49 



Aqropvron smithii Rydb. 



Aqropvron spicatum (Pursh) Scrib. & Smith 

 Festuca idahoensis Torrey ex Hook. 

 Festuca scabrella Elmer 

 Lithospermum ruderale Dougl . ex Lehm. 

 Pinus ponderosa Dougl. ex Laws. & Laws. 

 * Poa pratensis L. 



Poa secunda Presl. 



Pseudotsuga menziesii (Mirb.) Franco 



Rosa woods ii Lindl . 



Stipa comata Thurb. ex Wats. 



Stipa occidentalis Trin. & Rupr. 



* = introduced species 



4. Dominance and frequency of the taxon: In 



Montana, populations are variable in size, and 

 range from 10 plants up to 10,000 plants. The 

 mean population size is ca. 1300; however, of 

 the eight currently known sites, six have 100 

 or fewer plants. Canopy coverage of this 

 species is generally quite low except in very 

 localized areas. Most populations consist of 

 scattered individual plants. 



5. Successional phenomena: Silene spaldingii is 

 associated with successionally advanced fescue 

 grasslands. The species appears to tolerate 

 moderate grazing that results in an increase of 

 Poa pratensis at some sites in Montana (Peter 

 Lesica, pers. comm.). However, it is suspected 

 that a population has been extirpated in the 

 state of Oregon as a result of overgrazing 

 (Jimmy Kagan, pers. comm.). 



6. Dependence on dynamic aspects of biotic 

 associations and ecosystem features: Unknown. 



7. Other endangered, threatened, rare, or 

 vulnerable species occurring in habitat of this 

 taxon: The following species is found in the 

 vicinity of the Tobacco Valley sites. This 

 bird is known to have a limited distribution in 

 Montana, but is more widespread elsewhere. 



Tvmpanuchus phasianellus coJumbianus 

 (Columbian sharp-tailed grouse) - listed 

 as "critically endangered" in Montana (SI) 

 by The Montana Natural Heritage Program. 



