45 



Ferry Reseirvior) , along the free-flowing Yellowstone River, 

 and along Big Horn River, and other Yellowstone River 

 tributaries. 



1. ASSOCIATED VEGETATION: The species associated with Rorippa 

 calycina in Wyoming are mainly pioneer riparian species, and 

 include noxious weeds among them (from Lichvar 1981; exotic 

 species are asterisked). Note: Among the species on the 

 following list of associated species from Wyoming, the 

 asterisked species are exotic. 



Common name Scientific name 



Thickspike wheatgrass Agropyron dasystachyum 



Ragweed Ambrosia psilostachya* 



Goosefoot Chenopodium alba 



Bull thistle Cirsium vulgare* 



Gumweed Grindelia squarrosa 



Foxtail barley Hordeum jubatum 



Baltic rush Juncus balticus 



Hoary aster Machaeranthera canescens 



Cusick's bluegrass Poa sandbergii 



Puzzling cinquefoil Potentilla paradoxa 



Russian thistle Salsola iberica* 



Poson suckleya Suckleya suckleyana 



Salt cedar Tamarix chilensis* 



Verbena Verbena bracteata 



The emergent shoreline vegetation at the Garfield County 

 site was submerged under 1993 highwater conditions, and 

 included: 



2. TOPOGRAPHY: The species is found at the base of slopes 

 within riparian or palustrine habitat that is temporarily 

 flooded; a narrow zone marking old shorelines of rivers, 

 ponds and lakes. 



3. SOIL RELATIONSHIPS: The largest Wyoming populations are 

 found in loose, non-alkaline, sandy littoral edges. It may 

 also be found in alkaline settings, and on clay substrate 

 (Lichvar 1981) . The Garfield County site had alkaline clay 

 substrate around an eutrophic reservior. 



4. CLIMATE FACTORS: Persistentsepal yellowcress is adapted to 

 a continental climate with seasonal water level 

 fluctuations. 



