Print Report
G489 Pleuraphis mutica - Sporobolus airoides - Panicum obtusum Semi-Desert Lowland Grassland Group
Type Concept Sentence: This lowland group is characterized by a moderately dense to dense graminoid layer of perennial grasses that are typically dominated by Panicum obtusum, Pleuraphis mutica, Sporobolus airoides, and/or Sporobolus wrightii occurring in mesic swales and depressions and along drainages across the Chihuahuan Desert and adjacent Sky Islands and Sonoran Desert, extending into limited areas of the southern Great Plains, generally on deep, fine-textured soils.
Common (Translated Scientific) Name: Tobosa Grass - Alkali Sacaton - Vine-mesquite Semi-Desert Lowland Grassland Group
Colloquial Name: Chihuahuan Semi-Desert Lowland Grassland
Hierarchy Level: Group
Type Concept: This is the common lowland grassland group that occurs in the northern Chihuahuan Desert, adjacent southwestern Great Plains, and Sky Islands west to the Sonoran Desert. Vegetation in this group is characterized by a moderately dense to dense graminoid layer of perennial grasses that is typically dominated by Pleuraphis mutica and/or Sporobolus airoides with Panicum obtusum often present. Dense stands can occur in mesic swales and depressions and along drainages, where Sporobolus wrightii and Pleuraphis mutica (tobosa swales) dominate, sometimes with other mesic graminoids such as Pascopyrum smithii, Panicum hallii, Panicum hirsutum, or Panicum obtusum. Sporobolus airoides is more common in alkaline soils. In degraded stands, Scleropogon brevifolius or Aristida spp. may codominate. Bouteloua gracilis or Bouteloua dactyloides may become important in northern stands transitioning into the Great Plains and on degraded stands. Scattered shrub or succulent species may be present, especially on degraded sites and along drainages and in depressions. Stands are found on alluvial flats, loamy plains and basins, sometimes extending up into lower piedmont slopes and on broad mesas. This group includes mesic grasslands that occur in relatively small depressions or swales and along drainages that receive runoff from adjacent areas. Occupying low topographic positions, these sites generally have deep, fine-textured soils that are neutral to slightly or moderately saline/alkaline.
Diagnostic Characteristics: This group is characterized by a moderately dense to dense graminoid layer dominated by perennial grasses. Dominant species are Pleuraphis mutica and /or Sporobolus airoides often with Panicum obtusum present. Bouteloua gracilis may codominate on broad alluvial plains and flats in northern transition areas. In mesic swales and depressions and along drainages, Sporobolus wrightii or other mesic graminoids such as Pascopyrum smithii or Panicum obtusum may be codominant or sometimes dominant. Scattered shrubs and succulents may be present, but do not have higher cover than perennial grasses.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: This grassland group grades into ~Chihuahuan Desert Foothill-Piedmont & Lower Montane Grassland Group (G490)$$ in the foothills and piedmont desert grasslands and into ~Great Plains Shortgrass Prairie Group (G144)$$ in similar loamy plains land positions in the Great Plains where Bouteloua gracilis, Bouteloua dactyloides, or Pleuraphis jamesii are dominant grasses.
NRCS Ecological Site Description MLRA 42 SD-2 Loamy Ecological Site (NRCS 2006) describes this group on the Jornada Experimental Range with State-and-Transition Model showing shifts in species composition with land use. Degraded stands often have scattered desert scrubs such as Larrea tridentata, Flourensia cernua, and Prosopis glandulosa present.
NRCS Ecological Site Description MLRA 42 SD-2 Loamy Ecological Site (NRCS 2006) describes this group on the Jornada Experimental Range with State-and-Transition Model showing shifts in species composition with land use. Degraded stands often have scattered desert scrubs such as Larrea tridentata, Flourensia cernua, and Prosopis glandulosa present.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This group is characterized by a moderately dense to dense herbaceous layer dominated by perennial grasses, sometimes with scattered shrub and succulent species present with low cover.
Floristics: This group is characterized by a moderately dense to dense graminoid layer dominated by perennial grasses. Dominant grasses are Pleuraphis mutica and/or Sporobolus airoides with Panicum obtusum often present. In mesic swales and depressions and along drainages, Sporobolus airoides, Sporobolus wrightii, Schizachyrium scoparium var. scoparium, and Pleuraphis mutica (tobosa swales) dominate, sometimes with other mesic graminoids such as Pascopyrum smithii, Panicum hallii, Panicum hirsutum, or Panicum obtusum. Sporobolus airoides is often associated with more alkaline (to gypsic), poorly drained areas and Sporobolus wrightii with less alkaline, better drained areas. If present, Distichlis spicata, Allenrolfea occidentalis, and Suaeda spp. are characteristic of more saline and alkaline sites. In degraded stands, Scleropogon brevifolius or Aristida spp. may codominate (Brown et al. 1979, Brown 1982a, Brown 1982c, Muldavin et al. 2000b, 2013b). In northern and transitional areas with the Great Plains, Bouteloua gracilis or Bouteloua dactyloides (= Buchloe dactyloides) may become important (Muldavin et al. 2000b, 2013b). With tobosa swales, sand-adapted species such as Yucca elata may grow at the swale''s edge in the deep sandy alluvium that is deposited there from upland slopes (Dick-Peddie 1993). In degraded stands, Scleropogon brevifolius or Aristida spp. may codominate. Scattered shrubs such as Atriplex canescens, Ephedra torreyana, Ericameria nauseosa, Fallugia paradoxa, Flourensia cernua, Gutierrezia sarothrae, Krascheninnikovia lanata, Larrea tridentata, Cylindropuntia imbricata (= Opuntia imbricata), Prosopis glandulosa, Rhus microphylla, and Yucca spp. may be present, especially on degraded sites and along drainages and in depressions.
Dynamics: Impermeable caliche and argillic horizons are common on these sites. These layers restrict deep percolation of soil water and may favor the shallower rooted grasses over more deeply rooted shrubs like Larrea tridentata and Prosopis spp. (McAuliffe 1995). Pleuraphis mutica is relatively tolerant of livestock grazing. In west-central Arizona, livestock have nearly eliminated all native grasses except Pleuraphis mutica from semi-desert grassland (Brown 1982a). Stands codominated by Scleropogon brevifolius are characteristic of sites with past heavy grazing by livestock (Whitfield and Anderson 1938).
Environmental Description: This group occurs in the northern Chihuahuan Desert and adjacent Sky Islands and Sonoran Desert, extending into limited areas of the southern Great Plains on alluvial flats, loamy plains and basins sometimes extending up into lower piedmont slopes and on broad mesas. Included in this group are the mesic grasslands that occur in relatively small depressions or swales and along drainages that receive runoff from adjacent areas. Occupying low topographic positions, these sites generally have deep, fine-textured soils (loams or clay loams) that are neutral to slightly or moderately saline/alkaline. During summer rainfall events, precipitation generally does not rapidly run off and ponding is common in depressions on the typically flat or gently sloping sites. Sites may be relatively mesic if they receive runoff from adjacent areas.
Geographic Range: This grassland group is found from the northern to central Chihuahuan Desert and extends into Trans-Pecos Texas, north into the southwestern Great Plains and extends into southeastern Arizona. Stands are described from Jornada del Muerto Basin, Marfa grasslands and Marathon Basin, south to central Chihuahua and Coahuila, Mexico.
Nations: MX,US
States/Provinces: AZ, CO, MXCHH, MXCOA, MXSON, MXTAM, NM, TX
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.837734
Confidence Level: Low
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
| Type | Name | Database Code | Classification Code |
|---|---|---|---|
| Class | 3 Desert & Semi-Desert Class | C03 | 3 |
| Subclass | 3.A Warm Desert & Semi-Desert Woodland, Scrub & Grassland Subclass | S06 | 3.A |
| Formation | 3.A.2 Warm Desert & Semi-Desert Scrub & Grassland Formation | F015 | 3.A.2 |
| Division | 3.A.2.Na North American Warm Desert Scrub & Grassland Division | D039 | 3.A.2.Na |
| Macrogroup | 3.A.2.Na.3 Black Grama - Bullgrass - Tobosa Grass Chihuahuan Semi-Desert Grassland Macrogroup | M087 | 3.A.2.Na.3 |
| Group | 3.A.2.Na.3.d Tobosa Grass - Alkali Sacaton - Vine-mesquite Semi-Desert Lowland Grassland Group | G489 | 3.A.2.Na.3.d |
| Alliance | A3185 Tobosa Grass Lowland Desert Grassland Alliance | A3185 | 3.A.2.Na.3.d |
| Alliance | A3186 Alkali Sacaton - Big Sacaton - Vine-mesquite Lowland Desert Grassland Alliance | A3186 | 3.A.2.Na.3.d |
Concept Lineage: No Data Available
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: = Alkali Sacaton - Tobosagrass (701) (Shiflet 1994)
= Tobosa Grass - Scrub Series - 143.12 (Brown et al. 1979)
= Tobosa Grass - Scrub Series - 143.12 (Brown et al. 1979)
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- NHNM [Natural Heritage New Mexico]. No date. Unpublished data on file. Natural Heritage New Mexico, University of New Mexico, Albuquerque.
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