Pascopyrum smithii (Elymus lanceolatus) Plant Association 



syn. Agropyron smithii (Agropyron dasystachyum) 



ELYLAN (PAS SMI); thick-spiked wheatgrass (western wheatgrass) 



MTNHP rank: G3G5/S4 



Environment: This is a major plant association throughout Carter County and is the predominant 

 grassland association of BLM lands in the southern part. It occurs on fine textured soils derived 

 from shale parent materials, most commonly on lower slopes of rolling hills and along intermittent 

 drainages. As here described, the association generally occurs in mesic (water collecting) 

 topographic positions, and a small fraction may qualify as jurisdictional wetlands. It is perhaps most 

 consistently found as a clayey range site, but is also found on shallow clay, overflow, silty, and other 

 range sites. Floodplain examples of the type are seasonally flooded in most years and may be 

 flooded intermittently after summer storms. 



Vegetation: This association is characterized by high cover (70-90% in the plots) of the 

 rhizomatous wheatgrasses, Elymus lanceolatus and/or Pascopyrum smithii. Elymus lanceolatus was 

 the species identified in our 4 plots and is probably the more common in southern Carter County, but 

 the two species may grow intermixed and are difficult to distinguish, especially in vegetative 

 condition. We have chose to include communities with either grass dominant in the same plant 

 association, due to the difficulty of distinguishing the two species, the possibility of hybridization 

 (Great Plains Flora Association 1986), and their apparently overlapping ecological distributions. We 

 refer to the type by the more widely-recognized name, PASSMI, pending taxonomic and community 

 classification review. 



Under good range condition, other grasses are poorly represented, but Stipa viridula was present in 

 trace amounts in all plots (see description of ELYLAN - STIVIR for stands with Stipa viridula well 

 represented). Most stands have been invaded by the exotic annual grasses Bromus japonicus or B. 

 tectorum. These species are abundant in poor condition upland examples of this type, and the exotic 

 rhizomatous grass Poa pratensis is abundant in floodplain stands. Waif shrubs {Artemisia tridentata 

 ssp. wyomingensis, Sarcobatus vermiculatus) from surrounding communities occur in many stands, 

 and the low shrub Rosa arkansana had 30% cover in one plot within a tall exclosure (but much 

 lower cover outside). Forb diversity is relatively low (18 species in 4 plots), but the alien hdelilotus 

 officinalis had about 20% cover in the plot within an exclosure (less cover outside), and Helianthus 

 maximiliani had about 30% cover in a floodplain plot. Forbs with high constancy (75%) were 

 Achillea millefolium, Aster falcatus, Thermopsis rhombifolia, Tragopogon dubius, and Vicia 

 americana. 



Bottomland stands often grade to greasewood communities (SARVER/ELYLAN) and upland stands 

 often grade to sagebrush steppe (ARTTSW/ELYLAN) but the controlling factors among these types 

 are not always clear. 



Soils: Soils are "heavy", primarily clays and silty clays rated as nonsaline and just verging into the 

 alkaline range ( defined as pH 8.5-10), judging by their high pH values (see inset below), though we 

 have no exchangeable sodium data for confirmation. 



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