E. HABITAT 



1. ASSOCIATED VEGETATION: Vegetation associated with this species 

 in the Sweetgrass Hills represents Potentilla fruticosa - Festuca 

 idahonis association with codominance or major cover 

 contributions by Agropyron dasystachyum and Stipa comata . Other 

 common species at the site include Oxytropis sericea , Agropyron 

 spicatum , Cerastium arvense, Galium boreale , Potentilla fruticosa 

 and Artemisia frigida . 



Associated vegetation at both Sweetgrass Hills sites includes a 

 conspicuous display of species which increase under grazing 

 pressure, such as Oxytropis sericea and Cerastium arvense (Figure 

 5) . Both Sweetgrass Hills sites, including the undisturbed site, 

 are located along vehicle routes (Figure 6) . This is suggestive 

 that while Halimolobos virgata presence may be positively 

 correlated with increaser species and with disturbance regimes, 

 it is infrequent and inconsistently found under these conditions, 

 signifying low habitat fidelity. 



The Tendoy Mountains sites are in localized areas of woody steppe 

 or scrub communities. Associated species in the Limekiln Canyon 

 site are Artemisia tridentata , Agropyron spicatum , Chrysothamnus 

 viscidif lorus and Arabis holboelii as well as disturbance 

 species. ^ Associated species in the Pileup Canyon site are 

 Cercocarpus ledifolius , Artemisia tripartita , Festuca idahonis , 

 Poa pratensis , Poa nevadensis , Juncus balticus . Iris 

 missouriensis , and Antennaria microphylla . The site at the 

 south end of the Pioneer Mountains has limited information on 

 associated vegetation. Species associates mentioned on the 

 collection label include Agropyron spicatum and Koeleria 

 cristata . 



Most of the Halimolobos virgata specimens collected in Wyoming 

 and reviewed by Walter Fertig in the Rocky Mountain Herbarium 

 "have limited habitat data, but they seem to reflect a wide range 

 of habitats, with habitat descriptions including "greasewood" , 

 "rolling sagebrush plains and rocky slopes", "rocky flats", 

 "ravine below limber pine slopes", "limestone outcrops and grassy 

 slopes", "dry, clayey soil", "roadside weed", "slightly alkaline 

 flats" and "open slopes and ridges and badlands, sandstone and 

 shales" (Fertig pers. commun.). 



2. TOPOGRAPHY: Most Montana sites are on gentle topography in a 

 foothills setting, but at least one site, in Pileup Canyon of 

 Beaverhead County, is in a terrace bottom setting which is moist 

 in the spring. The other Tendoy Mts. site in Limekiln Canyon is 

 a droughty upper slope setting, though the plants are growing 

 under partial shade. The Sweetgrass Hills population above Sage 

 Creek is on an open sandstone bench above the valley (Figure 5) . 



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