressors are evident. For example, a stressor may be recent tree removal or
mowing. Less recent mowing or tree removal would be included only if the effect of those
stressors is still currently evident (e.g., old tree stumps). The term is synonymous with"
direct threats" as defined by Salafsky et al. (2008) or with "stressors" as used by the U.S.
EPA (Young and Sanzone 2002). The checklist is taken from Faber-Langendoen et al. (2011).
See also Collins et al. (2006). For guidance on completing the stressors checklist form, see
section below.
Rationale: The overarching purpose of this checklist is to identify likely anthropogenic
causes for diminished wetland conditions. A list of potential stressors corresponds to each
of the major ecological attributes of wetland condition. Thus, relationships between
stressors, attributes, and their component metrics might be surmised. In some cases, a
single stressor may cause deviation from "good" condition, but in most cases multiple
stressors interact to affect wetland condition (EPA, 2002).
There are four underlying assumptions about the presumed correlation between ecological
condition or integrity and the stressors: (1) deviation from a "good" condition can be
explained by a single stressor or multiple stressors acting on the wetland; (2) increasing the
number of stressors acting on the wetland causes a decline in its condition [there is no
assumption as to whether this decline is additive (linear), multiplicative, or is best
represented by some other non-linear mode]; (3) increasing either the intensity or the
proximity of the stressor results in a greater decline in condition; and (4) continuous or
chronic stress causes further declines in condition. We rate stressor levels and condition
levels separately so that we test these assumptions, by exploring correlations between the
stressor levels and the levels of integrity, including the use of a Human Stressor Index
(Rocchio 2007, Faber-Langendoen et al. 2011). Some wetlands may be very resistant to
change in the face of high levels of stress, which is informative. Some of the condition
metrics used to assess ecological integrity include stressors to a certain degree (e.g.,
70
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surrounding land use is a guide to rating alterations to water source), so care must be taken
in how these correlations are developed.
Seasonality: The Stressor Checklist is not particularly sensitive to seasonally, except for
Vegetation stressors.
Office and Field Indicators: The assessment of this attribute is the same across all wetland
classes. For each attribute, a variety of human actions that are likely sources of stress are
listed, and their presence, and likelihood of affecting the AA (assessment area) in question,
are recorded in the table. Stressors associated with Vegetation, Soil / Substrate, and
Hydrology are assessed within the AA itself. Adjacent land uses are scored only for those
land uses in the 100 meter Buffer surrounding the AA.
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Stressor Checklist Form
A complete set of stressors is presented in Table 16.1 below.
Table 16.1 Level 2 Stressor Checklist.
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Stressors: direct threats; "the proximate (human) activities or processes that have caused, are
causing the destruction, degradation, and/or impairment of biodiversity and natural
processes."
Important Points about Stressors Checklists.
1. Stressors checklists must be completed for all 4 categories (B, V, S, H).
2. Buffer Perimeter is the entire perimeter around the AA. up to a distance of 100 m. Rely on
imagery in combination with what you can field check.
3. Assess Buffer Perimeter Stressors and their effects within the Buffer Perimeter (NOT how buffer Stressors may impact the AA).
4. Stressors for Vegetation, Soils, and Hydrology are assessed across the assessment area: AA.
5. Some Stressors may overlap (e.g., 10 [Passive recreation] may overlap with 24 [Trampling]); choose only 1 and note overlap.
Assess for up to
next 20 yrs.
A= Small
B = Restricted
C = Large
D = Pervasive
Threat Scope (% of AA affected)
Affects a small (1-10%) proportion
Affects some (11-30%)
Affects much (31-70%)
Affects most or (71-100%)
Assess for up to
next 20 yrs.
A = Slight
B = Moderate
C = Serious
D = Extreme
Threat Severity within the Scope(degree of
degradation of AA)
Likely to only slightly degrade/reduce
Likely to moderately degrade/reduce
Likely to seriously degrade/reduce
Likely to extremely degrade/destroy or eliminate
D
E
V
E
L
O
P
R
E
C
V
E
G
Buffer(100 m)
STRESSORS CHECKLIST
1. Residential, recreational buildings, associated pavement
2. Industrial, commercial, military buildings, associated pavement
3. Utility/powerline corridor
4. Sports field, golf course, urban parkland, lawn
5. Row-crop agriculture, orchard, nursery
6. Hay field
7. Livestock, grazing, excessive herbivory
8. Roads (gravel, paved, highway), railroad
9. Other (specify):
10. Passive recreation (bird-watching, hiking, trampling, camping)
11. Active recreation (ATV, mountain biking, hunting, fishing, boats)
12. Other (specify):
13a. Tree resource extraction (e.g., clearcut, selective cut)
13 b. Shrub/herb resource extraction (e.g., medicine, horticulture)
14. Vegetation management(cutting, mowing)
15. Excessive animal herbivory, insect pest damage
16. Invasive exotic plant species
17. Pesticide or vector control, chemicals (give onsite evidence)
18. Other (specify):
Scope
Sever
ASSESSMENT AREA
Vegetation
Scope
Sever
Soil /Subs
Scope
Sever
Hydrology
Scope
Sever
Comments (circle stressor #)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
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CONTINUED
STRESSORS CHECKLIST
Nat
Dis
S
0
1
L
H
Y
D
R
O
L
O
G
Y
19. Altered natural disturbance regime (specify expected regime)
20. Other (specify):
21 . Excessive sediment or organic debris (recently logged sites),
gullying, erosion
22. Trash or refuse dumping
23. Filling, spoils, excavation
24. Soil disturbance (trampling, vehicle, livestock, skidding, etc.)
25. Grading, compaction, plowing, discing, fire lines
26. Physical resource extraction (rock, sand, gravel, etc.)
27. Other (specify):
28. Point source discharge (treatment water, non-storm
discharge, septic)
29. Non-point source discharge (urban runoff, farm drainage)
30. Dam, ditch, diversion, dike, levee, unnatural inflow, reservoir
31 . Groundwater extraction (water table lowered)
32. Flow obstructions (culverts, paved stream crossings)
33. Engineered channel (riprap, armored channel bank, bed)
34. Actively managed hydrology (e.g., lake levels controlled)
35. Tide gate, weir/drop structure, dredged inlet/channel
36. Other (specify):
Buffer [100m]
Scope
Sever
Vegetation [AA]
Scope
Sever
Soil / Subst. [AA]
Scope
Sever
Hydrology [AA
Scope
Sever
Comments (circle stressor(s)
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
Stressors Very Minimal or Not Evident (check box, if true)
II
I I
I I
*Hydrology Stressors will often cross between buffer and AA. For example, ditches in the buffer may directly impact hydrology of the AA.
Minimize listing in both columns unless you are sure of the impacts. If ditches occur in both the buffer and the AA, then both should be listed.
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Guidance on Completing the Stressor Checklist Form
Stressors are rated if they are observed or inferred to occur in the present (i.e. within a 10
year timeframe), or occurred anytime in the past with effects that persist into the present.
Stressors are not assessed if they are projected to occur in the near term, but do not yet
occur.1 It may be of interest to assess Stressors that are projected to occur in the near or
long term (e.g., projected sea level rise and its impact on salt marshes, but they should be
scored separately).
1 Thus listing of Stressors for an AA differs from a Threats Impact approach used to assess overall threats
that influence the conservation status of an ecosystem type (see Master et al. 2012).
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Stressors may be characterized in terms of scope and severity. Scope is defined as the
proportion of the AA that can reasonably be expected to be affected by the stressor with
continuation of current circumstances and trends. Severity is the degree of degradation
within the scope from the stressor, which can reasonably be expected to occur now or in
the near term (within 10 years) with continuation of current circumstances and trends.
The following guidance is under review, and is adapted from Master et al. (2012).
1. Record an estimate of the scope and severity for applicable individual
stressors to the wetland (Table 16.2).
Table 16.2. Ratings for Stressor Scope and Severity
Stressor Scope (typically assessed within a 10-year time frame)
Pervasive = Affects all or most (71-100%) of total AA
Large = Affects much (31-70%) of the total AA
Restricted = Affects some (11-30%) of the total AA
Small = Affects a small (1-10%) proportion of the total AA
Unknown
Stressor Severity - within the scope(assessed within max of 10 years)
Extreme = Likely to extremely degrade/destroy or eliminate AA (71-100%)
Serious = Likely to seriously degrade/reduce AA (31-70%)
Moderate = Likely to moderately degrade/reduce AA (11-30%)
Slight = Likely to only slightly degrade/reduce AA (1-10%)
2. The impact of each stressor is scored automatically from the scope and
severity values, and a letter grade is assigned (Table 16.3).
Table 16.3. Stressor Impact Scoring.
Stressor Impac
Calculation
Severity
Extreme
Serious
t Sco
Pervasive
Very High
High
Moderate Medium
Slight | Low
Large
High
High
Medium
Low
je
Restricted
Medium
Medium
Low
Low
Small
Low 1
Low 1
Low |
Low |
Stressor Impact
A = Very High
B = High
C = Medium
D = Low
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3. After impact has been recorded for all applicable stressors, use these impact values
to calculate an overall stressor impact for the major ecological attributes (buffer,
vegetation, soils, and hydrology) according to the guidelines in Table 16.4 below.
If the value for one or more impacts is a range, evaluate the highest (single and range)
values for every threat and then evaluate the lowest values to determine the range of
overall stressor impact. For example, three Medium-Low impacts could indicate an
overall stressor impact of High-Low, and four Medium-Low impacts indicate an overall
stressor impact of High-Medium.
Table 16.4. Guidelines for assigning an overall impact value.
Impact Values of Stressor
Categories
OVERALL STRESSOR
IMPACT
1 or more Very High, OR
2 or more High, OR
1 High + 2 or more Medium
1 High, OR
3 or more Medium, OR
2 Medium + 2 Low, OR
1 Medium + 3 or more Low
1 Medium, or 4 or more Low
1 to 3 Low
Very High
High
Medium
Low
4. After impact has been recorded for the major ecological attributes, use these impact
values to assign an overall stressor impact to the AA, again using Table 16.4 above (e.g.,
if Vegetation and Soils have a High Rating, then Overall Stressor Impact is Very High).
Ratings can be summarized using Table 16.5.
If the value for one or more major ecological attributes is a range, evaluate the highest
(single and range) values for every major attribute and then evaluate the lowest values
to determine the range of overall threat impact. For example, three Medium-Low
impacts indicate an overall threat impact of High-Low, and four Medium-Low impacts
indicate an overall threat impact of High-Medium.
Table 16.5. Stressor Summary Form
Major Ecological Attribute
Landscape Context
Vegetation
Soil
Hydrology
Overall Stressor Impact
Impact
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APPENDIX 1. Template for Metrics Protocols
Text Box. Template for Metric Description
Metric Name: A brief descriptive name for the metric
Definition: A brief explanation of the metric.
Background: Information on the origin and development of the metric.
Metric Type: Types include:
Condition metric: Emphasizes assessment of an aspect of the ecosystem's "inherent" attributes,
and which is relevant to ecological integrity (e.g. diagnostic native pecies, hydrologic connectivity).
Stressor metric: Emphasizes assessment of stressors to ecosystem (e.g., invasive species, ditches).
Tier: Metrics may belong on one of more "tiers," referring to levels of intensity of effort required to
document a metric. Tier 1 metrics use relatively simple, often qualitative, levels of information,
such as may be available from relatively basic interpretations of remote sensing imagery. Tier 2
typical requires qualitative or semi-quantitative data, such as is gathered through rapid field
assessments. Tier 3 typically requires intensive quantitative analysis, either from remote sensing
or field data, or both.
Example: Landscape Connectivity
Tier 1: Metric based on classifying land cover into natural vs cultural (Mclntyre and Hobbs 1999).
Tier 2: Metric based on modeling connectivity. For example, Circuitscape represents landscapes
as conductive surfaces, with resistance levels assigned to habitats that vary in their
permeability to ecological processes (McRae et al. 2008).
Tier 3: Metric based on integrating field observations in the landscape with remote sensing
imagery to assess landscape connectivity.
Rationale for Selection of the Variable: A brief explanation of the merits of the metric
Measurement Protocol: A summary of the methods used to assess the metric, including use of remote
sensing imagery and field collection methods.
Metric Rating: Specify the narrative and numerical ratings for the metric, from excellent to poor.
Metric Rating
EXCELLENT (A)
GOOD (B)
FAIR(C)
POOR(D)
Metric Name & Wetland Type(s) to which it applies
Metric Rating Description
Metric Rating Description
Metric Rating Description
Metric Rating Description
Data for Metric Rating: Published data that support the basis for the metric rating
Scaling Rationale: A brief summary of the rationale for how the A through D ratings were developed.
Confidence that reasonable logic and/or data support the metric: Confidence rating is based on the level
of data suDoortins the ratins and its scalins. Hish. Medium. Low. Provisional.
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APPENDIX 2. Field Methods
• Introduction
Field methods for applying ecological integrity assessments vary, depending on the purpose of
the assessment. Field methods depend, in part on the sampling design of the project; however,
discussions of sampling design are beyond the scope of this report.
• Defining the Assessment Area
AA: 0.5 ha (minimum) to 20 ha (maximum).
AA: Flexible area based on all or part of a polygon.
Observations and Guidelines: What follows are a series of observations and guidelines that
may be helpful for designing a field survey protocol for ecological integrity assessments.
First, the level of inference must be established. Most commonly, for ecological surveys, this is
an occurrence of a wetland, at the scale of a site. We refer to this as the "Assessment Area"
(AA). Accordingly, we may define the AA as "the entire area, sub-area, or point of an
occurrence of a wetland type."
Described below are three possible sampling strategies if the occurrence at a site is the focus:
1) Conduct an assessment survey of the entire area of the occurrence, e.g., a rapid
qualitative assessment.
2) Conduct an assessment survey of a typical sub-area(s) of the occurrence.
3) Collect data using one or more plots, placed in a representative or un-biased
location(s), in the assessment area or sub-area (see Appendix 3).
In all three cases, the intent is to assess the ecological integrity of a particular wetland
occurrence.
But the level of inference could also be the entire wetland area of a jurisdictional area (e.g.,
national park, natural area, state, or nation). The intent of an assessment may be to evaluate
the ecological integrity of "the park's wetlands," rather than any one particular wetland
occurrence. In this case, several options exist. For example, one could first identify all
occurrences of wetlands, and map their areal extent. Then one could either sample:
1) A subset of the occurrences, and infer the condition of the park's wetlands from this
survey.
2) A series of points across the entire wetland area irrespective of the occurrences, and
infer the overall condition of the park's wetlands.
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Various combinations of these two approaches are also possible. What is lost in the latter
approach is a site-specific ecological assessment area, since the park boundaries determine the
area being considered. But if individual wetlands are ecologically delineated and assessed, then
averaged together across the park, it would still be possible to think of such an assessment as
being comprised of AAs within the park.
Here, our primary focus is working at the level of an occurrence; that is, an entire local wetland
polygon or cluster of polygons of a particular type. The goal is to assess the integrity of this
occurrence, irrespective of property type, management regime, or size.
• Guidelines for Field Methods for Ecological Integrity Assessments
A few guidelines are provided for conducting wetland assessments:
1. Locate, and if desired, map (see step 5 below) the occurrence of a wetland type. Locations
may be based on office information, or from previous field visits. Establish a preliminary
Assessment Area (AA).
2. Classify the wetland type. Wetlands can be classified using a variety of classifications.
Examples of classifications include the U.S. National Vegetation Classification (USNVC, FGDC
2008, Faber-Langendoen et al. 2009), National Wetland Inventory types (Cowardin et al. 1979),
Ecological Systems (Comer et al. 2003), Hydrogeomorphic (HGM) type (Smith et al. 1995), or
individual state classifications. Knowing the USNVC Formation, NWI type, and HGM type is
helpful in applying some of the metrics, as some have variants based on these categories. For
example, assessing the Hydrologic Connectivity metric of a freshwater marsh found along a
river corridor requires a different form of the metric than for marshes found in depressions.
3. Provide standard office and field data collection protocols, regardless of the intent of the
survey, since the fundamental metrics of ecological integrity need to be included. Protocols for
how to measure the metrics are all briefly described above. In many cases the metrics can be
documented from remote sensing/aerial photographs imagery; in other cases, by walking an
assessment area (site); yet in others, by taking a few relatively simple field measures.
4. A field crew (usually two people) should be able to complete a rapid field assessment within
two to four hours (excluding travel time to or from the site), plus two hours preparation time
assessing the imagery (see #4 below). After the crew leaves the field, the field forms are
essentially complete. Field crew expertise should be akin to that needed for wetland
delineation; that is, field crews should have some knowledge of hydrology, soils, and
vegetation, sufficient to assess hydrologic dynamics, perhaps examine a soil core for mottling
and other features, and be able to identify all prominent native and exotic species.
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5. Where metrics can be assessed, at least preliminarily from the office, compile the needed
information for the office part of the assessment. Many sources of information can help
determine the condition and threats to a site (see Rocchio 2007):
• Aerial photographs
• Satellite imagery
• Digital Orthophoto Quadrangles (1 m resolution)
• CIS layers (e.g., roads, utility lines, trails, mines, wilderness areas, National Land Cover
Dataset, irrigation, ditches, and groundwater wells),
• Element occurrence records from Natural Heritage Programs
• State or Federal Agency surveys
• Soils map
• Etc.
6. It is helpful to map the extent of the occurrence as part of the field survey (see Rocchio
2007), using the following steps.
A. Estimation of Wetland Boundaries
The first step is to map the wetland area. Readily observable ecological criteria such as
vegetation, soil, and hydrological characteristics are used to define wetland boundaries,
regardless of whether they meet jurisdictional criteria for wetlands regulated under the
Clean Water Act.
B. Delineating Wetland Type Boundaries
The second step is to delineate the targeted type present within the wetland boundary.
Type descriptions can be used to guide the delineation of the type boundaries in the field.
A minimum map size criterion should be specified, and each patch of a wetland type would
be considered separate potential AAs or sub-AAs. If a patch is less than the minimum map
size then it would be considered to be associated with internal variation of the type in
which it is embedded.
C. Size of Occurrence
Once the targeted type boundaries are delineated, then size can be used to further refine
AA boundaries. For example, depending on the size or variation of the wetland area, the AA
may consist of the entire site or only a portion of the wetland/riparian area. For small
wetlands or those with a clearly defined boundary (e.g., isolated fens or wet meadows) this
boundary is almost always the entire wetland. In very large wetlands or extensive and
contiguous riparian types, a sub-sample of the area can be defined as the AA for the project.
For other project purposes such as regulatory wetland projects, there may be multiple AAs
in one large wetland (see Land Use Related Boundaries below).
D. Land Use Related Boundaries
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Significant change in management or land use may result in distinct ecological differences.
If such changes are large-scale, they could require two separate evaluations (two AAs)
within the occurrence. If the two AAs differ strongly in ecological integrity, they could be
considered separate occurrences or a "range-rating" could be applied to the occurrence
(e.g., A/C). Some examples follow:
• A heavily grazed wetland on one side of a fence line and ungrazed wetland on the other
could result in separate AAs.
• Natural changes in hydrology occur across a broadly defined wetland. For example, a
drastic change in water table levels or fluctuations or confluence with a tributary could
dictate using sub-AAs, and, perhaps a change in type.
• Anthropogenic changes in hydrology. For example, ditches, water diversions, irrigation
inputs, and roadbeds that substantially alter a site's hydrology relative to adjacent areas
could require sub-AAs, if ecological integrity varies substantially.
Full AA-Fen
Sub AA Intact Fen
Plot A-Intact Fen
Sub AA-Disturbed Fen
Plot B-Disturbed Fen
Full AA-Riparian
Plot C-Riparian Shrublan
Figure A2.1. Example of delineated Assessment Areas (AAs). Although contiguous with each other, the
fen and riparian shrubland were delineated as distinct AAs because they were distinct wetland types
(e.g., fen vs. riparian shrubland). The fen was divided into sub-AAs due to a human-induced disturbance
(e.g., ditching) which could significantly alter a large portion of an otherwise contiguous wetland type
(e.g., intact vs. disturbed fen). A decision as to whether to formally recognize two sub AAs within a
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larger AA or to simply incorporate the variation into a single evaluation depends on the observed
differences in integrity and the size of the AA versus sub-AAs (adapted from Rocchio 2007).
7. For rapid assessments, the entire AA should be assessed, including, as much as is feasibly
possible, the 100 m buffer around the AA (typically aided by aerial photography or other
imagery). Assessment will consist of a walk-around, scoring metrics based on visual
observations.
8. For intensive assessments, vegetation plots can be subjectively placed within the AA to
maximize capturing abiotic / biotic heterogeneity within the AA, or randomly placed (see
Appendix 3). Capturing heterogeneity within the plot ensures adequate representation of local,
micro-variations produced by such things as hummocks, water tracks, side-channels, pools,
wetland edge, and micro-topography in the floristic data. Plots can also be placed objectively, if
enough plots are laid.
The following guidelines can be used to determine plot locations within the AA:
• The plots can be located using a series of unbiased selected points in the AA or sub-AA.
• Large upland areas and other substantial inclusions which differ from the targeted type
should be excluded from plots; however, mesic micro-topographic features such as
hummocks, if present, can be included in the plots.
• Localized, small areas of human-induced disturbance can be included in the plot
according to their relative representation of the AA. Large areas of human-induced
disturbance should be delineated as a separate sub-AA.
References for Appendix 2
Comer, P., D. Faber-Langendoen, R. Evans, S. Gawler, C. Josse, G. Kittel, S. Menard, M. Pyne, M.
Reid, K. Schulz, K. Snow, and J. Teague. 2003. Ecological Systems of the United States: A
Working Classification of U.S. Terrestrial Systems. NatureServe, Arlington, VA.
Cowardin, L. M., V. Carter, F. C. Golet, and E. T. LaRoe. 1979. Classification of the wetlands and
deepwater habitats of the United States. U.S. Fish and Wildlife Service, Washington, D.C.,
USA.
Faber-Langendoen, D., D.LTart, and R.H. Crawford. 2009. Contours of the revised U.S. National
Vegetation Classification standard. Bulletin of the Ecological Society of America 90:87-93.
Federal Geographic Data Committee.2008. Vegetation Classification Standard, version 2 FGDC-
STD-005, v2. Washington, DC.
Rocchio, J. 2007. Assessing Ecological Condition of Headwater Wetlands in the Southern Rocky
Mountain Ecoregion Using a Vegetation Index of Biotic Integrity. Colorado Department of
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Natural Resources, and U.S. Environmental Protection Agency, Region VIM. Colorado Natural
Heritage Program, Colorado State University, Fort Collins, CO.
Online: http://www.cnhp.colostate.edu/reports.html.
Smith, R. D., A. Amman, C. Bartoldus, and M. M. Brinson. 1995. An approach for assessing
wetland functions using hydrogeomorphic classification, reference wetlands, and functional
indices. Technical report TR WRP-DE-10, and operational draft. U.S. Army Engineers
Waterways Experiment Station, Vicksburg MS.
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APPENDIX 3. Vegetation Plots
Although vegetation plots are not typically included in Level 2 assessments, they may be added
as part of an "enhanced" Level 2, and they are part of the standard approach for Level 3
assessments. Here we describe the key considerations in choosing a vegetation plot approach
(adapted from Jennings et al. 2009). We note that the 0.1 ha hybrid plot approach, typically
with one or more 100 to 400 m2 subplots, contains many desirable features for sampling
vegetation, including for EIA purposes (see especially Mack 2007). The method is fully
described in Peet et al. 1998; however,
typically not needed for EIA purposes.
described in Peet et al. 1998; however, their nested methodology below the 100 m2 level is
• Plot Size and Design
Two fundamentally different approaches are commonly used for recording vegetation: (a) data
is recorded from a single large plot, and (b) data is recorded from a set of smaller plots
distributed within the stand. Both types of plot designs provide adequate data for vegetation
classification, but each method has its own requirements and advantages.
Data from a single large plot: This is an efficient, rapid method for collecting floristic and
physiognomic data. The plot size is chosen to ensure that it is small enough to remain relatively
uniform in habitat and vegetation, yet is large enough to include most of the species that occur
within the community or wetland type. This approach permits statistical assessment of
variation among stands but not within stands. Recommended plot size varies depending on the
structure of vegetation (such as the size of individual plants, their spacing, and the number of
canopy layers) and the need to capture an adequate proportion of the stand's species
composition and structure. In most temperate hardwood or conifer forests, plots of between
200 and 1,000 m2 are adequate for characterizing both the herb and the tree strata, while in
many tropical forests, plots between 1,000 and 10,000 m2 are required. Grassland and
shrubland vegetation may require plots between 100 and 400 m2, while vegetation containing
very sparse vascular vegetation (sometimes dominated by non-vascular vegetation), such as
open cliff, talus, or desert vegetation may require plots between 1,000 and 2,500 m2 (McAuliffe
1990; see Chytry and Otypkova 2003 for plot sizes used by European phytosociologists). We do
not recommend any particular plot shape; indeed shape may depend on the local environment
and wetland type (e.g., riparian stands tend to be linear).
Data from a set of subplots: Taking multiple subplots within a community or wetland type is an
alternative to the single large plot sampling method. This approach yields data that can assess
the internal variability within the AA and can more precisely estimate the average abundance of
each species across the AA. It is often used to measure responses to experimental
manipulations of vegetation. Investigators using the multiple subplot method may locate
subplots randomly or systematically within the stand. The observation unit can be a quadrat,
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line-transect, or point-transect, and can be of various sizes, lengths, and shapes. Quadrats for
ground layer vegetation typically range from 0.25 to 5.0 m2 and anywhere from 10 to 50
quadrats may be placed in the stand. Although subplots may be distributed through a large
portion of the stand, the total area from which data are recorded may be smaller than that
from a single large plot.
Finally, the choice between a single large plot vs. multiple subplots must consider the tradeoff
between a better ability to estimate the precision of species abundance values obtained from
small, more widely distributed subplots compared to the more complete species list and more
realistic assessment of intimate co-occurrence obtained using the single large plot. A
disadvantage of relying on subplots to characterize the stand is that a large number of small
sample units may be needed to characterize the full floristic composition of the stand. Yorks
and Dabydeen (1998) describe how reliance on subplots can result in a failure to assess the
importance of many of the less abundant species in a plot. Consequently, whenever subplots
or transects are used, a list of "additional species present" within a larger part of the stand,
such as some fixed area around the subsamples, should be included. For example, the
California Native Plant Society protocol uses 50-meter point transects supplemented with a list
of all the additional species in a surrounding 5x50 m area (Sawyer and Keeler-Wolf 1995).
Hybrid approaches: A hybrid sampling method combines advantages from the above
approaches. Indeed, the 1,000 m2 (50 x 20 m) Whittaker plot approach comes as close to a
standard method for vegetation sampling as any (Whittaker 1960, Naveh and Whittaker 1979,
Stohlgren et al. 1995, Peet et al. 1998, Mack 2007). Sometimes, several somewhat large
subplots (e.g., >100 to 400 m2 in a forest) are established within the full plot to capture internal
variability. An alternative plot method uses a series of nested plots to describe the different
layers, with the largest plot for the tree layer, and progressively smaller subplots for the shrub,
herb, and nonvascular strata. Although efficient with respect to measures of abundance for the
common species, this method risks under-representing the floristic richness of the lower strata
which are often more diverse than the upper strata, and may contain many diagnostic species.
This problem can be ameliorated by listing all species found within the largest plot used to
sample the upper stratum.
Still, no one plot size is correct a priori: The widely applied 1,000 m2 Whittaker plot method
noted above and the 375 m2 Daubenmire (1968) plot method both contain a series of subplots
for herbaceous vegetation. With adequate documentation, the hybrid approach can yield data
compatible with many other types of sampling while providing data on compositional variation
as a function of the scale of observation.
• Plot Data
Three types of plot data are needed for effective vegetation classification: vegetation data, site
data, and metadata. Of these, vegetation data on floristics and physiognomy are the primary
focus. Site or habitat data, such as soil attributes, topographic position, and disturbance
history, are also important, but because environmental variables that are significant in one
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region may be insignificant in another region, the selection of such variables will vary by
vegetation type. Floristic composition and cover estimation requires direct estimation of the
canopy cover for each plant species. It is preferable to estimate the cover of each species in
each vertical canopy stratum or by major growth forms. To assess vegetation structure, the
total canopy cover should also be determined for each stratum or major growth form of
vegetation (i.e., tree, shrub, herb layer or growth form). These measurements of species and
stratum/growth form cover allow for a three-dimensional representation of the vegetation in a
plot in order to characterize the vegetation.
References for Appendix 3
Chytry, M. and Z. Otypkova. 2003. Plot sizes used for phytosociological sampling of European
vegetation. Journal of Vegetation Science 14: 563-570.
Daubenmire, R.F. 1968. Plant communities: A textbook of plant synecology. Harper and Row, New
York.
Jennings, M.D., D. Faber-Langendoen, O.L. Loucks, R.K. Peet, and D. Roberts.2009. Standards for
associations and alliances of the U.S. National Vegetation Classification. Ecological
Monographs 79: 173-199.
Mack, J.J. 2007. Developing a wetland IBI with statewide application after multiple testing
iterations. Ecological Indicators 7: 864—881.
McAuliffe, J. R. 1990. A rapid survey method for the estimation of density and cover in desert plant
communities. Journal of Vegetation Science 1:653-656.
Naveh, Z. and R.H. Whittaker. 1979. Structural and floristic diversity of shrublands and woodlands
in northern Israel and other Mediterranean areas. Vegetatio 41:171-190.
Peet, R. K., T. R. Wentworth, and P. S. White. 1998. The North Carolina Vegetation Survey protocol:
A flexible, multipurpose method for recording vegetation composition and structure.
Castanea 63:262-274.
Sawyer, J. 0. and T. Keeler-Wolf. 1995. A manual of California vegetation. California Native Plant
Society, Sacramento, CA.
Stohlgren, T.J., M.B. Falkner, and LD. Schell. 1995. A modified-Whittaker nested vegetation
sampling method. Vegetatio 117:113-121.
Whittaker, R.H. 1960. Vegetation of the Siskiyou Mountains, Oregon and California. Ecological
Monographs 30:279-338.
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Yorks, I.E. and S. Dabydeen. 1998. Modification of the Whittaker sampling technique to assess
plant diversity in forested natural areas. Natural Areas Journal 18:185-189.
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APPENDIX 4. Descriptions of Major Wetland Formations in the USNVC.
Major wetland categories used to guide formation distinctions are described below (from Faber-Langendoen et al. 2012). Types,
definitions, environmental features, and growth forms are adapted from the National Wetlands Working Group (1997) in Canada
and Mackenzie and Moran (2004), with linkage to major wetland types described by Mitsch and Gosselink (2000) and by the
National Wetland Inventory (NWI, Cowardin et al. 1979).
Wetland
Category
Bog
Definition
Bogs are shrubby, nutrient-poor
peatlands with distinctive
communities of ericaceous shrubs
and hummock-forming Sphagnum
species, sometimes with sedges,
adapted to high acid and oxygen-poor
soil conditions. Trees >2 m have
<10% cover (rarely, raised bogs may
contain some forested stands).
Vegetation of bogs and poor fen often
overlap and are sometimes treated
together as "acid peatland."
Environmental
features
+/- ombrotrophic
pH<4.5
>40 cm fibric/mesic
peat
Growth forms
Stunted needle-
leaved tree, low
shrub, dwarf
shrub
(ericaceous),
sphagnum
Mitsch &
Gosselink
(2000) type
Peatland
NWI Wetland Class
Palustrine Moss-Lichen (PML)*+/-
Palustrine Emergent (PEM)
Palustrine Scrub-Shrub (PSS)
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Fen
Fens are peatlands where
groundwater or stream inflow
maintains relatively moderate to high
mineral content within the rooting
zone. Sites are characterized by non-
ericaceous shrubs, sedges, grasses,
reeds, and brown mosses. Trees >2 m
have <10% cover. Forested fen
included under Swamp Forest. Ranges
from poor fen to rich fen. Poor fens
overlap with bogs and are sometimes
together as "acid peatland" separate
from "alkaline peatland."
Groundwater-fed
pH >4.5(approximate
ranges include poor fen 4.5-
5.5, medium or
intermediate fen 5.5-6.5,
rich fen 6.5-7.5 and
extremely rich fen > 7.5).
>40 cm fibric/mesic
peat (including marly
peat)
Low shrub (often
non-ericaceous),
sedge (often
fine), grass, reed,
and brown
moss, with or
without
sphagnum
Peatland
Palustrine Moss-Lichen (PML)+/-
Palustrine Emergent (PEM)
Palustrine Scrub-Shrub (PSS)
Freshwater A marsh-wet meadow is a shallowly
Marsh, Wet flooded or saturated wetland
Meadow & dominated by emergent grass-like,
Shrubland forb or shrub vegetation. A
(non-tidal and fluctuating water table is typical in
tidal) marshes and wet meadows, with
early season high water tables and
some flooding dropping through the
growing (or dry) season, and exposure
of the substrate or drying of the
profile possible in late (or high of dry)
season or drought years. Shrub
wetlands (shrub carrs) occupy similar
sites to wet meadows. Trees >2 m
have <10% cover.
Mineral soils or well-
humified peat, or
rarely marl or rocky
substrates. Protracted
shallow flooding (0.1
to 2.0 m), prolonged
soil profile saturation,
or freshwater or
oligohaline tidal
inundation.
Grass, sedge
(often coarse),
forb, low shrub,
tall shrub
Freshwater
marsh
(emergent),
Tidal
freshwater
marsh,
Riparian
ecosystems
(wetland,
herb/shrub)
Palustrine Emergent (PEM)
Palustrine Scrub-Shrub (PSS)
Riverine Tidal Emergent (non-
persistent) (R1EM2)
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Salt Marsh
Flooded &
Swamp Forest
(non-tidal and
tidal)
Mangrove
Aquatic
Vegetation
(non-tidal and
tidal)
Salt marshes are intertidal to
supratidal ecosystems that are
flooded diurnally (or less), sometimes
with freshwater inputs, and has
communities dominated by salt-
tolerant emergent graminoids and
succulents. Trees >2 m have <10%
cover.
A swamp forest is a tree-dominated
mineral or peat wetland, on sites with
a flowing/flooded or fluctuating semi-
permanent, near or at surface water
table. A flooded forest occur on sites
where flooding varies from temporary
(<7 days) to semi-permanent (>180
days). Trees >2 m have >10% cover.
Mangroves occur in the inter-tidal
and brackish backwater of estuarine
areas in tropical regions. Mangroves
include tree and shrub forms of
mangrove of all heights.
Aquatic wetlands are shallow waters
dominated by rooted, submerged and
floating aquatic plants. They are
associated with permanent still or
slow-moving waters, such as shallow
potholes, ponds, rivers and lakes.
Aquatic plants may occur in mineral
or in well-humified sedimentary peat.
Emergent growth forms <10% cover,
hydromorphic growth forms >1%
cover.
Intertidal and
supratidal zones,
semi-diurnal to
diurnal, flooding by
brackish or saltwater
[n.b. inland non-tidal
saline wet meadows
may also be placed
here]
Mineral soils or well-
humified peat.
Temporary to
semipermanent
flooding (0.1 to 2 m
deep), or freshwater
or oligohaline tidal
inundation.
Intertidal and
supratidal zones,
semi-diurnal to
diurnal, flooding by
brackish or saltwater
+/-Permanent deep
flooding (0.5 -2m),
substrate can be
muck, sand, marl or
rocky substrates
Grass, sedge,
forb, halophytic
(succulent) forb,
halophytic shrub
broad-leaved
tree, needle-
leaved tree, tall
shrub, forb,
graminoid,
hydromorphic
herb (rarely)
Mangrove,
halophytic
shrub,
halophytic
(succulent) forb,
graminoids
Hydromorphic
(aquatic) herb
Salt marsh,
[Inland saline
marsh]
Freshwater
swamps,
Riparian
ecosystems
(wetland, tree)
Mangrove
Freshwater
marsh
(aquatic)
Estuarine Intertidal Emergent (E2EM)
Estuarine Intertidal Scrub-Shrub
(E2SS)
Palustrine Forested (PFO)
Estuarine Intertidal Forested (E2FO)
(mainly freshwater)
Estuarine Intertidal Forested (E2FO)
Palustrine Aquatic Bed (PAB)
Riverine Tidal Aquatic Bed (R1AB)
Lacustrine Aquatic Bed (L2AB)
*NWI PML= mosses or lichens cover substrates other than rock (emergents, shrubs, or trees make up less than 30% of the areal cover)
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References for Appendix 4
National Wetlands Working Group. 1997. Wetlands of Canada. C. D. A Rubec, editor. Ecological Land Classification Series No. 24.
Environment Canada, Ottawa, and Polyscience Publications, Inc., Montreal. 452 pp.
Cowardin, L. M., V. Carter, F. C. Golet, and E. T. LaRoe. 1979. Classification of the wetlands and deepwater habitats of the United
States. U.S. Fish and Wildlife Service, Washington, D.C., USA.
Faber-Langendoen, D., C. Josse, G. Navarro, T. Keeler-Wolf, D. Meidinger, E. Helmer, B. Hoagland, G. Fults, S. Ponomarenko, J.-P.
Saucier, D. Tart, A. Weakley. 2012b. Classification and description of world formation types. Federal Geographic Data
Committee, FGDC Secretariat, U.S. Geological Survey. Reston, VA, and NatureServe, Arlington, VA.
MacKenzie, W.H. and J.R. Moran. 2004. Wetlands of British Columbia: a guide to identification. Research Branch, B.C. Ministry of
Forestry, Victoria, B.C. Land Management Handbook. No. 52.
Mitsch, W. J. and J. G. Gosselink. 2000. Wetlands, 3rd edition. J. Wiley & Sons, Inc. 920 pp.
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APPENDIX 5. Descriptions of Hydrogeomorphic Classes.
See hydrogeomorphic class definitions below from NRCS (2008). Table 1 provides a full definition; Table
2 (Smith et al. 1995) provides a brief tabular overview.
Table 1 Definitions of hydrogeomorphic wetland classes (modified from Brinson et al. 1995)
HGM CLASS I Definition
RIVERINE
Riverine wetlands occur in flood plains and riparian corridors in association with stream
channels. Dominant water sources are often overbank flow from the channel or subsurface
hydraulic connections between the stream channel and wetlands. However, sources may be
interflow and return flow from adjacent uplands, occasional overland flow from adjacent
uplands, tributary inflow, and precipitation. At their headwater, RIVERINE wetlands often are
replaced by SLOPE or DEPRESSIONAL wetlands where the channel morphology may disappear.
They may intergrade with poorly drained flats or uplands. Perennial flow in the channel is not a
requirement.
DEPRESSIONAL
Depressional wetlands occur in topographic depressions. Dominant water sources are
precipitation, ground water discharge, and both interflow and overland flow from adjacent
uplands. The direction of flow is normally from the surrounding uplands toward the center of the
depression. Elevation contours are closed, thus allowing the accumulation of surface water.
Depressional wetlands may have any combination of inlets and outlets or lack them completely.
Dominant hydrodynamics are vertical fluctuations, primarily seasonal. Depressional wetlands
may lose water through intermittent or perennial drainage from an outlet, by evapotranspiration
and, if they are not receiving ground water discharge, may slowly contribute to ground water.
Peat deposits may develop in depressional wetlands. Prairie potholes are a common example of
depressional wetlands.
SLOPE
Slope wetlands normally are found where there is a discharge of ground water to the land
surface. They normally occur on sloping land; elevation gradients may range from steep hillsides
to slight slopes. Slope wetlands are usually incapable of depressional storage because they lack
the necessary closed contours. Principal water sources are usually ground water return flow and
interflow from surrounding uplands, as well as precipitation. Hydrodynamics are dominated by
downslope unidirectional water flow. Slope wetlands can occur in nearly flat landscapes if
ground water discharge is a dominant source to the wetland surface. Slope wetlands lose water
primarily by saturation subsurface and surface flows and by evapotranspiration. SLOPE wetlands
may develop channels, but the channels serve only to convey water away from the SLOPE
wetland. Fens are a common example of slope wetlands.
MINERAL SOIL
FLATS
Mineral soils flats are most common on interfluves, extensive relic lake bottoms, or large historic
flood plain terraces where the main source of water is precipitation. They receive no ground
water discharge, which distinguishes them from DEPRESSIONAL and SLOPE wetlands. Dominant
hydrodynamics are vertical fluctuations. Mineral soil flats lose water by evapotranspiration,
saturation overland flow, and seepage to underlying ground water. They are distinguished from
flat upland areas by their poor vertical drainage, often due to spodic horizons and hardpans, and
low lateral drainage, usually due to low hydraulic gradients. Mineral soil flats that accumulate
peat can eventually become the class ORGANIC SOIL FLATS. Pine flatwoods with hydric soils are a
common example of MINERAL SOIL FLAT wetlands.
ORGANIC SOIL
FLATS
Organic soil flats, or extensive peatlands, differ from mineral soil flats, in part because their
elevation and topography are controlled by vertical accretion of organic matter. They occur
commonly on flat interfluves, but may also be located where depressions have become filled
with peat to form a relatively large flat surface. Water source is dominated by precipitation,
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while water loss is by saturation overland flow and seepage to underlying ground water. Raised
bogs share many of these characteristics, but may be considered a separate class because of
their convex upward form and distinct edaphic conditions for plants. Portions of the Everglades
and northern Minnesota peatlands are common examples of organic soil flat wetlands.
ESTUARINE Estuarine Fringe wetlands occur along coasts and estuaries and are under the influence of sea
FRINGE level. They intergrade landward with Riverine wetlands where tidal currents diminish and
riverflow becomes the dominant water source. Additional water sources may be ground water
discharge and precipitation. The interface between the estuarine fringe and Riverine classes is
where bidirectional flows from tides dominate over unidirectional ones controlled by flood plain
slope of Riverine wetlands. Because estuarine fringe wetlands frequently flood and water table
elevations are controlled mainly by sea surface elevation, estuarine fringe wetlands seldom dry
for significant periods. Estuarine fringe wetlands lose water by tidal exchange, by saturated
overland flow to tidal creek channels, and by evapotranspiration. Organic matter normally
accumulates in higher elevation marsh areas where flooding is less frequent and the wetlands
are isolated from shoreline wave erosion by intervening areas of low marsh. Spartina alterniflora
salt marshes are common examples of estuarine fringe wetlands.
LACUSTRINE Lacustrine fringe wetlands are adjacent to lakes where the water elevation of the lake maintains
FRINGE the water table in the wetland. In some cases, these wetlands consist of a floating mat attached
to land. Additional sources of water are precipitation and ground water discharge, the latter
dominating where lacustrine fringe wetlands intergrade with uplands or SLOPE wetlands.
Surface water flow is bidirectional, usually controlled by water-level fluctuations such as seiches
in the adjoining lake. Lacustrine fringe wetlands are indistinguishable from depressional
wetlands where the size of the lake becomes so small relative to fringe wetlands that the lake is
incapable of stabilizing water tables. Lacustrine fringe wetlands lose water by flow returning to
the lake after flooding, by saturation surface flow, and by evapotranspiration. Organic matter
normally accumulates in areas sufficiently protected from shoreline wave erosion. Unimpounded
marshes bordering the Great Lakes are a common example of lacustrine fringe wetlands.
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Table 2 (Smith etal. 1995)
Hydrogeomorphic Classes of Wetlands Showing Dominant Water Sources, Hydrodynamics,
and Examples of Subclasses
Hydrogeomorphic
Class
Riverine
Depressional
Slope
Mineral soil flats
Organic soil flats
Estuarine fringe
Lacustrine fringe
Water Source (dominant)
Overbank flow from
channel
Return flow from
groundwater
and interflow
Return flow from
groundwater
Precipitation
Precipitation
Overbank flow from estuary
Overbank flow from lake
Hydrodynamics
(dominant)
Unidirectional and
horizontal
Vertical
Unidirectional,
horizontal
Vertical
Vertical
Bidirectional,
horizontal
Bidirectional,
horizontal
Examples of Regional Subclass
Eastern USA
Bottomland
hardwood forests
Prairie pothole
marshes
Fens
Wet pine
flatwoods
Peat bogs;
portions of
Everglades
Chesapeake Bay
marshes
Great Lakes
marshes
Western USA
and Alaska
Riparian forested
wetlands
California vernal
pools
Avalanche chutes
Large playas
Peat bogs
San Francisco
Bay
Flathead Lake
marshes
References for Appendix 5
Smith, R. D., Ammann, A., Bartoldus, C, and M.M. Brinson. 1995. An approach for assessing
wetland functions using hydrogeomorphic classification, reference wetlands, and functional
indices, Technical Report WRP-DE-9, U.S. Army Engineer Waterways Experiment Station,
Vicksburg, MS.
Natural Resources Conservation Service. 2008. Hydrogeomorphic Wetland Classification
System: An Overview and Modification to Better Meet the Needs of the Natural Resources
Conservation Service. USDA Technical Note No. 190-8-76.
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