Among the significant examples of plant 

 associations, as determined by their outstanding 

 quality and condition, several are considered 

 potentially rare or vulnerable across their entire 

 distribution. The Douglas fir / littleseed ricegrass 

 forest (Pseudotsuga menziesii/Oryzopsis 

 micrantha p.a.) is a well-developed plant 

 association found only in central Montana that is 

 rare on account of its geographical restriction, 

 even if it is not under widespread threat. Three 

 other plant associations may possibly be globally 

 rare and are in varying stages of status evaluation 

 in cooperation with adjoining states and provinces. 

 They include: Rocky Mountain juniper/ 

 Wyoming big sagebrush woodland (Juniperus 

 scoulorum / Artemisia tridentata ssp. 

 wyomingensis Woodland), Indian ricegrass / 

 lemon scurf-pea sparse vegetation (Oryzopsis 

 hymenoides / Psoralea lanceolata p.a) as found in 

 sand dunes, and the porcupine needlegrass - 

 thickspike wheatgrass grassland (Stipa curtiseta / 

 Elymus lanceolatus Herbaceous Vegetation). We 

 believe that most or all of the other high global 

 ranks (G1-G3) for plant associations on Table 2 

 are artifacts of gaps in research or literature review. 



There was relatively little overlap between plant 

 association features at different sites. This may 

 reflect the system of selecting sites or the inherent 

 diversity within the NWR system. Even in cases of 

 overlap, the "redundant" plant association features 

 differed in their ecological context. For example, 

 two significant stands of Artemisia tridentata ssp. 

 wyomingensis / Pascopyrum smithii were 

 identified: on York Island, and on Fourth Ridge 

 just to the west. Yet they differed in that the York 

 Island shrubland is pervasive across the uplands 

 and represents a typical landscape, while the 

 Fourth Ridge shrubland is part of a juniper 

 woodland mosaic in an extreme example in an 

 unusually harsh setting. Two sites of Pascopyrum 

 smithii -Nasella viridula p.a were documented at 

 Mullan Trail RNA and in the Hell Creek area, the 

 former in a glaciolacustrine setting and the latter 

 in an unglaciated setting where the community is 

 a post-fire serai stage. Many sites had vestiges or 



patches of Stipa comata - Bouteloua gracilis - 

 Carex filifolia, but only Spring Creek had more 

 than 10 acres in good condition and surrounded 

 by more-or-less intact upland landscape 

 approaching good representation of the grassland 

 system and processes. Even the two RNAs 

 established to represent prairie dogs towns were 

 studies in contrast: an exotic species had taken 

 over in Prairie Dog Island RNA whereas native 

 species associated with early serai conditions 

 prevail across the prairie dog town site of Manning 

 Corral Prairie Dog Town RNA. 



Other recurrent patterns appear in collectively 

 considering these 12 sites. They include some of 

 the few protected public lands in eastern Montana 

 with intact mesic, productive plant associations. 

 Such inventory features include the once- 

 widespread Pascopyrum smithii-Nasella viridula 

 p.a. of Mullan Trail RNA as mentioned above. 

 The other associations of high biomass are highly 

 localized features like the Stipa curtiseta - Elymus 

 lanceolatus p.a. of Tepee Hills RNA, restricted to 

 north-facing slopes. 



The largest RNA, the Missouri River Bottomlands 

 RNA, is in a class by itself, encompassing riverine 

 processes and succession, and containing relatively 

 large Missouri River islands, relatively large stands 

 of plains cottonwood, and erodible valley slopes. 

 The presence of intact landscape processes, as well 

 as the plant association compohents, are enhanced 

 by representation of active geological processes, 

 which enhance system sustainability. Geological 

 processes are also captured in the sandhills 

 segment of the Medicine Lake Wilderness Area, 

 the largest sandhills in Montana with its aeolian 

 processes and succession. The Medicine Lake 

 sandhills also have the highest numbers of 

 Montana plant species of special concern among 

 study sites because of the uncommon sand dune 

 habitat. The third notable RNA example of 

 geological process are the avalanche chutes of the 

 Sheep Mountain RNA, although the RNA 

 includes only small portions of two chutes. 



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