SUMMARY 



The open plains of Carter County, Montana represent some of the most extensive and unbroken 

 rangeland resources of the state, and among the lesser known in the biological literature. Baseline 

 botany and vegetation baseline inventories were conducted on BLM-administered lands in the 

 county to document these resources in terms of their biological diversity significance. 



Eighteen Montana plant species of special concern have been documented in Carter County, half of 

 them on BLM lands, including two species that grow exclusively in a small segment of the Great 

 Plains. There are very few occurrences of these nine species, reflecting the lack of suitable habitat 

 for most of them. A preliminary county flora of 507 species was also compiled. 



Over seventy vegetation types (plant associations) have been documented in Carter County, the 

 majority of them occurring on BLM lands. There is only one that is declining from a rangewide 

 perspective (Plains cottonwood/westem snowberry; Populus deltoides/Symphoricarpos 

 occidentalis), and at least two plant associations dominated by bur oak {Quercus macrocarpd) that 

 are peripheral and occur in no other places of the state. Detailed sampling and description is provided 

 for 19 vegetation types that include the common plant associations on BLM lands. 



The results point to a landscape-level diversity most closely linked to soils and topography features, 

 including a high concentration of Montana plant species of special concern that require sandy 

 habitat. Among the most distinguishing vegetation features of the county is the extensive natural 

 vegetation on shale plains and contribution of thick-spiked wheatgrass (Elymus lanceolatus) among 

 the prevailing vegetation types. These findings contribute to the body of baseline information on 

 features in the Powder River Resource Area and in the state, documenting that many of the features 

 are more common than previously known. They provide dimension to a state perspective that can 

 only be found in this far comer of the state in the heart of the Great Plains. 



