36 



P. lemhiensis . 



An unusual phenomenon that illustrates the 

 possible long-term sensitivity of P. lemhiensis 

 to grazing was observed at the Badger Pass 

 North (019) site in 1987. Numerous plants were 

 found growing up through the branches of 

 sagebrush shrubs, many of which were dead. 

 This may have been a result of the moderate 

 livestock grazing that has occurred in the 

 area. The microhabitat under the shrubs 

 appears open enough for seedling establishment, 

 and the mature plants are then apparently 

 protected from browsing once they grow into the 

 shrub canopy. This phenomenon was not observed 

 at any other location in Montana. 



2. Competition. 



a. Intraspecific: The density of P. 

 lemhiensis is low at virtually all known 

 locations in Montana, and intraspecific 

 competition is probably not an important 

 factor in determining population size or 

 structure. 



b. Interspecific: At the Big Hole National 

 Battlefield (006) , sampling of vegetation 

 in areas with and without P. lemhiensis 

 indicated that the occurrence of the 

 species is correlated with vegetation 

 density (Ramstetter, 1983). Penstemon 

 lemhiensis was found growing most 

 freguently in areas of lower vegetation 

 cover, and rarely in areas of higher 

 cover; this pattern of sensitivity to high 

 vegetation density was not apparent for 

 the other plant species associated with P. 

 lemhiensis . In particular, areas of 

 higher sagebrush and bunchgrass cover 

 contained the fewest occurrences of P. 

 lemhiensis . Additionally, it was 

 theorized that P. lemhiensis occurs more 

 often on steeper slopes at the Battlefield 

 site, where natural soil slippage may be 

 greater, because the sagebrush and 

 bunchgrasses are not as dominant as they 

 are on more gradual slopes. 



Further evidence for the apparently poor 

 competitive ability of P. lemhiensis is 

 provided by the observation that, in 

 several populations, individuals have 



