&EPA
United States
Environmental Protection
Agency
Issue Paper
Advances in Restoration Science
Number 2:
Opportunities in Nitrogen Management Research:
Improving Applications for Proven Technologies and
Identifying New Tools for Managing Nitrogen Flux and
Input in Ecosystems
Eric E. Jorgensen
[ADVANCES in
RESTORATION SCIENCE
The presence and distribution of undesirable quantities of bioavailable nitrogenous compounds in the
environment are issues of long-standing concern. Importantly for us today, deleterious effects
associated with high levels of nitrogen in the ecosystem are becoming everyday news events. Excess
nitrogen in the environment is associated with many large-scale environmental concerns, including
eutrophication of surface waters, toxic algae blooms, hypoxia, acid rain, and global warming.
Unfortunately, releases of nitrogen associated with anthropogenic activities are expected to rise
throughout the foreseeable future. Whereas our current technologies for managing nitrogen in the
environment are stressed, it is reasonable to project that they are likely to fail under the increased loads
of nitrogen that are projected for the future. The potential scale of the undesirable consequences are
such that it is prudent for us to consider reasonable management and research responses now. This
Issue Paper describes a proposed three-part research and management program that is a measured
response to concerns about nitrogen pollution, particularly in the eastern United States. The program
describes: 1) steps to be taken with regard to landscape management that will improve our knowledge
of nitrogen release and management as it relates to land use; 2) investigations needed that will improve
our understanding of the factors that prevent full implementation of nitrogen management technology
in the high use landscapes that comprise 35.2% of the land cover in the eastern United States; and,
3) research that is needed to help uncover cause-and-effect relationships among trophic levels that will
provide new tools for managing nitrogen, especially on low use landscapes that comprise 64.8% of the
land cover in the eastern United States.
For further information contact Eric Jorgensen (580) 436-8545 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.
Nitrogen is added to ecosystems in enormous quantities through anthropogenic activities (Smil, 1990;
Vitousek et al., 1997). Further, these additions have been increasing; a trend that is projected to
continue (Brimblecombe and Stedman, 1982; Galloway et al., 1994; U.S. EPA, 1995; Vitousek et al.,
1997). Because nitrogen is frequently a limiting nutrient for plants and animals, increased quantities
of nitrogen in the ecosystem alters competitive relationships among terrestrial and aquatic organisms.
This phenomenon is usually manifested as eutrophication, but acidification of forested watersheds and
nitrate pollution to ground water are also symptomatic (e.g., Baker ,1992; Likens, 1992; Wedin and
Tilman, 1996; Asner et al., 1997). Excess nitrogen is not tightly retained by ecosystems but is highly
mobile (e.g., Vitousek et al., 1997) and it occurs in ecosystems under a variety of guises (i.e., nitrogen
species; NO3, NH4, NO2, DON, TN, etc.), each of which varies in its mobility and potential for use by
organisms and expression in site biogeochemistry. Therefore, concern about nitrogen management
in ecosystems is focused not only on the amount of nitrogen present but also its transport and cycling.
Nitrogen, particularly nitrate, easily moves fromterrestrial ecosystems into surface and ground waters,
including lakes, streams, rivers, and estuaries (e.g., Kahl et al., 1993; Peterjohn et al., 1996). As
nitrogen concentrates in surface and ground water sinks, increasingly frequent observations of
undesirable effects associated with eutrophication, algae blooms, hypoxia, and toxicity are observed
(Kelly et al., 1990; Likens,1992; Gilbert and Terlizzi, 1999). Today, acid rain phenomena in North
America are largely associated with excess nitrogen (Aber et al., 1989; Gilliam et al., 1996). Finally,
nitrogen affects plant growth, and therefore interacts with atmospheric CO2 (Shaver et al., 2000).
Wedin and Tilman (1996) have suggested that increasing amounts of nitrogen in the environment may
be associated with global warming and climate change (see also Vitousek et al., 1997; Shaver et al.,
2000).
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While the aforedescribed risks associated with anthropogenic
nitrogen are recognized, management options for containing and
mitigating them are poorly developed. In order to weigh risks and
assess management options, it is important that a thorough
understanding of the interactions and transport of nitrogen in
terrestrial and aquatic ecosystems and the atmosphere be
developed. The scope and magnitude of the nitrogen problem is
such that there are many research needs and many opportunities
for management intervention. It appears that a three-part nitrogen
risk management research program, integrating basic and applied
research, will contribute substantially to development of a multi-
scale management approach that will maximize nitrogen retention
and sequestration in terrestrial and managed landscapes, thereby
reducing loadings to aquatic ecosystems.
The description of the research program that follows results from
an expectation that the ability of terrestrial and freshwater aquatic
ecosystems to optimally retain, sequester, and transform nitrogen
can be manipulated, indeed enhanced, through application of
appropriate management technologies. This research program
would seekto identifythose technologies, and identify opportunities
for application of existing techniques. This view, that management
of nitrogen will be accomplished through management of terrestrial
and freshwater aquatic ecosystems, necessarily neglects the
impact of direct atmospheric deposition. This particular source of
nitrogen input must be managed at the point of production or (as
described herein) after it is deposited in terrestrial or aquatic
ecosystems. Terrestrial and freshwater ecosystems represent
important points in the nitrogen cycle that are amenable to
management, and that, if successful when managed together, can
produce measurable benefits to water quality and aquatic resources
in both freshwater and estuarine ecosystems.
Research Program
While it is possible to conduct research on a problem as pervasive
and interrelated with biotic interactions as nitrogen in many
subject areas, in many landscapes, and over multiple spatial and
temporal scales, it appears that there is good potential to provide
measurable changes to the flux and input of nitrogen through and
into the environment, particularly in aquatic ecosystems, through
a research program that conducts applied and basic research in
three areas.
Area 1 - Landscape Management
GIStechnology is rapidly reaching a level of sophistication sufficient
to characterize watershed and landscape physical, biological,
and chemical parameters. Where it is possible to characterize it
is also possible to plan and manage. This proposed research area
would seekto develop landscape management techniques and
recommendations to guide planners' decisions regarding
appropriate zoning, development, and land use. The research
would characterize and model physical and remotely sensed
properties of landscapes and watersheds, and associate these
properties with concentrations of nitrogen ions in terrestrial and
aquatic ecosystems. These characterizations and models would
allow planners to identify potential landscapes and watersheds at
risk from eutrophication and acidification to facilitate proactive
land use planning. The characterizations and models would allow
identification of landscapes and watersheds that are potentially
highly perturbed by excess nitrogen, thereby facilitating efficient
targeting of restoration and management actions. The
characterizations and models would allow identification of
landscape and watershed attributes that are highly correlated with
risk from excess nitrogen, thereby providing clear guidance for
prescription of specific restoration and management techniques
and suggesting research themes for investigating methodologies
of maximizing and optimizing landscape and watershed retention,
sequestration, and transformation capability for nitrogen (e.g.,
Magill et al., 1996; Mander et al., 2000).
The following research tasks need to be addressed in this area:
Task 1.1 Characterize and Model the Relations of Watershed
and Upstream Land Uses and Physical and Biological
Properties to the Concentration and Load of Targeted Nitrogen
Ions in Terrestrial and Aquatic Ecosystems - Including
Estuaries, Lakes, Rivers, Streams, Ground Water, and
Sediment.
Water that is present in or entering the lakes, rivers, streams,
and ground water of a watershed is the product of a large
spatial and temporal scale integration that reflects the types
and distribution of land uses at large in the watershed and the
physical, and biological interactions occurring therein.
Task 1.2 Associate Characterizations and Models of Nitrogen
Ion Concentrations and Loads in Watersheds from Task 1.1
with Known and Predicted Exposure Risk Levels for Biota
and Health to Identify Watersheds and Landscapes that are
Currently Adversely Affected by Excess Nitrogen and Those
that are at Risk Attributable to Increasing Amounts of Nitrogen.
Where an important goal of risk management is to predict and
prevent future problems and to mitigate effects in already
heavily impacted watersheds, an important priority is to
develop and refine models that work in currently heavily
impacted watersheds and those soon to be at riskfrom further
nitrogen deposition.
Task 1.3 Identify Watershed and Landscape Land Use and
Physical and Biological Parameters thatare Highly Correlated
with Nitrogen Ion Concentrations and Loads in Terrestrial and
Aquatic Ecosystems.
Where reduction of adverse effects can be most rapidly
achieved when cause and effect are known and consequences
are certain, identification of non-optimum land use practices
that may heavily impact at-risk watersheds is a priority.
Task 1.4 Prescribe Watershed and Landscape Specific
Restoration and Management Actions, Regarding
Manipulation of Parameters Identified in Task 1.3, to Contain
and/or Reduce Risks Associated with Excess Nitrogen
Concentration and Loading.
The nature of the nitrogen problem is such that prevention at
the source is frequently not an economically or socially
desirable option; therefore, containment of the effects of
nitrogen release is desirable through implementation of
appropriate risk reduction technologies remote from the point
of release.
Task 1.5 Identify and Prioritize Research Questions and Tasks
Indicated by the Results of Task 1.3 that Hold Substantial
Probability of Providing Measurable Refinements and
Improvements to the Techniques Prescribed by Task 1.4.
Through adaptive management, apply the skills developed
through an increasing level of management activity and
research to finding new and more effective and efficient
means for managing excess nitrogen in watersheds.
Advances in this research area will provide managers and planners
with coarse-scale correlative-tools that have a substantial
probability of providing measurable reductions to the rate of flux
and amount of nitrogen leaching to surface and ground waters,
and estuaries. These coarse-scale tools can reasonably be
expected to provide immediate management benefits. However,
the ultimate ability of management actions prescribed based upon
correlative tools to produce a large widespread benefit is unclear.
The ability of prescribed management actions can certainly be
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improved and optimized through phased implementation of
improvements to correlative tools that are based upon cause-and-
effect knowledge of the system.
Area 2 - Management of High Use Landscapes
Problems associated with excess nitrogen have been recognized
for decades and are frequently associated with increasing land
use intensity and economic activity (i.e., urbanization and row
cropping). These problems include, but are not limited to, economic
loss attributable to excess fertilization, septic field failure, acid
rain, eutrophication of aquatic ecosystems, and pollution from
municipal sewage outfalls. Cover of high use lands increased
34.3% between 1982 and 1997 in the eastern United States from
60.4 to 81.1 million acres whereas cover of cropped lands
decreased 9.9% during the same period (USDA, 2000). Together,
developed and cropped lands accounted for 35.2% of the land
cover in the eastern United States in 1997 (USDA, 2000). Impacts
to watersheds of nitrogen from these high use lands are well
known and must be accounted for. Because problems have been
associated with nitrogen for many years, numerous techniques
have been developed to minimize, or in some cases eliminate,
nitrogen leaching from high use lands to the environment.
Prescription and regulation of nitrogen management techniques
is not centralized, but falls within the authority of numerous
federal, state, and local agencies and governments. Frequently,
application of known techniques at any given local site occurs as
a matter of opportunity when willing landowners interact with
knowledgeable managers and planners. This loosely organized
system leaves significant opportunity for the identification of high
use watersheds and landscapes where application of known
nitrogen management techniques is under-utilized.
The following research tasks need to be addressed in this area:
Task 2.1 Inventory and Organize in a Central Database All
Known Sources of Nitrogen that are Associated with High
Use Landscapes, including Urbanized, Agricultural, Industrial,
and Recreational Areas. Concurrently, Inventory and Organize
in a Central Database Management Methods and
Measurements of Effectiveness for Nitrogen Management in
these Landscapes.
Historically, it has only been poorly recognized that land use
practices and nitrogen release are related; therefore,
knowledge of land uses and expected contributions to the
nitrogen problem is excessively dispersed, in the literature,
among professionals, and among management agencies.
There appears to be an opportunity to achieve significant
economy of scale improvements for the organization of
nitrogen data and information.
Task 2.2 Inventory and Model Relationships Among Physical,
Biological, Social, Economic, and Demographic Parameters
on a Watershed Specific Basis, to the Distribution of Known
Sources of Nitrogen (Task 2.1) in Conjunction with the
Distribution of the Application of Management Methods
(Task 2.2).
Management of nitrogen falls to no single entity or agency.
Therefore, many opportunities exist for the application of
state-of-the-art management interventions where currently
inadequate or absent interventions are accepted.
Task 2.3 Rank, Prioritize, and Identify Watersheds Along a
Gradient of Discordance Between the Distribution of Sources
of Nitrogen and the Distribution of the Application of
Management Methods Determined in Task 2.2.
With the strong intent to improve the situation, we should
identify watersheds that are substantive contributors to the
nitrogen problem where even current management
technologies are not being used.
Task 2.4 Provide Watershed Specific Recommendations in High
Priority Watersheds Identified in Task2.3 to Local Managers
and Planners - in Ecological, Engineering, Environmental,
Economic, and Social Sciences - for Application of Known
Nitrogen Management Methods for High Use Landscapes.
It is reasonable to expect that local economic and social
factors may be correlated with utilization of current nitrogen
managementtechnologies. These factors should be identified
so that programs can be developed to help local stakeholders
improve their environment and contribute to national and or
regional nitrogen management goals.
Advances in this research area will help to relieve adverse impacts
to watersheds in high use landscapes while concurrently
contributing to measurable downstream improvements of water
quality and habitat for aquatic biota in receiving waters, particularly
estuaries. Because nitrogen management techniques already
exist for many anthropogenic sources of nitrogen in high use
landscapes, measurable reductions to the rate of flux and amount
of nitrogen leaching to surface and ground water in these
landscapes should be able to be realized through identification of
under-utilized targets for technique application.
Area 3 - Management Techniques for Low Use Land-
scapes
Despite the recognition that excess nitrogen in the environment
has notable undesirable properties, and despite decades of
research and management practice aimed at minimizing and
eliminating nitrogen leaching from its point of production or release,
we currently face a substantial and apparently growing problem
related to excess nitrogen. One explanation for this is that
ecosystems are slowly losing their ability to optimally retain,
sequester, and transform nitrogen. Thus, nitrogen is more readily
leaching to surface and ground waters, and estuaries. By a large
majority, most of the land where the ability of the ecosystem to
process nitrogen may be degraded occurs in low use landscapes,
including parklands, wilderness, grazing lands, and forests.
Together, these land uses accounted for 68.8% of the land cover
in the eastern United States during 1997 (USDA, 2000).
The ability of these lands to retain and sequester nitrogen is not
well understood, although it is clearthat increasing the amount of
nitrogen inputto these landscapes frequently leads to a decreasing
ability of these landscapes to optimally retain, sequester, and
transform nitrogen. Thus, the more nitrogen that is added, the less
is retained.
This being the case, it is clearthat our ability to reduce uncertainty
regarding nitrogen management results attainable from Research
Areas 1 and 2 can be greatly enhanced through an improved
understanding of the contribution of low use landscapes to nitrogen
management. Further, there is every reason to expect that
management techniques and prescriptions can be developed for
low use landscapes that will maximize and enhance their ability to
retain, sequester, and transform nitrogen, especially nitrogen
inputs attributable to atmospheric deposition.
The following research tasks need to be addressed in this area:
Task 3.1 Measure the Ability of Landscapes and Vegetative
Communities from Multiple Ecological Settings, and their
Associated Consumer, Decomposer, and Microbial
Communities, to Retain, Sequester, and Transform Nitrogen,
and Measure their Retention, Sequestration, and
Transformation Responses to Increased Levels of Nitrogen
Flux and Input.
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Measures of the basic ability of ecosystems to assimilate and
process nitrogen, and their ability to respond and adapt to
greater levels of nitrogen input are notably lacking but certainly
needed.
Task 3.2 Measure the Interaction of Landscapes and Vegetative
Communities with Producer, Consumer, Decomposer, and
Microbial Activity Relative to the Ability of Landscapes and
Vegetative Communities to Retain, Sequester, and Transform
Nitrogen.
An ability to understand and manipulate nitrogen cycling
through the ecosystem, at the level of cause-and-effect
relationships, would provide powerful tools for predicting
watershed susceptibility to increased amounts of nitrogen
and more importantly, for development of new nitrogen
management tools for a wide variety of landscapes under
many types of land use.
Task 3.3 Provide Management Recommendations for
Landscapes and Vegetative Communities Resulting from
Tasks 3.1 and 3.2, for Manipulating Sites to Optimize and
Maintain Nitrogen Retention, Sequestration, and
Transformation.
With an improved understanding of the cause-and-effect
relationships underlying nitrogen cycling, it would be possible
to tailor management interventions that will be optimum in
specific watersheds in association with specific land uses.
Task 3.4 Obtain Metrics for Projecting with Confidence how Site
Succession will Affect Nitrogen Retention, Sequestration,
and Transformation Characteristics and Identify Indicator
and Monitoring Criteria that can Predict Site Senescence.
Ecosystems change with time. Where it is desirable to predict
future conditions, the ability to predict and therefore manage
nitrogen in ecosystems must account for succession in
ecological communities.
Task 3.5 Develop Techniques and Methods for Manipulating
Producer, Consumer, Decomposer, and Microbial Individuals,
Populations, and Communities to Manage for Maintained
Native Biodiversity on Landscapes and Watersheds to
Concurrently Maximize Nitrogen Retention, Sequestration,
and Transformation Characteristics.
It is desirable that we integrate nitrogen management with
interrelated environmental concerns, most particularly native
species management, in an effort to increase management
effectiveness and benefit.
Advances in this research area, while of a basic scientific nature,
hold the promise of allowing spatially extensive low use landscapes
to maintain and improve their ability to retain, sequester, and
transform nitrogen. In this regard, they can serve as nitrogen sinks
- offsetting to some extent the degraded ability of even the best-
managed high use landscapes to use nitrogen. Just as the
manipulation of plants, regarding their ability to produce food, has
provided the foundation forthe green revolution, so is it reasonable
to expect that analogous manipulations of plants and other biota
-including individuals, populations, and communities-can produce
desirable outcomes for nitrogen management.
Conclusion
The research program for nitrogen management described herein
constitutes a reasonable - measured response - to an
environmental problem that isjust beginning to be fully understood.
A program of combined applied and basic research in the Ecological,
Engineering, Environmental, Economic, and Social Sciences is
described that will identify landscapes and watersheds at riskfrom
excess nitrogen and prescribe management responses in both
high and low use landscapes. The program will indicate fruitful
directions for future research, leading to the development of
techniques and methods for manipulating producers, consumers,
decomposers, and microbial communities for the purpose of
maximizing and optimizing landscape and watershed nitrogen
retention, sequestration, and transformation ability.
Notice
The U.S. Environmental Protection Agency through its Office of
Research and Developmentfunded 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.
Literature Cited
Aber, J.D., K.J. Nadelhoffer, P. Steudler, and J.M. Melillo. 1989.
Nitrogen saturation in northern forest ecosystems. Bioscience
39:378-386.
Asner, G.P., T.R. Seastedt, and A.R. Townsend. 1997. The
decoupling ofterrestrial carbon and nitrogen cycles. Bioscience
47:226-234.
Baker, L.A. 1992. Introduction to nonpoint source pollution in the
United States and prospects for wetland use. Ecological
Engineering 1:1-26.
Brimblecombe, P. and D.H. Stedman. 1982. Historical evidence
for a dramatic increase in the nitrate component of acid rain.
Nature 298:460-462.
Galloway, J.N., H. Levy II, and P.S. Kasibhatla. 1994. Year2020:
consequences of population growth and development on
deposition of oxidized nitrogen. Ambio 23:120-123.
Gilliam, F.S., M.B. Adams, and B.M. Yurish. 1996. Ecosystem
nutrient responses to chronic nitrogen inputs at Fernow
Experimental Forest, West Virginia. Canadian Journal of Forest
Research 26:196-205.
Gilbert, P.M. and D.E. Terlizzi. 1999. Co-occurrence of elevated
urea levels and dinoflagellate blooms in temperate estuarine
aquaculture ponds. Applied and Environmental Microbiology
65:5594-5596.
Kahl, J.S., S.A. Norton, I.J. Fernandez, K.J. Nadelhoffer, C.T.
Driscoll, and J.D. Aber. 1993. Experimental inducement of
nitrogen saturation at the watershed scale. Environmental
Science and Technology 27:565-568.
Kelly, C.A., J.W.M. Rudd, and D.W. Schindler. 1990. Acidification
by nitric acid - future considerations. Water, Air, and Soil
Pollution 50:49-61.
Likens, G.E. 1992. The ecosystem approach: its use and abuse.
Excellence in Ecology 3. Ecology Institute, Oldendorf/Luhe,
Germany. 166 pp.
Magill, A.M., M.R. Downs, K.J. Nadelhofer, R.A. Hallett, and J.D.
Aber. 1996. Forest response to four years of chronic nitrate
and sulfate additions at Bear Brooks Watershed, Maine, USA.
Forest Ecology and Management 84:29-37.
Mander, U., A. Kull, and V. Kuusemets. 2000. Nutrient flows and
land use change in a rural catchment: a modelling approach.
Landscape Ecology 15:187-199.
Peterjohn, W.T., M.B. Adams, and F.S. Gilliam. 1996. Symptoms
of nitrogen saturation in two central Appalachian hardwood
forest ecosystems. Biogeochemistry 35:507-522.
Shaver, G.R., J. Canadell, F.S. Chapin III, J. Gurevitch, J. Harte,
G. Henry, P. Ineson, S. Jonasson, J. Melillo, L. Pitelka, and L.
Rustad. 2000. Global warming and terrestrial ecosystems: a
conceptual framework for analysis. Bioscience 50:871-882.
-------
Smil, V. 1990. Nitrogen and phosphorus. In B.L Turner II, W.C.
Clark, R.W. Kates, J.F. Richards, J.T. Mathews, and W.B.
Meyer (eds), The Earth as transformed by human action; global
and regional changes in the biosphere over the past 300years.
Cambridge University Press, United Kingdom. 713 pp.
USDA. 2000. Summary report 1997 national resources inventory
(revised December 2000).
U.S. EPA. 1995. An SAB report: ecosystem management;
imperative for a dynamic world. EPA-SAB-EPEC-95-003.
Vitousek, P.M., J. Aber, R.W. Howarth, G.E. Likens, P.A. Matson,
D.W. Schindler, W.H. Schlesinger, and G.D. Tilman. 1997.
Human alteration of the global nitrogen cycle: causes and
consequences. Issues in Ecology 1:1-16.
Wedin, D.A. and D. Tilman. 1996. Influence of nitrogen loading
and species composition on the carbon balance of grasslands.
Science 274:1720-1723.
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