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Astragalus qilvif lorus . . . (threeleaved milk- 

 vetch) 

 Astragalus spatulatus . . . . (tufted milk-vetch) 

 Atriplex confertif olia . . . (shadscale) 



Bouteloua gracilis (blue grama) 



Calamovilfa longifolia . . . (prairie sandgrass) 

 Chrysothamnus nauseosus . . (common rabbit-brush) 



Comandra umbellata (bastard toad-flax) 



Cryptantha celosioides . . . (northern cryptantha) 

 Eriogonum paucif lorum . . . . (few flowered- 

 buckwheat) 



Festuca idahoensis (Idaho fescue) 



Gutierrezia sarothrae . . . . (broom snakeweed) 



Haplopappus acaulis (cushion goldenweed) 



Haplopappus armerioides . . (thrifty goldenweed) 

 Hymenopappus f ilifolius . . (Columbia cut-leaf) 



Juniperus scopulorum (Rocky Mountain 



juniper) 



Koeleria cristata (prairie junegrass) 



Linum perenne (blue flax) 



Musineon divaricatum (leafy musineon) 



Opuntia polyacantha (plains pricklypear) 



Oxytropis sericea (white locoweed) 



Phlox hoodii (Hood's phlox) 



Phlox alyssifolia (alyssum-leaved phlox) 



Pinus ponderosa (ponderosa pine) 



Poa secunda (Sandberg's bluegrass) 



Yucca glauca (soapwell) 



Zigadenus venenosus (meadow death-camus) 



Dominance and frequency of the taxon: In 



Montana, most populations are large, and range 

 from ca. 50 to 3,000 plants (mean ca. 1000). 

 The individual plants of a population are often 

 broadly dispersed across the landscape, and 

 therefore canopy coverage of this species is 

 often low. Population distribution appears to 

 be related to available substrate. 



Successional phenomena: Astragalus barrii 

 populations are associated with the harsh 

 edaphic and environmental conditions of 

 badlands areas. These areas receive limited 

 rainfall, and are subject to high light 

 intensities; thus, soil water evaporation is 

 high, and is probably a limiting factor in 

 plant establishment and survival. These types 

 of harsh sites are common habitats for species 

 in the genus Astragalus (Barneby 1964) . 



