dominance by Elymus lanceolatus as well as Pascopyrum smithii. Cooper et al. (1995) described an 

 A. tridentata ssp. tridentata / Pascopyrum smithii community confined to alluvial fans and terraces 

 in southwestern Montana which has a remarkable floristic similarity to our ARTTSW / ELYLAN 

 (PASSMI) plots. Heidel (1996) described an ^. tridentata ssp. wyomingensis/Pascopyrum smithii 

 type on upland breaks above the Missouri River in Fergus County (Heidel 1996). However, our plots 

 for this type in southeastern Montana have a much broader distribution across the landscape. The 

 differences in habitat occupied are reflected in the differing subspecies of big sagebrush. An 

 Artemisia tridentata/Elymus lanceolatus habitat type occupying shale derived clay soils was 

 described from the Yellow Triangle of Montana (Jorgensen 1979); both Elymus lanceolatus and 

 Pascopyrum smithii were indicated dominants, and, in contrast to our plots, Pseudoroegneria spicata 

 was common. Our plots of ARTTSW/PASSMI resemble, in most respects, descriptions oi Artemisia 

 tridentata/Pascopyrum smithii (ARTTRI/PASSMI) in the literature, and may be best considered a 

 local variation of that type. Numerous studies have documented ARTTRI/PASSMI communities 

 from eastern Montana (Culwell and Scow 1982, Culwell et al. 1986, DeVelice et al. 1995, Hansen 

 and Hoffman 1988, Northern Energy Resources Co. 1979, Olson-Elliot and Associates 1980), 

 western North Dakota (Hansen et al. 1984, Jensen et al. 1992), and eastern Wyoming (Thilenius et 

 al. 1995). The study by Jensen et al. (1992) designates Artemisia tridentata ssp. wyomingensis as the 

 dominant shrub in their type from western North Dakota. The ecological significance of big 

 sagebrush subspecies is demonstrated by differences between Artemisia tridentata ssp. 

 wyomingensis/Pascopyrum smithii communities (including our ARTTSW/ELYLAN) in eastern 

 Montana, which are climax plant associations usually occupying upland positions. They contrast 

 with Artemisia tridentata ssp. tridentata/Pascopyrum smithii communities of southwestern 

 Montana, most of which are thought to be grazing disclimaxes and are confined to alluvial terraces 

 (Cooper etal. 1995). 



Although vast acreages of ARTTSW/ELYLAN (PASSMI) in Carter County are severely impacted 

 by grazing, there are also large tracts of the community in good to excellent condition, especially in 

 remote locations. Changing demographics may be partially responsible for the abandonment of 

 remote rangelands, and their resulting recovery from past overgrazing. We have noted in the field 

 (locations usually remote or long rested from grazing), sampled one plot (JV0045) and observed in 

 the stand tables of Hansen and Hoffman (1988) and Jensen et al. (1992) that some stands have higher 

 cover (usually exceeding 5%) of Nasella viridula {Stipa viridula), concomitantly reduced coverages 

 ofBouteloua gracilis and soils that are slightly coarser textured (primarily loams) than the sites 

 which support modal examples of ARTTSW / ELYLAN (PASSMI). It should be noted both 

 studies cited above document the potential natural community type of ARTTSW / AGRSMI with 

 exclosure sites or sites long-rested from grazing. Jensen et al. (1992) document that in grazing- 

 impacted serai stages of ARTTSW / AGRSMI the cover of Stipa comata and B. gracilis increases, 

 that of P. smithii decreases and N. viridula sharply decreases and eventually is extinguished. We 

 suggest that quite possibly, on lighter-textured soils, such as silty alluvium, or on moister positions, a 

 plant association distinct fi-om ARTTSW / PASSMI (ELYLAN) be recognized as A. tridentata ssp. 

 wyomingensis / P. smithii - Nasella viridula. Within our study area so much of the landscape has 

 been grazing-impacted it is difficult to ascertain whether the any particular stand supporting higher 

 cover of A^. viridula reflects a condition of reduced grazing-impact or less stressful conditions in 

 regard to soil moisture. We have kept one plot separate in the Constancy/Cover Appendix (A) that 

 has appreciable cover of A^. viridula (column heading ARTTSW / PASM-NAVI ) so that it may be 

 compared to the modal condition for this type (ARTTSW / PASM (ELLA). 



41 



