not describe this type for the Bighorn Canyon NRA; however, it is 

 described for Wyoming (Bourgeron and Engelking 1992). 



Natural Heritage Program Rank- G3/S3 



19. Artemisia pedatif ida - Atriplex nuttallii c.t. 



(ARTPED-ATRNUT; birdfoot sagebrush-Gardner saltbush) 



(9 Stands) 



Environment- ARTPED-ATRNUT is common on alluvial fans and 

 terraces and occasionally moderate slopes at 4,100 to 5,000 feet 

 in the outwash plains. It is most common in the south and west 

 portions of our study area. In adjacent sites v/ith less saline 

 soils Aqropyron spicatum rather than Atriplex nuttallii is 

 codominant. Somewhat better-drained soils are dominated by 

 Artemisia tridentata and Aqropyron smithii . Sarcobatus 

 vermiculatus may also be common on adjacent sites. 



Vegetation- Typically this type has a moderate cover of low 

 shrubs with sparse grass and forb components. Both Artemisia 

 pedatif ida and Atriplex nuttallii were present in all stands with 

 mean canopy covers of 33% and 9% respectively. Artemisia 

 tridentata was common in ca. 1/3 of the stands. Poa sandbergii 

 and Aqropyron spicatum each occurred in ca. half of the stands 

 with mean cover of 20% and 3% respectively. Aqropyron smithii 

 and Poa juncif olia are common in some stands. Forbs are poorly 

 represented. Allium textile , Musineon divaricatum and 

 Platyschkurhia inteqrifolia are present in most stands, and 

 Opuntia polyacantha and Vicia americana are common in some plots. 

 Bryophytes and lichens are present but uncommon. 



Soils- ARTPED-ATRNUT occurs on deep soils derived from shales and 

 clays interbedded with sandstone. Coarse fragments and gravels 

 are absent, and surface texture varies from silt-loam to clay. 

 The soil subgroup at all three soil characterization sites was 

 Ustic Torriorthent . pH varied from 7.2 to 9.0, and conductivity 

 ranged from 205 to 489 uhmos/cm- (3 stands) . 



Other Studies- Kratz (1988) probably includes this community in 

 his Artemisia pedatif ida / Aqropyron spicatum type described from 

 the same area. Knight et al. (1987) do not describe this type 

 for the Bighorn Canyon NRA, and it has not been described 

 elsewhere (Bourgeron and Engelking 1992). 



Natural Heritage Program Rank- G2/S2 



23 



