Pascopyrum smithii (Elymus lanceolatus) - Nasella viridula Plant Association 



(syn. Agropyron smithii (A. dasystachyum) - Stipa viridula) 

 ELYLAN(PASSMI) / NASVIR; thick-spiked wheatgrass (western wheatgrass)/green needlegrass 



MTNHP rank: G4/S3 



Environment: ELYLAN (PASSMI)/ NASVIR is a distinctive but localized grassland type which 

 was sampled twice in the South Cottonwood/Duncan Creek drainage, where it occupies both 

 northerly and southerly aspect side slopes of low relief shale ridges in clayey range sites. This is not 

 a typical mesic side slope setting for it, so the surrounding features and their associations are 

 described for context. There are occasional eroded "blowouts" in the same area with little grass cover 

 and dominated by Eriogonum paucijlorum (ERIPAU). Downslope positions with alluvial soils have 

 higher grass cover (included in our description of ELYLAN). The eroded shale ridgetops (some with 

 bentonite cores) are dominated by Atriplex gardneri (ATRGAR/ELYLAN). There is little evidence 

 of recent grazing in these grasslands; the stand at Duncan Creek is within an allotment, which has 

 been ungrazed for 12 years or more (C. Fruit, pers. commun.). 



Vegetation: The plots have moderate cover dominated by the grasses Elymus lanceolatus (syn. 

 Agropyron dasystachyum), with about 30% cover, and Nasella (syn. Stipa) viridula, with about 10% 

 cover. Other grasses are limited to Oryzopsis hymenoides common in one plot and Muhlenbergia 

 cuspidata present in trace amount in the other. The shrub Gutierrezia sarothrae is present in both 

 plots. There is high diversity and distinctive assemblage of forbs (14 and 20 species in the plots) 

 with the following species constant: Aster falcatus, Cryptantha celosoides, Dalea Candida, 

 Eriogonum paucijlorum, Hymenoxys acaulis, Phlox hoodii, Senecio canus, and Tragopogon dubius. 

 The selenium indicators Astragalus racemosus (a BLM Watch species) and Stanleya pinnata were 

 found in one plot and were observed in nearby similar habitat outside of the other plot. 



Soils: Presence of selenium at these sites is indicated by species which require high selenium in soil, 

 and their associated smell. 



Comments: Relict grasslands dominated by Elymus lanceolatus or Pascopyrum smithii with an 

 important component of Nasella (Stipa) viridula were described from southwestern North Dakota 

 (Whitman 1979) and Saskatchewan (Coupland 1961). The latter report, and a relict area report 

 (Quinnild and Cosby 1959) note the difficulty of distinguishing between Elymus lanceolatus and 

 Pascopyrum smithii, especially in vegetative condition, but none the less, document their occurrence 

 and relative abundance in communities and suggest causal mechanisms. Coupland states that Elymus 

 lanceolatus is more abundant on cooler, fmer-textured soils, while Pascopyrum smithii is more 

 abundant on warmer, sandier soils and on disturbed soils, and that this adaptation is reflected in the 

 geographical distribution of their community types, with Elymus lanceolatus types becoming less 

 common to the south. Quinnild and Cosby documented communities dominated by each species on 

 ungrazed butte tops, and suggested that dominance of Elymus lanceolatus on one butte top reflected 



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