&EPA
www.epa.gov/research
science   in  ACTION
INNOVATIVE RESEARCH FOR A SUSTAINABLE FUTURE
    Changes in Tree Species in Riparian Zones of Urban Streams May Have
    Effects on Restoration and Storm Water Control Efforts.
     Research Value:

     A riparian zone is the land and
     vegetation within and directly
     adjacent to surface water
     ecosystems, such as lakes arid
     streams. The vegetation in
     riparian zones provides
     ecosystem services to
     communities to help them
     remain sustainable;  services
     such as reducing flooding and
     bank erosion and reducing
     levels of pollutants in streams.
     So, a healthy riparian zone
     benefits a community
     economically by reducing
     property damage, increases the
     quality of life by providing
     more recreational oppor-
     tunities for people and habitat
     for a diverse community of
     terrestrial and aquatic animals,
     and helps protect public health
     by aiding in pollution control.
     Riparian zones are considered
     green infrastructure in similar
     fashion as things like green
     roofs and rain gardens because
     they provide the same kind of
     ecosystem services.

     In cities such as Cincinnati,
     OH and Baltimore, MD, tree
     species characteristic of
     lowland areas have
     disappeared from urban
     riparian zones and have been
           replaced by typical upland tree
           species 1>2. This change in
           tree species could affect the
           riparian zones by making them
           less effective at flood control
           and at providing quality
           habitat for organisms such as
           stream fish.

           Differences in hydrology and
           pollution in urban vs. rural
           areas are prime suspects for
           this change in tree species
           near streams in urban areas.
           By sorting out which stressors
           are more likely the cause of
           this change in species, this
           study can provide useful
           information to those  trying to
           preserve and restore riparian
           zones in their' communities.

           Research Background:

           Ozone in srnog at ground level
           in the troposphere (as opposed
           to the protective ozone layer
           in the stratosphere), is a
           pollutant that may be
           responsible for the
           disappearance of some ozone-
           sensitive lowland tree species3
           in urban areas. Though once
           at high concentrations in
           smog, ground-level ozone
           concentrations have been
           lowered in many cities, likely
           through EPA-developed
regulations in the Clean Air
Act, first enacted in 1963.
 Magnified image of a tree core from
  a chestnut oak. Numbers on the
   image show the annual rings.
If the shift towards upland
species is due to decades of
high ozone exposure prior to
regulation, then restoring
lowland species to urban
riparian zones may once again
be of hydrologic benefit.
However, if the same species
shift was due to lower water
tables and more severe
droughts in urban areas, then
replanting urban riparian
          U.S. Environmental Protection Agency
          Office of Research and Development (ORD), National Risk Management Research Laboratory (NRMRL)
          Land Remediation and Pollution Control Division (LRPCD)

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zones with lowland species
would not be successful.

By analyzing annual growth
rings of trees to see if patterns
are evident in growth
associated with location or
years, this study may separate
the effects of urban pollution
from persistent hydrologic
changes such as drought.
The growth and species
abundance data from the urban
and rural riparian zones in
Baltimore and Cincinnati will
be used to shed light on the
following question:

What are the roles  of
ground-level tropospheric
ozone and urban hydrology
in determining riparian tree
species composition?
Outcomes and Impacts:

Results of this study, which
was begun in 2010, are
expected to be available by
late 2011.  When the study is
completed, the results of this
investigation have
implications beyond these two
cities.  This research has
potential impact on the
conservation of riparian zones
and storm water management,
both of which are critically
important to communities in
terms of then economies and
public health. This
information can be useful to a
number of community groups
which are already working to
preserve and restore their
riparian zones. Follow-up
studies that expand on the
knowledge gained in this
study are likely as well.
                                   LAND RESEARCH PROGRAM
                                   WEB SITES; www.epa.gov/ord/lrp
                                   www.epa.gov/nrmrl/lrpcd

                                   CONTACTS
                                   Technical Inquiries.
                                   Terry Loecke. 513-569-7730. EPA/
                                   ORD/NRMRL/ LRPCD/ESMB
                                   loecke. teiryfS epa. go v

                                   Communications Inquiries
                                   Roger Yeardley. 513-569-7548.
                                   EPA/ ORD/NRMRL/ LRPCD
                                   yeardley roger ci epa.gov
                                                                       REFERENCES
1 Groffman PM, et aL (2003) Down by the
riverside: urban npanan ecology. Frontiers in
Ecology and Environment 1:315-321

2. Pennuigtou DN, Hansel JR and Gorchov
DL (2010) Urbanization and npanan forest
woody communities: Diversity, composition.
and structure within a metropolitan landscape.
Biological Conservation 143:182-194

3. Coulston, J. W., G. C. Smith, et al. (2003).
"Regional assessment of ozone sensitive tree
species using bioindicator plants."
Environmental Monitoring and Assessment
83:113-127
                                  National Risk Management Research Laboratory
                                  Land Remediation and Pollution Control Division
                                                  EPA/600/F-11/003
                                                  April 2011
                                                                                    www.epa.gov/nrmrl

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