Invalid Unit Specified
G288 Larrea tridentata - Flourensia cernua - Acacia neovernicosa Chihuahuan Mixed Desert Scrub Group

The U.S. National
Vegetation Classification
Type Concept Sentence: This desert scrub group forms the extensive desert scrub that occurs in the broad desert basins and plains extending up onto dissected gravelly alluvial fans and piedmonts and foothills in the Chihuahuan Desert and is characterized by a moderate to sparse shrub layer (<10% cover on extremely xeric sites) that is dominated by Larrea tridentata sometimes with other species such as Acacia constricta, Acacia neovernicosa, Agave lechuguilla, Bernardia obovata, Dasylirion leiophyllum, Flourensia cernua, Fouquieria splendens, Lycium spp., Mimosa aculeaticarpa var. biuncifera, Mortonia scabrella, Opuntia engelmannii, Parthenium incanum, Viguiera stenoloba, and Yucca spp.
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Common (Translated Scientific) Name: Creosotebush - American Tarwort - Viscid Acacia Chihuahuan Mixed Desert Scrub Group
Colloquial Name: Chihuahuan Creosotebush - Mixed Desert Scrub
Hierarchy Level: Group
Type Concept: This group is the extensive desert scrub that occurs in the broad desert basins and plains extending up onto dissected gravelly alluvial fans and piedmonts (bajadas), and foothills in the Chihuahuan Desert below the chaparral zone. The vegetation has a moderate to sparse shrub layer (<10% cover on extremely xeric sites). Larrea tridentata is the most common dominant, often covering entire landscapes in near monotypic stands. Stands can also be codominated or dominated by a mix of thornscrub or other desert scrub species such as Agave lechuguilla, Bernardia obovata, Dasylirion leiophyllum, Flourensia cernua, Fouquieria splendens, Lycium spp., Mimosa aculeaticarpa var. biuncifera, Mortonia scabrella, Opuntia engelmannii, Parthenium incanum, Rhus microphylla (in ephemeral washes), Viguiera stenoloba, and Yucca spp. Stands of thornscrub dominated by Acacia constricta or Acacia neovernicosa are included in this group, and can be especially prolific on limestone substrates (but not always). If present, Prosopis glandulosa does not dominate the shrub layer, but may codominate in a mixed stand with Larrea tridentata. Grasses are common but generally have lower cover than shrubs. Common species may include Bouteloua eriopoda, Bouteloua ramosa, Dasyochloa pulchella, Muhlenbergia porteri, Pleuraphis mutica, and Scleropogon brevifolius. Some shrublands have a sparse understory, sometimes with a pebbly desert pavement on the soil surface. It has recently expanded into former desert grasslands in the northern portion of its range. Substrates are typically coarse-textured loams on gravelly plains and slopes. Soils are alluvial, typically non-saline, and frequently calcareous, sometimes with a petrocalic layer and are often derived from limestone and, to a lesser degree, igneous rocks. Stands can extend upslope on to colluvial slopes with cobbly skeletal soils.
Diagnostic Characteristics: The moderate to sparse shrub layer is typically strongly dominated or codominated by Larrea tridentata, often with Flourensia cernua. Other desert scrubs may dominate some stands, but Larrea tridentata is usually present. This group also includes thornscrub dominated by Acacia constricta, Acacia neovernicosa, and Acacia greggii.
Rationale for Nominal Species or Physiognomic Features: Larrea tridentata is listed as the typical dominant species mixed with a variety of Chihuahuan Desert indicator species. Flourensia cernua is added as frequent codominant, but listing other species from the many possible indicator species that may or may not be present would be misleading, especially Acacia spp. that are generally absent except where they dominate.
Classification Comments: This broadly defined group forms the matrix vegetation of the Chihuahuan Desert.
Similar NVC Types:
G490 Chihuahuan Desert Foothill-Piedmont & Lower Montane Grassland, note:
G819 North American Warm Desert Ruderal Scrub, note:
Physiognomy and Structure: The vegetation has a moderate to sparse (<10% cover on extremely xeric sites), xeromorphic evergreen short-shrub layer (<2 m tall). Understory dwarf-shrub and herbaceous layers and emergent tall shrubs may be absent or present.
Floristics: This Chihuahuan Desert scrub group has a moderate to sparse shrub layer (<10% cover on extremely xeric sites). Larrea tridentata is the most common dominant, often covering entire landscapes in near monotypic stands. Stands can also be codominated or dominated by a mix of thornscrub or other desert scrub species such asAgave lechuguilla, Aloysia wrightii, Baccharis pteronioides, Bernardia obovata, Dasylirion leiophyllum, Fouquieria splendens, Jatropha dioica, Koeberlinia spinosa, Krameria erecta, Leucophyllum minus, Lycium spp., Mimosa aculeaticarpa var. biuncifera, Mortonia scabrella (= Mortonia sempervirens ssp. scabrella), Opuntia engelmannii, Parthenium incanum, Rhus microphylla (in ephemeral washes), Viguiera stenoloba, and Yucca spp. (Brown 1982b, MacMahon and Wagner 1985, Henrickson and Johnston 1986, MacMahon 1988, Dick-Peddie 1993). In the southern Chihuahuan Desert, stands are dominated by Larrea tridentata with Agave parryi (= Agave scabra), Cylindropuntia kleiniae (= Opuntia kleiniae), Cylindropuntia imbricata (= Opuntia imbricata), and Yucca filifera (Huerta-Martínez et al. 2004). Stands of thornscrub dominated by Acacia constricta, Acacia neovernicosa, or Acacia greggii are included in this group, and can be especially prolific on limestone substrates (but not always). If present, Prosopis glandulosa does not dominate the shrub layer, but may codominate in a mixed stand with Larrea tridentata. Grasses are common but generally have lower cover than shrubs. Common species may include Bouteloua curtipendula, Bouteloua eriopoda, Bouteloua gracilis, Bouteloua hirsuta, Bouteloua ramosa, Dasyochloa pulchella, Muhlenbergia porteri, Pleuraphis mutica, and Scleropogon brevifolius. Some shrublands have a sparse understory, sometimes with a pebbly desert pavement on the soil surface.
Dynamics: In the U.S., much of this scrubland is thought to be a result of recent expansion of Larrea tridentata into former desert grasslands and steppe in the last 150 years as a result of drought, overgrazing by livestock, and/or decreases in fire over the last 70-250 years (Buffington and Herbel 1965, Ahlstrand 1979, Donart 1984, Dick-Peddie 1993, Gibbens et al. 2005). This group includes vast areas of loamy plains that have been converted from Pleuraphis mutica and Bouteloua eriopoda desert grasslands to Larrea tridentata scrub. This group also includes invasive Flourensia cernua shrublands that occur in former (degraded) tobosa (Pleuraphis mutica) flats and loamy plains. Presence of Scleropogon brevifolius is common in these invasive stands. Dick-Peddie (1993) suggested that absence of Flourensia cernua as codominant and presence of Dasyochloa pulchella, Acourtia nana, and Yucca elata may be indicators of recent conversion of desert grasslands into desert scrub, but more research is needed. Conversely, sparse understory Larrea tridentata shrublands on remnant early Holocene erosional surfaces often with shallow calcareous soils and desert pavement may indicate pre-historic distributions of Larrea tridentata desert scrub in the Chihuahuan Desert (Stein and Ludwig 1979, Muldavin et al. 2000b).
Environmental Description: This group is the extensive desert scrub that occurs in the broad desert basins and plains extending up onto dissected gravelly alluvial fans and piedmonts (bajadas), and foothills in the Chihuahuan Desert below the chaparral zone. It has recently expanded into former desert grasslands in the northern portion of its range. Stands occur in flat to gently sloping desert basins and on alluvial plains to moderately steep piedmont slopes below the chaparral zone. Soil/substrate/hydrology: Substrates are typically coarse-textured loams on gravelly plains and slopes. Soils are alluvial, typically non-saline, and frequently calcareous, often with a petrocalic layer and derived from limestone, or to a lesser degree igneous rocks (Brown 1982b, MacMahon and Wagner 1985, Henrickson and Johnston 1986, MacMahon 1988, Dick-Peddie 1993). Stands can extend upslope on to colluvial slopes with cobbly skeletal soils.
Geographic Range: This desert scrub group forms the matrix vegetation in the in the Chihuahuan Desert.
Nations: MX, US
States/Provinces: AZ, MXCH, MXSO, NM, TX
US Forest Service Ecoregions (2007)
Domain Name:
Division Name:
Province Name: Southwest Plateau and Plains Dry Steppe and Shrub Province
Province Code: 315    Occurrence Status: Confident or certain
Section Name: White Mountains-San Francisco Peaks-Mogollon Rim Section
Section Code: M313A     Occurrence Status: Confident or certain
Omernik Ecoregions: 22:P, 22g:P, 22m:P, 23:P, 23a:P, 23b:P, 23c:P, 23e:P, 23f:P, 24:P, 24a:P, 24b:P, 24c:P, 24d:P, 24e:P, 24f:P, 24g:P, 24h:P, 25:P, 25j:P, 25k:P, 26:P, 26h:P, 26n:P, 26o:P, 26q:P, 30:P, 30d:P, 31:P, 31b:P, 79:P, 79a:P, 79b:P, 79c:P, 79e:P, 81:P, 81k:P, 81l:P
Plot Analysis Summary:
Confidence Level: Moderate
Confidence Level Comments:
Grank: GNR
Greasons:
Concept Lineage:
Predecessors:
Obsolete Names:
Obsolete Parents:
Synonomy: = Chihuahuan Desert Scrub (Larrea Scrub Phase) (Henrickson and Johnston 1986)
= Chihuahuan Desert Scrub (Mixed Desert Scrub Phase) (Henrickson and Johnston 1986)
= Chihuahuan Desertscrub, Creosotebush-Tarbush Series - 153.21 (Brown et al. 1979)
Concept Author(s): D.E. Brown, C.H. Lowe, and C.P. Pase (1979)
Author of Description: K.A. Schulz and E. Muldavin
Acknowledgements: E. Muldavin
Version Date: 05Nov2015
References:
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