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CEGL002151 Pinus edulis - (Juniperus monosperma, Juniperus deppeana) / Bouteloua gracilis Open Woodland

Type Concept Sentence: No Data Available

Common (Translated Scientific) Name: Two-needle Pinyon - (One-seed Juniper, Alligator Juniper) / Blue Grama Open Woodland

Colloquial Name: No Data Available

Hierarchy Level:  Association

Type Concept: This widespread woodland association occurs in Colorado, Oklahoma, New Mexico, and possibly Texas and east-central Arizona. It is known from the foothills and mountains of the southern Colorado Front Range, New Mexico, and the hills, canyons, escarpments and other breaks in the southwestern Great Plains. Elevations range from 1525-2445 m (5000-8000 feet), but may be higher in stands in southern New Mexico. Stands occur on gently sloping low hills and plains, on flat to moderate slopes along drainages and on mesatops, and on moderate to steep rocky slopes of foothills, mountains and canyons. The soils are variable but are typically shallow, gravelly calcareous, finer-textured soils (clay loam or silty clay) with a caliche layer or bedrock outcrops not uncommon. Parent materials include limestone, sandstone, and basalt. The ground surface is may be characterized by scattered grass patches and litter amid an equal amount of exposed soil and gravel. The vegetation is characterized by an open to moderately dense tree canopy (10-60% cover) codominated by Pinus edulis and Juniperus monosperma with a grassy understory dominated by Bouteloua gracilis. Pinus edulis may be present with relatively small cover in some stands. Juniperus deppeana or Juniperus coahuilensis may replace Juniperus monosperma in southern stands. Other species of Juniperus such as Juniperus scopulorum may be present at upper elevations. The shrub canopy ranges from low to high cover. If Quercus gambelii is present, it has less than 5% cover. Scattered Agave spp., Cercocarpus montanus, Dasylirion wheeleri, Ericameria nauseosa, Gutierrezia sarothrae, Opuntia spp., Tetradymia canescens, or Yucca spp. may be present. The herbaceous layer is moderately dense to dense and is dominated by the warm-season, perennial shortgrass Bouteloua gracilis. Associated graminoids include Aristida spp., Achnatherum hymenoides, Elymus elymoides, Koeleria macrantha, Hesperostipa comata, Hesperostipa neomexicana, Muhlenbergia torreyi, and Pleuraphis jamesii. Muhlenbergia montana is absent or scarce (<1% cover). Forb cover is typically low, but may be moderately diverse. Species such as Cryptantha cinerea var. jamesii, Eriogonum jamesii, Hymenopappus filifolius, and Mentzelia spp. are common.

Diagnostic Characteristics: No Data Available

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: The two Pinus edulis / Bouteloua gracilis plant associations are treated as phases in Stuever and Hayden (1997b). In the USNVC we are including stands with southern Great Plains, Chihuahua Desert floristic affinities in ~Pinus edulis - (Juniperus monosperma, Juniperus deppeana) / Bouteloua gracilis Open Woodland (CEGL002151)$$, and stands with the Colorado Plateau and Great Basin floristic affinities in ~Pinus edulis - (Juniperus osteosperma) / Bouteloua gracilis Woodland (CEGL000778)$$. Both of these associations may include stands codominated by Juniperus deppeana in their southern extent. Stuever and Hayden (1997b) also described a Juniperus deppeana phase (recognized by the its dominance in the stand) and hillslope phase, which occurs on slopes >15% and may have low cover of grasses (<5% cover). More survey is needed to fully understand the distribution and ecological relationships between these three species of Juniperus.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: No Data Available

Floristics: This plant association is characterized by an open to moderately dense tree canopy (10-60% cover) codominated by Pinus edulis and Juniperus monosperma with a grassy understory dominated by Bouteloua gracilis. Pinus edulis may be present with relatively small cover in some stands. Juniperus deppeana or Juniperus coahuilensis may replace Juniperus monosperma in southern stands. Other species of Juniperus such as Juniperus scopulorum may be present at upper elevations. The shrub canopy ranges from low to high cover. If Quercus gambelii is present, it has less than 5% cover. Scattered Agave spp., Cercocarpus montanus, Dasylirion wheeleri, Ericameria nauseosa, Gutierrezia sarothrae, Opuntia spp., Tetradymia canescens, or Yucca spp. may be present. The herbaceous layer is moderately dense to dense and is dominated by the warm-season, perennial short grass Bouteloua gracilis. Associated graminoids include Aristida spp., Achnatherum hymenoides (= Oryzopsis hymenoides), Elymus elymoides, Koeleria macrantha, Hesperostipa comata (= Stipa comata), Hesperostipa neomexicana (= Stipa neomexicana), Muhlenbergia torreyi, and Pleuraphis jamesii (= Hilaria jamesii). Muhlenbergia montana is absent or scarce (<1% cover). Forb cover is typically low, but may be moderately diverse. Species such as Cryptantha cinerea var. jamesii (= Cryptantha jamesii), Eriogonum jamesii, Hymenopappus filifolius, and Mentzelia spp. are common. Other forbs may include Ipomopsis multiflora, Astragalus sp., and Erigeron divergens.

Dynamics:  Pinus edulis is extremely drought-tolerant and slow-growing (Powell 1988, Little 1987, Muldavin et al. 1998a). It is also non-sprouting and may be killed by fire (Wright et al. 1979). The effect of a fire on a stand is largely dependent on the tree height and density, fine fuel load on the ground, weather conditions, and season (Wright et al. 1979, Dwyer and Pieper 1967). Trees are more vulnerable in open stands where fires frequently occur in the spring, when the relative humidity is low, wind speeds are over 10-20 mph, and there is adequate fine fuels to carry fire (Wright et al. 1979). Under other conditions, burns tend to be spotty with low tree mortality. Large trees are generally not killed unless fine fuels, such as tumbleweeds, have accumulated beneath the tree to provide ladder fuels for the fire to reach the crown (Jameson 1962). Closed-canopy stands rarely burn because they typically do not have enough understory or wind to carry a fire (Wright et al. 1979).

Altered fire regimes, cutting trees for fencing, and improper grazing by livestock have significant impacts on the quality of sites. Grazing by livestock can modify the fire regime by removing the fine fuels that carry fire. Fire, livestock grazing, and trampling by recreationalists and vehicles disturb cryptogamic soil crusts that help maintain soil structure, reduce soil erosion, provide habitat for plants and preserve biological diversity (Ladyman and Muldavin 1996). More study is needed to understand and manage these woodlands ecologically.
Environmental Description:  This widespread woodland association occurs in Colorado, Oklahoma, New Mexico, and possibly Texas and east-central Arizona. It is known from the foothills and mountains of the southern Colorado Front Range, New Mexico, and the hills, canyons, escarpments and other breaks in the southwestern Great Plains. Elevations range from 1525-2444 m (5000-8000 feet), but may be higher in stands in southern New Mexico. Stands occur on gently sloping low hills and plains, on flat to moderate slopes along drainages and on mesa tops, and on moderate to steep rocky slopes of foothills, mountains and canyons. The soils are variable but are typically shallow, gravelly calcareous, finer-textured soils (clay loam, silty clay) with a caliche layer or bedrock outcrops not uncommon. Parent materials include limestone, sandstone, and basalt. The ground surface is may be characterized by scattered grass patches and litter amid an equal amount of exposed soil and gravel.
Geographic Range: This widespread woodland association occurs in Wyoming, southern Colorado, western Oklahoma, New Mexico, and possibly Texas and east-central Arizona.

Nations: US

States/Provinces:  AZ?, CO, NM, OK, TX?


Confidence Level: High

Confidence Level Comments: No Data Available
Grank: G5?

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.2 Two-needle Pinyon - One-seed Juniper Southern Rocky Mountain Woodland Macrogroup M897 1.B.2.Nc.2
Group 1.B.2.Nc.2.c Two-needle Pinyon - One-seed Juniper - Rocky Mountain Juniper Woodland Group G253 1.B.2.Nc.2.c
Alliance A3577 Two-needle Pinyon - One-seed Juniper Grassy Woodland Alliance A3577 1.B.2.Nc.2.c
Association CEGL002151 Two-needle Pinyon - (One-seed Juniper, Alligator Juniper) / Blue Grama Open Woodland CEGL002151 1.B.2.Nc.2.c
Concept Lineage: No Data Available

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: = Juniperus monosperma / Oryzopsis micrantha Plant Community (Shaw et al. 1989)
< Pinus edulis - Juniperus deppeana / Bouteloua gracilis Habitat Type (Kennedy 1983a)
> Pinus edulis - Juniperus monosperma / Bouteloua gracilis Plant Community (Francis 1986)
= Pinus edulis - Juniperus monosperma / Bouteloua gracilis Vegetation Type (Dick-Peddie 1993)
> Pinus edulis / Bouteloua gracilis - Eriogonum spp. Plant Community (Francis 1986)
< Pinus edulis / Bouteloua gracilis (Stuever and Hayden 1997b)
= Pinus edulis / Bouteloua gracilis PA (Muldavin and Mehlhop 1992)
> Pinus edulis / Bouteloua gracilis PA, Juniperus deppeana Phase (Muldavin et al. 1994a)
< Pinus edulis / Bouteloua gracilis Plant Association (Larson and Moir 1987)
= Pinus edulis / Bouteloua gracilis Plant Association (Muldavin et al. 1998d)
> Pinus edulis-Juniperus deppeana/S/Bouteloua gracilis Vegetation Type (Dick-Peddie 1993)
= Pinyon Pine/Blue Grama PA (Muldavin et al. 2000b) [(Pinus edulis/Bouteloua gracilis: PINEDU/BOUGRA)]
Concept Author(s): K.A. Schulz

Author of Description: K.A. Schulz and K.S. King

Acknowledgements: No Data Available

Version Date: 05-21-10
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