Wikipedia

Pinyon–juniper woodland

Pinyon–juniper woodland, also spelled piñon–juniper woodland, is a biome found mid-elevations in arid regions of the Western United States, characterized by being an open forest dominated by low, bushy, evergreen junipers, pinyon pines, and their associates.[1][2] At lower elevations, junipers often predominate and trees are spaced widely, bordering on and mingling with grassland or shrubland, but as elevation increases, pinyon pines become common and trees grow closer, forming denser canopies.[3] Historically, pinyon-juniper woodland provided a vital source of fuel and food (particularly piñon nuts) for indigenous peoples of the American Southwest,[1] and the nuts continue to be a traditional food;[4] nut-collecting was also adopted by the Spanish in the 1500s and the nuts are still traditionally harvested in Hispanic communities today.[4]

Single-leaf pinyon–Utah juniper woodland in northeastern Nevada near Overland Pass at the south end of the Ruby Mountains

As of the early 2020s, pinyon-juniper ecosystems have been under pressure from heavy natural gas extraction in southern Colorado and New Mexico.[5] They have also been historically destroyed by land managers in the United States in favor of livestock pasture, due to a lack of perceived economic value.[4]

Ecology

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Both pinyon pine and juniper species reproduce exclusively through seed production, and produce most of their seeds during mast years, which occur about every three to five years.[5] The seeds produced by the pinyon pines in mast cycles are the primary influence on population growth in the habitat; in lean years some animals move away in a nomadic fashion.[1] Birds and small mammals in the ecosystem are the main distribution method for these seeds.[5] An important example is the pinyon jays, a keystone species[4] that is the primary distribution mechanism for pinyon pine seeds, having formed a mutualistic relationship with the trees.[6]

Pinyon-juniper woodlands support a number of native species including the pinyon mouse and the pinyon jay.[5] The woodlands also serve as refuges for desert and mountain animals attempting to escape heat or cold; few animals other than the pinyon jay stay in the ecosystem year-round.[1] However, they serve as important habitat for a number of endangered species, including Woodhouse's scrub jay and the gray vireo.[4]

Subtypes

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Pinyon-juniper savannah
 
Pinyon-juniper persistent woodland
 
Pinyon-juniper shrubland

Pinyon–juniper woodland has three major subtypes based on vegetation: pinyon-juniper savannah, pinyon-juniper wooded shrubland, and pinyon-juniper persistent woodland.[7]

Pinyon-juniper savannah

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Pinyon-juniper savannahs are dominated by grasses and forbs, with dense undergrowth and savannah-like sparser trees. Monsoon summer rains are common in pinyon-juniper savannahs, since they favor the growth of warm-season grasses. Common grass species are blue grama, other species of grama grass, new mexico muhly, curlyleaf muhly, and needle and thread grass.[7]

Pinyon-juniper persistent woodlands

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Pinyon-juniper persistent woodlands are dominated by trees, with a variety of tree ages, often in areas with winter or bi-modal precipitation. Persistent woodland sites are usually unproductive, with thin soils and sparse ground or shrub cover, often occurring on rocky or rugged terrain.[7]

Pinyon-juniper wooded shrublands

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Pinyon-juniper wooded shrublands are transition zones where pinyon-juniper woodland is expanding or contracting, often bordering other vegetation types. In absence of fire, they shift from grass and forb-dominated, to shrub-dominated, to tree-dominated communities over time. Common shrub species are big sagebrush, other species in that genus, antelope bitterbrush, rabbitbrush, mountain mahogany, and snakeweed.[7]

Range

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Range of pinyon–juniper Woodlands in the Western United States

Today, pinyon–juniper woodland range spans from New Mexico, to the eastern Sierra Nevada, the Colorado Plateau, the Great Basin, and higher elevations of Mountain ranges of the Mojave Desert.[2] The woodland's range includes the Mogollon Rim in the south, to its northern extent in the Snake River Plain.[8] Pinyon-juniper woodland occurs interspersed with sagebrush in the D-35, D-36, D-38, D-39, E-49, and E-51 Major Land Resource Areas.[5][clarification needed]

It typically occurs at between 4,500 to 7,500 ft (1,400 to 2,300 m). Historically, however, the range and elevations of pinyon-juniper woodland have shifted based on differences in climate. On the order of 10,000 years ago during the Wisconsin glaciation, pinyon-juniper woodlands occurred in areas that today are the Chihuahuan, Mojave, and Sonoran desert lowlands, and since then pinyon-juniper altitude ranges have continued to change based on changing moisture and temperature ranges over time.[2]

In the last 200 years specifically, the area occupied by pinyon-juniper woodlands has increased by two to six times. This is attributed to a number of factors, but especially the direct and indirect effects of climate, overgrazing and altered fire regimes. Specifically, the wet period between the 1800s and 1900s boosted tree establishment, and livestock grazing both eliminated perennial grass cover that would hinder tree establishment, and removed fine fuels that could start large fires.[9]

Due to its temperature tolerance, pinyon generally does not naturally grow north of northern Utah, as well as some portions of southern Wyoming and Idaho.[5] Pinyon-juniper woodlands prefer areas with cold winters and hot, dry summers.[1] Usually, the habitat experiences freezing temperatures 150 or more days a year, with 6 to 20 in (150 to 510 mm) of annual precipitation, mostly falling as snow.[1]

Arizona and New Mexico

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The pinyon–juniper woodland is one of the most prevalent types of coniferous woodland in northern Arizona and New Mexico.[10] In Arizona the great basin woodland species are Juniperus arizonica, Juniperus californica in western Arizona, Juniperus deppeana, Juniperus monosperma, Juniperus osteosperma, Juniperus scopulorum at higher elevations, Pinus monophylla var. fallax below the Colorado plateau, and Pinus edulis on the Colorado plateau.[11][better source needed] In Arizona the great basin woodland includes many species of oaks: Quercus turbinella, Quercus gambelii at higher elevations, Quercus grisea, Quercus arizonica, and Quercus emoryi.[12][better source needed] In Southern Arizona, Pinus discolor, Juniperus deppeana, and Pinus leiophylla make up the conifer woodland with many oak species.[13][better source needed]

California

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In California, pinyon-juniper woodland is mainly found on the eastern side of the Sierra Nevada, and also somewhat in the Transverse Ranges and Peninsular Ranges, as well as several isolated patches on desert mountaintops.[1] In the eastern Sierra Nevada, the habitat forms in the transition zone between the wetter conifer forests to the west and the drier deserts to the east, in the gradient that forms due to the mountains' rain shadow.[1]

Utah and Canyonlands region

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The pinyon–juniper plant community covers a large portion of Utah and the Canyonlands region. Singleleaf ash (Fraxinus anomala), and Utah serviceberry (Amelanchier utahensis) are codominants of pinyon pine and Utah juniper. In this region, the community occurs on rocky soils or jointed bedrock.[14][better source needed]

Mojave Desert

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In the steppes adjoining the Mojave Desert, this vegetation type can be found in areas receiving 12 to 20 in (300 to 510 mm) inches of annual precipitation, and between 4,500 to 8,000 ft (1,400 to 2,400 m).[15][better source needed] Associates include bitterbrush (Purshia glandulosa), Apache plume(Fallugia paradoxa), desert sagebrush (Artemisia tridentata), green ephedra (Ephedra viridis), mountain mahoganies (Cercocarpus spp.), and buckwheats (Eriogonum spp.).[15][better source needed] In the Mojave, pinyon–juniper woodlands are generally above the Joshua Tree woodlands vegetation type, and requires more annual precipitation.[15][16]

Sierra Nevada

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In the eastern Sierra Nevada, the elevation range is 4,000 to 5,500 ft (1,200 to 1,700 m) in the north, and 5,000 to 8,000 ft (2,000 to 2,000 m) feet in the southern reaches of the range. Pinyon–juniper woodland requires 12 to 20 in (300 to 510 mm) of annual precipitation, so is generally located above the sagebrush scrub vegetation type, which can survive on an average of 7 in (180 mm) per year. It is located below the alpine zone. There is often an understory dominated by sagebrush (Artemisia tridentata) and its associates. Co-dominants include Jeffrey Pine (Pinus jeffreyi) and an understory of sagebrush scrub or rabbitbrush scrub (Ericameria spp.).[17][better source needed]

See also

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References

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  1. ^ a b c d e f g h "Pinyon-Juniper Woodland". Habitats Alive!. California Institute for Biodiversity. 6 September 2012. ISBN 978-0971125919.
  2. ^ a b c "Pinyon–Juniper Woodlands – Introduction & Distribution (U.S. National Park Service)". www.nps.gov. Retrieved 2018-01-26.
  3. ^ Muldavin, Esteban; Triepke, F. Jack (1 July 2019). "North American Pinyon–Juniper Woodlands: Ecological Composition, Dynamics, and Future Trends" (PDF). North American Pinyon' Juniper Woodlands: Ecological Composition, Dynamics, and Future Trends. pp. 516–531. doi:10.1016/B978-0-12-409548-9.12113-X. ISBN 9780128160978. S2CID 213465284. Retrieved 5 February 2022.
  4. ^ a b c d e Note, Sara Van (2022-10-19). "In New Mexico, Unraveling the Plight of the Pinyon Jay". Undark Magazine. Retrieved 2024-08-26.
  5. ^ a b c d e f Gibson, Yvette (2 Jan 2023). "Pinyon-Juniper Woodland Ecosystems". Rangeland Ecosystems of the Western US. Oregon State University.
  6. ^ Ligon, J. David (March 1978). "Reproductive Interdependence of Pinon Jays and Pinon Pines". Ecological Monographs. 48 (2): 111–126. doi:10.2307/2937295. ISSN 0012-9615. JSTOR 2937295.
  7. ^ a b c d "Pinyon-Juniper Woodlands - Species Composition and Classification". US National Park Service. Retrieved 2024-08-26.
  8. ^ Cronquist, (1972).
  9. ^ "Between a Rock and a Hard Place: Understanding and Managing Pinyon and Juniper Woodlands in a Changing Climate" (PDF). Science You Can Use Bulletin. August 2021. Retrieved 20 Nov 2023.
  10. ^ Dick-Peddie, (1999) pp. 87.
  11. ^ "Pinus monophylla (Singleleaf piñon) description - the Gymnosperm Database".
  12. ^ "SEINet Portal NetworkResearch Checklist: Sedona/Oak Creek Canyon".
  13. ^ "SEINet Portal NetworkResearch Checklist: Chiricahua National Monument".
  14. ^ Damian Fagan, Canyon Country Wildflowers, p. 3
  15. ^ a b c Pam MacKay, Mojave Desert Wildflowers, p19-20
  16. ^ Adrienne Knute, Plants of the East Mojave, p31.
  17. ^ Karen Wiese, Sierra Nevada Wildflowers, 2013, p. 18

Sources

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  • Dick-Peddie, William A. (1999). New Mexico Vegetation: Past, Present, and Future. University of New Mexico Press. p. 280. ISBN 0-8263-2164-X.
  • Cronquist, Arthur; Arthur H. Holmgren; Noel H. Holmgren; James L. Reveal; James Reveal; Noel Holmgren (1972). Intermountain Flora - Vascular Plants of the Intermountain West, U.S.A. - Geological and Botanical History of the Region, its Plant Geography and a Glossary. Vol. 1. The New York Botanical Garden Press. p. 270. ISBN 0-89327-300-7.
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