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United States

Environmental Protection

Agency

Issue Paper

Number 1:

Research Needs in Riparian Buffer Restoration

Eric E. Jorgensen, Timothy J. Canfield and Paul M. Mayer

Riparian buffer restorations are used as management tools to produce favorable water quality impacts;

moreover, the basis for riparian buffers as an instrument of water quality restoration rests on a relatively

firm foundation. However, the extent to which buffers can restore riparian ecosystems, their

functionality and species composition, are essentially unknown. In light of the foregoing, two broad

areas of research are indicated. First, data are needed to document the relative effectiveness of

riparian buffers that differ according to width, length, and plant species composition. These questions,

of managing buffer dimension and species composition for functionality, are of central importance even

when attenuation of nutrient and sediment loads alone are considered. Second, where ecosystem

restoration is the goal, effects to in-stream and terrestrial riparian biota need to be considered.

Relatedly, the effects of the restoration on the landscape need to be considered. Particularly, at what

rate do the effects of the riparian buffer on in-stream water quality, biota, and habitat diminish

downstream from restored sites? Answers to these important questions are needed to further the

advance of riparian restoration from art form to science and to maximize the societal value of future

restorations.

For further information contact Eric Jorgensen (580) 436-8545, or Timothy Canfield (580) 436-8535,

or Paul Mayer (580) 436-8647 at the Subsurface Protection and Remediation Division of the National

Risk Management Research Laboratory, Office of Research and Development, U.S. Environmental

Protection Agency, Ada, Oklahoma.

Riparian Restoration through Buffer Management

Aquatic ecosystems have been altered through the combined effects of municipal, industrial, and

agricultural activities (National Research Council, 1992). Municipalities spend large amounts of money

to remedy non-point pollution problems in their drinking water (Schultz et al., 1995). Nonpoint pollution

is the major remaining cause of surface water pollution (U.S. EPA, 1989; Baker, 1992). Sedimentation

and excess nutrients are the two leading nonpoint pollution problems in rivers and estuaries (Baker,

1992). Nitrogen and phosphorus contribute to eutrophication of surface waters and nitrogen is

frequently limiting in estuaries (Smith et al., 1987), thereby altering biotic interactions and competitive

regimes. Estuaries are the ultimate sinks for most riverine discharge in the eastern United States.

Buffer strips, areas of planted or preserved vegetation between developed land and surface water, are

effective at reducing sediment and nutrient loads (Lowrance et al., 1985; Groffman et al., 1990; Castelle

et al., 1994; see also reviews in Castelle et al., 1992). Buffer strips reduce the severity of impacts to

riparian areas caused by storm events (Bertulli, 1981) that can incise channels and adversely affect

riparian ecosystem function (Henshaw and Booth, 2000). A relatively sound scientific foundation exists

to support the use of riparian buffer strips to manage nutrients and sediment and to support an

expectation of their success as an ecosystem management tool. (Bren, 1993; National Association of

Conservation Districts, 1994; NRC, 1992; USDA, 1996). Further, it is also believed that even greater

benefits will be realized through incorporation of wetlands as components of buffers (Zak and Grigal,

1991; Niswander and Mitsch, 1995); that is, while either buffers or wetlands alone are expected to

provide benefit, integration of these together will likely provide unexpectedly high rates of success

(Lowrance et al., 1995).

The role of denitrification, a microbially meditated process, in processing nutrient inputs to riparian

zones is an area of primary importance (Jones and Holmes, 1996; Boulton et al., 1998). Denitrification

requires anaerobic conditions and is strongly influenced by ground-water dynamics (Burt et al.,1999;

Devito et al., 2000), typically occurring in hyporheic zones (Dahm et al., 1998; Baker et al., 1999) where

stream geomorphology interacts with ground water and affects sediment deposition, nutrient flux, and

stream temperature (Naiman, 1988; Naiman et al., 1994; Fennessy and Cronk, 1997). Interaction of

these factors can produce high quality habitat for biota including fish (Boulton et al., 1998).

In the eastern United States, agriculture, forestry, and other economic developments are frequently

conducted in areas that closely border rivers, streams, and reservoirs. Restoration of these border

Advances in Restoration Science
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areas, in the form of buffer strips, should have a measurable

impact on water quality (Rodgers and Dunn, 1992). This may be

especially true in lower order streams where nutrient processing

can be especially efficient (Alexander et al., 2000; Peterson et al.,

2001). Nonetheless, substantial questions remain: how do buffers

function in various landscapes and precisely which ecosystem

services can buffer strips restore (Osborne and Kovacic, 1993;

Schultz et al., 1995)?

Design criteria have been identified as an area of information

deficiency (van der Valk and Jolly, 1992). In the ecosystem

context, design criteria refer not only to functional relationships

sufficient to produce a desired water quality result, but also refer

to functional relationships relative to wildlife, biodiversity,

sustainability, and aesthetics. Although riparian buffer areas have

been proposed and are being evaluated as a nutrient management

method nationwide, the exact design requirements of these riparian

areas (including size of buffer zone, species composition,

interaction between surface and ground water, stream flow

regulation, provision of in-stream habitat, function for terrestrial

wildlife, sediment transport reduction, and maintenance of biotic

integrity) are incompletely understood and must be evaluated

along with nutrient management.

Research Environment

We will now describe the scope and content of research projects

that are needed to help elucidate, define, and quantify the function

of riparian buffers as instruments for riparian restoration.

Frequently, function and design criteria for reducing nutrient

inputs are of central interest to buffer designers. Therefore,

function and design criteria for riparian buffers for reducing nutrient

inputs are of central interest. However, ecosystem and/or

watershed restoration are by definition concerned with more than

water quality. The ecological functions and landscape

characteristics of riparian buffers as expressed by soil, flora, and

fauna are also of primary interest and do interact with nutrients to

a large degree.

The efficacy of riparian buffers as tools of ecosystem restoration

can be established by measuring and comparing effects among

three types of riparian buffers: TYPE 1 areas are stream reaches

that have received plantings and undergo associated management

with the purpose of restoring the riparian buffer; TYPE 2 areas are

stream reaches that are initially similar to those in TYPE 1 but that

do not receive plantings or undergo associated management to

restore the riparian buffer; and, TYPE 3 areas are stream reaches

that are effectively undisturbed or mature, and that represent

stream reaches that TYPE 1 areas are supposed to resemble 30+

years after initiation of the restoration. Comparing these three

basic types of stream reach will allow researchers to quantify

restoration endpoints (TYPE 3 areas), and measure success

(TYPE 2 areas contrasted with TYPE 1 and TYPE 3 areas).

These measures of endpoints and success are critical components

of restoration and are frequently the subject of administration,

management, landowner, and researcher initiated questions for

which there is too often little or no data. This is a void that research

can fill.

Research Questions

There are five general questions driving riparian buffer research:

1) What are the characteristics of existing riparian buffer zones

and surrounding landscape areas?

2) How do riparian areas function?

3) Where should riparian buffers be placed on the landscape?

4) What aspects of riparian ecosystems can be restored with

riparian buffers?

5) How effective is the restoration?

These general questions guide development of focused research

needs. In the enumeration of tasks that follows, it will be apparent

that some tasks are closely related and may be accomplished

together. The tasks are not meant to describe discrete research

efforts; rather, they are meant to describe discrete data needs

that, although in some cases are related, stand on their own as

being important areas where information relative to determining

the ecological function of riparian buffers is needed, including

restoration of water quality, in-stream and terrestrial riparian

habitat for flora and fauna, and landscape function relative to

adjacent land use, upstream activities, and downstream benefits.

Water Quality Effects

Task 1: In-Stream Water Quality as a Function of Riparian

Buffer Condition.

Where water quality, especially regarding reduction of nutrients

and suspended sediments, is an important motivation for

developing restored riparian buffers, data concerning the

ability of restorations to provide these services, compared to

unrestored and mature communities, are needed.

Task 2: In-Stream Water Quality as a Function of Riparian

Buffer Width.

The width of riparian buffer can affect water quality at the

stream. It is unclear whether these improvements to water

quality accumulate linearly with increasing buffer width, or

whether the rate of improvement declines with increasing

buffer width.

Task 3: In-Stream Water Quality as a Function of Riparian

Buffer Length.

It is reasonable to expect that the length (of stream reach) of

restored riparian buffer will affect water quality to at least the

extent of buffer width. The effect of buffer length needs to be

quantified.

Task 4: In-Stream Water Quality as a Function of Riparian

Buffer Plant Community Composition.

It is hypothesized that the composition of the plant communities

that make up restored riparian buffers will have an impact on

the resulting in-stream water quality (i.e., nutrients and

sediment). The effects of plant community composition and

interactions with buffer condition, width, and length need to

be determined.

Task 5: Measure the Relative Contributions of First, Second,

and Third Order Streams to Watershed Loads of Nutrients

and Sediment.

Although there is substantial speculation, the relative

contributions of first, second, and third order streams to

watershed loads of nutrients and sediment need to be more

clearly quantified. This information can be used to target

restoration activities to locations where the greatest amounts

of nutrients and sediment are entering the system.

Task 6: Measure the Relative Contributions of Mixed Riparian

and Wetland Complexes to Watershed Loads of Nutrients

and Sediment.

There is substantial reason to expect that wetland restorations,

integrated and designed as part of riparian restoration, can

enhance the ability of these riparian areas to remove and

reduce nutrients and sediment from non-point source runoff.

It is thought that the dynamic nature of the wetland system,

coupled with the long-term stability of the riparian area, will

have a synergistic effect and function better than either type

system (riparian or wetland) alone. The effect of integrating
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wetland and riparian restoration needs to be better understood

and evaluated.

In-Stream Flora and Fauna Effects

Task 1: In-Stream Flora Response to Riparian Buffer

Restoration.

Ultimately, a primary reason for restoring riparian buffers is

restoration of riverine flora. The re-establishment and growth

of native aquatic plants is an important water quality and

habitat result that is expected to follow riparian buffer

restoration. The effects of restoration condition and buffer

width and length on the ability of riverine vegetation to reestablish and prosper needs to be documented.

Task 2: In-Stream Fauna Response to Riparian Buffer

Restoration.

Ultimately, a primary reason for restoring riparian buffers is

restoration of riverine fauna. The re-establishment of native

aquatic fauna is an important water quality and habitat output

that is expected to follow riparian buffer restoration. The

effects of restoration condition and buffer width and length on

the ability of riverine fauna to re-establish and prosper needs

to be documented.

Task 3: Document the Characteristics of Plant and Animal

Communities Associated with In-Stream Riparian Habitat.

Determine population and community characteristics and

habitat associations of extant in-stream flora and fauna.

What changes could be expected if buffer restorations are

implemented?

Terrestrial Riparian Flora and Fauna Effects

Task 1: Riparian Buffer Terrestrial Flora Response to Riparian

Buffer Restoration.

An important reason for restoring riparian buffers is restoration

of associated terrestrial riparian-habitat dependent flora. The

re-establishment and growth of native terrestrial plants is an

important restoration and conservation result that is expected

to follow riparian buffer restoration. The effects of restoration

condition and buffer width and length on the ability of terrestrial

vegetation to re-establish and prosper needs to be

documented.

Task 2: Riparian Buffer Terrestrial Fauna Response to Riparian

Buffer Restoration.

An important reason for restoring riparian buffers is restoration

of associated terrestrial riparian-habitat dependent fauna.

The re-establishment of native terrestrial fauna is an important

restoration and conservation result that is expected to follow

riparian buffer restoration. The effects of restoration condition

and buffer width and length on the ability of terrestrial fauna

to re-establish and prosper needs to be documented.

Task 3: Riparian Buffer Terrestrial Microbe Response to

Riparian Buffer Restoration.

Microbial communities play a substantial role in the nitrogen

cycle and are especially important relative to the production

and retention of nitrate. The role of microbial denitrifying

activity relative to buffer condition and buffer width needs to

be documented. It is not expected that buffer length will affect

microbial denitrifying activity to any great extent.

Task 4: Document the Characteristics of Plant and Animal

Communities Associated with Terrestrial Riparian Habitat.

Determine population and community characteristics and

habitat associations of extant terrestrial - riparian habitat

dependent - flora and fauna. How do these conditions differ

from the desired state and what changes are expected if

buffers are restored?

Task 5: Measure the Benefits to Terrestrial Diversity from the

Placement of Riparian Buffers, and Document Interactions

between Such Diversity and Buffer Function, Sustainability,

and Succession.

Buffer placement on the landscape can be expected to play

a substantial role in determining its final functionality. This is

especially true regarding effects on diversity, where the size

and shape of the restored buffers will interact with proximity

to other restorations and undisturbed native sites to determine

the ultimate benefit. The interaction of these various conditions

relative to use of riparian buffers as tools to conserve

biodiversity needs to be documented.

Task 6: Determine the Extent to Which Riparian Buffers

Function as Habitat for Terrestrial Species and the Extent to

Which They Function as Corridors and Refugia.

Riparian buffers have the capacity to act as dispersal corridors,

refugia, or habitat for many terrestrial fauna. These tendencies

need to be documented and management prescriptions

regarding buffer size and placement need to be formulated to

assure that restored riparian buffers function as intended.

Landscape Scale Considerations

Task 1: Mapping of Stream Reaches and Watersheds that are

Highly Suitable for Riparian Buffer Restoration Based Upon

Proximity of Denitrifying Subsurface Strata.

Research indicates that an important factor that limits nitrate

concentration in surface waters is the proximity of denitrifying

strata to the surface. In areas where this denitrifying stratum

is below the root zone of plants, little water quality impact

relative to reduction of nitrate concentration in surface waters

can be expected. It is necessary to map the extent of these

denitrifying strata and determine the miles of stream reach

where water quality restoration relative to nitrate loading is so

limited.

Task 2: Determine Whether Relationships Exist Between

Watershed Size and Proportionate Land Use and the Design

Requirements of Riparian Buffer Restorations.

The type and extent of land uses that are found within

individual watersheds may play an important role in

determining the types and extents of buffer restorations that

are appropriate. In some cases, large extensive restorations

may be necessary to provide desired improvements to water

quality and habitat; in other watersheds, several small

restorations may provide equivalent improvements. The

ecological, social, and economic characteristics of individual

watersheds that may affect the types and extent of necessary

restorations need to be documented.

Task 3: Determine the Landscape Conditions and Spatial

Extent Over Which Substantive Ecosystem Benefits Cannot

be Expected to be Achieved with Restored Riparian Buffers

Alone.

Riparian buffers cannot address all resource management

questions. The subset of questions that buffers can be used

to impact needs to be distinguished from the subset that they

cannot. Particularly, spatial and temporal scale concerns

need to be addressed relative to this question.

Task 4: Measure the Distribution of Riparian Buffer Widths

Associated with Each Stream Order and Document Their

Distribution.

Determine the extant coverage and frequency distributions of
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buffer widths by stream order. Assess how these values

compare among watersheds, particularly contrasting

watersheds with good versus poor water quality.

Task 5: Measure the Effects of Improvements Attributable to

Riparian Buffer Restoration in Parts of the Watershed not

Directly Restored. Particularly, to What Extent are

Downstream Areas Cumulatively Impacted?

Determine the extent to which the water quality and in-stream

biota of areas downstream of riparian buffer restorations can

be positively affected. In particular, is it realistic to expect

water quality and habitat to improve in estuaries because of

riparian buffer restorations?

Task 6: Measure and Document Interactions Among Upstream

Land Use and Downstream Aquatic and Terrestrial Effects.

To an extent, restoration of riparian buffers can only be

expected to produce a limited suite of outputs. The effects of

upstream activities also play a large role in determining the

final function of the buffers on the landscape. The extent to

which upstream activities limit the range of outcomes that can

be seen downstream needs to be documented.

Monitoring and Indicators

Task 1: Determine Which Variables to Monitor to Assess

Restoration Success Over Short, Intermediate, and Long

Time Periods.

Identify indicators that can be used to assess short,

intermediate, and long-term performance and function of

restored riparian buffers. Identify the variability of the indicators

– determine the conditions under which they can be

appropriately used – and assess error rate.

Task 2: Identify Biotic and Abiotic Indicators, and Sampling

Schedules for Such Indicators, that will Help Determine

Restoration Effectiveness and Measure Senescence - Such

that the Need to Renovate or Otherwise Maintain Restored

Riparian Buffers can be Determined.

Identify indicators and concurrent monitoring schedules that

can track restoration senescence and predict the need to

conduct renovation – including expected renovation benefits

and costs.

Physical Sciences

Task 1: Measure the Extent to Which Restored Riparian Buffers

Influence Hydrology.

Riparian buffers are hydrologically connected to streams and

stream processes. Thus, to what extent are water quality and

habitat limited by the characteristics of hydrology that may be

amenable to engineered manipulations? For example,

denitrification, a microbially mediated process in which nitrate

nitrogen is converted to gaseous nitrogen, is strongly

influenced by ground-water dynamics in riparian zones. When

the water table is close to the soil surface, nitrate in the ground

water interacts with carbon-rich soils in an anaerobic

environment creating high potential for denitrification. Natural

or anthropogenic factors that lower water tables greatly

reduce riparian denitrification potential and other

biogeochemical processes.

Task 2: Measure the Extent to Which Riparian Buffers Influence

Flood Plain Processes.

Riparian zones represent a distinct component of stream

flood plains. Riparian zones and associated buffers may

influence annual overbank flows and/or in-stream flow

dynamics, consequently affecting biogeochemical processes.

For example, beavers (Castor canadensis) are natural

engineers that manipulate stream flow dynamics through

construction of impoundments. Such impoundments may

have watershed-wide influences on sediment deposition,

nutrient flux, and stream temperature.

Task 3: Measure the Extent to Which Riparian Buffers Influence

Hyporheic Zone Processes.

Riparian buffers may influence the way in which ground water

and surface water interact in stream ecosystems. Such

hyporheic zones are regions of high microbial activity that

greatly influence rates and fluxes of nutrients and oxygen

through assimilation and respiration. Consequently, hyporheic

zones represent productive, high quality habitats for both

invertebrates and vertebrates including fish.

Task 4: Document Differences in Restoration Potential for

Riparian Zones in Urbanized Areas versus Streams in Less

Affected Ecosystems.

In urban areas, high volume diversions of storm water runoff

into stream channels cause stream incision that disconnects

floodplains from ground water processes. Similarly, infiltration

of runoff is reduced under zones of pavement or other

impervious surfaces, thereby reducing riparian water tables

in urban watersheds. The extent to which effects attributable

to these and related alterations limit stream restoration

potential needs to be well understood.

Socio-Economic Perspectives

Task 1: Measure Economic Impacts of Riparian Buffer

Restorations, Especially Relative to Reduced Crop Yields

Attributable to Buffer Shading and Competition, But Also

Accounting for Economic Gains Attributable to Improved

Nutrient Management.

Where the establishment of restored riparian buffers depends

to a large extent on the cooperation of private landowners,

especially agriculturists, the economic impacts of buffer

placement relative to crop shading and potential competition

need to be documented in concert with potential economic

benefits that may accrue due to improved efficiency in use of

fertilizer and to improved fin- and shell-fish fisheries.

Integrated Research

Task 1: Determine Whether Riparian Buffer Function Varies

Quantitatively or Qualitatively in Relationship to Varying

Types of Adjacent Land Use. This Includes the Functions of

Nutrient and Sediment Attenuation and Provision of In-Stream

and Terrestrial Riparian Habitat for Plants and Animals.

The questions of whether and how adjacent land use affects

riparian buffer function – for water quality improvement and

for provision of plant and animal habitat - need to be

investigated. For instance, do buffers adjacent to industrial,

residential, and farming operations provide the same quality

and quantity of benefit, or does the adjacent land use limit the

effectiveness of the buffer in some regard?

Task 2: Measure Differences in Riparian Buffer Function,

Especially Relative to Nutrient and Sediment Attenuation –

but also Including Provision of In-Stream and Terrestrial

Riparian Plant and Animal Habitat - Among First, Second,

and Third Order Streams.

Just as adjacent land use can be expected to have an

influence on buffer, stream order may also have an effect.

Wherein a buffer in a first order stream may intercept 70% of

the water that enters the stream and may therefore have a

large effect on water quality and habitat – so may a buffer in

a third order stream only intercept 10% of the water entering
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the stream, and thereby have a small effect on water quality

and habitat.

Task 3: Measure the Rate at Which Benefits Attributed to

Restored Riparian Buffers are Attenuated Downstream,

Especially Relative to Nutrients and Sediment.

Realistically, riparian buffer restorations can only be conducted

along a relatively modest number of stream reaches. It is

thought that these will be mostly first, second, and third order

streams. The ability of supposed water quality improvements

occurring within these stream reaches to propagate

downstream and be maintained is unknown.

Task 4: Determine Types of Engineering Controls that can be

Used to Complement Restored Riparian Buffers to Provide or

Enhance Benefits Relative to Nutrient and Sediment

Attenuation, and Provision of In-Stream and Terrestrial

Riparian Plant and Animal Habitat.

Under what conditions can engineering controls be used to

complement riparian buffer restorations? Which engineered

solutions have the greatest promise of working? What are the

complementary benefits to terrestrial and aquatic riparian

ecosystems that are expected from engineered solutions?

Task 5: Measure the Effects of Above-Ground Biomass, Plant

Communities, and Animal Communities on Surface Water

Runoff and Surface Water/Ground Water Interactions,

Especially Relative to Nutrient and Sediment Transport.

Animal communities affect plant communities and plant

communities affect subsurface chemistry, and ultimately

interact with the chemical characteristics (particularly regarding

nutrients) of in-stream water and in-stream habitat. Therefore,

interactions between terrestrial riparian flora and fauna and

the chemical characteristics of riparian ecosystems need to

be understood to help design buffers that will remove or

otherwise retain nutrients and sediment.

Conclusion

This issue paper identifies subject areas where there are critical

data gaps concerning the function of riparian buffers as ecosystem

and watershed restoration tools. We acknowledge that whereas

there is a reasonable foundation of data to support an expectation

that restored riparian buffers can provide some water improvement

relative to reduced loads of nutrients, there are insufficient data

concerning other benefits to aquatic and terrestrial riparian biota

and habitat to allow the generalization that restored riparian

buffers can function as tools for ecosystem restoration. Therefore,

we identify research that focuses on water quality measured at the

stream while concurrently measuring other biotic and abiotic

responses.

Restoration of the Nation’s waters will require manipulation of

upstream watersheds, including buffer management. The relative

contributions of activities in these watersheds and the ability to

manage the effects of these activities with riparian buffers are

important questions that bear upon research needs described in

this paper. Care must be taken to ensure that the contributions of

all watersheds are considered and statistically represented in any

proposed management solutions that rely upon buffers. The

effects of small headwater, first, and second order watersheds

relative to the larger ones need to be clearly understood.

Notice

The U.S. Environmental Protection Agency through its Office of

Research and Development funded and managed the preparation

of this Issue Paper. It has been subjected to the Agency’s peer

and administrative review and has been approved for publication

as an EPA document. The authors acknowledge help provided by

Frederick W. Kutz on an earlier draft of the paper.

Literature Cited

Alexander, R.B., R.A. Smith, and G.E. Schwarz. 2000. Effect of

stream channel size on the delivery of nitrogen to the Gulf of

Mexico. Nature 403:758-761.

Baker, L.A. 1992. Introduction to nonpoint source pollution in the

United States and prospects for wetland use. Ecological

Engineering 1:1-26.

Baker, M. A., C.N. Dahm, and H.M. Valett. 1999. Acetate retention

and metabolism in the hyporheic zone of a mountain stream.

Limnology and Oceanography 44:1530-1539.

Bertulli, J.A. 1981. Influence of a forested wetland on a southern

Ontario watershed. In A. Champagne, ed. Proceedings of the

Ontario wetlands conference. Federation of Ontario Naturalists

and Dept. of Applied Geography, Ryerson Polytechnical Inst.,

Toronto, Ontario. 193 pp.

Boulton, A.J., S. Findlay, P. Marmonier, E.H. Stanley, and H.M.

Valett. 1998. The functional significance of the hyporheic zone

in streams and rivers. Annual Review of Ecology and

Systematics 29:59-81.

Bren, L. L. 1993. Riparian zone, stream, and floodplain issues: a

review. J. Hydrol. 150: 277–299.

Burt, T.P., L.S. Matchett, K.W.T. Goulding, C.P. Webster, and

N.E. Haycock. 1999. Denitrification in riparian zones: the role

of floodplain hydrology. Hydrological Processes 13:1451-1463.

Castelle, A.J., C. Conolly, M. Emers, E.D. Metz, S. Meyer, M.

Witter, S. Mauermann, T. Erickson, and S.S. Cooke. 1992.

Wetland buffers: use and effectiveness. Publication 92-10.

Adolfson Assoc., for Shorelands and Coastal Zone Management

Program, Washington Dept. of Ecology, Olympia, WA.

Castelle, A.J., A.W. Johnson, and C. Conolly. 1994. Wetland and

stream buffer size requirements; a review. Journal of

Environmental Quality 23:878-882.

Dahm, C.N., N.B. Grimm, P. Mormonier, H.M. Valett, P. Vervier.

1998. Nutrient dynamics at the interface between surface

waters and groundwaters. Freshwater Biology 40:427-451.

Devito, K.J., D. Fitzgerald, A.R. Hill, and R. Aravena. 2000. Nitrate

dynamics in relation to lithology and hydrologic flow path in a

river riparian zone. Journal of Environmental Quality 29:1075-

1084.

Fennessy, M.S. and J.K. Cronk. 1997. The effectiveness and

restoration potential of riparian ecotones for the management

of nonpoint source pollution, particularly nitrate. Critical Reviews

in Environmental Science and Technology 27:285-317.

Groffman, P.M., A.J. Gold, T.P. Husband, R.C. Simmons, and

W.R. Eddleman. 1990. Final report; Narrangansett Bay project;

an investigation into multiple uses of vegetated buffer strips.

University of Rhode Island, Kingston.

Henshaw, P.C. and D.B. Booth. 2000. Re-equilibration of stream

channels in urban watersheds. Journal of the American Water

Resources Association 36:1219-1236.

Jones, J.B. Jr. and R.M. Holmes. 1996. Surface-subsurface

interactions in stream ecosystems. Trends in Ecology and

Evolution 11:239-241.
6

Lowrance, R., R. Leonard, and J. Sheridan. 1985. Managing

riparian ecosystems to control nonpoint pollution. Journal of

Soil and Water Conservation 40:87-91.

Lowrance, R., G. Vellidis, and R. K. Hubbard. 1995. Denitrification

in a restored riparian forest wetland. Journal of Environmental

Quality 24:808-815.

Naiman, R.J. 1988. Animal influences on ecosystem dynamics.

BioScience 38:750-752.

Naiman, R.J., G. Pinay, C.S. Johnston, and J. Pastor. 1994.

Beaver influences on the long-term biogeochemical

characteristics of boreal forest drainage networks. Ecology

75:905-921.

National Association of Conservation Districts. 1994. Riparian

ecosystems in the humid U.S: functions, values and

management. Washington, D.C.

National Research Council (NsRC). 1992. Restoration of aquatic

ecosystems. National Academy Press, Washington, D.C. 552

pp.

Niswander, S.F. and W.J. Mitsch. 1995. Functional analysis of a

two-year-old created in stream wetland: hydrology, phosphorus

retention, and vegetation survival and growth. Wetlands 15:212-

225.

Osborne, L.L. and D.A. Kovacic. 1993. Riparian vegetated buffer

strips in water-quality restoration and stream management.

Freshwater Biology 29:243-258.

Peterson, B.J., W.M. Wollheim, P.J. Mulholland, J.R. Webster,

J.L. Meyer, J.L. Tank, E. Marti, W.B. Bowen, H.M. Valett, A.E.

Hershey, W.H. McDowell, W.K. Dodds, S.K. Hamilton, S.

Gregory, and D.D. Morrall. 2001. Control of nitrogen export

from watersheds by headwater streams. Science 292:86-90.

Rodgers, Jr., J.H. and A. Dunn. 1992. Developing design guidelines

for constructed wetlands to remove pesticides from agricultural

runoff. Ecological Engineering 1:83-95.

Schultz, R.C., J.P. Colletti, T.M. Isenhart, W.W. Simpkins, C.W.

Mize, and M.L. Thompson. 1995. Design and placement of a

multi-species riparian buffer strip system. Agroforestry Systems

29:201-226.

Smith, R.A., R.B. Alexander, and M.G. Wolman. 1987. Waterquality trends in the nation’s rivers. Science 235:1607-1615.

USDA. 1996. Engineering field handbook. Chapter 16; streambank

and shoreline protection. NRCS.

U.S. EPA. 1989. Nonpoint sources: agenda for the future. WH-556.

U.S. EPA, Office of Water, Washington, D.C., 31 pp.

U.S. EPA. 1997. 1997 Update to ORD’s strategic plan.

EPA/600/R-97/015.

van der Valk, A.G. and R.W. Jolly. 1992. Recommendations for

research to develop guidelines for the use of wetlands to control

rural nonpoint source pollution. Ecological Engineering 1:115-

134.

Zak, D.R. and D.F. Grigal. 1991. Nitrogen mineralization, nitrification

and denitrification in upland and wetland ecosystems. Oecologia

88:189-196.
7

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