Western Juniper Woodlands - Is Mine Like Yours?

by Tim DeBoodt, OSU Extension Service
from the Western Juniper Newsletter, Vol. 2, No. 1, Summer 1997.
This is the third in a series of newsletter articles which respond to commonly-asked questions about western juniper woodland management and science. It is a condensed version of a talk given by Tim Deboodt, OSU Crook County Extension Agent, at Western Juniper Forum '97, with input from Rick Miller and Jeff Rose, Eastern Oregon Research Center, Burns, OR.

There is increasing interest in management of landscapes referred to as "juniper woodlands". Based on countless hours of conversation with numerous private citizens and public land managers, it is my experience that visions of what should happen are profoundly affected by exposure to particular sites. Communication becomes difficult and conflicts arise when reference points differ.

Are We Talking About the Same Thing?

Not all western juniper woodlands are alike. Differences in soil types, slope, aspect, precipitation and other weather influences, understory vegetation, and current management practices all influence how a stand has developed and how it will respond to management activities. Research is underway concerning how these factors interact and influence a specific site. However, shared terminology and concepts are needed to facilitate discussion and communication.

Rick Miller and Jeff Rose, Eastern Oregon Research Center in Burns, Oregon, with the help of others, are developing terminology and concepts which will enhance our ability to communicate with each other, and classify woodlands and their successional stages based on easily identifiable characteristics. These characteristics include: Canopy cover; leader growth of dominant trees; degree of crown lift (die-off of lower branches); potential berry production; tree recruitment; growth of young trees; and condition of the shrub layer. The Key Characteristics Table below offers a preliminary description of this classification system.

Old Growth and Tablelands Classification

In addition to the woodland development stages illustrated in the Key Characteristics Table, classification systems for old growth and juniper tablelands are being developed. These stands have unique attributes. For example, old growth stands are mainly found on shallow soils underlain by fractured bedrock. Old growth is also found on deeper soil sites, such as Juniper Mountain in Lake and Harney Counties, and the pumice soils of the Mazama ecological province in Central Oregon.

Old growth trees are considered to be those established prior to 1870 (Anglo settlement). They often have flat tops, massive irregular trunks, deeply furrowed bark, and few large basal limbs. A bright yellow-green lichen also becomes abundant. Although determining exact age is difficult due to rot, trees between 500-800 years are not uncommon. Differences in understory components between old growth and post-settlement woodlands have not been fully described.

Juniper tablelands are another type of woodland and have not been well studied. They occur on extensive flats (less than 5% slope) with low sagebrush as a dominant shrub. Trees greater than six feet in height typically were established prior to 1870. Soils are shallow, rocky, and high in clay. Plant diversity is greater in the interspaces, but understory cover is greatest under the tree canopy. Potential canopy cover at full occupancy is estimated at about 20%. Establishment and growth rates are slower than on mountain big sagebrush and aspen sites. Effects of increased tree density on understory vegetation have not been determined.

A common classification system that is easy to understand and which illustrates site conditions is an important tool for those who have to manage or want to provide input about the management of western juniper woodlands. Communication between scientists, natural resource management professionals, and interested public is enhanced, and public input is more effective if it is pertinent to the site in question.

DRAFT - Key Characteristics: Western Juniper Woodland Successional Stages
Key Characteristics Early Transitional Mid Transitional Late Transitional Closed Stand
Tree Canopy Open; canopy cover <5%; expanding Canopy cover 6-20%; actively expanding Canopy cover 21-35%; canopy expansion greatly reduced Canopy cover >35%; canopy expansion stabilized
Leader Growth
(Dominant Trees)
Good terminal & lateral growth Good terminal & lateral growth Good terminal growth, reduced lateral growth Good to reduced terminal growth; no lateral growth
Crown Lift
(lower limb die-off)
(Dominant Trees)
Absent Absent Reduced lateral growth of lower limbs Present (for productive sites)
Potential Berry Production Low Moderate to High Low to Moderate Scarce to Low
Tree Recruitment Active Active Reduced; limited to within drip line Absent
Growth
(Understory Trees)
Good terminal & lateral growth Good terminal & lateral growth Greatly reduced terminal & lateral growth; reduced ring growth Absent; some mortality; greatly reduced ring growth
Shrub Layer Intact Nearly intact to showing mortality around dominants >40% mortality >85% mortality

For more information, contact Tim DeBoodt, OSU Crook County Extension, 541-447-6228.