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Ecological Guidelines for Management
and Restoration of Pinyon and Juniper
Woodlands
Lee E. Eddleman
Abstract-An approach is suggested for developing general guidelines that in turn form the basis for site specific guidelines to be used
in the management and restoration of pinyon-juniper woodlands.
Guidelines are based on the establishment of goals, objectives and
problem statements. This is followed by a structural and functional
analysis ofthe land area under consideration for treatment. Finally
a functional analysis relating the area under consideration to
landscape as a whole is suggested.
At the outset it must be stated that this paper is intended
to provide guidelines suitable for the determination of ecologically based management actions on pinyon-juniper woodlands. As such it may also be adaptable to other arid and
semi-arid systems. It is purposefully ambiguous in some
areas to avoid the quagmire of hard and fast rules.
Many problems arise in the development of site specific
ecological guidelines for the management and restoration of
pinyon-juniper woodlands. All attempts to do so are underlain by a set of assumptions that mayor may not be correct
and are driven by expectations, desires and objectives that
mayor may not be realistic in terms of either the supporting
science or the available resources. Assumptions are likely
based on social values, understanding of ecological theories
and interpretation of ecological data, each of which need to
keep as distinct as possible (Scarnecchia 1995 and Tausch
1996). As yet, we do not have comprehensive, whole system,
ecological research on our arid land areas; at best we have
partial research on a few areas. The manager is therefore
faced with the formidable task of formulating suitable assumptions, developing reasonable objectives and applying
guidelines in an appropriate manner from less than adequate research data, not so succinct and frequently conflicting ecological theories, shifting social values as well as
observations and experience.
In spite of the lack of a comprehensive understanding
of most arid ecosystems we are certainly not bereft of the
basics. Ecological principles and guidelines applicable to
the management and restoration of pinyon-juniper woodlands can be found in, or can be derived from, a variety of
comprehensive publications including range management
In: Monsen, Stephen B.; Stevens, Richard, comps. 1999. Proceedings:
ecology and management of pinyon-juniper communities within the Interior
West; 1997 September 15-18; Provo, UT. Proc. RMRS-P-9. Ogd~n, UT: U.S.
Department of Agriculture, Forest Service, Rocky Mountam Research
Station.
Lee E. Eddleman is Professor of Rangeland Resources, Department of
Rangeland Resources, Oregon State University, Corvallis, OR 97331.
366
(Holechek and others 1998), grazing management
(Heitschmidt and Stuth 1991), improvement of rangelands
(Vallentine 1989) and improvement of game ranges
(Plummer and others 1968). More specifically, Evans (1988)
considered many ecological relations in developing strategies for management of pinyon-juniper woodlands for a
variety of products and values, and Aldon and others (1995)
provides a very useful checklist of critical questions that
should be addressed prior to initiation of any management
scheme in the pinyon-juniper type. In the actual application
of guidelines the manager is faced with the question: does
the guideline fit this particular piece of land and does it fit
in the context oflinked resource units?
Ecological guidelines should have broad scale applicability across the main pinyon-juniper woodland as well as
juniper woodlands of the Northwest and southern Great
Plains. Each site, the ecological site (U.S. Department of
Agriculture 1997), is unique within itself and it is equally
unique in its connectivity to surrounding sites. Connectivity
has been defined as the degree to which patches of a given
type are joined by corridors into a lattice of nodes and links
(Wiens and others 1993). In woodlands connectivity could be
considered as the degree to which a site is functional linked
to other sites or landscape units of the system. This linkage
is both spatial and temporal and is through mechanisms of
emigration-immigration for materials such as water, sediment, nutrients, energy, flora and fauna (Schlesinger and
others 1990, Tongway 1990 and Wilcox and Breshears 1995).
Site specific internal attributes and external connectivity
attributes require not only site-specific fine filter guidelines
but also spatially and temporally scaled guidelines.
Establishment of guidelines for management and restoration of pinyon-juniper woodlands implies that standards
exist and that we are capable of directing or redirecting
ecological processes to attain those standards. Setting ecological standards is a distinctly human process and is therefore an arbitrary value judgement that shifts with shifting
personal and societal values. We would like to think that
pinyon-juniper woodlands have their own inherent ecological standards, and at certain temporal-spatial scales perhaps they do. Words such as natural and healthy pervade
the literature and our concept of these words, as applied to
a particular site, seem to provide the driving force for the
establishment of standards. However, Lawton (1997) has
pointed out that ecosystems change continuously at all timescales diverging more and more as we move back in time and
Tausch (1996) points out that climate has continually changed
in the past and it is likely to do so in the future. Lawton
concludes that the true situation is that we have no benchmark virgin state that we can refer back to. Recognition of
change and the processes associated with change should
USDA Forest Service Proceedings RMRS-P-9. 1999
allow us to formulate our site objectives and standards
more realistically focusing on trajectories and functional
standards (Lawton 1997, Tausch 1996).
If the above is true, then standards and guidelines developed around concepts of sustainability should be called into
question and carefully evaluated, particularly as to their
spatial-temporal scale. As noted above, it also may require
that we focus our standards and guidelines on functional
attributes of ecosystem components rather than composition of structural components. Key functional attributes
should be the internal attributes of the ecosystem that
control rate and magnitude of those processes that can lead
to degradation or visa-versa to desired conditions. At the
same time aspects of plant composition and other surface
structures have been found to be useful indicators of site
function (de Soyza and others 1997). Approaches suggested
by the Committee on Rangeland Classification (National
Research Council 1994) are a good step toward the application offunctional ecology to determination and management
of rangeland health and are applicable to pinyon-juniper
woodlands.
Guidelines
Ecological guidelines useful in the management and restoration of pinyon-juniper woodlands have been placed to a
degree in a question format. Questions best tend to force
critical thinking considerably beyond the simple answers of
yes and no and, hopefully, push responsible parties to find
solutions from a variety of sources. Meaningful site-specific
guidelines can be developed from a well thought out set of
goals, objectives, problem statements, land area analyses
and landscape analyses.
Goals and Objectives
Clear concise goals and objectives are required at the
outset of any management or restorations action. Establishment of goals and objectives requires that the desired pattern and function of woodlands have been determined at
both the landscape level and at the level of the unit of
land, or land area, under consideration for management or
restoration action.
Questions that need to be asked and answered include
those below.
• What are the desired short-term and long-term ecological goals?
• What are the objectives and what is the spatial-temporal
framework for measurement? (Literally how much per
unit of space per unit of time)
• How do the goals for the land area under consideration
fit within the goals for the landscape as a whole?
• What are the assumptions that underlie each objective?
Unless considerable thought is put into making sure
these questions have been answered, conflicts and crosspurposes may not be identified and the reality of success
may be illusive. Ecological goals for woodlands should include components of sustain ability, productivity and a component of conservation of natural abiotic and biotic resources. Goals and objectives must be definable, achievable
USDA Forest Service Proceedings RMRS-P-9. 1999
and measurable. They should provide a clear statement of
the desired direction of change, if any, for soils, plants and
animals, and identify desired future woodland conditions.
The degree of success should be measurable on both temporal and spatial scales. Knowing the degree to which one's
assumptions rely on social values, ecological theory, ecological data or observation and experience will help adjust
confidence in reaching the goals and objectives.
As an example, for a particular land area the manager
may set a goal of maximizing the infiltration of precipitation
into soil storage at all times of the year. Short-term aspects
might be focused on normal precipitation events during the
growing season while long-term aspects might be focused on
abnormal hydrological events year-round. Objectives could
include reaching a condition of zero runoff during the
growing season from rainfall events with intensities less
than 25 mm per hour and totals less than 13 mm in a 10 year
period.
Problem Statement
The next step in the process is to state precisely and clearly
the apparent ecological problem as it exists on the land area
under consideration. This statement should be as comprehensive as possible and based on field observation and as
much site-specific and local information as is available. It
should identify structural components that control rates
and amounts of change and processes that appear associated
with degradation. Degradation as used in this paper is the
degree to which pattern and process have been altered and
the land area under consideration rendered less favorable
for the desired plant community or communities identified
in the goals and objectives (modified from Tongway 1990).
As an example, a part of the problem statement may be
that runoff is excessive as indicated by too much bare
ground, an abundance of rills, long reaches for runoff and
high sediment deposition on lower upland areas and drainage channels.
Land Area Analysis _ _ _ _ __
Kind of Woodland
An inventory and analysis of the temporal and spatial
nature of the woodland on the land area under consideration
is needed since the kind of woodland presently on the land
area determines in a large degree the management and
restoration practices to be applied.
Questions that need to be asking and answered include
those below.
• What is the age class structure of the trees?
• What is the size class-spatial structure of the trees?
Old woodlands have a variable number of very old trees
present and the land area appears to have been in woodland
for several hundreds of years. Pattern of plants, soils and
animals, and processes, both biotic and abiotic, may appear
spatially and temporally controlled by the tree component of
the woodland. The tree component may appear to be stable;
however in the last century degradation in these woodlands
may be ongoing at several scales. Degradation may be due
367
to a variety of causal factors including the addition of too
many livestock and subsequent long-term overgrazing, particularly in the spring, and the removal or deletion of fire
from the system.
New woodlands are those that have largely developed this
century and there is not an indication they were previously
present. These woodlands contain mature trees; the larger
individuals may have recently begun to slow down their
growth rates and mortality factors are not strongly in evidence. Patterns and processes in these communities may be
largely under the control of the woodland. There is a relatively high probability that in many of the new woodlands
tree densities will reach very high levels prior to mortality
factors setting in, followed by a density decline to some lower
level. The expansion and development of new woodlands is
usually attributed to altered fire regimes, overgrazing by
domestic livestock and optimal climate for establishment
(Miller and Wigand 1994).
Degradation in new woodland communities may be due,
firstly, to the trees themselves. In the above scenario we
should expect both deletions and additions of flora and
fauna to occur as woodlands move toward high tree densities. Altering the fire regime, continued over-grazing, additions of alien plant species and perhaps extreme climatic
events, such as the drought of the 1930s, may also be
contributing significantly to patterns and processes in young
woodlands. Since young woodlands have largely developed
in the absence of fire, fire, therefore, remains an unknown
factor in the long-term development of woodland pattern
and process.
Developing woodlands must also be considered as
they are areas which are being newly invaded by trees but
have not as yet reached the stage where pattern and process
are dominated by trees. These future woodlands may be
developing due to the removal offire from the existing plant
community. Overgrazing by domestic livestock and the
addition of alien plant species may contribute to their
development and to various degradation processes.
An example could be a yOll;ng woodland with a broad
spectrum of age classes. Older trees are roughly 100 years
old, provide a 20 percent canopy cover and number 125/ha.
In addition, smaller trees number 50/ha.
Understory Vegetation
The proportions and density of understory vegetation
components must be determined on each functional unit
within the land area under consideration in order to predict
possible transitions in pattern and process to potentially
new stable states.
Questions that need to be asked and answered include
those below.
• What functional groups of understory plant species are
present and what ones are absent?
• What plant species are missing that should be present
and conversely what plant species are present that
should be absent?
• Is the apparent vigor or health of the shrub species
sufficient to maintain them in the community or has a
threshold been crossed and extinction expected?
368
• Is the density oflong-lived herbaceous and shrub species
sufficient to respond to disturbance factors, both natural and man caused?
• What are the assumptions made in answering each
question?
An example could be that shrubs are sparse, live plants
have low leaf areas and recent high mortality is evident.
Herbaceous plants are mostly annuals made up of early
ephemeral forbs and scattered alien grasses. Some early
spring species of perennial bunchgrasses and tap-rooted
forbs, as well as scattered individuals of late spring, early
summer and fall perennial forb and grass species are present.
All perennial plants in interspace areas are small, widely
spaced and appear to be of low vigor. Potential response of
the understory to management or restoration actions appears possible, but long term.
Functional
The land area is the local area under consideration and
may be made up of one to several ecological sites, or one to
several distinct functional units. The area of interest must
be delineated to assess functional attributes.
Questions that need to be asked and answered include
those below.
• What distinct ecological sites, or functioning units, are
present?
• What ecological factors currently dominate and control
on-site pattern and process and how do they do so?
• To what degree and specifically how do trees individually and collectively control on-site pattern and process?
• What are the assumptions made to support the
conclusions?
• What causal factors led to current site conditions?
• What is the degree of degradation?
• What ecological thresholds currently restrict transitions to goal oriented ecological conditions?
• What assumptions were made in answering each
question?
Thinking in spatial-temporal scales will greatly aid in
understanding how an area functions. Spatially scaled functional units suggested by Wilcox and Breshears (1995) or
those suggested by Tongway (1990) and Anderson and
Hodgkinson (1997) are very useful. Temporally scaled functions should at least include key seasonal aspects of moisture input, and plant growth and reproduction.
Woodland ecological sites may be mosaics or contain
inclusions limited in area but significant in the functioning
of the site at particular spatial or temporal scales. For
example, areas of old growth trees on rock outcrops located
within an otherwise seemingly uniform expanse of mature
soils may be too small to separate out as distinct ecological
sites, but they will function differently from the other parts
of the site and, therefore, significantly contribute to site
processes as a whole. Slight changes in topographic position
may alter ecological functions, but given present ecological
site classification protocol may be included in a single site.
(Tongway 1990, Burke and others 1995, Herrick and Whitford
1995).
USDA Forest Service Proceedings RMRS-P-9. 1999
Basic processes of concern are those associated with the
hydrologic cycle, nutrient cycle and energy flow. Also of
primary concern are successional processes in the functional
groups of plants and processes associated with functional
structures for animal habitat (National Research Council
1994, U.S. Department of Agriculture 1997).
Identification of the causal factors of degradation to a
particular land area is complex. Additionally, degradation of
one area may be caused by treatments in other areas. This
relationship is particularly evident in riparian systems
(Briggs 1996), but is also true for most upland systems as
well.
The degree to which certain ecological factors function as
thresholds restricting transition to desire future conditions
must be assessed (Laycock 1991, Reitkerkand vande Koppel
1997, Reitkerk and others 1997, Tausch and others 1995,
Westoby and others 1989). Degree oftree dominance, present
and potential dominance ofinvasive alien plant species, lack
of plant species and individuals to respond, shallow soils,
clayey or sandy textured soils, slopes receiving direct solar
radiation all seasons of the year, surface soil loss, high
surface water runoff and intense spring frost action may
constitute some of the thresholds to be crossed. From the
threshold assessment both treatment type and treatment
magnitude can be estimated including management changes
as well as additions and deletions of organisms and abiotic
materials.
As an example, it could be determined that the land area
under question should function to intercept and accumulate
resources from the slopes above, but appears to be functioning as a source area, as well as a flow-through area for
surface water. Secondly, it may be determined that runoff
and interception dominate the initial hydrologic processes
and that following precipitation events, transpiration by
the trees and evaporation from the surface 6 cm of soil in
interspace areas are the primary hydrologic processes.
Thirdly, soil analysis may show the presence of eroded soil
surfaces, deep, medium textured soils, generally well dispersed tree roots with the highest root mass just above and
in a moderately developed clayey horizon at 35 to 50 cm.
Consideration of management units and treatment areas
in isolation is no longer acceptable. It may be the case, for a
particular area of land, that initial floristics and relay
floristics are mechanisms determining composition of plant
species over particular time scales. However, each area is
linked to other areas in terms of a variety ofcri tical resources
that may strongly influence plant densities, vigor and energy values as well as rates and magnitude of processes.
In landscape analysis emphasis may need to be placed on
water flow, paying particular attention to the physical and
biological factors that control and dominate the water cycle.
The spatial conceptual framework scales and functional
units proposed by Wilcox and Breshears (1995) provide an
excellent comprehensible starting point in landscape analysis, oriented as it is toward water flow in the system.
Adjustments in scales and functional units may be needed
in other settings and where woodland management and
restoration is of concern. Of critical concern is the ecological
function of each land management area, ecological site and
functional unit for which restoration treatments are proposed. The degree of movement and accumulation of critical
resources is hypothesized to be the principle mechanism
controlling threshold levels of response in arid and semi-arid
systems (Anderson and Hodgkinson 1997, Burke and others
1995, Reitkerk and others 1997, Tongway 1990).
A patchwork land ownership is frequently encountered
within a landscape making landscape level analysis critical.
The land area under consideration may need to be managed
or restored in such a way as to mitigate potentially degrading processes initiated up-slope and to prevent the area from
being the focal point of processes which degrade down-slope
areas.
An example could be a landscape analysis that reveals
some ofthe water flowing over the surface is from slopes and
platea us above and most importantly surface water from offsite comes largely during snow-melt. Although the potential
for accumulation of water and nutrients is considered as
high, a question should arise as to altering management or
initiation of restoration practices on the source areas above.
Landscape Level Analysis
Management and Restoration
Actions ____________
A complete spatially temporally scaled landscape level
analysis relative to the land area in question is necessary to
assure selection of the right treatment area and the right
treatment and to prevent negative reactions off-site.
Questions that need to be asked and answered include
those below.
• How does the landscape function as a whole?
• What are the links (connectivity) from the land area
under consideration to adjacent and removed sites and
functional units?
• How does the particular site or land area under consideration fit functionally into the landscape?
• As to the natural resources of the landscape, which
areas are source-areas, which areas are flow-throughareas and which areas are run-on areas that intercept
or accumulate resource materials?
• What reasons are there to believe that the area under
consideration should function differently than it is?
• What are the assumptions made to support the conclusions?
USDA Forest Service Proceedings RMRS-P-9. 1999
Following the establishment of goals and objective and the
completion of the structural and functional assessment of
ecological factors, scaled from the functional unit up to the
landscape, the problem statement needs to be revisited and
revised, if necessary. Once this process is complete, sitespecific guidelines of what, when, where and how can be
addressed. Common actions considered in the management
and restoration of pinyon-juniper woodlands, such as burning, mechanical removal, seeding and grazing should draw
their ecological guidelines from a complete set of goals,
objective and land analysis. If needed guidelines cannot be
so derived, then some part or perhaps the whole set has
deficiencies.
There are an endless number of questions that can be
raised as to actions taken in ecological management and
restoration of pinyon-juniper woodlands, however the ecological guidelines for each activity must be found in the
goals, objectives and ecological land assessment.
369
For example, questions as to grazing by domestic livestock
can be answered only by asking if it will function to meet
goals and objectives for the land area given the present
structural and functional condition of the resources of that
land area.
More specifically, consideration of fall grazing requires
that the prescribed grazing meet short term and long-term
goals, objectives and that appropriate structural and functional resources in time and space are available to do so.
For instance, using the examples above, fall grazing may
be acceptable when the focus is on growing season capture
of water, however, when winter and early spring hydrological events are considered, fall grazing may become
unacceptable.
Consideration as to grazing rest time after additions of
species by seeding should be guided by goals, objectives and
land analysis. Desired direction, rate of change and area
function should determine what, when, where and how
grazing is to be initiated.
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USDA Forest Service Proceedings RMRS-P-9. 1999