26 



5. Seedling ecology: Unknown. However, very 

 small seedlings were rarely observed during 

 field surveys for A. barrii . or during research 

 on this group of Astragalus species (Roberts 

 1977) . 



6. Survival and mortality: Barneby (1964) asserts 

 that "(t)he ability to survive and subsequently 

 to require a difficult environment has enabled 

 members of the genus to colonize a great 

 variety of raw, newly exposed, often 

 unpromising habitats"; A, barrii is no 

 exception. Although A. barrii may not flower 

 yearly, vegetative spreading allows this 

 perennial species to augment its growth yearly. 



Individual plants of several other species in 

 the Orophaca group have been examined (Roberts 

 1977) , and were found to have minimum ages of 

 15 and 25 years. From the sizes of the mats 

 observed in many locations in s outheastern 

 Montana, it is likely that ( €hTs ))A. barrii is 

 also long-lived. Q^ 



A high mortality rate was observed for some 

 populations in more exposed locations in 1989. 

 The dry years of 1987 and 1988 probably 

 prompted these losses. See color slides p. 9. 



7. Overall assessment of taxon's reproductive 

 success: Most populations in Montana are 

 large, and seem to be well established. 



Population ecology of the taxon. 



/ 



A. General summary: Species in the genus Astragalus 

 rarely tolerate direct competition or shade cast by 

 other plants (Barneby 1964) . It was observed that 

 populations of A, barrii were most often found on 

 barren ground. Total vegetation cover (by ocular 

 estimation) rarely exceeded 50%, and was often 

 lower. 



B. Positive and neutral interactions: None observed. 



C. Negative interactions. 



1. Herbivores, predators, pests, parasites and 

 diseases: No predation on A. barrii 

 populations was observed, and it appears that 

 livestock do not prefer this species from 

 observations of on grazed allotments. 



