A conceptual approach to evaluating grassland restoration potential on Huron Wetland Management District, South Dakota Biological Technical Publication BTP-R6016-2012

              U.S. Fish & Wildlife Service
A Conceptual Approach
to Evaluating Grassland
Restoration Potential
on Huron Wetland
Management District,
South Dakota
Biological Technical Publication
BTP-R6016-2012
Laura Hubers, USFWS
ISBN-10: 193895601X
ISBN-13: 978-1-938956-01-0
i
U.S. Fish & Wildlife Service
A Conceptual Approach
to Evaluating Grassland
Restoration Potential
on Huron Wetland
Management District,
South Dakota
Biological Technical Publication
BTP-R6016-2012
Murray K. Laubhan 1
Bridgette Flanders-Wanner 2, 4
Rachel A. Laubhan 3
1 U.S. Fish and Wildlife Service, Region 6, Division of Biological
Resources, Stafford, KS
2 U.S. Fish and Wildlife Service, Huron Wetland Management District,
Huron, SD
3 U.S. Fish and Wildlife Service, Quivira National Wildlife Refuge,
Stafford, KS
4 Current Address: U.S. Fish and Wildlife Service, Branch of Refuge
Biology, Vancouver, WA
Cover image: Waubay National Wildlife Refuge
Photo credit: Laura Hubers, USFWS
ii A Conceptual Approach to Evaluating Grassland Restoration Potential
Author Contact Information:
Murray K. Laubhan
U.S. Fish and Wildlife Service, Region 6
Division of Biological Resources
1434 NE 80th Street
Stafford, KS 67578
Phone: (620) 486-2393
E-mail: Murray_Laubhan@fws.gov
Bridget Flanders-Wanner
U.S. Fish and Wildlife Service, Region 1
Branch of Refuge Biology
1211 SE Cardinal Court, Suite 100
Vancouver, WA 98683
Phone: (360) 604-2558
E-mail: Bridgette_Flanders-Wanner@fws.gov
Rachel A. Laubhan
U.S. Fish and Wildlife Service
Quivira National Wildlife Refuge
1434 NE 80th Street
Stafford, KS 67578
Phone: (620) 486-2393
E-mail: Rachel_Laubhan@fws.gov
Recommended citation:
Laubhan, M. K., B. Flanders-Wanner, and R. A.
Laubhan. 2012. A conceptual approach to evalu-ating
grassland restoration potential on Huron
Wetland Management District, South Dakota. U.S.
Department of Interior, Fish and Wildlife Ser-vice,
Biological Technical Publication FWS/BTP-R6016-
2012, Washington, D.C.
For additional copies or information, contact:
Wayne J. King
Chief, Division of Biological Resources
U.S. Fish and Wildlife Service, Region 6
P.O. Box 25486
Denver Federal Center
Denver, CO 80225-0486
Phone: (303) 236-8102
E-mail: wayne_j_king@fws.gov
Series Senior Technical Editor:
Stephanie L. Jones
Nongame Migratory Bird Coordinator
U.S. Fish and Wildlife Service, Region 6
P.O. Box 25486 DFC
Denver, Colorado 80225
Phone: (303) 236-4409
E-mail: Stephanie_Jones@fws.gov
ISSN 2160-9498 Electronic ISSN 2160-9497 Biological Technical Publications online:
http://library.fws.gov/BiologicalTechnicalPublications.html
Table of Contents iii
Table of Contents
List of Figures ........................................................................................................................................................ iv
List of Tables .......................................................................................................................................................... v
Acknowledgements ............................................................................................................................................. vi
Executive Summary ............................................................................................................................................ vii
Introduction ........................................................................................................................................................... 1
Review of the Literature ........................................................................................................................................ 3
Goal and Objective Setting ................................................................................................................................ 3
Spatial Scale.......................................................................................................................................................... 3
Temporal Scale .................................................................................................................................................... 3
Abiotic and Biotic Factors .................................................................................................................................. 4
Study Site .............................................................................................................................................................. 5
Conceptual Approach ........................................................................................................................................... 7
Goal and Objectives ............................................................................................................................................ 7
Spatial Scale......................................................................................................................................................... 7
Temporal Scale .................................................................................................................................................... 8
Abiotic and Biotic Factors .................................................................................................................................. 8
Climate ............................................................................................................................................................. 9
Soils ................................................................................................................................................................... 9
Topography ..................................................................................................................................................... 10
Vegetation ........................................................................................................................................................ 10
Wildlife ............................................................................................................................................................ 11
Framework Development ..................................................................................................................................... 13
Conclusions ......................................................................................................................................................... 15
Literature Cited ................................................................................................................................................... 17
iv A Conceptual Approach to Evaluating Grassland Restoration Potential
List of Figures
Figure 1. Level IV ecoregions in the eight-county region of the Huron Wetland Management District,
	
South Dakota (modified from Bryce et al. 1998). ...................................................................................................... 5
Figure 2. Simplified illustration of seed bank dynamics, including state variables (rectangles), primary
abiotic and biotic factors (octagons) influencing plant germination cues and survival (ovals), and common
examples of anthropogenic factors influencing abiotic and biotic factors (pentagons). Figure adapted from
Simpson et al. 1989. ................................................................................................................................................... 9
Figure 3. A conceptual approach for evaluating restoration potential of grasslands ........................................ 14
NameL oisft Sofe Tctaibolnes v
List of Tables
Table 1. Native and non-native species composition of native sod and planted native tracts administered by
Huron Wetland Management District, South Dakota, in 2003 (BFW). ............................................................... 5
Table 2. Dominant topographic features, soil properties, and climate conditions occurring in level IV
ecoregions that comprise Huron Wetland Management District (data from Bryce et al. 1998). ..................... 7
Status Review and Conservation Recommendations for the Gull-billed Tern
Acknowledgements
W. J. King provided funding and coordinated
activities associated with this report. The staff of
the Huron Wetland Management District conducted
a tour of district lands, summarized existing data,
and openly discussed management opportunities
and constraints that should be considered in
developing a conceptual management approach.
Reviews of earlier drafts greatly improved the
report, particularly those provided by D. Azure, P. M.
Drobney, J. S. Gleason, R. A. Gleason, K. W. Kelsey,
W. J. King, and C. Mowry. M. J. Artmann kindly
assisted in the development of tables and figures.
The findings and conclusions in this article are those
of the authors and do not necessarily represent the
views of the U.S. Fish and Wildlife Service.
vi A Conceptual Approach to Evaluating Grassland Restoration Potential
ENxaemcueti voef SSuemcmtioarny vii
Executive Summary
The 1997 National Wildlife Refuge System
Improvement Act requires each administrative unit
in the National Wildlife Refuge System to develop
a Comprehensive Conservation Plan (CCP). As
part of this planning process, biological goals and
objectives must be developed based on the best
available scientific information. To assist with
the CCP process, Huron Wetland Management
District (WMD) requested assistance in developing
a conceptual approach for evaluating ecological
restoration options of grassland tracts administered
by the district. Our approach was to summarize and
organize general concepts in a framework that could
be used to evaluate restoration potential rather than
attempt to develop management recommendations
that included specific planting techniques or
management strategies, although this also will be
required to ensure long-term success.
We developed our approach based on a review of
the literature to identify attributes that influenced
the success of past ecological restoration efforts.
We developed summaries of this information to
provide managers and biologists with an overview
of factors to consider when evaluating restoration
potential. Development of clear and unambiguous
goals and objectives was identified as a critical initial
consideration because they define expectations, help
determine strategies to be implemented, and form
the foundation of meaningful monitoring programs.
Consideration of scale (both spatial and temporal)
and biological factors (both abiotic and biotic) also is
important. Collectively, these attributes are useful
for determining the causes of grassland degradation,
defining the restoration potential of a site, and
identifying the most appropriate remediation
techniques.
We used these general concepts and attributes
to develop a conceptual hierarchical framework
for evaluating restoration potential of individual
grassland tracts on Huron WMD, which encompasses
approximately 17,790 km2 (6,869 mi2) in portions of
eight counties in east-central South Dakota. District
staff currently manages 4,644 ha (11,476 ac) of
grasslands, including 2,537 ha (6,270 ac) that have
never been tilled and are classified as native sod.
A focus of upland management is reconstructing
grasslands on previously farmed sites and restoring
existing grasslands (i.e., native sod with no
previous cropping history) that have been invaded
by non-native grasses to more native vegetation
communities.
The goal of ecological restoration on Huron WMD
is to restore native grasses and forbs that provide
the structure and resources necessary to support
populations of target migratory birds. However,
objectives had not yet been developed that identified
specific, measurable targets regarding plant
community composition or wildlife species. Thus, we
applied our approach to a set of example objectives
that included developing appropriate seed mixtures
for reconstruction projects that benefit migratory
birds, estimating the potential for non-native plant
species establishment, and determining wildlife
values that would be expected following restoration.
The framework we developed incorporated
attributes that could be used to assess site conditions
relative to the objectives as well as interim steps
that provide examples of how attribute information
can be combined to facilitate evaluation. Finally,
outcomes based on evaluation of the attributes are
identified to provide a means to assign priorities to
restoration projects.
Developing an approach for evaluating and
prioritizing sites for restoration is a complex
and uncertain process. Although much is known
regarding factors controlling plant community
establishment and the relationships between
plant communities and wildlife habitat suitability,
the relative importance of these factors often
varies among and within sites depending on
past perturbations and surrounding landscape
conditions. Consequently, a structured framework
can promote standardized evaluations and improve
communication on site, while providing a method to
systematically deconstruct complex problems and
provide greater objectivity when making restoration
decisions.
vviiiiii A S Ctaotnucesp Rtueavl iAepwp raonacdh C too Ensvealruvaatitnigo nG rRasescloanmdm Reesntdoraattiioonn sP footern tthiael Gull-billed Tern
© Chris Bailey
Name of Section 1
Introduction
The 1997 National Wildlife Refuge System
Improvement Act requires each administrative unit
in the National Wildlife Refuge System to develop
a Comprehensive Conservation Plan (CCP) that
includes biological goals and objectives that are based
on the best available scientific information. Goals are
general descriptions of desired future conditions, but
objectives are more specific and must be measurable,
achievable, results oriented, and time specific. In
many cases, objectives are habitat-based and specify
the guilds of wildlife species that will benefit from
attainment of each objective.
To assist with the CCP process, Huron Wetland
Management District (WMD) requested that we
synthesize information on ecological restoration
approaches for grasslands that would help them
develop goals and objectives to achieve a desired
grassland condition defined as a “a mixture of
native grasses and forbs that provide the structure
and foods necessary to support target migratory
bird species.” We decided the best approach was
to integrate relevant information from different
scientific disciplines into a framework that could
be used to evaluate ecological restoration potential
of different grassland tracts. Although some
information we used is based on studies conducted
outside the northern Great Plains, they were relevant
to Huron WMD because they addressed ecological
drivers (e.g., soils, moisture, and climate) that are
primary determinants of plant germination and
survival regardless of geographic location (Simpson
et al. 1989, Aronson and Le Floc’h 1996, Ehrenfeld
2000).
The desired outcomes used in the document are
examples developed by the authors and are not those
of Huron WMD. This document is not intended
to serve as a complete guide that includes post-establishment
management recommendations, but
as an example of the process. Consequently, on-the-ground
experience in restoring sites, in combination
with the literature used in the report, should be used
to evaluate the relevancy of the goals, attributes used
to evaluate site conditions, and desired outcomes.
Introduction 1
Status Review and Conservation Recommendations for the Gull-billed Tern
Review of the Literature
Goal and Objective Setting
The rapid rise of ecological restoration has resulted
in widely varying interpretations regarding what
is meant by the term and what constitutes success
(Palmer et al. 1997, Ruiz-Jaen and Aide 2005). Some
individuals advocate that restoration is as much ethical
as technical and should include historical, social,
cultural, political, aesthetic, and moral aspects, as well
as ecological principles (Higgs 1997). Even within a
single discipline such as ecology, restoration can range
from a focus on particular species to entire ecosystems
(Risser 1995, Falk et al. 1996, Kershner 1997). These
different approaches can result in widely varying
goals and objectives. Strict definitions of restoration
often have goals that refer to historic conditions and
objectives that mention emulating the structure,
function, diversity, and dynamics of the pre-defined
ecosystem (Aronson et al. 1993). Achieving this level of
success is rare because it is difficult both to determine
the exact structure and function of historic ecosystems
and to establish the full complement of species and
range of occurrence levels historically present (Cairns
1991, Lockwood and Pimm 1999). Consequently, some
practitioners have recommended evaluating restoration
projects in terms of achieving functional (e.g., erosion
control) or structural (e.g., species composition) goals
and objectives (Whisenant 1999, Piper and Pimm
2002), whereas others advocate defining restoration
categories (e.g., restoration, rehabilitation, reallocation)
that have different goals and objectives (Aronson et
al. 1993, Keddy 1999). In these latter scenarios, goals
do not necessarily bear an intrinsic relationship with
pre-disturbance ecosystem structure and function and
may even consist of innovative combinations of native or
introduced species (D’Antonio and Meyerson 2002).
Given this disparity, developing goals and explicit
objectives is the first and most important component of
a project. Clear and unambiguous goals and objectives
define expectations, help determine strategies to be
implemented, and form the foundation of meaningful
monitoring programs. Ehrenfeld (2000) discusses
some common restoration goals and objectives, the
implications of each from a practical perspective, and
suggests that there is no single paradigm or context
for setting goals and objectives; rather, goals and
objectives need to be developed for each project relative
to desired outcomes (Jordan et al. 1987, Buckley 1989).
In addition, goals and objectives should be established
based on a realistic expectation of what restoration
can accomplish. Factors to consider include extent
of degradation, information available for addressing
problems, and costs (Society of Ecological Restoration
2004). Ensuring that goals are realistic often can be
addressed by defining categories of restoration success
such as those described by Aronson et al. (1993).
Spatial Scale
The importance of various abiotic and biotic factors in
developing restoration goals and approaches can vary
depending on the spatial scale considered (Aronson and
Le Floc‘h 1996, Goldstein 1999). Reducing or removing
sources of degradation that compromise system
functionality often is recommended as an initial step in
ecological restoration to ensure long-term sustainability
(Whisenant 1995). Identifying the source of degradation
is important because the presence or absence of a plant
or animal species in a specific area may be controlled
by factors operating at scales much larger than the site
being evaluated for management (Byre 1997, White and
Walker 1997, George and Zack 2001). Understanding
the extent of degradation also is critical as more human
intervention often is required as degradation increases
and eventually it may not be possible to completely
reverse some damages. This concept, termed
thresholds of environmental change, is well established
in ecology (Holling 1973, Wissel 1984) and is being
applied in range management (Friedel 1991, Laylock
1991) to evaluate site conditions. Failure to consider
these scale-dependent factors can lead to erroneous
conclusions regarding remediation techniques, the most
appropriate plant species to restore, and, ultimately, the
ability of restoration projects to achieve intended goals.
Temporal Scale
Natural systems, including grasslands, are extremely
dynamic (Pickett and Parker 1994) and considerable
evidence indicates feedback occurs between species
composition and ecosystem processes. This feedback
causes many ecosystem processes to develop over
different time scales (Palmer et al. 1997, Kulmatiski
et al. 2006). Consequently, many communities exist in
perpetual states of nonequlibirium (Wiens 1984, Pickett
et al. 1992) and exhibit both physical and biological
variability (Horne and Schnieder 1995, Palmer and
Poff 1997). Perennial plant species tend to dominate
both terrestrial and aquatic systems during relatively
stable periods, whereas annuals tend to predominate
following shorter temporal scales. At shorter temporal
scales, dramatic changes in plant composition (e.g., forb
diversity) also can occur from late spring to winter in
the same year.
2 A Conceptual Approach to Evaluating Grassland Restoration Potential
RevNieawm ofe t hoef LSietcertiaotunr e 3 3
Although dynamic conditions are difficult to describe
succinctly, temporal changes in plant community
composition and structure are important considerations
when evaluating ecological restoration potential
and developing management strategies. Successful
establishment of a target plant community may require
the use of certain plant species, such as nitrogen-fixing
legumes in arid and semi-arid ecosystems, at specific
times during the restoration process (Jenkins et al.
1987, Jarrell and Virginia 1990, Paine 1996). Long-term
sustainability of a plant community also requires that
sufficient plant diversity be present to persist across the
full range of environmental fluctuations characteristic
of the site (Schulze and Mooney 1993, Davis and
Richardson 1995, Palmer et al. 1997). Adequately
incorporating the temporal dynamics of ecological
restoration projects may require a sequential, multi-step
process or defining the “potential” of a site at
different stages of succession based on climate, soils,
hydrology, seed type and availability, plant competition,
plant-animal interactions, and other factors (Palmer et
al. 1997).
Abiotic and Biotic Factors
Although restoration goals can focus on a range of
outcomes, a principle common to most restoration
approaches is the need to incorporate knowledge of
processes (Ehrenfeld 2000). Not only is knowledge of
processes (e.g., hydrology, nutrient cycling) necessary
to evaluate the full range of remediation measures
available, this knowledge is also critical to evaluating
outcomes (King and Hobbs 1996, Montalvo et al. 1997)
and, ultimately, to developing improved, site-specific
restoration methods (Ehrenfeld 2000). However,
ecological processes are complex assemblages of
interacting factors and direct measurement is often
not feasible. Therefore, indicators often must be used
as surrogate measures to assess abiotic and biotic
site conditions. Knowledge of landscape position, soil
physical structure and chemistry, and climate often
can be used to determine the range of soil moisture
conditions occurring at a site.
The specific abiotic factors to consider when developing
an approach to evaluate ecological restoration potential
are best determined by the goals that have been
established. A literature review documented that
factors considered in different projects were diverse
and tended to be individualistic (Ehrenfeld 2000).
However, from a management perspective, goals alone
often are not sufficient to limit the number of factors to
a manageable level and additional criteria must be used
to narrow the selection to those that are most relevant.
Several articles addressing this subject have been
published, including a list of vital ecosystem attributes
(Aronson et al. 1993), information syntheses that
provide general guidance (Whisenant 1995), and several
practical case histories (Tongway and Ludwig 1996,
Eliason and Allen 1997, Breshears et al. 2001, Sheley
and Krueger-Mangold 2003, King and Hobbs 2006).
A common feature of these articles is the importance
placed on identifying key abiotic and biotic factors
related to system structure and function in the context
of stated goals.
Bridgette Flanders-Wanner (USFWS)
Status Review and Conservation Recommendations for the Gull-billed Tern
and Japanese brome (B. japonicus) occur as
scattered inclusions, whereas introduced forbs
include sweet clover (Melilotus spp.) and alfalfa
(Medicago sativa). The primary noxious weeds
include leafy spurge (Euphorbia esula), Canada
thistle (Cirsium arvense), sow thistle (Sonchus
oleraceus), and wormwood (Artemesia spp.) (BFW).
Management of Huron WMD uplands are primarily
directed toward reconstructing grasslands on
previously farmed sites and restoring existing
grasslands (i.e., native sod with no previous cropping
history) that have been invaded by non-native
grasses to more native vegetation communities.
Reconstruction of previously farmed sites typically
begins with cropping for two years to promote a seed
bed that is relatively free of weeds. Corn (Zea mays)
is typically planted in the first year and soybeans
(Glycine max) in the second year. Soybeans are
used in the second year because this crop results
in a firm seedbed with little crop residue, which
facilitates reseeding native grass the following
spring. Approximately three years after an area has
been reseeded, some type of management is needed
to remove excess dead vegetation and stimulate
growth of planted natives. In contrast, grassland
restoration efforts attempt to shift the composition of
the existing plant community to a higher proportion
of native species and do not involve mechanical
disturbance of soil and use of crops.
The most common management treatments used
in both reconstruction (following initial seeding)
and restoration of Huron WMD grasslands are
prescribed fire, grazing, or a combination of these
strategies (BFW). Prescribed fire was used to treat
2,147 ha (5,305 ac) between 1999 and 2005, whereas
grazing and a combination of grazing and fire was
implemented on 1,240 ha (3,064 ac) and 1,414 ha
(3,494 ac), respectively, between 2000 and 2005
(BFW). The effectiveness of these treatments in
stimulating native species and reducing the incidence
of non-native species varied depending on location,
vegetation community, and time and intensity of
treatment.
Huron WMD was established on May 31, 1992
under the authority of the Migratory Bird Hunting
and Conservation Stamp Act (16 U.S.C. 718),
which authorizes the acquisition, lease, purchase,
or exchange of small wetland and pothole areas
designated as Waterfowl Production Areas (WPA).
Huron WMD encompasses eight counties in east-central
South Dakota, an area of approximately
17,790 km2 (6,869 mi2) (Fig. 1). In 2000, lands
administered by Huron WMD included 60 WPAs
(5,807 ha [14,350 ac]), 1,425 wetland easements
(27,843 ha [68,800 ac]), 147 grassland easements
(22,541 ha [55,700 ac]), and 63 conservation
easements (4,087 ha [10,100 ac]) (U.S. Fish and
Wildlife Service 2000). Although at least one WPA is
located in every county, the majority occur in Beadle,
Hand, and Jerauld counties (Fig. 1).
Huron WMD currently manages 4,644 ha (11,476
ac) of grasslands, including 2,537 ha (6,270 ac) that
have never been tilled and are classified as native
sod (Table 1). Approximately 2,411 ha (95% [5,957
ac]) of native sod are dominated by more than 50%
non-native species, whereas only 126 ha (5% [311 ac])
are dominated by more than 50% native species. The
remaining 2,107 ha (45% [5,206 ac]) of grasslands are
comprised of tracts that have been reseeded to native
plants (713 ha [1,762 ac]) or have been subjected to
some type of agricultural land-use practice (1,394
ha [3,444 ac]). Based on surveys of vegetation
composition on a portion of planted native tracts, it is
estimated that 521 ha (73% [1,287 ac]) are comprised
of >50% native species and 192 ha (27% [475 ac]) are
comprised of <50% native species (Table 1).
Huron WMD lands include both cool-season native
grasses dominated by green needlegrass (Nassella
viridula), western wheatgrass (Pascopyrum
smithii), and porcupinegrass (Hesperostipa spartea)
and warm-season grass dominated by big bluestem
(Andropogon gerardii), switchgrass (Panicum
virgatum), Indiangrass (Sorghastrum nutans),
and little bluestem (Schizachyrium scoparium)
that are intermixed with various native forb
species. The most common introduced terrestrial
species are smooth brome (Bromus inermis),
Kentucky bluegrass (Poa pratensis), and crested
wheatgrass (Agropyron cristatum). These are
perennial, sod-forming, cool-season species that
are drought resistant. In addition, tall wheatgrass
(Thinopyrum ponticum), intermediate wheatgrass
(T. intermedium), pubescent wheatgrass, quackgrass
(Elymus repens), downy brome (Bromus tectorum),
4 A Conceptual Approach to Evaluating Grassland Restoration Potential
Study Site
RevNiewam ofe t hoef LSietecrtaiotunr e 55
Figure 1. Level IV ecoregions in the eight-county region of the Huron Wetland Management District, South
Dakota (modified from Bryce et al. 1998).
66 A SCtoantcuesp tRuael vAiepwpr oaancdh tCo oEnvsaeluravtaintgio Gnr aRseslcaonmd Rmeesntodraattiioonn Pso ftoern ttiahle Gull-billed Tern
Conceptual Approach
Goal and Objectives
The goal of restoring native grasses and forbs that
provide the structure and resources necessary to
support target migratory birds was used as guidance
in developing the conceptual approach. Although
this goal contains general measures of success,
ecological restoration is still subject to interpretation
because general descriptions of plant community
composition (i.e., native grasses and forbs) may
not explicitly define expectations of restoration.
Approximately 988 species of native vascular plants
occur in the tall-grass prairie of the central United
States and adjacent Canada (Ladd 1997); however,
a given site is not suitable for all of these species.
In addition, non-native species dominate many
sites designated for restoration and long-term,
complete eradication often is not possible (Society
of Ecological Restoration 2004). Some tolerance
threshold for the non-native species may need to
be established, particularly on small restoration
projects that are located in highly modified
landscapes (D’Antonio and Meyerson 2002, Wilson
and Pärtel 2003). Plant species or plant species
groups important for providing necessary structure
and foods for target bird species should be identified
because habitat requirements of these species
differ depending on species, annual cycle event,
climate, and land-use conditions in the surrounding
landscape (Knopf and Samson 1995, Johnson and
Igl 2001, Hobbs and Norton 2004). These plant
species may not represent the entire complement
of desirable species, but they do represent critical
community components necessary for success.
Consequently, specific species or guilds must be
identified to ensure that the target plant community
achieves the purposes for which Huron WMD was
established. Finally, all metrics that will be used to
define success in achieving goals should be explicitly
stated. This goal only addresses biological aspects
even though political and cultural aspects also must
be considered, and often may override biological
considerations, when making decisions regarding
ecological restoration of some sites.
The existing description of desired condition
provides sufficient detail to develop an example
framework to evaluate ecological restoration
potential. However, if such an approach is used,
developing specific objectives that explicitly state
desired outcomes will be necessary to make cohesive
decisions regarding restoration priorities. Such
criteria also will be necessary to design a monitoring
program that can be used to periodically assess
progress and make sequential decisions regarding
the most appropriate strategies to implement.
Spatial Scale
The dynamic attributes of ecosystems, including
interactions among organisms and between
organisms and their environment, tend to be
multi-scaled (Lewis et al. 1996) and this must be
considered when evaluating ecological restoration
potential and possible strategies. At a large
spatial scale, Huron WMD encompasses portions
of five Level IV ecoregions (Bryce et al. 1998; Fig.
1). All of these ecoregions are dominated by soils
in the Order Mollisol with the exception of the
River Breaks, which also includes Aridisols and
Entisols. Long-term average annual precipitation
and annual growing season days also appear similar
among ecoregions, but closer inspection reveals that
combinations of these factors result in important
differences among ecoregions that are reflected in
soil Great Groups (i.e., differentiations within a soil
Order based on dominant processes [e.g., drainage]),
as well as soil temperature and moisture regimes
(Table 2). This information is valuable for evaluating
ecological restoration potential because these factors
can influence vegetation community composition
and structure at larger spatial scales. The James
River Lowland and the Missouri Coteau in the north
central portion of Huron WMD historically supported
vegetation transitional between tall-grass and mixed-grass
prairie and dominated by big bluestem, little
bluestem, switchgrass, Indiangrass, porcupinegrass,
green needlegrass, and prairie junegrass (Koeleria
macrantha). In contrast, ecoregions in the western
portion of Huron WMD (Southern Missouri Coteau
Slope, Southern Missouri Coteau, and River
Breaks) exhibit mesic soil temperatures and ustic
soil moisture regimes. Historically, vegetation
in these ecoregions was dominated by species
characteristic of the mixed-grass prairie, including
western wheatgrass, green needlegrass, needle-and-
thread (Hesperostipa comata), little bluestem,
and blue grama (Bouteloua gracilis). In addition to
these grasses, the natural vegetation of the River
Breaks also included juniper (Juniperus spp.) and
deciduous trees on north slopes and draws, as well
as cottonwood (Populus spp.) gallery forests on the
floodplains of the Missouri and James rivers (Gartner
and Sieg 1996).
CNonacmepet uoafl SAepcptriooanch 7
88 A SCtoantcuesp tRuael vAiepwpr oaancdh tCo oEnvsaeluravtaintgio Gnr aRseslcaonmd Rmeesntodraattiioonn Pso ftoern ttiahle Gull-billed Tern
Although broad community descriptions can help
establish general restoration guidelines, abiotic
and biotic factors also affect plant community
establishment, composition, and structure at finer
scales. Within a restoration site, differences in
soils and climate often occur with subtle changes
in topography, slope, and aspect. Such differences
can be sufficient to cause shifts in plant community
composition and structure across relatively short
distances. In many cases, these microsites support
vegetation that is not characteristic of the general
vegetation community at broader landscape scales.
Increasing the success of restoration projects
often requires considering this more site-specific
information to avoid errors regarding selection of
plant species to restore and strategies to implement.
Although a variety of spatial scales could be used
to develop an approach for evaluating ecological
restoration potential, we decided to use watersheds
for Huron WMD lands. Watersheds were selected
because evaluation at this scale is the most commonly
cited for setting restoration goals (Ehrenfeld
2000). Watersheds are applicable to all lands within
Huron WMD regardless of ecoregion, and most
lands currently administered by Huron WMD have
non-integrated drainage and have a well-defined
watershed (i.e., upland area that drains to an
isolated wetland) that can be defined using existing
spatial data. In addition, abiotic factors (e.g., soils,
topography) that affect ecological functions (e.g.,
nutrient cycling, hydrology) operate at this scale and
a watershed approach provides the ability to evaluate
functional changes caused by past land-use activities
that will be important when developing ecological
restoration strategies.
Temporal Scale
Temporal periodicity can significantly influence success
of ecological restoration efforts because some factors
controlling plant establishment and persistence exhibit
considerable variability within and among years. Specific
combinations of soil temperature, soil moisture, and
photoperiod are often required to break seed dormancy
and stimulate seed germination of many species. Climate
obviously influences these factors and if all requirements
are not met, germination does not occur during that year.
Even after initial establishment, these factors continue
to play a dominant role in determining annual growth,
survival, and reproduction of plants, as well as the species
that dominate the plant community.
It is difficult to explicitly incorporate temporal climate
variability in an evaluation of restoration potential, but
considering a range of values (e.g., quantiles, confidence
intervals) for important variables is often more appropriate
than using long-term averages. Local or on-site variation
in monthly precipitation and temperature can be compared
with the germination and growth requirements of plant
species when making decisions regarding appropriate
seed mixtures to plant on specific sites. Such information,
in combination with the plant species aggregations being
established or managed and the life history characteristics
of these species, can also be useful for establishing
guidelines regarding the proper time to implement various
management treatments (e.g., soil disturbance, prescribed
fire, grazing). Although the use of this information does
not guarantee success, it can help reduce erroneous
conclusions during the evaluation process.
Abiotic and Biotic Factors
Establishment of native vegetation suitable to support
the habitat requirements of target migratory birds is
the primary consideration in the ecological restoration
of grasslands on Huron WMD. Most reconstruction
projects involve planting of seeds, manipulation of
environmental conditions to stimulate germination
of seeds already in the seed bank, or a combination
of these techniques. In contrast, restoration projects
typically occur in native sod (i.e., areas that have never
been tilled) and focus on manipulation of existing
vegetation communities to promote native grasses and
forbs and suppress non-native species. In both cases,
understanding processes that control soil propagule
bank (e.g., seeds, vegetative propagules) and vegetation
dynamics are paramount (Fig. 2). In general, the
soil seed bank is comprised of an active and inactive
component. Seeds (planted or natural) in the active
component are capable of germination and are located
in the top 5 cm (2 in) of soil. Seeds in the inactive
component are buried deeper than 5 cm (2 in) in the soil
profile and cannot germinate because environmental cues
stimulating dormancy break and germination are not
received. Vegetative propagules (e.g., rhizomes, corms)
also exhibit active and inactive components, although the
depth of the transition zone tends to occur at greater soil
depths. The composition and density of propagules in
the active and inactive components constantly change.
Propagules already in the soil bank can be moved
between the active and inactive component by both
natural (e.g., rodents, water) and anthropogenic (e.g.,
harrowing) factors. In addition, inputs of reproductive
structures to the soil bank occur annually as a result of
seed production by plants on the site, propagule dispersal
(e.g., wind, water, animal) onto the site from nearby
areas, and by direct addition of propagules by humans.
Propagule loss occurs from both the active and inactive
components as a result of pathogens, predation, and
physiological or physical death.
Within the active component, only seeds that receive
appropriate environmental cues germinate. Primary
cues include photoperiod, soil temperature, soil oxygen,
soil salinity, and soil moisture (Simpson et al. 1989,
Baskin and Baskin 1998, Cronk and Fennessy 2001; Fig.
2). Each of these cues continues to influence survival and
reproductive potential following germination (Simpson et
al. 1989), but other factors are also important, including
nutrient availability, presence of fungal populations, and
adaptations to disturbance (Miller 1997, Reynolds et al.
2003, Kulmatiski et al. 2006). Although seemingly simple,
the pathways controlling germination, establishment,
CNonacmepet uoafl SAepcptriooanch 9
and survival are extremely complex because many
of the environmental factors influencing germination
are interrelated; soil temperature tends to increase
with increasing photoperiod and soil oxygen content
decreases as soil moisture increases. In addition, many
germination cues are directly and indirectly influenced
by other abiotic and biotic factors (Fig. 2) and the
tolerance of individual species to various environmental
factors tends to change depending on propagule type
(e.g., seed, rhizome) and life history stage (e.g., seedling,
adult). Finally, past human activities (e.g., agriculture)
have substantially altered interrelationships among
the factors that influence the short- and long-term
expression of the plant community. Such changes may
allow species suited to high resource availability to
succeed (Davis et al. 2000, Vinton and Goergen 2006) or
disrupt plant-soil feedback mechanisms that affect plant
community dynamics, including the invasion potential of
exotic species (Calderon et al. 2000, Symstad 2000). The
mixing and turning of soil during plowing stimulates the
breakdown of soil organic matter and the loss of carbon
to the atmosphere (Brye and Pirani 2004). The extent of
this loss can be extensive. In North Dakota, soil carbon
concentrations in the top 10 cm (4 in) of agricultural
soils decreased 33% in 25 years (Bauer and Black 1981).
These changes can significantly affect soil depth, texture,
and nutrient availability. Tillage also can significantly
alter moisture gradients by altering topography and the
hydraulic conductivity of soils (Bouma 1991, Messing and
Jarvis 1993, Fuentes et al. 2004).
The above discussion focused on the importance of
environmental conditions in assessing site potential
relative to plant community germination, establishment,
and sustainability. Evaluation of the expected value
of the plant community relative to migratory birds is
also important given that this was another priority we
wanted to consider. Ultimately, the avian response to
management should be evaluated directly through pre-and
post-project monitoring even though species-habitat
relationships often are used to initially evaluate potential
responses of target organisms. The most common
habitat attributes used to conduct such evaluations are
factors related to area (e.g., minimum area required,
edge effects, juxtaposition of different habitat types),
plant structure, and food production, which in turn are
influenced by plant composition. Habitat suitability, as
defined by these factors, varies among species and also
can change for a single species during different annual
cycle events (e.g., breeding, migration, wintering). Given
this variability, the most accurate evaluation of potential
habitat value for migratory birds requires comparing
anticipated site conditions relative to the requirements
of multiple species during the appropriate portion of
the annual cycle. Criteria for selecting a representative
suit of species can be based on numerous considerations,
including species mentioned in enabling legislation
or species of conservation concern that are provided
in various state, regional, and national conservation
plans. Given the dynamic nature of grassland plant
communities, another consideration is to select species
that represent the full range of vegetation conditions
that may occur at a site because various attributes,
Figure 2. Simplified illustration of seed bank dynamics, including state variables (rectangles), primary abiotic
and biotic factors (octagons) influencing plant germination cues and survival (ovals), and common examples of
anthropogenic factors influencing abiotic and biotic factors (pentagons). Figure adapted from Simpson et al. 1989.
1100 A SCtoantcuesp tRuaelv Aiepwpr oaancdh tCo oEnvsaeluravtaintgio Gnr Raseslcaonmd Rmeesntodraattiioonn Pso ftoern ttihale Gull-billed Tern
such vegetation structure and types of foods, can differ
markedly depending on type of disturbance (e.g., fire,
mowing, herbicide application, soil disturbance) and time
since the last disturbance occurred. Selecting species
that characterize a broad range of plant community
composition and structural requirements will help
prevent underestimating the avian value of the site.
Developing this species list may seem overwhelming,
but it is possible to select a pool of relatively few species
to represent restoration objectives. While the current
number of breeding bird species documented in the
Great Plains is approximately 320 (Johnsgard 1979),
developing suitable grassland restoration objectives for
a local area may focus on as few as 32 bird species to
receive priority consideration (Knopf and Samson 1995).
Huron WMD has yet to develop site-specific information
on many of the abiotic and biotic factors we identified as
important for evaluating ecological restoration potential.
Therefore, we conducted a search to identify potential
sources of existing information that could be used to
evaluate site potential during the interim. With respect
to vegetation, we concentrated on selecting factors that
influence initial germination and early establishment
because most management activities conducted on Huron
WMD directly impact these factors. Incorporation
of these factors into site evaluations has the potential
to help determine the extent of degradation, aid in
developing possible remediation measures, and identify
appropriate seed mixtures for planting. Many of these
factors operate at the watershed scale. In contrast,
factors used to evaluate migratory bird benefits focused
on defining species-habitat relationships. Although other
factors influence bird use, species-habitat relationships
can be directly linked to ecological restoration efforts and
provide a cohesive method to evaluate potential outcomes
with the realization that pre- and post-monitoring of the
avian community also is important.
Climate.--Climate variables influencing germination and
early establishment include precipitation, evaporation,
and ambient temperature, which are primary
determinants of soil temperature and soil moisture.
Because these factors exhibit high spatial and temporal
variability across Huron WMD, site-specific information
would be valuable. In the absence of local information,
annual and seasonal ranges could be used to evaluate
overall site conditions and constraints (High Plains
Regional Climate Center 2006, National Climatic Data
Center 2006).
Soils.--Important characteristics of soils include the
depth, drainage class, texture, and organic matter
content of soil horizons (Nelson and Anderson 1983).
Drainage class (e.g., well drained, moderately well
drained, very poorly drained) provides a measure of the
residency time of soil water, whereas texture and organic
matter content provides a measure of the moisture and
nutrient retention capacity of soils (Fig. 2). In general,
soils high in sand tend to retain water for only a short
period and have lower nutrient concentrations and
moisture concentrations than soils higher in clay and silt.
Collectively, these soil properties influence key factors
that control germination and early establishment of plant
species. Abrupt discontinuities in species distributions
can often be explained by differences in soil depth and
texture (Nelson and Anderson 1983). General soil
attribute data can be obtained from county soil maps
and in both tabular and spatial forms (U.S. Department
Agriculture 2006).
Topography.--Slope and aspect are among the most
important topographic variables because they influence
soil moisture and temperature (Kline 1997). In general,
slope influences soil moisture gradients, whereas
aspect influences the time and extent of soil exposure
to drying winds and sunlight. Steeper slopes tend to
exhibit steeper soil moisture gradients over a smaller
area, with low elevations typically being the wettest and
higher elevations being driest. Within this context, south
slopes tend to be the hottest and north slopes tend to
be the coolest. Collectively, these factors can result in
diverse environmental niches within a watershed that
support distinct vegetation communities. For example,
changes in species composition that occur with gradual
elevation shifts often are due to moisture gradients (Dix
and Smeins 1967, Clambey and Landers 1978). General
information on slope and aspect often can be determined
from a combination of aerial photographs, digital
elevation models, topography data, or other remotely
sensed data (U.S. Geological Survey 2006). Depending
on resolution and data type, subtle differences in
topography may not be detected and field reconnaissance
may be required. Equipment necessary to development
site-specific information is readily available and time
requirements are minimal to moderate. Additional
advantages of on-site reconnaissance include ground-truthing
soils information and documenting plant species
composition and distribution.
Vegetation.--Information on climate, soils, and
topography must be considered in the context of
plant ecology to be useful in evaluating restoration
potential. Important plant information includes a list
of plant species grouped into functional guilds that
currently or historically occupied sites being considered
for restoration, knowledge of factors that control
germination, establishment, and survival of plants
in each functional guild, and physical traits of plants
that provide wildlife value. Functional groups can be
defined using several different classification methods
(e.g., life form, growth form, metabolic pathway) alone
or in combination. The most commonly used categories
include annual/perennial, grass/forb, and cool-season/
warm-season, but other combinations can be developed
depending on restoration goals.
Relative to plant germination and establishment, the
most important factors include type of seed dormancy
(e.g., none, physical, physiological) and environmental
conditions required to break seed dormancy (e.g.,
scarification, cold stratification) and stimulate
germination (Simpson et al. 1989, Baskin and Baskin
1998, Cronk and Fennessy 2001; Fig. 2). In addition
to these factors, nutrient and moisture requirements,
as well as disturbance tolerance are important for
CNonacmepet uoafl SAepcptriooanc h 1111
result in the expected response. In general, this could
occur due to inappropriate timing of a management
treatment or planting an inappropriate seed mixture.
Conversely, the lack of response could be caused by
environmental conditions that are outside human
control. Differentiating between these causes is difficult,
but understanding plant germination and growth
requirements can help prevent drawing inappropriate
conclusions. In addition, the species or functional species
groups currently or recently occupying the restoration
site can provide insight to environmental conditions
that may influence plant germination and establishment
(Bever 1994, Reynolds et al. 2003), or indicate potential
changes in ecological processes or abiotic factors that
have occurred due to past land use activities (Kulmatiski
et al. 2006). For example, the presence of drought-tolerant
species near a stream course could indicate
a change in soil properties or a disruption in the soil
moisture gradient.
Numerous approaches can be used to develop lists
of current and historic plant species. The vegetation
distribution map and plant community inventory
produced by Huron WMD are ideal sources for
developing a list of current plant species, whereas species
comprising historic communities can be obtained from
various geographic databases, publications, and surveys
(e.g., General Land Office, railroad rights-of-way). The
list of historic species does not need to be exhaustive
because some species may compensate functionally
for other species (Naeem et al. 1994, Tilman et al.
1994, Kindscher and Wells 1995, Piper 1995, Tilman
1996), but this list should include annuals, perennials,
determining plant survival (Miller 1997, Reynolds et al.
2003, Kulmatiski et al. 2006). Physical traits that often
are important for determining wildlife value include
growth form, plant height, and food production potential
(Laubhan et al. 2006).
Collectively, information on the ecology of individual
plant species can serve several useful purposes. Species
autecology is important in determining appropriate
species to plant (reconstruction) and designing
management treatments (reconstruction and restoration)
(Simberloff 1990, Vitousek 1990). Seed mixtures
comprised of more drought-tolerant species may be
more applicable in semi-arid areas (e.g., south-facing
hillslopes), whereas a greater complement of mesic
species may be more appropriate near drainages where
soil temperatures are cooler and moisture is more
available. From a management treatment perspective,
application of fire or grazing should be timed to match
the appropriate growth stage or annual cycle event of
plants species being managed. This information can
be used to time treatments to more effectively control
undesirable plants (e.g., treatment applied when plant
species is most vulnerable to stress) or, conversely, to
stimulate desirable species (e.g., treatment applied
to increase sunlight penetration and moisture during
initiation of growth in spring). Knowledge of historic
and/or current native plant distributions also helps
define potential species composition at different times
during the restoration process (Palmer et al. 1997)
and can be useful in evaluating project success. For
example, application of a management treatment or seed
mixture to stimulate certain desirable species may not
© Chris Bailey
1122 A S Ctoantcuesp tRuaelv Aiepwpr oaancdh Ctoo Envsaeluravtaintigo Gnr Rasesclaonmd mReesntodraattiioonn Ps oftoern ttihale Gull-billed Tern
and keystone species that are functionally important.
Mutualistic relationships exist between some animals
(e.g., pollinators) and plant species (Ries and Debinski
2001, Travers et al. 2011) or certain plant species may be
involved in the regulation of nutrients important during
initial establishment (Miller 1997). Following compilation
of the plant species list, information on plant germination
and growth requirements of these species can be located
in electronic databases, reputable websites and seed
catalogues, books, dissertations, and scientific journals.
In many cases, information on all important factors will
not be available for a given plant species. This is not
problematic because individual species can be grouped
into functional guilds.
Wildlife.--Habitat requirements vary depending on the
species and the annual cycle events that occur on the
site, but area requirements, nest site characteristics,
foraging site conditions, and foods are important factors
in determining habitat quality for many avian species.
Information on habitat requirements can be obtained
from numerous sources, including electronic databases,
literature syntheses, and scientific journals (Laubhan
et al. 2006), but the quality of data should be evaluated
relative to the intended purpose of use. Qualitative
information (e.g., tall, dense) is difficult to use in
evaluating habitat suitability because it only provides a
general impression of required conditions. In contrast,
quantitative measures (e.g., range, confidence intervals)
are more valuable because they can be compared directly
to vegetation measures collected on the site. In addition,
care should be exercised when interpreting off-site
information because habitat requirements reported from
different geographic areas may or may not be directly
applicable to sites on Huron WMD due to differences in
climate, plant composition, landscape conditions, or other
factors (Bakker et al. 2002, Laubhan et al. 2008).
FramNewamorek Dofe vSeelocptmioenn t 1133
Framework Development
Historically, the development of ecological
restoration strategies largely has been based on
knowledge gained from experiments to restore
degraded landscapes (King and Hobbs 2006). These
strategies may or may not be successful when
applied to sites that differ with respect to various
abiotic and biotic factors, which suggests that
formulation of a sound restoration approach requires
more than anecdotal information (Hobbs and Norton
1996, Choi 2004). Further, increasing the chance of
project success relative to desired goals requires not
only the capability to implement various techniques
(e.g., seed source, equipment), but also developing
an understanding of when different techniques are
most applicable.
To address the considerations described above,
numerous approaches have been developed to
evaluate a site and determine the most appropriate
restoration strategy. One approach is to use
reference sites (Society of Ecological Restoration
2004). Comparison of environmental conditions at
the reference site and degraded site can provide
valuable insight that can be used to develop realistic
goals and identify possible restoration scenarios.
Unfortunately, the utility of reference sites is
sometimes limited because they are difficult to
identify and the structure and function of these
areas may not be known (Michener 1997, White and
Walker 1997). Another approach, which is used in
this report, is to develop a decision analysis model
or schema that focuses on key attributes considered
critical to restoring structure and function (Aronson
et al. 1993, Milton et al. 1994, Box 1996, Ludwig
et al. 1997, Perrow and Davy 2002, Temperton et
al. 2004). Applicability of such models in a field
setting requires time- and cost-efficient collection of
relevant information. In the previous section, ideas
were provided on sources of data for potentially
important factors that are already available and
either free or relatively inexpensive to acquire. In
some cases, this information may not be of sufficient
quality and more costly methods of acquiring
necessary data may be necessary.
The framework developed for evaluating restoration
potential on Huron WMD lands is comprised of
goals, objectives, attributes, and outcomes (Fig. 3).
The goal represents the purpose of constructing the
decision model and objectives describe in more detail
what values will be considered when determining
priorities. Attributes represent the primary factors
identified in the previous section that are used to
assess site conditions relative to the objectives and
interim steps (ovals) are examples of how attribute
information can be combined to facilitate evaluation.
Outcomes (represented by the double boxes in Fig. 3)
are based on evaluation of the attributes and could be
used to assign priorities to restoration projects.
Huron WMD will establish grassland goals and
objectives during the CCP process that may differ
somewhat from the general description used
in this report. As an example, we developed a
conceptual schema based on the goal of evaluating
the reconstruction potential of individual WPAs in
Huron WMD. Obviously, there are numerous other
objectives (e.g., developing appropriate management
strategies for restoring native sod communities)
and attributes that could be included to provide a
more thorough evaluation. Given that on-site data
regarding additional attributes on Huron WMD
lands currently is limited and management decisions
cannot be postponed until this data is collected,
© Chris Bailey
1144 A SCtoantcuesp tRuael vAiepwpr oaancdh tCo oEnvsaeluravtaintgio Gnr aRseslcaonmd Rmeesntodraattiioonn Pso ftoern ttiahle Gull-billed Tern
interrupted the soil moisture gradient along a
slope. This information could be used to delineate
and map zones with unique abiotic properties
in the restoration site that could influence plant
species composition, ease of establishment, and
areas where more intensive management may
be required. Topographically low, poorly drained
alluvial soils (typically rich in organic matter) that
would support plants requiring increased soil
moisture could be separated from adjacent toe-slopes
with rapid drainage (typically moderate amounts
of organic matter) that would support more xeric
species. The environmental characteristics of each
zone could then be compared with the germination/
reproductive requirements of available plant species
in the various functional groups to help determine
appropriate seed mixtures for each zone. The value
(or priority) of restoring the site could be determined
by comparing current wildlife values with anticipated
post-restoration values based on differences in the
amount of contiguous grassland area provided, plant
structure, and food resources that would occur if
restoration is successful.
we developed our approach based on available
information to assist Huron WMD in the decision
process.
Example objectives were designated as developing
appropriate seed mixtures for reconstruction
projects that benefit migratory birds, estimating the
potential for non-native plant species establishment,
and determining wildlife values that would be
expected following restoration. To accomplish the
evaluation, attributes were grouped into three
categories (abiotic, land-use history, and biotic) to
aid interpretation. The abiotic attributes include
topographic and soils data from the watershed
encompassing the site. In this example, the
topographic and soils data would be intersected
using a geographic information system to delineate
unique combinations of soils, slopes, and aspects.
In addition, information on altered soil structure
and/or hydrology caused by past land-use activities
could be incorporated into this matrix (Fig. 3). Field
examination could reveal that tillage has caused the
loss of soil organic matter or aerial photography
could identify the presence of terraces that have
Figure 3. A conceptual approach for evaluating restoration potential of grasslands.
Name oCf oSnecclutsioionn s 15
Conclusions
Developing an approach for evaluating and
prioritizing sites for restoration is a complex
and uncertain process. Although much is known
regarding factors controlling plant community
establishment and relationships between plant
communities and wildlife habitat suitability,
the relative importance of these factors often
varies among and within sites depending on past
perturbations and surrounding landscape conditions.
Detailed information regarding many of these
factors often is limited on specific sites and intra- and
inter-annual climate variability make it impossible to
accurately predict future environmental conditions.
Therefore, it is not possible to develop a single
restoration strategy that is appropriate for all sites,
or even all landscape conditions within a site, and
even management treatments that are appropriately
tailored to a site may not yield expected results.
Given this uncertainty, general schemas that
incorporate abiotic and biotic factors related to the
dynamic processes influencing plant community
composition and structure must be developed to
guide restoration.
The conceptual framework we developed is
intended to serve this purpose, but additional work
must be accomplished before this model could be
implemented because the objectives used in the
model are examples developed by the authors and
the attributes selected for inclusion are based on
a review of the literature rather than field data
collected on Huron WMD. Hopefully, Huron WMD
will continue to develop this approach because a
conceptual framework assists in the identification of
attributes important in evaluating outcomes. Most
individuals recognize the impact of abiotic factors
and past land use in determining plant community
composition and structure, but this contributes
little to developing management approaches if
specific factors and their relationship to achieving
goals are not defined. A structured framework
also promotes standardized evaluations and can
improve communication as it provides a method to
systematically deconstruct complex problems and
provide greater objectivity when making restoration
decisions (Cipollini et al. 2005). Finally, frameworks
that incorporate abiotic and biotic factors as primary
determinants of expected outcomes can facilitate
implementing an adaptive management process
(Walters and Holling 1990, Haney and Power 1996).
1166 A SCtoantcuesp tRuael vAiepwpr oaancdh tCo oEnvsaeluravtaintgio Gnr aRseslcaonmd Rmeesntodraattiioonn Pso ftoern ttiahle Gull-billed Tern
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