Great Basin Pinyon and Juniper
Ecology, History, Restoration

Intermountain pinyon-juniper woodlands are not a relatively homogenous plant community type, which is frequently inferred. In reality, pinyon-juniper woodlands are complex ecosystems that continually change in time and space.

Purpose

Pinyon (Pinus spp.) and juniper (Juniperus spp.) woodlands occupy over 78,000 square miles of the Great Basin and northern Colorado Plateau. These woodlands have persisted for tens of thousands of years and provide important biodiversity and habitat for many species across the region. Yet, relatively recent infill of new trees into old-growth woodlands and expansion of trees into adjacent sagebrush-steppe, riparian, and aspen communities have created a considerable mix of concerns around wildfire, drought-mortality, invasive species, watershed function, tree removal, and loss of habitat, biodiversity, and resilience.

This website provides background information on the ecology and management of PJ woodlands useful to the interested public and emerging information important to resource managers.
1)    PJ 101 provides a brief introduction to and description of PJ woodlands with links to more in-depth information.
2)    FAQ (Frequently Asked Questions) briefly addresses questions related to the ecology and management of PJ woodlands.
3)    Tools provides information and concepts for evaluating landscapes, which are specifically useful for predicting disturbance or vegetation management responses in PJ woodlands.
4)    Literature provides brief summaries and links to recently published PJ woodlands studies. Study findings are highlighted and discussed in terms of our current understanding.

This website will be continually updated with new articles, questions, and tools.

Knowledge and experience allow us to better understand complex ecosystems.

Author: Richard (Rick) Miller

Use of photos: Photos from this website may be used only for non-profit purposes with credit given to the photographer.

P-J 101

Taxonomy

Distribution & Climate

Soils & Topography

Overstory/Understory Relationships

Invasive Species

Seed Ecology

Pests

Frequently Asked Questions

Questions in this section frequently come up in workshops, field tours, symposia, and general discussions related to pinyon-juniper woodlands. They are closely linked to woodland ecology, resilience, resistance to invasives, and restoration. Most are addressed in more depth in referenced citations and Miller et al. 2019.

How do we know if woodlands are old-growth (presettlement) or post-settlement?

This question (Distinguishing Old-Growth (Presettlement) from Post-Settlement Woodlands) is answered in the Restoration Tools and Concepts section of the website.

How big is the largest western juniper (Juniperus occidentals)?

The largest western juniper is found in eastern Oregon. Its dimension are 233 inches in circumference (6.2 ft in diameter),…

Indian Paintbrush?

Over two dozen species of Indian paintbrush grow in the Intermountain Region, many of these are associated with pinyon-juniper woodlands….

Restoration Tools and Concepts

“Removing pinyon-juniper woodlands in former sagebrush ecosystems to increase understory cover has a long management history, and short- and long-term monitoring reveal different understory plant community responses.” (Ernrst-Brock et al. 2019)

Reading Landscapes: Predicting Post-Disturbance Succession

One of the most valuable landscape manager skills is to be able to predict the short and long-term response of plant communities, watersheds, and landscapes to disturbance and vegetation management. A skillful manager is an expert detective, having a knowledge of the key components that drive plant succession and adept to pulling together all of the available evidence.

Distinguishing old-growth (presettlement) and post-settlement woodlands

“Expansion of pinyon and juniper woodlands with climate and anthropogenic-related disturbances over the past 150 years, makes distinguishing historic old-growth and post-settlement woodlands difficult”

Distinguishing post-settlement from old-growth or reestablishing persistent woodlands after a stand-replacing event is an important step to making vegetation management decisions. Proper identification can help identify potential vegetation and characteristics of the ecological site, including the historic disturbance regime.

Several tree form and bark characteristics in addition to the presence of large dead wood can help distinguish old-growth (presettlement) woodlands from encroaching post-settlement woodlands (Table 1, Figs. 1-5). Key characteristics to evaluate relate to tree age, woodland structure, and ecological site characteristics. Additional information is available in Miller et al. 2007; Tausch et al. 2009; Miller et al. 2019 (see p. 57).

Table 1. Tree characteristics and the presence of old large wood can be used to distinguish old-growth (presettlement) and post-settlement woodlands.

Fig. 1. Western and Utah juniper bark changes with age from thin and flaky (left) to fibrous and thick with well developed vertical furrows (right) (Photos: Rick Miller, Oregon State University).

Fig. 2. Old-growth Utah juniper with fibrous deeply furrowed bark (left). Old-growth singleneedle pinyon with thick plate-like bark (right) (Photos: Schell Creek Range, NV, Rick Miller, Oregon State University).

Fig 3. This tree exhibits several old growth characteristics; large dead limbs covered in lichen, portions of the trunk are dead, little branch leader growth, and bird cavities (Photo: Juniper Mountain, OR, Rick Miller, Oregon State University).

Fig 4. Pinyon and Utah juniper create a patchwork of old and young stands across this landscape, with age often related to aspect and soils. This old-growth woodland is on a south aspect with very shallow rocky soils and limited understory vegetation. Younger stands of trees occupy the more productive soils (Photo: Henry Mountains, Utah, Rick Miller, Oregon State University).

Fig 5. Walking through this stand one can find a low density of old standing live and dead trees in addition to large stumps and logs. Prior to a fire, 100+ years ago this was an open juniper shrubland with mountain big sagebrush, bitterbrush, and Idaho fescue in the understory (Photo: Walker Butte, eastern Oregon Rick Miller, Oregon State University).

Fig 6. In very olds woodlands standing dead can accumulate over centuries. Standing dead trees with few to no remaining branches (shown in the picture) slowly weather-away and can remain standing for three or more centuries (Photo: Horse Ridge, eastern Oregon by Rick Miller Oregon State University).

Field Guides & Syntheses: for evaluating pinyon & juniper woodlands, post-fire recovery, and selecting the most appropriate treatments.

Miller, R. F., J. D. Bates, T. J. Svejcar, F. B. Pierson, and L. E. Eddleman. 2007. Western juniper field guide: asking the right questions to select appropriate management actions. US Department of Interior/ US Geological Survey Circular 1321. 57 p.

Tausch, R. J., R. F. Miller, B. A. Roundy, and J. C. Chambers. 2009. Pinon and juniper field guide: asking the right questions to select appropriate management actions.in US Department of Interior, editor. U.S. Geological Survey. Circular 1335. 96 p.

Miller, R. F., J. C. Chambers, and M. Pellant. 2015. A field guide for rapid assessment of post-wildfire recovery potential in sagebrush and pinon-juniper ecosystems in the Great Basin. USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-338:70.

Miller, R. F., J. C. Chambers, and M. Pellant. 2014a. A field guide for selecting the most appropriate treatment in sagebrush and pinon-juniper ecosystmens in the Great Basin. USDA Forest Service Gen. Tech. Rep. RMRS-GTR-322.

Miller, R. F., J. C. Chambers, D. Pyke, F. B. Pierson, and C. J. Williams. 2013. A review of fire effects on vegetation and soils in the Great Basin Region: Response and ecological site characteristics. USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-308. 127 p.

Miller, R. F., J. C. Chambers, L. B. Evers, J. C. Williams, K. A. Snyder, B. A. Roundy, and E. A. Pierson. 2019. The ecology, history, ecohydrology, and management of pinyon and juniper woodlands in the Great Basin and Northern Colorado Plateau of the western United States. Gen. Tech. Rep. RMRS-GTR-403. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 284 p

Evaluating post-fire severity

Fire severity describes the effects of fire on ecological processes, soil, flora, and fauna; degree to which a site has been altered or disrupted by fire. Fire severity is typically rated in three categories: low, moderate, and high.

The level of fire severity has a large impact on combustion of invasive and native seed, mortality of perennial herbaceous plants, soil crust connectivity, reductions in litter, and the overall resilience and resistance of a site, which impacts postfire succession and nutrient, hydrologic, and energy cycles. Post-fire severity can be assessed on burned sites using the evidence listed below (from Miller et al. 2015).

Indicators of hight fire severity in the above photo are: 1) 99% litter consumption, 2) few shrub skeletons remain, 3) tree bark and foliage consumed, 4) soil surface loose and powdery, and 5) grass crowns consumed

Environmental gradients of resilience and resistance

Conceptual model of (A) resilience to disturbance and (B) resistance to invasives as they relate to three environmental gradients: soil temperature and moisture regimes, elevation, and productivity. Soil moisture availability is also modified by soil characteristics. (A) The solid blue line in the top graph is the resilience as it relates to elevation (dashed dark blue line above and red line below adjust for aspect), soil temperature/moisture regimes, and productivity. (B) The solid green line in the bottom graph represents potential resistance to invasive annual grasses in the reference state, and the red line is the decline in resistance as a result of a site that is in an at-risk-phase (example depleted perennial herbaceous understory) or global climate change. Common plant communities along this gradient are Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis, ARTRw), mountain big sagebrush (A.t. spp. vaseyana, ARTRv), and mountain big sagebrush and snowberry (Symphoricarpos occidentalis, ARTRv-SYOR). (Chambers et al. 2014).

Predicting post-disturbance succession

A conceptual model of the primary components that influence plant succession following disturbance or vegetation management treatment. Consideration of key characteristics of these primary components substantially increases the ability to predict outcomes following disturbance and vegetation management (Miller et al. 2013, 2014, and 2015).

Primary components are the basis for a series of key questions to be addressed when evaluating site resilience to treatment applications, evaluating resistance to invasive annual grasses, and predicting post-treatment responses.

Linking ecological site characteristics to resilience and resistance

Primary components of an ecological site are climate, topography, and soils; all of which influence available moisture, temperature, and potential vegetation and productivity. Ecological site characteristics determine soil temperature and moisture regimes, potential vegetation, and resilience to disturbance and resistance to invasive plants. The regimes are identified in soil maps as mesic (warm), frigid (cool), cryic (cold), aridic (dry), and xeric (moist). Potential vegetation + disturbance history + seed availability + time since disturbance or treatment determine current vegetation. If all of the ecological site characteristics are favorable for treatment and the site attributes and processes are all functioning within the natural range of variability, then levels of resilience to treatment application and resistance to invasive species are near potential for that site. However, if the site is not at potential because one or more components are below potential or missing, for example, perennial grasses are severely depleted or invasive annual grasses are abundant, resilience to disturbance and/or resistance to and invasive annual grasses will be lower than potential (Fig. 1 adapted from Miller and others 2013 and Chambers and others 2014).

New Literature

What determines the effectiveness of pinyon-juniper clearing treatments? Evidence from the remote sensing archive and counter-factual scenarios

Consequences of pinyon-juniper woodland fuel reduction: Prescribed fire increases soil erosion while mastication does not

Long-term effects of tree expansion and reduction on soil climate in a semiarid ecosystem

Spatial patterns of tree cover change at a dry forest margin are driven by initial conditions, water balance and wildfire

Treatment longevity and changes in surface fuel loads after pinyon–juniper mastication

More Literature

Author

Rick Miller Professor Emeritus, Northern Great Basin Experimental Range, Oregon State University. Rick Miller has applied his background in plant and disturbance ecology to over 40 years of work in the northern and central Great Basin. His research has focused on plant succession resulting from shifts in natural and anthropomorphic disturbance regimes. He has worked closely with the BLM, US FWS, NPS, USFS, and private landowners throughout his career.