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Symposium on Pinyon and Juniper Ecology,
Restoration, and Management: Introduction
Stephen B. Monsen
Richard Stevens
Pinyon and juniper woodlands provide human, wildlife,
soil, water, and other ecologically important resources. These
woodlands are an integral part of the landscape of large
geographical regions of the Interior Western United States.
Conditions and diversity of this type are critical. Managing
pinyon and juniper woodlands to sustain tree and understory associations becomes more practical as the ecology of
this type is better understood. For example, knowing how to
manipulate management practices could help in modifying
successional changes on a landscape basis.
To help reach the goal of increased knowledge, a
multi agency-supported symposium brought Federal, State,
and local government officials, university researchers, private companies, and private individuals together for 4 days
in the autumnof1997 at Brigham Young University, Provo,
UT. This resulting proceedings is a step toward accumulating knowledge, and perhaps will foster cooperation and
partnerships among the large array of private and public
entities interested in the vast Interior Western ecosystem.
In this introduction we highlight some of the themes and
critical issues that arose during the symposium, noting some
of the management options.
The Western Setting
Within the Interior West, different species of pinyon and
juniper occur wi th diverse shrubs and herbs forming distinct
associations. The total area occupied by pinyon and juniper
woodlands is not precisely mapped and described because
various associations exist with different assembly of species,
highly variable tree densities, and age classes, making the
task of mapping difficult. In addition, climatic and biotic
factors influence changes in plant composition, creating
both expansion and decline of common woodlands.
Recent studies have better defined the interaction between environment and vegetative changes in pinyon and
juniper woodlands and non-tree species than have previously existed. For example, changes are evident in the paleoecological records, and multiple stages of plant succession
have been identified and can be used to predict general
changes in landscape ecology. More recent studies show us
the influence of disturbances on the long-term patterns
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. Ogden, UT: U.S.
Department of Agriculture, Forest Service, Rocky Mountain Research
Station.
Stephen B. Monsen is Botanist, Rocky Mountain Research Station, Shrub
Sciences Laboratory, 735 North 500 East, Provo, UT 84606. Richard Stevens
was Project LeaderlResearch Biologist (retired), Division of Wildlife Resources, Great Basin Experiment Station, Ephraim, UT 84627.
USDA Forest Service Proceedings RMRS-P-9. 1999
of change and the potential recovery of specific plant
associations.
Of particular concern is the presence and effect of thresholds on successional development of these woodlands. Although other plant communities may also express stages or
thresholds as changes occur, once particular thresholds are
reached within a pinyon and juniper woodland, subsequent
changes are set and are not likely altered. Factors affecting
these changes may include topography, soils, climate, history of use, fires, and tree presence. Influences operate over
extended periods, affecting large regions and landscapes.
Highly variable plant communities currently exist due to
different stages of plant succession and to the recent expansion of both pinyon and juniper.
Understanding the structure and composition of pinyon
and juniper woodlands is essential in identifying thresholds
and their influence on returning communities to earlier
status through management or active restoration. Selection
of sites for improvement can be based on a better understanding of the ecological status and potential for natural
recovery. Woodlands that support a sufficient array of understory species and can recover by elimination of tree
competition can be better defined and treated. Sites that
may require seeding to restore understory herbs and shrubs
or may be subject to weed invasion can also be better
identified.
Management Issues
Many pinyon andjuniper communities within the West, like
many other plant associations, have been subjected to intensive livestock grazing. This impact, along with recent changes
in fire regimes and localized tree harvesting, has contributed to changes in tree presence, age structure, density, and
particularly to the composition of understory species. Loss of
habitat, diminished watershed conditions, and the recent
increase of weeds have created serious management problems. In addition, increases in wildfire frequency caused by
the presence of annual weeds, and increases in the frequency
of devastating wildfires within overgrown stands of trees,
are a more recent problem associated with disturbed woodland conditions. The decline and loss of understory species
coupled with an increase in tree overstory ultimately results
in a loss of species richness and likely conversion to a
dominance of undesirable weeds. Recent appearance of more
troublesome and persistent perennial weeds within pinyon
and juniper communities creates additional need to retain
native understory species.
These issues have been a concern to land managers for a
long time. Various interagency steering committees and
organizations (including this symposium) have addressed
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these and other issues. Ecology of pinyon and juniper communities was the first topic addressed in this conference.
Although considerable information is lacking, a much better
understanding of the distribution, community composition,
and patterns of change, particularly of disturbed woodlands,
is now available. Descriptions of stages and patterns of
community degradation are better identified and understood. Factors influencing annual weed invasion and resulting conversion of woodlands to annual grasslands coupled
with increasing fire frequency is also much better documented. Areas and sites that have degraded with diminished amounts of understory species and are likely to revert
to weeds can now be better identified and treated.
Management Alternatives _ _ __
Artificial restoration of pinyon and juniper woodlands has
received considerable attention. Practices that included
removal of existing trees to reduce competition have often
been criticized as unnecessary, site destructive, and not
ecologically sound. However, examination of existing information does not support these assumptions. Restoration or
enhancement of any disturbed community including shrubland associations, upland herb communities, or weed-infested sites requires reduction of existing competition, creation of suitable seedbeds, and actual seeding. In most
situations, elimination of competition is accomplished by
mechanical tillage or application of selective herbicides.
Plowing, dis king, or related tillage treatments are the most
common means of mechanical treatment. These procedures
reduce competition and aid in creation of required seedbeds.
Such practices can seriously disturb soils and tend to eliminate most existing vegetation.
Chaining and cabling practices were selectively tested
and adapted to treat woodlands as minimal impacts occur to
soils and understory species. Chaining has proven to be the
most versatile practice available to selectively reduce trees,
prepare diverse seedbeds, and facilitate planting mixtures
of seed. Percent of trees remo,:,"ed and percent and depth of
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soil surface that is tilled can be easily regulated by modifying
operational procedures. Chaining coupled with aerial seeding of select species that require minimal seedbed preparation has proven universally successful within this communitytype. Including the use oftractor-mounted seed dribblers
to plant seeds that benefit from being more deeply incorporated in the soil has provided the necessary method required
to seed most species. These techniques provide the means to
successfully restore most species native of the pinyon and
juniper woodlands by seeding.
Significant progress has been achieved in developing
native seeds in sufficient amounts required to restore diverse communities. Seeds are now available from commercial companies are adapted ecotypes of many native species
that can be used on a variety of sites. This has resulted in a
slow but steady transition from rehabilitation plantings
involving the use of introduced species to more complete
restoration plantings using site-adapted native species. A
much greater array of native species is currently available to
restore pinyon and juniper communities than any other
vegetative type that exists in the West. Ifproperly planned,
restoration of native communities through artificial seedings
can be achieved on large projects. Regulations are in place to
assure native seed of site-adapted ecotypes and species are
harvested, produced, and marketed.
Older plantings in pinyon and juniper communities demonstrate that altering tree encroachment and restoration of
diverse communities is attainable and can be ecologically
maintained. Restoring communities to improve watershed
stability, improve wildlife habitat, and prevent weed encroachment is feasible and ecologically attainable. Seeding
introduced species, principally perennial grasses, to protect
disturbances and prevent further site degradation can be
successful, but can interfere with natural recovery processes.
We hope future conferences and partnerships will continue our knowledge sharing, always keeping in mind that
sustaining and restoring pinyon and juniper woodlands will
play a major role in achieving and maintaining a diverse
ecosystem in the Interior Western United States.
USDA Forest Service Proceedings RMRS-P-9. 1999