Common (Translated Scientific) Name: American Tarwort / Tobosa Grass Shrubland

Colloquial Name: No Data Available

Hierarchy Level:  Association

Type Concept: On White Sands Missile Range, New Mexico, this is a major community in the Jornada Del Muerto and Tularosa basins. This type predominantly occurs in swales or broad drainages along lower alluvial plains and basin bottoms, at elevations of 1160 to 2040 m (3800-6700 feet). Generally, slopes are flat to very gentle. Soils are derived from alluvial deposits from the surrounding mountains. Typically, coarse materials are absent from soil surfaces. Ground surfaces are characterized by patches of bare soil and scattered litter. Surface soils range from silty loam to silty clays. This community has a shrub layer dominated by Flourensia cernua with an understory dominated by Pleuraphis mutica. The shrub layer has a moderately open canopy and is evenly spaced across the landscape. Diversity is generally low with Larrea tridentata, Prosopis glandulosa, Lycium berlandieri, and Atriplex canescens common associates. The grassy understory is generally well-represented to luxuriant, but can be patchy in some areas. Overall, the grass layer is moderately diverse and is occupied by large patches of Pleuraphis mutica and intermittent patches of Scleropogon brevifolius. Other common associates include Bouteloua gracilis, Muhlenbergia porteri, and Sporobolus airoides. The forb layer is poorly represented and scattered, growing on both barren patches and within the grasses. Acourtia nana, Solanum elaeagnifolium, Euphorbia dentata, and Phemeranthus aurantiacus are some of the forbs found in this diverse layer. An Atriplex canescens phase may occur, primarily in the southern Tularosa basin.

Diagnostic Characteristics: No Data Available

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: Stands of this type are generally large and continuous over flats but become patchy when limited to swales or broad drainages. While Flourensia cernua dominates this type, the understory codominants may vary from Sporobolus airoides to Scleropogon brevifolius. At least some of these stands are probably remnants of historic Pleuraphis mutica or Sporobolus airoides grasslands invaded by Flourensia cernua during this century (Buffington and Herbel 1965). Chihuahuan shrublands dominated by Larrea tridentata or Prosopis glandulosa generally occur upslope. Lower elevations grade into lowland grassland communities such as Tobosagrass/Alkali Sacaton PA (Muldavin et al. 2000b) or ~Sporobolus airoides - Scleropogon brevifolius Grassland (CEGL001692)$$. Although Flourensia cernua and Pleuraphis mutica have similar habitat requirements (depositional, fine soils), Flourensia cernua cannot establish in a closed grass canopy, but quickly colonizes openings as it has more motile seed than Pleuraphis mutica (Buffington and Herbel 1965, Montana et al. 1995). Flourensia cernua competes strongly with Pleuraphis mutica for water and as a result more bare soil patches are created around Flourensia cernua shrubs (Montana et al. 1995). Less grass cover decreases water infiltration that leads to drier soils (Wood et al. 1987). Larrea tridentata, an occasional associate with Flourensia cernua in this community, is not limited by dry soil conditions because it exploits deeper water sources than either Flourensia cernua or Pleuraphis mutica (Buffington and Herbel 1965, Stein and Ludwig 1979, Montana et al. 1995).

Similar NVC Types: No Data Available

note: No Data Available