Kentucky bluegrass (Poa pratensis), Japanese brome 

 (Bromus japorucus), and on occasion, intermediate 

 wheatgrass (Agropyron intermedium). Areas with 

 abundant weed populations have very Uttle hlasella 

 viridula, indicating it may be susceptible to grazing and 

 competitive effects. The forb component is sparse and 

 species poor; only the non-native increasers yellow 

 sweetclover (Melibtus officinalis), white sweetclover 

 (Melilotus alba) , and goat's beard (Tragopogon dubius) 

 occur in greater than trace amounts. Yarrow (Achillea 

 millifolium) is the only native with greater than 50% 

 cor«tancy. 



Atriplex gardneri Dwarf Shrubland 



[ATRGAR] 

 Gardner's saltsage dwarf shrubland 



This plant association is found along the valley slopes 

 as small patches in a complex mosaic of other sparse 

 vegetation that is more widespread. Surrounding 

 vegetation includes stands dominated by black 

 greasewood {Sarcobatus vermiculatus) and Wyoming big 

 sagebrush (Artemisia tridentata ssp. wyomingensis) . Our 

 sample plot differed from these types only in having but 

 a trace of Sarcobatus vermiculatus but clearly there is a 

 continuum in substrate properties that is reflected to 

 some degree in the vegetation mosaic. It should also be 

 noted that in the course of reconnaissance Gardner's 

 saltsage (Atriplex gardneri) was found to occur with 

 coverages greater and less than 10% (the sparse cover 

 cutoff) which would give some of these stands a sparse 

 cover designation. Overall the cover is greater than 

 10% giving stands an aspect closer to the type as 

 described for southeastern Montana (Vanderhorst et al. 

 1998) . Within the RNA, ARTGAR occurs both on 

 slope aprons, where alkali-laden fine-textured 

 slopewash accumulates, as well as on slope shoulders 

 and narrow crests and even mid-slope positions of any 

 aspect; virtually anywhere bentonite lenses or unusual 

 shale substrates are exposed. 



The vegetation is close to being a monospecific layer of 

 the dwarf-shrub Atriplex gardneri, its cover ranging from 

 5 to 30 (40)%. Depauperate specimens of black 

 greasewood (Sarcobatus vermiculatus) generally 

 constitute the only other shrub present. Bottlebrush 

 squirreltail (Sitaruon hystrix) , indian ricegrass (Oryzopsis 

 hymenoides) and thick-spike wheatgrass (Elymus 

 lanceolatus) are the graminoids most often found here, 

 but not greater than trace amounts. Tall seablite 

 (Suaeda moquinii) and plains bahia (Picradermpsis 

 oppositifoUa) are the only recurrent forbs in this 

 commuruty. 



Populus deltoides I Symphoricarpos occidentaiis Roodplain 



Woodland 



[POPDEL/SYMOCC] 



- plains Cottonwood / western snowberry floodplain 



woodland 



Floodplain woodlands are areally extensive 

 communities as broken bands along the Missouri River 

 on the older portion of alluvial bars and outer edges of 

 the river's floodplain; see Hansen et al. (1995) for a 

 discussion of riverine geomorphology explaining the 

 genesis of these stands. Some of the stands 

 representing this community type are flooded virtually 

 every year or at least heavily influenced by the 

 seasonally fluctuating watertable; other stands are more 

 removed, do not experience yearly flooding and their 

 roots are less watertable influenced. During 

 reconnaissance, all degrees of anthroprogenic 

 modification were noted including plowing, seeding to 

 alien species, cutting, domestic stock grazing and 

 browsing in this type. Some stands of plains 

 cottonwoood (Populus deltoides) had nothing more than 

 combinations of quackgrass (Agropyron repens), smooth 

 brome (Bromus inermis), Kentucky bluegrass (Poa 

 pratensis), leafy spurge (Euphorbia esula), and American 

 licorice (Glycyrrhiza lepidota) in the understory. Stands 

 were sampled that appeared least disturbed, but that is 

 not to say they were undisturbed. 



Hansen et al. (1995) interpret this community as both 

 a mid-seral stage of floodplain development and a 

 browsing-induced disclimax (by whitetail deer?) of the 

 plains Cottonwood/ redosier dogwood forest (Populus 

 deltoides I Comus sericeus Forest). If that were the case, 

 then animal scouring of these stands is phenomenally 

 thorough because our inventory was able to find no 

 more than one stem of Comus seriseus in the RNA. The 

 common chokecherry (Prunus virgiruarui) and western 

 serviceberry (Amelanchier alnifolia) were also scarce. In 

 younger or more mesic representations of this type, 

 canopy cover of the Populus deltoides may exceed the 

 60% crown cover limit for woodlands. The three 

 sampled stands of this type are relatively mature to "old 

 growth" with average diameters of 16-20 inches in two 

 stands and the third with 34-44 inch stems remaining 

 and number of downed and dying veterans. Rotten 

 heartwood precluded obtaining ages on these stems. 

 The mortality in the stand with trees of the largest 

 diameter has resulted in less than 30% tree canopy 

 cover and with no Populus deltoides reproduction 

 because of no fresh alluvium being deposited. This 

 stand will is likely to become a Symphoricarpos 

 occidentaiis 'dominated shrubland. Woods rose (Rosa 

 woodsii) is the second leading shrub species followed 



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