other Studies. — This type has been described in Montana by 

 Mueggler and Stewart (1980). 



11. Atriplex nuttallii/Oryzopsis hymenoides Type 

 (ATRNUT/ORYHYM; Nuttall saltbush/Indian ricegrass; G3G4 S2?) 



Vegetation. — Total vegetation cover in this badlands type 

 seldom exceeds 5%. Characteristic species include Atriplex 

 nuttallii , Chrysothamnus nauseosus . and Oryzopsis hymenoides . 



Physical Setting. --The type occurs on steep badland sites at 

 elevations around 5000 feet. Bare soil cover totals at least 

 60% and most of the remaining ground cover is comprised of 

 coarse fragments. The soil surface is unstable because of a 

 lack of adequate vegetation cover and gully erosion is common. 



Parent materials are sedimentary rocks and soils are very 

 shallow and poorly developed. Soils range from not gravelly 

 to very gravelly and are non-calcareous. Textures are gener- 

 ally very fine (e.g., silty clay loams) and available water 

 holding capacity is low. 



Adjacent Communities. --Vegetation on adjacent more stable 

 soils include the Artemisia trident at a/ Agropyron spicatum type 

 on non-alkaline soils and the Sarcobatus verm icu la tus/ Agro- 

 pyron smithii type on alkaline soils. 



Other Studies. — This type has not previously been reported in 

 Montana but has been reported in Colorado and is listed as 

 questionably present in Oregon and Wyoming (Bourgeron and 

 Engelking 1991) . 



12 . Cercocarpus ledifolius/ Agropyron spicatum Type 

 (CERLED/AGRSPI ; mountain mahogany/bluebunch wheatgrass; G5 S4) 



Vegetation. -- Cercocarpus ledifolius is abundant and the domi- 

 nant vegetation feature of this community type. Agropyron 

 spicatum is the only other species that is always well repre- 

 sented with cover exceeding 5%. 



Physical Setting. --The type generally occurs on steep mass 

 wasted slopes at elevations between 7000 and 8000 feet. The 

 total cover of soil, gravel, and rock usually exceeds 50% and 

 the soil surface is unstable because of a lack of adequate 

 vegetation cover. 



Parent materials are predominantly limestone and soils 

 are generally Ustorthents and are shallow (lithic) and very 

 gravelly to very cobbly. Textures are mostly loams. The 

 soils exhibit violent effervescence. Available water holding 



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