aggressively expanding over what appears to be inhospitable terrain. The wooded vegetation types 

 associated with moister environments, particularly riparian zones and woody draws (e.g. Populus 

 deltoides / Symphoricarpos occidentalis), are the least well-represented on BLM land and have been 

 extensively converted to cropland or invaded by exotic species {Bromus inermis, Poa pratensis, and 

 annual brome grasses). The G-ranks of these mesic vegetation types should be G3 or rarer. The 

 upland types (e.g. JUNSCO / ORYMIC, PINPON / PSESPl, PINPON / SCHSCO). though they 

 occur predominantly as small patches occasionally ranging to large patches, have many occurrences 

 and are secure to the extent all of them should be rated at least G3G4. 



Shrub-dominated communities are extensive in Carter County, particularly in the southern 2/3 of the 

 county where substrates are mainly shale. The three new plant associations documented in this study 

 are all shrub-dominated. The most common upland shrub type is the ARTTSW/PASSMI type. It 

 freely intergrades with grassland and with sparse vegetation types. This may be among the most 

 extensive examples in the state. It is one of the major types with a classification question that hinges 

 on the habitat specificity and distinction between the rhizomatous wheatrasses. The most common 

 lowland type is the ARTCAN / PASSMI type on floodplains and terraces. It is much better- 

 represented on private holdings outside the study area. Despite their low G-ranks and ubiquity in the 

 landscape these types are under continual threat of exotic species invasion and can also be degraded 

 in attempts to increase productivity through contour furrowing. 



Of the 34 herb-dominated or sparse vegetation types, 10 are ranked vulnerable or imperiled 

 rangewide (G1-G3), 10 have no definitive ranking and the remainder are demonstrably secure (G4 or 

 G5). On the basis of our Carter County survey we will recommend several rank changes among this 

 first group, particularly for the Schizachyrium scoparium / Muhlenbergia cuspidata, S. scoparium / 

 Carex inops, and S. scoparium / C. filifolia plant associations. Even though these types all occur as 

 small patches, their positions among secondary range in the landscape make them less vulnerable to 

 weed invasions and degradation. The Puccinellia nuttalliana and Artemisia longifolia / Oryzopsis 

 hymenoides types, are rated Gl? and G2 respectively. They are appropriate to rank G3 or greater 

 based on statewide sampling, reconnaissance and correspondence with neighboring Heritage 

 programs. 



It was beyond the scope of this baseline survey to produce a county vegetation key. In the future, it 

 might be an ideal interagency project to meld the several vegetation classifications that treat the 

 southeastern Montana landscape and produce an integrated classification with a working key. This 

 would require additional sampling in Carter and adjacent counties, and compilation of all cover- 

 based community data collected elsewhere in Carter County (e. g. Hansen and Hoffman 1988, 

 Hansen et al. 1995). It might also include or consider data from surrounding counties and states, and 

 from Natural Resource Conservation Service (NRCS/SCS) vegetation production data into a 

 common format (e. g. ECODATA or ECADs). 



The plant associations described in the following text are grouped by the tallest species among the 

 dominants as presented in Table 3. Scientific names are used throughout the following descripfions, 

 and are cross-referenced by common names and six-letter acronyms in Appendix B. 



17 



