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CEGL000798 Pinus edulis / Achnatherum scribneri Open Woodland

Type Concept Sentence: No Data Available

Common (Translated Scientific) Name: Two-needle Pinyon / Scribner''s Needlegrass Open Woodland

Colloquial Name: No Data Available

Hierarchy Level:  Association

Type Concept: The center of distribution for this association is the central mountain corridor of New Mexico with outliers in southeastern Colorado. It is specifically known from the Sierra Oscura, San Andres Mountains, and Organ Mountains of the south-central Rio Grande corridor, and likely in the Manzano, Sandia, and Sacramento mountains. This association is typically found at mid to high elevations of 1890-2590 m (6200-8500 feet), on north-facing mountain slopes. Slope positions vary from gentle dipslopes to steep escarpments. The larger stands are particularly evident on the long, gently sloping dipslopes of the major fault block mountains. Soils range from well-developed Mollisols or Alfisols with high nutrient status to drier and more poorly developed Inceptisols. Although gravel and cobble content can be high, water-holding capacity is probably moderate. Secondary calcium carbonate accumulations can occur, including indurated petrocalcic horizons, which can limit root penetration. At El Malpais National Monument in west-central New Mexico, this association occurs between 2135 and 2380 m (7000-7800 feet) in elevation on gently rolling mesatops, gentle footslopes and shoulder slopes of low hills, and steep sideslopes of low hills. Substrates are typically derived from Permian sandstone and occasionally limestone formations. Ground surface cover is variable and can be dominated by gravel, rock or litter. It is characterized by a moderately open to relatively dense and tall overstory of Pinus edulis (>9 m [30+ feet]) with Juniperus monosperma (or occasionally Juniperus deppeana) scattered in the subcanopy. Pinus edulis regeneration is usually present, Juniperus monosperma less so. A grassy understory of well-represented to abundant Achnatherum scribneri or Achnatherum lobatum is diagnostic; Bouteloua gracilis often shares the dominance. Muhlenbergia pauciflora can be common but is clearly not the dominant. Scattered shrubs occur, but total shrub cover seldom exceeds 5%. Cercocarpus montanus, Yucca baccata, Quercus x pauciloba, and Opuntia phaeacantha are the most conspicuous shrub species. Forb species richness is high (66 species), and cover reaches 5% in some stands. They may commonly include Hymenoxys richardsonii, Tetraneuris argentea, and Eriogonum jamesii.

Diagnostic Characteristics: No Data Available

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: No Data Available

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

Floristics: This association is characterized by a moderately open to relatively dense and tall overstory of Pinus edulis with Juniperus monosperma (or occasionally Juniperus deppeana) scattered in the subcanopy. Pinus edulis regeneration is usually present, Juniperus monosperma less so. A grassy understory of well-represented to abundant Achnatherum scribneri (= Stipa scribneri) or Achnatherum lobatum (= Stipa lobata) is diagnostic; Bouteloua gracilis often shares the dominance. Muhlenbergia pauciflora can be common but is clearly not the dominant. Scattered shrubs occur, but total shrub cover seldom exceeds 5%. Cercocarpus montanus, Yucca baccata, Quercus x pauciloba (= Quercus undulata), and Opuntia phaeacantha are the most conspicuous shrub species. Forb species richness is high (66 species), and cover reaches 5% in some stands.

Dynamics:  No Data Available
Environmental Description:  This association is typically found at mid to high elevations of 1890-2590 m (6200-8500 feet), on north-facing mountain slopes. Slope positions vary from gentle dipslopes to steep escarpments. The larger stands are particularly evident on the long, gently sloping dipslopes of the major fault block mountains. Soils range from well-developed Mollisols or Alfisols with high nutrient status to drier and more poorly developed Inceptisols. Although gravel and cobble content can be high, water-holding capacity is probably moderate. Secondary calcium carbonate accumulations can occur, including indurated petrocalcic horizons, which can limit root penetration. At El Malpais National Monument in west-central New Mexico, this association occurs between 2135 and 2380 m (7000-7800 feet) in elevation on gently rolling mesatops, gentle footslopes and shoulder slopes of low hills, and steep sideslopes of low hills. Substrates are typically derived from Permian sandstone and occasionally limestone formations. Ground surface cover is variable and can be dominated by gravel, rock, or litter.
Geographic Range: The center of distribution for this association is the central mountain corridor of New Mexico with outliers in southeastern Colorado. It is specifically known from the Sierra Oscura, San Andres Mountains, and Organ Mountains of the south-central Rio Grande corridor, and likely in the Manzano, Sandia, and Sacramento mountains.

Nations: US

States/Provinces:  CO, NM


Confidence Level: Low

Confidence Level Comments: No Data Available
Grank: G3

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 CEGL000798 Two-needle Pinyon / Scribner''s Needlegrass Open Woodland CEGL000798 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: = Pinus edulis / Stipa scribneri PA (Muldavin and Mehlhop 1992)
= Pinus edulis / Stipa scribneri Plant Association, Stipa lobata Phase (Muldavin et al. 1994a)
? Stipa columbiana type (Kennedy 1983b)
= Pinyon Pine/Scribner''s Needlegrass PA (Muldavin et al. 2000b) [(Pinus edulis/Stipa scribneri; PINEDU/STISCR)]
Concept Author(s): E. Muldavin and P. Mehlhop (1992)

Author of Description: E. Muldavin and M.E. Hall

Acknowledgements: No Data Available

Version Date: 05-24-10
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