Juniper Workshop 2000

Workshop on Dynamics and Management of Juniper Woodlands in the Bighorn Basin

8-9 June 2000

Sponsored by:
The Nature Conservancy
University of Wyoming, Department of Botany
National Science Foundation (Ecology Program)
United States Geological Survey Desert Laboratory

Organizers:
Stephen T. Jackson (UW)
Phil Shephard (TNC)
Julio L. Betnacourt (USGS)

Executive Summary

The expansion of Utah juniper woodlands into rangelands in Wyoming and adjacent states during the past century is well-documented but poorly understood. Woodland expansion presents a management challenge for ranchers and public-land managers committed to maintaining sage-grasslands and mosaic patterns of vegetation on the Wyoming landscape. This workshop brought together academic researchers, resource managers, and ranchers to share information and discuss management issues.

Four researchers from the University of Wyoming (S.T. Jackson, S.T. Gray, M.E. Lyford) and the U.S. Geological Survey (J.L. Betancourt) presented results of an ongoing study of Utah juniper invasion and dynamics in Wyoming. Key conclusions include:

• Utah juniper is a relatively recent constituent of the Bighorn Basin flora and vegetation. Studies of fossil packrat middens indicate that populations were established in southern Bighorn Canyon as early as 4700 years ago. However, colonization of foothills sites in the Bighorn, Pryor, and Bridger Ranges did not occur until 2500-2000 years ago, initiated by a regional change in climate. Similar trends are noted for other key species in these foothills sites, including ponderosa pine and curl-leaf mountain mahogany.
• Utah juniper has probably not yet colonized all suitable sites and areas in the region. It appears to be expanding northward from the Dry Medicine Lodge and Alkali Creek drainages into the Webber Creek and Trapper Creek drainages. Scattered young individuals in upper Webber Canyon represent colonization within the last half-century.
• The spread of Utah juniper in the Bighorn Basin has consisted of scattered, individual colonizing events from long-distance seed dispersal. These colonizations are followed by local infilling and backfilling. Utah juniper invasion, like most other plant invasions, occurs as a "spotting" process rather than an advancing front.
• Demographic studies indicate that Utah juniper seedling establishment in the Bighorn Basin occurs frequently, often under sagebrush and other "safe-site" shrubs. Once established, Utah juniper individuals grow slowly; 70 to 90 years may be required for individuals to reach heights exceeding 4 feet.
• Repeat photography (1900-1930 and 1998-1999) indicates substantial local expansion of Utah juniper populations on shallow rocky and deep colluvial soils. Field inspection of these photo sites indicates that much of this expansion may be attributable to recovery from late 19th Century fires (possibly during the droughts of the 1870s and 1890s). Fires may have been an important component of pre-grazing Utah juniper stand dynamics. Utah juniper populations on steep slopes of the Chugwater Formation have been relatively stable during the past century, perhaps owing to absence of late 19^th Century fires.
• Tree-ring climate reconstructions spanning the last 800 years at upper (Powder River Pass) and lower treeline (Trapper Creek, Big Pryor Mountain, Tensleep Preserve) indicate that the 20th Century is unique in being warmer than any of the previous seven centuries, and in being characterized by warm and relatively wet conditions. Earlier warm periods were typically accompanied by droughts, and wet periods tended to be relatively cool. The 1990s were the warmest decade in the last 800 years. Continued warming will exacerbate the effects of future droughts on Wyoming ecosystems.
• Long-term climate records from tree-rings in the eastern Bighorn Basin region show unusual persistence of wet or dry, cool or warm conditions over several years to several decades. For example, wet years tend to be followed by wet years, dry years by dry years, warm years by warm years. This natural persistence in Wyoming climate affects land use and management windows. For a cattle rancher, this means that cow and calf operations may be subject to prolonged episodes of boom and bust. For prescribed burning, this means that opportunities lost during a climatically favorable period may be lost for a decade or more.
• The expansion of Utah juniper populations in the Bighorn Basin is a complex phenomenon in which long-term population dynamics (i.e., migration, post-colonization infilling), climatic change, and land-use practices are all involved. More information on land-use history, fire history, and juniper population dynamics and climate response are desirable for informed and effective management.
• In some areas, Utah juniper expansion may be an inevitable outcome of natural processes, and hence very expensive and difficult to "control".
• The ability of junipers to concentrate nutrients in soils beneath shrub canopy, resulting in spatial patchiness of soil-nutrient pools, is documented in the Southwest. If this happens in Wyoming, it may render conversion of old, established juniper stands to sage-grassland difficult to impossible. Management efforts may best be focused on recently invaded sites, where soil nutrients are more spatially homogeneous. Research is needed to determine the magnitude and rate of nutrient concentration under Utah juniper canopy in the Bighorn Basin.

Three managers from The Nature Conservancy (P. Shephard), Bureau of Land Management (K. Stinson), and Bighorn Canyon National Recreation Area (S. Morstad) presented summaries of management goals and experience at their respective situations. Key points included:

• Resource managers are committed to reducing encroachment of Utah juniper and Rocky Mountain juniper into mixed-grass grasslands, sage steppe, pine woodlands, and cushion-plant communities. Goals vary among agencies and landowners, ranging from maintaining biodiversity and endangered species to maximizing forage for livestock and wildlife.
• Prescribed fire is the most commonly applied management tool. Mechanical removal of trees is often applied to manipulate fuel loads and fire behavior.
• Prescribed burns are often hampered by spotting and by lack of sufficient fine fuels to carry a fire through the woodland understory.
• Burning is most successful during drought periods and in old stands where dead juniper fuel has accumulated.

Following a field trip to examine historical photo sites and a recently burned Utah juniper stand, workshop participants engaged in a discussion (D.H. Knight, UW, served as moderator). Key points emerging from that discussion included:

• Landowners and land managers must decide on the desired management outcome. Managers must determine what they want the landscape to look like based on their overarching objectives. Managing to "restore" landscapes to mimic 19th Century configurations may be futile in the face of a changing climate and dynamic ecosystems.
• Careful attention must be paid to identify the key rare species and biodiversity centers in the foothills regions, and to ensure that management practices are compatible with maintaining those populations and habitats.
• Managers should keep track of multi-year climate cycles (e.g., El Niño-Southern Oscillation (ENSO)) and use them in their management plans. ENSO events can now be predicted 6-8 months in advance, and this information can be valuable in planning prescribed burns or anticipating severe fire seasons. Scientists also share responsibility for keeping managers informed about these cycles and their implications.
• "One size fits all" approaches to management will inevitably result in serious failures. Factors controlling the dynamics of Utah juniper woodlands or Ponderosa pine ecosystems are likely to vary significantly across the western U.S., and even within the Bighorn Basin.
• Management decisions should take into consideration the history and attributes of individual stands. There is not likely to be a single, universally applicable strategy for maintaining diversity or maximizing forage. Each stand is a realization of both natural processes and human activities. Juniper control can be successful in some situations, and it may be justifiable based on management objectives.
• Modeling juniper distributions in relation to environmental variables will be invaluable in identifying areas where invasion might occur in the near future.
• Historical studies of ecosystems and land use are necessary to understand and manage landscapes realistically and economically. Tree-ring and fire-scar studies of Ponderosa pine stands adjacent to old Utah juniper stands would be especially useful in assessing pre-grazing fire frequencies in Utah juniper woodlands. The USDA/DOI Fire Sciences Program (http://jfsp.nifc.gov/) may be a source of funding for studies of fire history and the feasibility and effects of fuels reduction in Utah juniper woodlands.
• Additional studies of juniper demography, including recruitment and mortality, would be valuable. Local managers can aid researchers by identifying recruitment and mortality episodes in juniper stands.

Workshop participants agreed that the workshop and discussions provided an excellent opportunity to share information and develop ideas for effective and informed management. Public outreach is critical. Participants identified lack of communication among researchers, managers, and landowners as a key concern. Follow-up activities should include:

• Organization of a field trip in summer 2001 for a larger group (including scientists, managers, and ranchers) that will provide an update on research results as well as discuss management implications.
• Creation of a web page for resource managers, ranchers, and scientists to share data, insights, and information on Utah juniper woodland ecology and management.

List of Workshop Participants

Jerry Altermatt
Wyoming Game and Fish
P.O. Box 28
Basin, WY 82410

Julio Betancourt
U.S. Geological Survey
Tucson, AZ 85745
jlbetanc@usgs.gov

Orrin Connell
Fire Trax
Big Horn, WY 82833
rxfire@cyberhighway.net

Doug Downs
Bighorn National Forest
P.O. Box 1141
Worland, WY 82401
ckdowns@trib.com

Tom Easterly
Wyoming Game and Fish
132 N. 5th
Greybull, WY 82446
teaste@tctwest.net

Steve Gray
University of Wyoming
Botany Department
Laramie, WY 82071
sgray@uwyo.edu

Bud Harrison
Wyoming Game and Fish
2820 State Hwy20
Cody, WY 82414

Mike Healy
LU Ranch
P.O. Box 699
Worland, WY 82401

Ann Humphrey
The Nature Conservancy
101 Rome Hill Rd.
Tensleep, WY 82442
tncten@tctwest.net

Kevin Hurley
Wyoming Game and Fish
Thermopolis, WY 82443
khurley@trib.com
307-864-9375

Steve Jackson
University of Wyoming
Botany Department
Laramie, WY 82071
jackson@uwyo.edu
307-766-2819

George Jones
Wyoming Natural Diversity Database
3381 University Station
Laramie, WY 82071-3381
gpjones@uwyo.edu

Dennis H. Knight
University of Wyoming
Botany Department
Laramie, WY 82071
dhknight@uwyo.edu

Judy Knight
Laramie, WY 82701
jeknight@uwyo.edu

Mark Lyford
University of Wyoming
Botany Department
Laramie, WY 82701
mahler@uwyo.edu

Suzanne Morstad
National Park Service
Bighorn Canyon National Recreation Area
P.O. Box 941
Basin, WY 82410
307-548-2251

Bill Robertson
Wyoming Game and Fish
434 6th Ave. N.
Greybull, WY 92446
bedrob@tctwest.net

Ken Stinson
Bureau of Land Management
P.O. Box 119
Worland,WY 82401

Phil Shephard
The Nature Conservancy
101 Rome Hill Road
Ten Sleep, WY 82442
tncten@tctwest.net