Field observations suggest that this type would be more widespread if 

 grazing were less intensive. Reed and Peterson (1961) notes that while the 

 response of most vegetation to grazing is variable, S. viridula consistently 

 decreases with increased grazing. 



Andropogon scoparius Community Type (Ansc c.t. ). The Ansc c.t. is most 

 common on cool, well -drained uplands, although found on many different kinds 

 of sites, Hanson and Whitman (1938) associate a similarly named type with 

 areas where snow accumulates. They feel that this type is successional on 

 eroded soils. These authors note that A. scoparius is an important species 

 because it stabilizes runoff and erosion, holds drifting snow, and hastens 

 soil development. White (1961) suggests that A. scoparius may be associated 

 with low soil fertility on clay-textured soils. 



Hanson and Whitman (1938) suggest that A. scoparius is little grazed 

 except in time of drought, but many consider it to be a decreaser under 

 grazing and it is noticeably scarce on overgrazed range. Because cattle 

 graze mostly the leaves of this species until late August, when they begin 

 to graze the stalks (Jameson and Huss 1959), the Ansc c.t. appears to be 

 little grazed even when it is being used by cattle. 



Psoralea esculenta , and to a lesser extent Echinacea pallida , are 

 associated with A. scoparius dominance. Some species associated with above 

 average soil moisture, such as Psoralea argophylla , Solidago missouriensis , 

 and Cirsium undulatum , are often a component of the Ansc c.t. Other minor 

 associates are Asclepias verticillata , Antennaria spp. , Artemisia dracun - 

 culus , and Yucca glauca . 



Andropogon scoparius - Calamovilfa longifolia Community Type (Ansc - 

 Calo cTt . ). Many Ansc c.t. communities contain C. longifolia , but stands 

 must contain over 5% absolute coverage of C^. longifol ia to be a member of 

 the Ansc-Calo c.t. The average from reconnaissance plots contained 17.5% 

 absolute coverage of C^. longifolia . Typically this species becomes a dom- 

 inant with erosion and a reduction in A. scoparius coverage. The amount of 

 bare soil for this type is over twice the amount of bare soil for the Ansc 

 c.t. and average soils are a bit lighter in texture. 



Slope-slope aspect values for the Ansc-Calo c.t. sites indicate de- 

 cidedly warmer sites than values for the Ansc c.t. sites. This can be taken 

 at face value, or it may be that livestock use is intensified on the warmer 

 aspects in the Ansc c.t. sites especially when snow is present resulting in 

 habitats better suited to C^. longifolia . Soil Ph may be low on Ansc-Calo 

 c.t. sites, and plant nutrition can be a problem. 



The genera Astragalus and Petal ostemon are usually present in Ansc- 

 Calo c.t. Aristida longiseta was present in about half the stands sampled. 

 Lygodesmi a juncea , found usually on light soils, was most constantly pre- 

 sent in this type. Juniperus horizontal ii. and some Ansc c.t. associates 

 were usually present. 



Andropogon scoparius - Agropyron spicatum Community Type (Ansc-Agsp 

 c.t. ) The Ansc-Aqsp c.t. is often found on warm aspects of scoria hills 



29 



