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A2109 Pinus monophylla - Juniperus osteosperma Grassy Open Woodland Alliance

Type Concept Sentence: This open woodland and savanna alliance is characterized by diagnostic tree species Pinus monophylla that forms an open to moderately dense tree layer often with Juniperus osteosperma or, less frequently, Juniperus californica in southern California, with an understory dominated by an open to dense layer of perennial grasses and lacking significant cover of shrubs. It occurs on dry mountain slopes, foothills, plateaus and ridges in the Great Basin region and eastern foothills of the Sierra Nevada, and south in scattered locations throughout southern California, including desert mountain ranges.

Common (Translated Scientific) Name: Singleleaf Pinyon - Utah Juniper Grassy Open Woodland Alliance

Colloquial Name: Great Basin Singleleaf Pinyon - Utah Juniper Grassy Open Woodland

Hierarchy Level:  Alliance

Type Concept: These open woodlands and tree savannas are characterized by diagnostic tree species Pinus monophylla which forms an open to moderately dense tree layer often with Juniperus osteosperma or, less frequently, Juniperus californica in southern California. Juniperus osteosperma may also dominate stands as long as there is significant presence of Pinus monophylla that characterizes the stand as a pinyon-juniper stand and not the more xeric, typically lower elevation ~Juniperus osteosperma Great Basin Shrubby Woodland Alliance (A4370)$$. At higher elevations and on relatively mesic sites, such as along drainages, Juniperus scopulorum may be present and sometimes dominant. Other conifers are absent or accidental with very low cover. The understory is characterized by an open to dense herbaceous layer. Scattered shrubs may be present but do not form a layer and do not exceed cover of herbaceous layer. Perennial grasses typically dominate the herbaceous layer, although forbs species are present and can be diverse. Characteristic species include Achnatherum hymenoides, Bouteloua gracilis, Elymus elymoides, Hesperostipa comata, Leymus cinereus, Pleuraphis jamesii, Poa fendleriana, Poa secunda, and Pseudoroegneria spicata. The non-native, invasive annual grass Bromus tectorum may become abundant and dominate the understory of highly disturbed stands. This open woodland and savanna alliance occurs on dry mountain ranges of the Great Basin region and eastern foothills of the Sierra Nevada, and south in scattered locations throughout southern California, including desert mountain ranges. Stands occur on warm, dry sites on mountain slopes, foothills, plateaus and ridges in ranges of the Great Basin and southern California, usually on erosional terrain or upper alluvial slopes. Elevations range from 1000 to 2800 m. The climate is semi-arid, with approximately 20-45 cm of precipitation annually. Substrates are variable but often rocky with shallow soil.

Diagnostic Characteristics: This alliance is characterized by the diagnostic tree species Pinus monophylla which forms an open to moderately dense tree layer often with Juniperus osteosperma or, less frequently, Juniperus californica in southern California. Juniperus osteosperma may also dominate stands as long as there is significant presence of Pinus monophylla with which to characterize the stand as pinyon-juniper. Characteristic species include Achnatherum hymenoides, Bouteloua gracilis, Elymus elymoides, Hesperostipa comata, Poa fendleriana, Poa secunda, Pleuraphis jamesii, and Pseudoroegneria spicata.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: This alliance currently contains ~Pinus monophylla - Juniperus osteosperma / Leymus cinereus Wooded Grassland (CEGL000835)$$ which was described qualitatively from a single location in southern Idaho. Vegetation similar in composition has been described from southern California (Barbour and Major 1977) and Nevada (Blackburn 1967, Blackburn et al. 1969). The low-elevation woody vegetation of the Great Basin has been traditionally lumped into Pinus monophylla (singleleaf pinyon) or pinyon-juniper woodlands, and further classification work is needed to differentiate true woodlands from the savanna-like stands in this alliance. It is likely that these savannas are much more widely distributed than presently documented.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: These are sparse savannas and open woodland (5-30% cover) characterized by needle-leaved evergreen trees of low stature (<20 m). Scale-leaved evergreen trees are often present and may be codominant in the tree layer. The herbaceous layer is usually of low to moderate cover (20-40%) and dominated by tall perennial bunch grasses (0.5-1.5 m tall).

Floristics: These open woodlands and tree savannas are characterized by diagnostic tree species Pinus monophylla which forms an open to moderately dense tree layer often with Juniperus osteosperma or, less frequently, Juniperus californica in southern California. Juniperus osteosperma may also dominate stands as long as there is significant presence of Pinus monophylla that characterizes the stand as a pinyon-juniper stand and not the more xeric, typically lower elevation ~Juniperus osteosperma / Shrub Understory Woodland Alliance (A3496)$$. At higher elevations and on relatively mesic sites, such as along drainages, Juniperus scopulorum may be present and sometimes dominant. Other conifers such as Abies concolor, Pinus aristata, Pinus flexilis, and Pinus ponderosa are absent or accidental with very low cover. The understory is characterized by an open to dense herbaceous layer. Scattered shrubs and dwarf-shrubs, such as Cercocarpus ledifolius, Gutierrezia sarothrae, and Opuntia sp., may be present but do not form a layer and do not exceed cover of herbaceous layer. Perennial grasses typically dominate the herbaceous layer, although forbs species are present and can be diverse. Characteristic species include Achnatherum hymenoides, Aristida purpurea, Bouteloua gracilis, Elymus elymoides, Hesperostipa comata, Leymus cinereus, Pleuraphis jamesii, Poa fendleriana, Poa secunda, and Pseudoroegneria spicata. Common forbs include Penstemon linarioides, Eriogonum umbellatum, and Hymenoxys richardsonii. The non-native, invasive annual grass Bromus tectorum may become abundant in disturbed stands and dominate the understory of highly disturbed stands.

Dynamics:  Pinus monophylla is a slow-growing, long-lived tree and stands appear somewhat static over time compared to more productive forests. Regeneration occurs primarily under nurse shrubs or adult trees, where canopy shading minimizes drought stress for seedlings (Koniak 1985). These woodlands are expanding into adjacent steppe grasslands in many areas, reportedly in connection with livestock grazing and altered fire regimes. Many of these woodlands have been intensively altered to enhance livestock forage.
Environmental Description:  These woodlands occur on warm, dry sites on mountain slopes, foothills, plateaus and ridges in ranges of the Great Basin and southern California, usually on erosional terrain or upper alluvial slopes. Elevations range from 1000 to 2800 m. The climate of the region is characterized as semi-arid, with warm summers and cold winters. Average annual precipitation is 27 cm (20-45 cm), and shows a peak during April through June, when more than 30% of the annual total is received. Summers are typically dry and there is usually extreme variation in yearly totals. In the Great Basin, these woodlands occur on intermediate slopes above pools of cold-air drainage. Upper elevation limits are determined by local climate and/or the presence of competing tree species. Soils are variable, but generally coarse-textured and well-drained and derived from gneiss, schist, quartzite, and amphibolite. Soil pH is usually nearly neutral or alkaline.
Geographic Range: The core distribution of this woodland alliance is the Great Basin, but it extends out into adjacent ecoregions primarily west into the foothills of the Sierra Nevada, south on scattered mountain ranges of the Mojave Desert and east into the transition zone with the Colorado Plateau. A second substantial range occurs along interior slopes in the Transverse and Peninsular ranges of southern California.

Nations: US

States/Provinces:  AZ, CA, ID, NV, UT


Confidence Level: Low

Confidence Level Comments: No Data Available
Grank: GNR

Greasons: No Data Available
Type Name Database Code Classification Code
Class 1 Forest & Woodland Class C01 1
Subclass 1.B Temperate & Boreal Forest & Woodland Subclass S15 1.B
Formation 1.B.2 Cool Temperate Forest & Woodland Formation F008 1.B.2
Division 1.B.2.Nc Western North American Pinyon - Juniper Woodland & Scrub Division D010 1.B.2.Nc
Macrogroup 1.B.2.Nc.1 Singleleaf Pinyon - Utah Juniper - Western Juniper Intermountain Woodland Macrogroup M896 1.B.2.Nc.1
Group 1.B.2.Nc.1.c Singleleaf Pinyon - Utah Juniper Woodland Group G899 1.B.2.Nc.1.c
Alliance A2109 Singleleaf Pinyon - Utah Juniper Grassy Open Woodland Alliance A2109 1.B.2.Nc.1.c
Association CEGL000835 Singleleaf Pinyon - Utah Juniper / Basin Wildrye Wooded Grassland CEGL000835 1.B.2.Nc.1.c
Association CEGL002969 Singleleaf Pinyon - Utah Juniper / Needle-and-Thread Open Woodland CEGL002969 1.B.2.Nc.1.c
Association CEGL003154 Singleleaf Pinyon / Big Sagebrush / Squirreltail Open Woodland CEGL003154 1.B.2.Nc.1.c
Association CEGL005396 Singleleaf Pinyon - Utah Juniper / Blue Grama Open Woodland CEGL005396 1.B.2.Nc.1.c
Association CEGL005440 Singleleaf Pinyon - Utah Juniper / (Muttongrass, Sandberg Bluegrass) Open Woodland CEGL005440 1.B.2.Nc.1.c
Concept Lineage: [proto-alliance A2109] This alliance is composed of 4 herbaceous understory associations from Old Alliance II.A.4.N.a. Pinus monophylla - (Juniperus osteosperma) Woodland Alliance (A.543) and one association from Old Alliance V.A.6.N.b. Pinus monophylla Wooded Tall Herbaceous Alliance (A.1487). A.543 (in part) and A.1487 (in part).

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: >< Pinus monophylla (Singleleaf pinyon woodlands) Alliance (Sawyer et al. 2009) [87.040.00]
>< Singleleaf Pinyon Series (Sawyer and Keeler-Wolf 1995)
>< Singleleaf Pinyon-Utah Juniper Series (Sawyer and Keeler-Wolf 1995)
Concept Author(s): K.A. Schulz, in Faber-Langendoen et al. (2013)

Author of Description: K.A. Schulz

Acknowledgements: We have incorporated significant descriptive information previously compiled by M. Jennings and D. Sarr.

Version Date: 03-14-14
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