Some minor members of this community type are Co mandra umbellata . 

 Echinacea pallida , Eriogonum pauciflorum , Gaura coccinea , Petalostemon s pp. , 

 Liatris punctata , and Yucca glauca . 



Juniperus horizontal is/Andropogon scoparius-Aqropyron spicatum Com - 

 munity Type (Juho/Ansc-Aqsp c.t. ). The Juho/Ansc-Aqsp c.t. is frequently 

 found on cool aspects of scoria hills and also in badlands, but not bad- 

 lands of the Bear Paw formation. J. horizontal is can also be found in 

 coulees on light soils. Livestock use is light, but deer browse on the 

 juniper. J^. horizontalis can be an important species in prevention of 

 erosion on steep slopes. 



This type and the Ansc-Agsp c.t. are dominant on scoria hills. Yucca 

 glauca is occasionally a dominant on warm aspects. Ribes cereum is some- 

 times found on outcrops. 



Hanson and Whitman (1938) observed a Mentzelia decapetala *- Juniperus 

 horizontalis type on scoria buttes and identified the grass dominants as 

 Agropyron spicatum and Muhlenbergia cuspidata . with a number of shrubs also 

 occurring on the scoria buttes. The authors suggested that as the scoria 

 buttes weathered into scoria hills, grasses would become more abundant while 

 shrubs would decrease. 



J^. horizontalis has a definitely contagious population dispersion. A. 

 spicatum is most often found interspersed with juniper, and Aiiiropoqon 

 scoparius is usually the dominant grass in areas not containing juniper, 

 J. horizontalis apparently hybridizes with J. scopulorum . Some secondary 

 species found in the Ansc-Agsp c.t. are Solidago missouriensis . Echinacea 

 £alj_ida_, Linum perenne , Petalostemon purpureum and Artemisia dracunculus . 

 Bouteloua curtipendula may be present in this type, but it has not been 

 found in the proposed mine area. 



Calamovilfa lonqi folia Community Type (Calo c.t.) . The Calo c.t., a 

 very uncommon type, can be found on eroded, course textured soils on warm 

 aspects. On better developed soils Asclepias verticil lata is a major asso- 

 ciate. The Calo c.t. shows some secondary species with A. scoparius dom- 

 inated community types, and may also contain Chenopodium leptophyllum . 

 Astragalus missouriensis , and Petalostemon candidutp . 



Yucca glauca Community Type (Yugl c.t.) . The Yugl c.t. occurs on sites 

 similar to Ansc-Calo c.t. sites, though soils are usually courser. Calamovilfa 

 lonqifolia, Andropoqon scoparius , and to a lesser extent Carex filifolia and 

 Stj_£3 comata , are frequent associates, and Muhlenbergia cuspidata may be a 

 co-dominant. Possibly Y. glauca acts as an increaser species on these latter 

 sites. Y^. glauca may also be associated with the outcrops of bedrock material. 



Chrysopsis villosa was present in all samples. Solidago missouriensis , 

 Artemisia dracunculus , Aristida longiseta , Cirsium undulatum , Petalostemon spp. , 

 and Ratibida columnifer a are minor associates. Mel i lotus officinale s and 

 Agropyron spicatum turned up in a few samples. 



* Mentzelia decapetala was found only twice on scoria hills in the study 

 area. 



31 



