distantly by species of gooseberry (Rihes spp.) and 

 willow {Salix spp) , which are seldom present with 

 greater than 5% cover. In the better condition stands, 

 western wheatgrass {Pacopyrum smithii) and green 

 needlegrass (Nasella viridula) are the dominant 

 graminoids and their cover approachs 30%. Commonly, 

 alien graminods such as smooth brome {Bromus 

 mermis), quackgrass {Aropyron repens), intermediate 

 wheatgrass (Agropyron intermedium) , and Kentucky 

 bluegrass (Poa pratensis) dominate this component. In 

 the sample stands, the forb compoent is minor; the only 

 time a significant forb presence was noted was in the 

 case of exotic species such as Canada thistle (Cirsium 

 arvense), yellow sweet clover (Melilotus officinalis), and 

 black medic QAedicago lupulina) . Canada goldenrod 

 {Solidago canadensis) was the only native forb occurring 

 in more than half the study plots. 

 [Plots NHMTECRN98SC0018, 

 NHMTECRN98SC0026, NHMTECRN98SC0030] 



Sarcobatus vermiculatus / Atriplex gardneri Intermittently 



Flooded Shrubland 



[SARVER/ATRGAR] 



greasewood / Gardner's saltsage intermittently flooded 



shrubland 



This association, or one affiliated to it in name, has 

 previously been identified only from the southeastern 

 and Bighorn Basin regions of Montana and adjoining 

 lands in Wyoming. It has been characterized as a small 

 to large feature occurring on alkali-affected alluvial 

 flats, thus the title of intermittently flooded shrubland. 

 More recently this same type has been noted in Carter 

 County to occur on badland formations (Vanderhorst 

 et al. 1998). The two plots representing this association 

 on the RNA occur on dissected. Bear Paw Shale 

 uplands, bentonite inclusions, and slope aprons with 

 rill, gully and sheet erosion and with plant pedicelling. 

 Ground cover is a monotonous expanse of grayish-tan 

 exposed clayey substrate lacking soil development and 

 with traces of gravel. The vegetative physiognomy of 

 these plots does not technically qualify as shrubland but 

 rather as dwarf shrublands verging on sparse vegetation 

 (< 10% total canopy cover). It may be advisable to 

 change the modifier name of the type because even the 

 intermittent flooding is inferred and may not if fact be a 

 significant ecological driver. This type is extensive and 

 recurrent along the Missouri River valley, with so much 

 exposed valley slope. Part of this landscape mosaic 

 supports patches of Gardner's saltsage (Atriplex 

 gardneri) or rillscale (A. suckleyi) alone, without 

 Sarcobatus vermiculatus. These species may define two 

 different associations in the provisional statewide 



classification, but do not necessarily represent two 

 distinctly-different environments. 



Dominance in the shrub canopy shifts between Atriplex 

 gardrieri and Sarcobatus vermiculatus but their cover, 

 singly or combined, does not exceed 15-20%. 

 Wyoming big sagebrush (Artemisia tridentata ssp. 

 wyomingensis) is present in trace amounts. The 

 graminoid layer is depauperate to nonexistent and the 

 forb component usually follows suit, except for the 

 sporadic, unexplainedly high coverages of rillscale 

 (Atriplex suckleyi). Tall seablite (Suaeda moquinii) is 

 consistently present in trace amounts. [Plots 

 NHMTECRN98SC0023, NHMTECRN98SC0029] 



Sarcobatus vermiculatus / Pascopyrum smithii Shrubland 



[SARVER/PASSMI] 



greasewood / western wheatgrass shrubland 



This community is predominantly a large patch type 

 that develops on the heavy silt to clay loam soils of 

 alluvial fans, toeslope or slope apron positions and old 

 river terraces on nearly level terrain with at most 2-3% 

 slope. Many of these stands receive considerable 

 slopewash including entrained fines from the adjacent 

 erosive uplands. It differs markedly from the previously 

 described black greasewood (Sarcobatus vermiculatus)- 

 type immediately above in that it is sufficiently 

 productive that litter forms and accumulates leaving 

 little exposed soil. Most often this type is noted to 

 grade to the Artenusia caruL I Pascopyrum smithii (silver 

 sagebrush / western wheatgrass) association, that occurs 

 on less salt-affected positions. Together with the 

 Artemisia carm shrubland, it is an integral component of 

 the riparian mosaic in this landscape, though none of 

 the representations inventoried on the RNA met the 

 requirements for a jurisdictional wetland. 



The shrub canopy is dominated by Sarcobatus 

 vermiculatus, usually in excess of 25% canopy cover. 

 Both silver sagebrush (Artemisia carta) and rubber 

 rabbbitbrush (Chrysothamnus nauseosus) are 

 consistendy present, their cover seldom exceeding 

 10%. The three plots represented sites inferred to be in 

 good condition by their high cover values (>60%) for 

 the dominant grass, western wheatgrass (Pascopyrum 

 smithii) . Other high constancy graminoids are alkali 

 bluegrass (Poa juncifoUa) , green needlegrass (Nasella 

 viridula) and the annual weed Japanese brome (Bromus 

 japonicus); the combined cover of native graminoids 

 apart from Pascopyrum smithii usually does not exceed 

 10-15%. The forb composition reflects past 

 disturbance with a variable assemblage of weedy, 

 increaser species present, but their coverages usually 



26 



