The grass Koeleria macrantha is 100 % constant in our plots. The grasses Poa secunda and Stipa 

 viridula have greater than 50% constancy, though S. viridula did not occur in greater than trace 

 amounts. Although an attempt was made to sample stands in good condition, the annual exotic grass 

 Bromusjaponicus was found in all but one plot; in degraded examples of the type this weed often 

 surpasses Elymus lanceolatus or Pascopyrum smithii in cover. Cover and diversity of forbs is quite 

 low; Achillea millefolium, which occurred in all but one plot, is the only forb with higher than 50% 

 constancy. The soil lichen, Parmelia chlorochroa, which is favored by grazing (MacCracken, 

 Alexander, and Uresk 1983), occurred in all but one plot. 



Adjacent plant communities are primarily grasslands, most commonly dominated by Elymus 

 lanceolatus, but also include shrublands dominated by Sarcobatus vermiculatus. There are all 

 degrees of ecotone width, though often it is broad (> 30 ft.) between these shrub-dominated and 

 grass-dominated sites with no obvious difference in controlling variables. Fire and herbicide 

 spraying generally create abrupt ecotones but evidence of fire is difficult to spot when fires bum hot 

 and consume all shrub biomass to the point of dishing out the stem base to below the ground line 

 (occurs in years of high biomass/ftiels production). A. tridentata ssp. wyomingensis has been noted 

 as being strongly positively associated with medium to heavy soils in southeastern Montana and the 

 Dakotas and absent on coarse-textured soils (Johnson 1979) however, our limited soils data show 

 complete overlap ofE. lanceolatus- (or Pascopyrum smithii) dominated communities with 

 ARTTSW/ELYLAN, so far as textural class is concerned. 



Soils: Parent materials are principally shales and mudstones but this community type occurs as well 

 on alluvium and sandstone, if there is a compensating factor such as shallow depth to bedrock, which 

 perches water within reach of grass roots. Soil reaction is consistently mildly basic (exception plot 

 19) and conductivities are mostly low with the exception of plots 27 and 38 ; there is no ready 

 explanation for these anomalous values. Soil texture is typically heavy with the silty clay class 

 probably predominant but sandstones will weather to loams and silt loams. 



Comments: It is possible that the potential vegetation type for many of the alluvial sites supporting 

 this association is actually ARTTSW/ELYLAN-NASVIR but that concentrated livestock use 

 reduced the high canopy cover of Nasella viridula (syn. Stipa viridula). Although this plant 

 association is abundant in Carter County, it has never been described from eastern Montana under 

 the name here assigned, which specifies a combination of subspecies of sagebrush with potential for 



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