Plant species of concern and plant associations of Powder River county, Montana E1C3380F-9100-4DF5-BBE8-6E6321664192 Year: 2002 an elongated flowering stalk (Figure 5). A complete set of technical distinguishing characteristics hQ\}N^^w Astragalus barrii and Astragalus ftyalinus is summarized in Heidel and MaiTiott(1996). Habitats: Barr's Milkvetch is restricted to sparsely vegetated knolls, buttes, and barren hilltops, on calcareous soft shale and siltstone. It is often found at tlie rim of outcrops and midslope benches (Figure 6). These microhabitat settings represent thin silty ecologica
Plant species of concern and plant associations of Powder River county, Montana E1C3380F-9100-4DF5-BBE8-6E6321664192 Year: 2002 an elongated flowering stalk (Figure 5). A complete set of technical distinguishing characteristics hQ\}N^^w Astragalus barrii and Astragalus ftyalinus is summarized in Heidel and MaiTiott(1996). Habitats: Barr's Milkvetch is restricted to sparsely vegetated knolls, buttes, and barren hilltops, on calcareous soft shale and siltstone. It is often found at tlie rim of outcrops and midslope benches (Figure 6). These microhabitat settings represent thin silty ecological sites. Their clay fraction is high enough in places to classify tlie microhabitats as thin clayey. There is little or no soil profile development but there are generally no restrictive layers that would classify the microhabitats as a shallow ecological site. These microhabitats occur within predominantly silty ecological sites, but while tliey occupy a small fraction of the landscape, they are widespread and recurrent in part of BLM-administered lands (Figures 7 and 8). Figure 4. Photograph of Astragalus Irvaliuus (note white flowers) Figure 5. Photograph of Astragalus spathulatus (note stalked flowers) This species is restricted to uppei-and mid-slope topographic positions and does not occupy outwash or eroded gullies below die outcrops. It is most commonly found on slopes widi noitliem and eastern aspects and does not occur on steep soutli- facing slopes with their salt-affected vegetation. In otlier words, its habitat represents a small subset of outcrop settings and a small subset of tlie thin silty ecological site. In Powder River County, Bair's Milkvetch is found, almost witliout exception, on die Midway- Elso rocky soils on 35 to 70 slope (Parker et al. 1971). Appendix C-2
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