EPA/600/R-98/175
March 1999
Nanticoke Wetland
Assessment Study
by:
Dennis F. Whigham, Donald E. Weller, and Thomas E. Jordan
Smithsonian Environmental Research Center
Box 28
Edge water, MD 2103 7
Agreement Number: CR826817-01-0
Project Officer:
Mary E. Kentula
Western Division
National Health and Environmental Effects Laboratory
Corvallis, OR 97333
National Health and Environmental Effects Laboratory
Office Of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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DISCLAIMER
This project has been funded by the U.S Environmental Protection Agency and
conducted through assistance agreement number CR826817-O1-O to the Smithsonian
Environmental Research Center. This document has been subjected to the Agency 1 s peer and
administrative review and approved for publication. The official endorsement of the Agency
should not be inferred. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
This document should be cited as:
Whigham, D.F., D.E Weller, and T.E. Jordan. 1999. Nanticoke Wetland Assessment Study.
EPA/600/R-98/1 75. U S. Environmental Protection Agency, Western Division, National Health
and Environmental Effects Laboratory, Corvallis, Oregon.
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INTRODUCTION
The overall objective of the study is to assess the ecological conditions of wetlands in the
Nanticoke River watershed of Maryland and Delaware. Itis one part of a multi-faceted effort
coordinated by EPA’s Environmental Monitoring and Assessment Program (EMAP), EPA
Region ifi, Chesapeake Bay Program, and Commonwealths of Maryland and Delaware.
Following a listing of four objectives and a generalized descnption of the Nanticoke River
watershed, the study plan is divided into four sections Section I is a descnption of the
Hydrogeomorphic (HGM) approach that we will use to assess wetland conditions. Section II is a
description of the proposed activities, Section ifi contains a preliminary schedule. Section IV is a
projected list of products.
Specific objectives are:
1. Use the hydrogeomorphic (HGM) approach to classify and assess ecological conditions in
non-tidal rivenne and depressional wetlands of the Nanticoke River watershed. The
assessments will be performed by conducting field surveys of wetlands in combination
with digital spatial data analyzed with a geographic information system (GIS)
Completion of Objective I will result in measurements of ecological conditions in non-
tidal rivenne and depressional wetland sites in the watershed. The sites chosen for study
will be statistically chosen using EPA protocols to be representative of the entire
watershed.
2. Use data from individual wetlands (Objective 1) to predict ecological conditions of non-
tidal nvenne and depressional wetlands in the watershed. Objective 2 will be
accomplished by determining mathematical relationships between wetland conditions and
GIS variables obtained in Objective 1. The mathematical relationships will be used in
combination with GIS to predict wetland conditions over the entire watershed.
3. Objectives 1 and 2 are based on the important premise that the HGM approach accurately
predicts ecological conditions in wetlands. The third objective will be to verify this
premise by comparing results of HGM assessments at individual wetlands with
measurements of ecological processes at the same sites. This part of the project will
focus on denitnfication, a specific component of the nitrogen cycle. The importance of
denitrification in wetlands in the highly agricultural Nanticoke River watershed is
descnbed in more detail below.
4. A fourth objective of the project will be to use denitrification rates measured at individual
wetlands (Objective 3) to predict rates of denitrification of all non-tidal riverine and
depressional wetlands in the watershed. Objective 4 will be accomplished by determining
mathematical relationships between denitrification rates and GIS variables obtained in
Objective 1. The mathematical relationships will be used in combination with GIS to
predict denitnfication rates in all non-tidal riverine and depressional wetlands in the
Nanticoke River watershed.
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The Nanticoke River drains approximately 700,000 acres of four counties in Maryland
and two counties in Delaware (Nature Conservancy 1994). Agriculture occupies about 42% of
the watershed and less than 2% is urban or suburban lands Forests cover approximately 45% of
the watershed, but many are intensively managed (Bohien and Friday 1997). Extensive
agriculture and forest management have only been possible because of drainage, a practice that
has had major impacts on wetlands in the watershed. Most of the losses of palustrine wetlands in
Delaware, for example, has resulted from “agricultural conversion, drainage by channelization
projects, and forestry practices” (Tiner 1985). Wetland losses in intertidal portions of the
watershed are minimal, but considerable pressures exist for conversion of inland (non-tidal)
wetlands (Tiner 1985, Tiner and Burke 1995). Water quality problems are common within the
watershed and are thought to be a reflection of the intensive agriculture (Phillips et al. 1993,
Maryland Department of the Environment 1994, Bohlen and Friday 1997, Jordan et al. 1997).
We anticipate that the greatest impacts to wetlands in the Nanticoke River watershed
have been and will continue to be to nvenne wetlands along small (ist and 2’ ’ order) streams and
to wetlands in the depressional and flats subclasses (sensu Brinson 1993). Accordingly, our
efforts will focus on the assessment of wetland conditions in non-tidal rivenne, primarily
headwater areas, wetlands associated with 1 St and 2 nd order streams, and depressional wetlands.
We will not assess ecological conditions in the more than 16,000 acres (@ 2% of the watershed)
of intertidal wetlands associated with the Nanticoke River watershed (Tiner 1985, Tiner and
Burke 1995). Our sampling of rivenne wetlands will, however, not preclude the inclusion of
forested nverine wetlands that are periodically influenced by tides. There is insufficient funding
in the project to sample intertidal wetlands and, based on conversations with wetland experts
from Delaware and Maryland, tidal wetlands are currently the least threatened wetland types in
the watershed.
The approach that we will use to conduct the study, the timetable that we will follow, and
expected products from the project are presented in the next four sections. The first year of the
study will be the Developmental Phase consisting of three related components. First, we will
produce a map of the distnbution of HGM wetland subclasses in the watershed. Second, we will
develop, test, and validate variables and models that will be used to assess wetlands in the
watershed. The third component will be the testing of methods for measuring denitrification.
The second year of the study will be the Assessment Phase when we will assess wetland
conditions in the watershed, measure denitnfication in a sub-set of wetlands chosen for
assessment, analyze and interpret data, and produce reports and scientific publications.
SECTION 1- HGM APPROACH TO WETLAND ASSESSMENT
We define ecological conditions to be the characteristics of individual wetlands. In the
HGM approach to wetland assessment (e.g., Smith et al 1995, Bnnson 1996, Rheinhardt et al
1997), wetland conditions are determined by quantifying vanables chosen to characterize (e.g.,
assess) wetland functions A variable is an attribute or characteristic of a wetland (e.g., plant
species diversity) or the surrounding landscape (e.g., land-use in areas adjacent to the wetland)
that influences the capacity of a wetland to perform a function. Functions are the normal
activities or actions that occur in wetland ecosystems. For each wetland that is assessed, a
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numencal value for each vanable is determined by observing the variable in the wetland or
surrounding landscape then assigning a scaled value (Variable Subindex) based on comparison to
predetermined reference standards. Reference standards are the conditions exhibited by a group
of reference wetlands that correspond to a level of functioning that is both charactenstic for the
reference subclass (e.g , depressional or nverine non-tidal wetlands) in the reference domain
(e.g., Nanticoke River watershed) and are sustainable over the long-term without human
intervention. Once Variable Subindices have been assigned to each variable, functions are
computed as Functional Capacity Index scores by mathematically combining variable Subindices
(e.g , Rheinhardt et al 1997).
Functions assessed using the HGM approach fall into three categones (hydrological,
biogeochemical, biologicallhabitat) and they are conceptually representative of ecological
conditions of a wetland at the time it was sampled. Functional Capacity Index scores and
Variable Subindices are useful not only in determining existing wetland conditions but also in
wetland restoration and mitigation.
One of the strengths of the HGM approach is that it not only can be used to assess overall
wetland conditions but the data can be analyzed to determine which variables differ from
reference conditions in each wetland or groups of wetlands. We will use matnces of Functional
Capacity Index scores and Variable Subindex values to provide a detailed analysis of conditions
for depressional and nvenne subclasses of wetlands in the watershed. For example, wetland
functions for depressional wetlands in the watershed might score high for a hydrology function
(e.g., the quantitative score for the function would be near the maximum value of 1.0). The same
wetlands, however, might score low for one of the biological/habitat functions (e.g., the
quantitative scores for the function would be near the minimum value of 0 0). The Variable
Subindex values can be analyzed to determine why the Functional Capacity Index score was low.
Continuing with the same example, it might be found that the wetlands which scored low for a
biological/habitat function had all been converted from forested wetlands to wetlands dominated
by weedy herbaceous species and they all also had low Variable Subindex values for
microtopography (i.e , the wetlands had been smoothed mechanically by farming activities).
This approach will allow us to provide a detailed analysis of conditions in the watershed from the
perspective of both variables and functions. Further descriptions of the application of HGM and
examples of its application can be found in Rhemhardt et al. (1997), Ainslie et al.(In press) and
Rheinhardt et al. (In review).
SECTION II- RESEARCH APPROACH
The primary goal of this study is to assess the ecological conditions of wetlands in the
Nanticoke River watershed. It is not the intention of this study to focus on delineation of wetland
boundaries in the watershed nor to perform a trends analysis on wetlands in the Nanticoke. We
propose to reach the pnmary objective by conducting the following procedures during the
Developmental and Assessment phases of this study.
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Developmental Phase
National Wetland Inventory (NWI) maps and state wetland maps from Delaware and
Maryland will be used to identify existing wetlands in the Nanticoke River watershed.
Wetlands mapped by NW! and by Maryland and Delaware are categorized using the
national classification system developed by Cowardin et al (1979).
2. The Smithsonian Environmental Research Center (SERC) will convert NW! designations
for wetlands into hydrogeomorphic classes as descnbed by Bnnson (1993). We
anticipate that there will be four dominant HGM wetland subclasses in the Nanticoke
River watershed: rivenne, fringe (both tidal freshwater and tidal brackish-estuarine),
depressional and flats. As stated in Section I, the scope of this project will only include
non-tidal nvenne and depressional wetlands. For simplicity, only non-tidal and
depressional wetlands will be discussed below as it is uncertain at this time how flats will
be handled.
NWI designations for wetlands will be converted to HGM classes through a senes of
discussions with NW! and EPA experts and with field testing. We recommend that EPA
engage Ralph Tiner to assist with this activity. Tiner is an employee of the US Fish and
Wildlife Service, and is an expert in NWI and has expenence in converting NWI
designations to HGM classes. We also assume that EPA personnel (e.g., Mary Kentula,
Charles Rhodes) and members of the research team from the parallel study in the Juniata
watershed in Pennsylvania (Robert Brooks and Dernce Heller Wardrop of Penn State
University) will be available to assist with this activity.
Once a protocol has been developed to convert NWI categories to HGM classes, SERC
will prepare a map of the distribution of HGM wetland classes in the Nanticoke River
watershed. The HGM watershed map and the associated GIS database will be made
available to the EMAP Design Team for the purpose of assisting SERC in identifying
wetland sites that will be sampled in the Assessment Phase.
3. SERC will coordinate with EMAP personnel to develop a sampling strategy, based on
their probability-based (random) sample survey approach, to locate potential non-tidal
nvenne and depressional wetland study sites in the Nanticoke River watershed.
4. Access to wetland study sites and sampling of wetlands will be done by field crews
organized and directed by the Wetland Coordinator who has been contracted by EPA to
direct these activities. As much as possible, SERC staff we will evaluate each site
identified by EMAP to determine its suitability for inclusion in this project. SERC will
be responsible for training the Wetland Coordinator who, in turn, will train and supervise
the field crews. SERC will assist in training field crews and will develop manuals
containing procedures that will be used by the field crews.
5. SERC will develop a list of variables and HGM fimctional models that will be used to
assess wetland conditions. There will be separate lists of variables and functions for non-
tidal riverine and depressional wetlands. The imtial list of vanables and functions will be
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based on existing draft HGM models for nverine and depressional wetlands in the
Chesapeake Bay region. When appropnate, we will also utilize draft vanables and
functions that have been developed for wetland flats in the southeast (Rheinhardt et al In
review)
6. A group of experts familiar with the two wetland classes and with HGM procedures will
be asked to review the list of variables and functions selected for the wetland sub-classes.
The list of variables will be revised based on comments and suggestions from the experts.
We recommend that EPA enlist Mark Brinson and Rick Rheinhardt (East Carolina
University), Leander Brown (Natural Resource Conservation Service) and Lyndon Lee
(L.C. Lee & Associates, Inc.) in this effort. SERC also anticipates that this effort will
benefit by interactions with EPA staff (Mary Kentula, Charles Rhodes and Art Spingarn)
and scientists (Rob Brooks and Denice Heller Wardrop) involved in the Juniata River
assessment study.
7. Procedures for sampling wetlands developed by SERC will be used by the Wetland
Coordinator and field crews to sample 25 non-tidal nvenne and 25 depressional wetlands.
The 50 wetlands will be sampled for purposes of testing, scaling, and revising the
preliminary lists of HGM variables. In HGM terminology, the 50 wetlands that will be
sampled are called Reference Wetlands and they will be selected, in conjunction with
EMAP, to represent the range of ecological conditions that are present in the watershed.
If possible, the range of ecological conditions will be represented by selecting Reference
Wetlands that are relatively un-impacted by human activities, wetlands that have been
impacted by natural and anthropogenic activities, wetlands that have been restored and
wetlands that have been converted to agricultural purposes. Data compiled from the 50
Reference Wetlands will be used to scale variables for the two subclasses of wetlands. In
addition, feed-back from the field crews will be used to revise protocols for field
sampling.
8. The revised list of variables and revised protocols for field sampling will be further
evaluated and tested by sampling a second set of 25 randomly chosen wetlands in each
subclass. The goals of this test will be: (1.) Continued refinement of the variables and
protocols used for sampling wetlands in the Nanticoke River watershed in 2000, (2.)
Determine if the protocols that have been developed effectively quantify differences
between wetlands. Wetlands that will be used in this test will be identified by the EMAP
Design Team, and selected by SERC and the Wetland Coordinator.
Assessement Phase
Site-Level Condition The EMAP Design Team will assist SERC in locating wetlands in the
two subclasses for sampling in the spring, summer, and autumn of 2000. The goal of this part of
the study will be to use the HGM procedures developed in the 1999 Developmental Phase to
determine the ecological conditions of wetlands in the Nanticoke River watershed in 2000 during
the Assessment Phase. The number of sites selected and eventually sampled will depend on the
number of field crews and number of individuals in the field crews At mimmum, we hope to
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sample 100-350 wetlands in each subclass.
Role of Denitrification As noted above, water quality issues are of major concern in the
Nanticoke River watershed. Agriculture has greatly increased discharges of nitrogen from the
Nanticoke and other coastal plain watersheds of Chesapeake Bay (Jordan et al. 1997).
Atmospheric deposition also adds significant nitrogen loads to non-agricultural lands as well as
agricultural lands in the Chesapeake watershed (Fisher and Oppenheimer 1991, Jordan et a!.
1995). Wetlands can remove nitrogen through denitriuication (the conversion of nitrate to nitrous
oxide and dinitrogen gases) and improve water quality (Peterjohn and Correll 1984, 1986,
Lowrance et al 1984, Bnnson et a!. 1984, Bowden 1987, Brodnck et a!. 1988, Weller et al. 1994,
Hill 1996, Jordan et al. in press). However, it is difficult to extrapolate denitrification rates to
large spatial scales because of the high spatial variability of denitnfication (Tiedje et a!. 1989).
The objectives of this part of the study are to: (1) Measure denitnfication rates in non-
tidal nverine and depressional wetlands, (2.) Determine the correlation between denitrification
rates and HGM variables that will be used to assess wetland conditions and with other landscape
variables represented in digital spatial data sets. These correlations will be used to predict
denitrification rates of non-tidal nverine and depressional wetlands in the Nanticoke River
watershed.
We will measure denitnfication in surface soils in situ using chambers placed over the
soil to trap emitted nitrous oxide (Yoshinari Ct al 1977). With this widely-used acetylene
inhibition technique (Tiedje et al. 1989), we will infer total denitnfication and the proportion of
dinitrogen produced by companng the nitrous oxide release with and without acetylene present.
We will also evaluate potential denitrification in response to nitrate loading, the dominant form
of nitrogen discharged from agricultural watersheds
We will also examine correlations between denitnfication and related vanables such as
pH, Eh (Platinum electrode), temperature, organic carbon, total nitrogen, nitrate, and ammonium
in the soil; and with dissolved nitrate, ammonium, and organic nitrogen in groundwater and in
overlying water (if present).
Landscape-Level Condition We will statistically evaluate relationships between HGM
variables and ecological conditions in non-tidal rivenne and depressional wetlands in the
Nanticoke River watershed. SERC will use appropriate variables and statistics to project data
from sites sampled in the field to the entire watershed. We will use ARC/INFO GIS software
already in use at SERC to organize and analyze the spatial data on ecological conditions and
landscape characteristics.
SERC has extensive experience in GIS technology in our ongoing studies of nutnent
discharge from Chesapeake Bay and Patuxent River watersheds. We already hold considerable
GIS data on the Nanticoke watershed, including data on NWI wetlands (to be updated with
revised NWI maps provided by EPA), stream maps from EPA’s Reach Files I and 3, USGS
digital elevation models, USGS hydrologic unit boundaries, land cover as estimated by remote
sensing, soils maps, geologic maps, and other data sets.
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SECTION III - SCHEDULE OF ACTIVITIES
Oct.-Dec., 1998 a. Initial discussions with EPA and revision of study plan based on
reviewer comments.
b. Meetings with MD and DE stakeholders and EPA staff to evaluate
goals and objectives of the project.
Jan.-May, 1999 a. Hire technicians.
b. Draft QAPP plan.
c. Compile NWI maps for watershed into SERC GIS database.
d. Discussions and meetings with NW! and HGM experts to convert
NWI maps for Nanticoke River watershed to HGM maps
e. Discussions and meetings with EPA EMAP to begin coordination
of efforts to select wetland sites that will be sampled in 1999
f Develop list of variables to be used in models of HGM functions
for nvenne and depressional wetland subclasses.
g. Develop protocols and field assessment sheets for sampling
Reference Standard wetlands
h. Discussions with Wetland Coordinator to develop protocols for
selecting, organizing and training field crews.
i. Conduct GIS analysis of landscape variables for Reference
Wetlands selected by SERC and Wetland Coordinator.
j. Conduct preliminary denitrification studies at a subset of Reference
Wetlands.
k. Prepare SOP’s and QAPP documentation for site selection,
inventory, and data management.
Jun.-July, 1999 a. Analyze data from Reference Wetlands provided by Wetland
Coordinator and data on landscape variables obtained by GIS
procedures at SERC.
b. Revise list of variables and protocols for sampling wetlands
c. Scale variables using data from Reference Wetlands.
d. Continue measurement of denitrification at a subset of Reference
Wetlands.
e. Discussions with Wetland Coordinator and field crews to prepare
for sampling second set of wetlands to test procedures.
Aug.-Oct., 1999 a. Wetland Coordinator and field crews sample second set of
wetlands.
b. SERC measure denitrification in sub-set of second set of wetlands.
Nov -March, 2000 a. SERC analyzes data from second set of wetlands to make
adjustments needed to conduce watershed assessment in 2000.
b. SERC prepares SOP’s and QA documentation for site selection,
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inventory, and data management for second year of project
c EPA EMAP, SERC, and Wetland Coordinator identif ’ and select
wetland sites that will be sampled in 2000
d. SERC analyzes GIS data for wetlands selected for second year of
project and prepare information for venfication by field teams
when they sample the sites.
e SERC analyzes nitrogen and carbon content of stored soil samples
form denitnfication measurements
f. SERC selects sub-set of wetlands that will be used for
measurements of denitrification and related vanables in 2000.
g. SERC and Wetland Coordinator train field crews for 2000 field
season
Apnl-Oct. 2000 a. Wetland coordinator and field crews sample wetlands.
b. SERC conduct denitnfication study at sub-set of wetlands.
Nov -Sept., 2001 a. Wetland Coordinator provide corrected data, onginal field sheets,
field notes and photographs of wetland sites to SERC.
b. SERC analyze data from wetland assessment and from
denitnfication study.
c. Prepare final report and prepare publications.
SECTION IV - LIST OF PRODUCTS
1. Semi-annual reports in the form of a memo to the Project Officer.
2. Final report, which may be in the form of a scientific publication (see #5 below)
3. Guidebook of procedures that can be used to assess wetland conditions at the level of an
individual wetland and at the watershed scale.
4. Ecological profiles of nvenne and depressional wetland subclasses in the Nanticoke
River watershed. The profiles would include: (1.) descriptions of the wetland subclass
based on results from the project and an analysis of relevant literature, (2) Summaries
and analysis of data collected dunng the project, (3.) Appendices of data or directions on
how to obtain the raw data electronically.
5. Scientific publications based on 3 and 4 above.
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LITERATURE CITED
Ainslie, W B., B A Pruitt, R.D. Smith, T H. Roberts, E.J. Sparks, and M.V. Miller. In press.
Regional Guidebook for Applying the Hydrogeomorphic Approach to Riverine, Low
Gradient Wetlands in Western Kentucky. Technical Report, Waterways Experiment
Station, U.S. Army Corps of Engineers, Vicksburg, MS.
Bohlen, C.C. and R. Friday. 1997 Ripanan and terrestrial issues in the Chesapeake A
landscape management perspective. Pages 95-125. In. R.D. Simpson and N L.
Christensen, Jr, eds Ecosystem Function and Human Activities. Reconciling
Economics and Ecology. Chapman & Hall, NY
Bowden, W.B. 1987. The biogeochemistry of nitrogen in freshwater wetlands. Biogeochemistry
4: 3 13-348.
Brinson, M.M. 1993. A hydrogeomorphic classification of wetlands U S. Army Corps of
Engineers Waterways Expenment Station, Vicksburg, MS. Wetlands Research Program
Technical Report WRP-DE-4.
Bnnson, M.M. 1996. Assessing wetland functions using. National Wetlands Newsletter,
January/February. Environmental Law Institute, Washington, D.C.
Bnnson, M.M , H.D Bradshaw, and E.S Kane. 1984 Nutrient assimilative capacity of an
alluvial floodplain swamp. Journal of Applied Ecology 21 1041-1057.
Brodrick, S.J., P. Cullen, and W. Maher. 1988 Denitnfication in a natural wetland receiving
secondary treated effluent. Water Resources Research 22:431-439.
Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1997. Classification of Wetlands and
Deepwater Habitats of the United States. U S. Fish and Wildlife Service, Washington,
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Fisher, D C. and M. Oppenheimer. 1991. Atmospheric nitrogen deposition and the Chesapeake
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Hill, A.R. 1996. Nitrate removal in stream nparian zones. Journal of Environmental Quality
25:743-755.
Jordan, T.E., D.L. Correll, D.E. Weller, and N.M. Goff. 1995 Temporal variation in
precipitation chemistry on the shore of the Chesapeake Bay. Water, Air, and Soil
Pollution 83:263-284.
Jordan, T.E., D.L. Correll, and D E. Weller. 1997. Effects of agriculture on discharges of
nutrients from Coastal Plain watersheds of Chesapeake Bay. Journal of Environmental
Quality 26: 836-848.
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Jordan, I.E , D E. Weller, and D L. Correll. In press. Denitrification in surface soils of a npanan
forestS Effects of water, nitrate, and sucrose additions. Soil Biology and Biochemistry
Lowrance, R, R Todd, J. Fail, 0. Hendnckson, R.. Leonard, and L. Asmussen. 1984. Ripanan
forests at nutrient filters in agncultural watersheds. Bioscience 34:374-377.
Maryland Department of the Environment (MDE) 1994. Chesapeake Bay Tnbutary Monitonng
Reports: Nanticoke River: Tidal fresh, August 1994 draft. Maryland Department of the
Environment, Baltimore, MD
Nature Conservancy. 1994. Nanticoke-Blackwater River Bioreserve Strategic Plan. Draft 6-10-
94. Maryland Nature Conservancy, Chevy Chase, MD.
Peterjohn, W.T and D.L. Correll. 1984. Nutnent dynamics in an agncultural watershed
Observations on the role of a npanan forest. Ecology 65:1466-1475.
Peterjohn, W T. and D.L. Correll. 1986. The effect of riparian forest on the volume and
chemical composition of baseflow in an agricultural watershed. Pages 244-262 In D.L
Correll, ed Watershed Research Perspectives. Smithsonian Institution Press,
Washington, D.C.
Phillips, P.J., J.M. Denver, R.J. Shedlock, and P.A. Hamilton. 1993. Effect of forested wetlands
on nitrate concentrations in groundwater and surface water on the Delmarva Peninsula.
Wetlands 13: 75-83
Rheinhardt, R.D., M.M. Brinson, and P.M. Farley. 1997. Applying reference wetland data to
functional assessment, mitigation, and restoration. Wetlands 17: 195-215.
Rheinhardt, R.D., M.C. Rheinhardt, and M.M. Brinson. In review. A Regional Guidebook for
Applying the Hydrogromorphic Approach to Wet Pine Flats on Mineral Soils in the
Atlantic and Gulf Coastal Plains.
Smith, R.D., A. Ammann, C. Bartoldus, and M M. Brinson. 1995. An Approach for Assessing
Wetland Functions Using Hydrogeomorphic Classification, Reference Wetlands, and
Functional Indices. Wetlands Research Program Technical Report WRP-DE-9. U.S.
Army Corps of Engineers Waterways Expenmental Station, Vicksburg, MS
Tiedje, J. M., S. Simkins, and P.M. Groffman. 1989. Perspectives on measurement of
denitnfication in the field including recommended protocols for acetylene based methods.
Plant Soil 115:261-284.
liner, R.W. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service, National Wetlands
Inventory, Newton Corner, MA and Delaware Department of Natural Resources and
Environmental Control, Wetlands Section, Dover, DE. Cooperative Publication.
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Tiner, R.W. and D.G. Burke. 1995. Wetlands of Maryland. U S. Fish and Wildlife Service,
Ecological Services, Region 5, Hadley, MA and Maryland Department of Natural
Resources, Annapolis, MD Cooperative Publication.
Weller, D.E., D.L. Correll, and T E. Jordan 1994 Denitnfication in npanan forests receiving
agricultural runoff Pages 117-132 In W.J. Mitch, ed. Global Wetlands. Elsevier, NY.
Yoshinan, T., R. Hynes, and R. Knowles. 1977. Acetylene inhibition of nitrous oxide reduction
and measurement of denitnfication and nitrogen fixation in soil. Soil Biology amd
Biochemistry 9:177-183
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