15 



BIG HOLE STUDY AREA 



Surveys in the Big Hole Area produced the largest number of new sensitive species records for a single 

 species: Astragalus platytropis. Also documented were new county records for two species that were 

 previously considered for BLM status and tracked by the state but have since been dropped: Gentiana 

 aquatica and Mimidus suksdorfli in Silver Bow County, and Gilia inconspicua in Madison County. 

 Wliile large areas have been heavily grazed, there were notable exceptions. Limestone outcrops, 

 alkaline flats, and wetlands were the primary habitats in this study area for the various target species. 

 Almost all of the spring-fed wetlands north of Rochester were on private land, and those that were 

 investigated on BLM lands were found to be degraded. We were unsuccessful in relocating Phacelia 

 scopulina, which is historically known from Montana only in the Melrose vicinity and described in the 

 following text. In the course of searching for it, we instead found Kochia americana, which had not 

 otherwise been collected in Montana since 1931. 



Both Astragalus platytropis and Kochia americana are plants of southern biogeographic affinities. Red 

 sage is a peripheral Great Basin species at its northern limits. Broad-keeled milkvetch is a disjunct 

 southern cordilleran species at distinctively low elevation zones in its northern disjunct populations. The 

 Phacelia scopulina is a disjunct Columbia Plateau species at its eastern limits. 



There are several sensitive species present immediately north of the study area, but they are either on 

 different substrates, in more mesic settings, and/or at higher elevations than those of the Big Hole Study 

 Area. 



