Print Report

A3101 Quercus arizonica - Quercus emoryi - Quercus grisea Scrub Woodland Alliance

Type Concept Sentence: This scrub woodland alliance is characterized by an open to moderately dense (10-60% cover), broad-leaved evergreen tree layer (encinal) dominated or codominated by diagnostic species Quercus arizonica, Quercus emoryi, Quercus grisea, or Quercus toumeyi. It is found in western Texas, southern New Mexico, southeastern Arizona and northern Mexico on sites ranging from gently to moderately sloping alluvial plains and bajadas to steep rocky slopes in canyons, foothills and mountains.

Common (Translated Scientific) Name: Arizona White Oak - Emory Oak - Gray Oak Scrub Woodland Alliance

Colloquial Name: Madrean Oak Scrub Woodland

Hierarchy Level:  Alliance

Type Concept: Woodlands included in this alliance are characterized by a typically open, broad-leaved evergreen tree canopy 3-15 m tall that is dominated or codominated by diagnostic species Quercus arizonica, Quercus emoryi, Quercus grisea, or Quercus toumeyi. Other non-diagnostic tree species may be present with less cover than evergreen oak trees, including Juniperus deppeana, Juniperus monosperma, Pinus discolor, Pinus edulis, and Quercus hypoleucoides. Shrubs are frequently present and may form an open to moderately dense shrub layer less than 3 m tall. Dominant shrubs include chaparral species such as Arctostaphylos pungens, Cercocarpus montanus, Garrya wrightii, Quercus turbinella, or Rhus spp., and some wide-ranging shrubs such as Brickellia spp., Gutierrezia sarothrae, Cylindropuntia imbricata, Opuntia phaeacantha, and Yucca baccata. The most diagnostic species are restricted to the Madrean region and include Agave spp., Dasylirion wheeleri, Ericameria laricifolia, Nolina microcarpa, Yucca madrensis, and juvenile tree species. The sparse to frequently dense graminoid layer is dominated by bunchgrasses. Dominant and character species include desert grasses such as Muhlenbergia emersleyi, Piptochaetium fimbriatum, or Schizachyrium cirratum, but stands can be very diverse. The usually sparse, but often diverse, forb layer may include species of Artemisia, Croton, Dichondra, Geranium, Macroptilium, Viguiera, and many others. Diagnostic of this woodland alliance is the tree layer dominated by Quercus arizonica, Quercus emoryi, and/or Quercus grisea. This alliance is found on rocky slopes in canyons and mountains in western Texas, southern New Mexico, southeastern Arizona and northern Mexico. Sites include moderate to steep slopes on all aspects in canyons and on piedmont and mountains slopes. Soils are often gravelly loams derived from a variety of parent materials. Soil and parent material are highly variable, but soils are often silty, sandy, gravelly or cobbly loam.

Diagnostic Characteristics: Diagnostic characteristics of this alliance include the dominance of evergreen oaks Quercus arizonica, Quercus emoryi, Quercus grisea, and/or Quercus toumeyi in the typically short (3-5 m tall, but up to 15 m tall), open to moderately dense (10-60% cover) tree canopy. Understory layers are variable, ranging from sparse to dense grass or shrub layers.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: Some stands in canyon bottoms are dense enough to be classified as forests (plot 91EM17 in Muldavin et al. 1994a). Other stands have a sparse tree layer. Bassett et al. (1987) report that at lower elevations these woodland stands become savannas. More work is needed to clarify the classification of these stands. Additionally, more compositional information is needed to fully describe associations in this alliance.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Vegetation in this woodland alliance is characterized by a typically open, broad-leaved evergreen short (3-5 m tall) tree canopy especially at lower elevations, but canopy height ranges from 3-15 m tall. A sparse to moderately dense mixed-shrub layer is present (0.5-3 m tall). The graminoid layer is sparse or, more typically, moderately dense and dominated by medium-tall, warm-season bunch grasses. The forb layer is generally sparse, but may have high species diversity. Cacti or rosette shrub succulents are commonly present. A sparse to moderately dense cover of xeromorphic succulent and broad-leaved shrubs and scattered evergreen trees is often present.

Floristics: Woodlands included in this alliance are characterized by a typically open, broad-leaved evergreen short (3-5 m tall) tree canopy especially at lower elevations, but range from 3-15 m tall. The open to dense tree canopy is dominated or codominated by diagnostic species Quercus arizonica, Quercus emoryi, Quercus grisea, or Quercus toumeyi. Other non-diagnostic tree species may be present with less cover than evergreen oak trees, including Juniperus deppeana, Juniperus monosperma, Pinus cembroides, Pinus discolor, Pinus edulis, Quercus gravesii (in Texas) and Quercus hypoleucoides. Shrubs are frequently present and may form an open to moderately dense shrub layer less than 3 m tall. Dominant shrubs include chaparral species such as Arctostaphylos pungens, Cercocarpus montanus, Garrya wrightii, Quercus turbinella, or Rhus spp., and some wide-ranging shrubs, rosette shrubs and succulents such as Brickellia spp., Gutierrezia sarothrae, Cylindropuntia imbricata (= Opuntia imbricata), Opuntia phaeacantha, and Yucca baccata. The most diagnostic species are restricted to the Madrean region and include Agave spp., Dasylirion wheeleri, Ericameria laricifolia, Nolina microcarpa, Yucca madrensis (= Yucca schottii), and juvenile tree species. The sparse to frequently dense graminoid layer is dominated by bunchgrasses. Dominant and character species include desert grasses such as Muhlenbergia emersleyi, Piptochaetium fimbriatum, or Schizachyrium cirratum, but stands can be very diverse with Leptochloa dubia, Muhlenbergia dubia, Muhlenbergia longiligula, and Muhlenbergia pauciflora. Other common graminoid species may be more widespread, such as Bothriochloa barbinodis, Bouteloua curtipendula, Koeleria macrantha, Panicum bulbosum (non-native), and Sporobolus flexuosus. The usually sparse, but often diverse, forb layer may include Artemisia spp., Croton fruticulosus, Dichondra brachypoda, Geranium caespitosum, Macroptilium gibbosifolium, Viguiera dentata, and many others. Diagnostic of this woodland alliance is the tree layer dominated by Quercus arizonica, Quercus emoryi, and/or Quercus grisea.

Dynamics:  Over the last century, the woody component in this alliance has increased in density over time in the absence of disturbance such as fire (Burgess 1995, Gori and Enquist 2003, Turner et al. 2003c, Schussman 2006a). This is correlated to a decrease in fire frequency that is related to a reduction of fine fuels that carry fire because of extensive livestock grazing. Frequent, stand-replacing fire was likely a key ecological attribute prior to 1890 (Wright 1980, Bahre 1985, McPherson 1995, Kaib et al. 1996). All species of Quercus in these stands resprout profusely after fire (McPherson 1992). More study is needed to understand the effects of altered fire regimes on the vegetation.
Environmental Description:  This alliance is found on rocky slopes in canyons and mountains in western Texas, southern New Mexico, southeastern Arizona and northern Mexico. Climate is semi-arid with hot summers and periods of cold weather in the winters with the possibility of snow. Mean annual precipitation is approximately 48 cm, but is highly variable with drought years not uncommon. Typically, one-third of the annual precipitation occurs in late winter and two-thirds in July through October, often as high-intensity convective storms during monsoon season. May through June is droughty with no precipitation. Stands occur in canyon and valley bottoms, gently to moderately sloping alluvial plains and fans, draws, and on colluvial mountain slopes where deep subsurface moisture is available to support the trees. One stand described by Bourgeron et al. (1993b) occurs at the edge of a playa. Sites are nearly flat to moderately steep (3-30%), but slopes may reach 80% in some rocky mountain slopes. Soil and parent material are highly variable, but soils are often silty, sandy, gravelly or cobbly loam derived from andesite, quartz monzonite, rhyolite, granite, alluvium or colluvium. Adjacent vegetation at higher elevations is often woodlands or forests dominated by Juniperus deppeana, Pinus discolor, or Pinus edulis. Near riparian areas, Juglans major forests are adjacent to the Quercus emoryi woodlands. At lower elevations, shrub or tree savannas or shrublands dominated by some of the species mentioned above are adjacent.
Geographic Range: Woodlands included in this alliance occur in the mountains of southern Trans-Pecos Texas, New Mexico, and southeastern Arizona. It may also be found in the Mexican states of Chihuahua, Coahuila, and Sonora.

Nations: MX,US

States/Provinces:  AZ, MXCHH, MXCOA, MXSON, NM, TX


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.1 Warm Temperate Forest & Woodland Formation F018 1.B.1
Division 1.B.1.Nd Madrean-Balconian Forest & Woodland Division D060 1.B.1.Nd
Macrogroup 1.B.1.Nd.1 Alligator Juniper - Mexican Pinyon - Arizona White Oak Madrean Lowland Evergreen Woodland Macrogroup M010 1.B.1.Nd.1
Group 1.B.1.Nd.1.a Arizona White Oak - Emory Oak - Mexican Blue Oak Woodland Group G201 1.B.1.Nd.1.a
Alliance A3101 Arizona White Oak - Emory Oak - Gray Oak Scrub Woodland Alliance A3101 1.B.1.Nd.1.a
Association CEGL000680 Arizona White Oak / Sideoats Grama Scrub Woodland CEGL000680 1.B.1.Nd.1.a
Association CEGL000681 Arizona White Oak / Bullgrass Scrub Woodland CEGL000681 1.B.1.Nd.1.a
Association CEGL000682 Emory Oak / Pointleaf Manzanita Scrub Woodland CEGL000682 1.B.1.Nd.1.a
Association CEGL000683 Emory Oak / Sideoats Grama Scrub Woodland CEGL000683 1.B.1.Nd.1.a
Association CEGL000684 Emory Oak / Common Sotol Scrub Woodland CEGL000684 1.B.1.Nd.1.a
Association CEGL000685 Emory Oak / Bullgrass Scrub Woodland CEGL000685 1.B.1.Nd.1.a
Association CEGL000686 Emory Oak / Pinyon Speargrass Scrub Woodland CEGL000686 1.B.1.Nd.1.a
Association CEGL000687 Emory Oak / Texas Bluestem Scrub Woodland CEGL000687 1.B.1.Nd.1.a
Association CEGL000688 Emory Oak / Mesa Dropseed Scrub Woodland CEGL000688 1.B.1.Nd.1.a
Association CEGL000689 Gray Oak / Sideoats Grama Scrub Woodland CEGL000689 1.B.1.Nd.1.a
Association CEGL000690 Gray Oak / Alderleaf Mountain-mahogany Scrub Woodland CEGL000690 1.B.1.Nd.1.a
Association CEGL000691 Gray Oak / Skunkbush Sumac Scrub Woodland CEGL000691 1.B.1.Nd.1.a
Association CEGL000975 Toumey Oak / Sideoats Grama Scrub CEGL000975 1.B.1.Nd.1.a
Association CEGL000976 Toumey Oak / Bullgrass Scrub CEGL000976 1.B.1.Nd.1.a
Association CEGL003521 Gray Oak / Alligator Juniper Scrub Woodland CEGL003521 1.B.1.Nd.1.a
Concept Lineage: New alliance combines 3 old alliances and clarifies the broad concept from open scrub woodland to moderately dense woodland (and savanna). These Madrean oak species often co-occur and may codominate some stands. Old Alliance II.A.2.N.a. Quercus arizonica Woodland Alliance (A.482), Old Alliance II.A.2.N.a. Quercus emoryi Woodland Alliance (A.483), Old Alliance II.A.2.N.a. Quercus grisea Woodland Alliance (A.478).

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: < 123.31 Encinal (Oak) Series in the Madrean Evergreen Forest and Woodland Biome * (Brown et al. 1979) [A group-level concept that is nearly equivalent although it includes Quercus oblongifolia and other oaks common in Mexico.]
> Quercus arizonica / Rhus trilobata Habitat Type (Bassett et al. 1987) [includes Quercus grisea and its hybrids to Q. arizonica. Relationship uncertain.]
> Quercus toumeyi / Muhlenbergia emersleyi PA (Bourgeron et al. 1995a)
> IB3a. Gray Oak Woodland (Allard 1990) [relationship uncertain]
> IB3e. Emory Oak Woodland (Allard 1990)
Concept Author(s): D.E. Brown, C.H. Lowe and C.P. Pase (1979)

Author of Description: K.A. Schulz

Acknowledgements: No Data Available

Version Date: 01-08-14
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