(poison ivy) . The more open areas are sagebrush (Artemesia 

 cana) grasslands (Bouteloua gracilis, Elymus cinereus, 

 Oryzopsis hymenoides, Stipa comata) with a diversity of native 

 herbs and shrubs. Weeds, besides the viney Clematis and 

 Humulus , are concentrated around the parking and picnic areas 

 and around the archeological digs and include Arctium minus 

 (burdock) , Alyssum desertorum (alyssum) , Ambrosia 

 artemesifolia (ragweed) , Bromus tectorum (downy brome) , 

 Cirsium arvensis (Canada thistle) , Marrubium vulgare 

 (horehound) , and Melilotus alba (sweetclover) . No MPSSC were 

 found or are known from elsewhere in Yellowstone County. 



Selkirk Fishing Access Site 



Habitat at this unusually large fishing access site along 

 the Musselshell River includes oxbow wetlands and adjoining 

 uplands. Vegetation consists of three more or less natural 

 types but none of these are pristine; these are 1) mixed grass 

 prairie uplands dominated by Elymus smithii (western 

 wheatgrass) and Stipa comata (needle and thread) and invaded 

 by Poa pratensis (Kentucky bluegrass) which are idle and 

 productive but recovering from overgrazing and depauperate in 

 forbs, including a portion with a high component of Ceratoides 

 lanata which may represent an uncommon plant association, 2) 

 unstable, sparsely vegetated silt slopes with a diverse 

 pioneer community which has, however, been disturbed by 

 construction of an irrigation channel and invaded by Centaiirea 

 maculosa (spotted knapweed), and 3) floodplains with oxbow 

 wetlands choked by Typha latifolia (cattails) and open forests 

 and thickets dominated by Populus angustuifolia (cottonwood) 

 and Salix bebbiana (willow) respectively, with understories 

 dominated by exotic species. In addition to knapweed two 

 other noxious weeds seen were Cyanoglossum officinale 

 (houndstongue) and Hyoscyamus niger (henbane) . No MPSSC are 

 known from Wheatland County, none were found at the site, and 

 none are suspected. 



Water Birch Fishing Access Site 



The floodplain woodlands which occupy most of this area 

 along Rock Creek are among the most extensive and most 

 pristine visited during this project. However, no MPSSC are 

 known from this kind of habitat, at least in Carbon County. 

 The woodlands are dominated by Populus balsamifera 

 (cottonwood) with a few Populus tremuloides (quaking aspen) 

 and have a brushy understory with Alnus incana (alder) , Cornus 

 stolonifera (dogwood) , Prunus virginiana (chokecherry) , and 

 species of Crataegus (hawthorn) , Rosa (rose) and 

 Symphoricarpos (snowberry) . Oddly, no water birch {Betula 

 occidentalis) was seen. A few exotic species are scattered in 

 the woods but are nowhere aggressively weedy; these include 

 Centaurea maculosa (spotted knapweed) , Chrysanthemum 

 leucanthemum (ox-eye daisy) , Cirsium arvense (Canada thistle) , 

 Dactylis glomerata (orchardgrass) , Glycyrrhiza lepidota 



21 



