VEGETATION: 



The variation in aspect, soil depth as it affects water 



holding capacity, and slope runoff produce a number of 



distinct environments in a relatively confined area (see 



Figure 3, Tepee Hills RNA plant communities and 



associations). 



forbs, reflecting the mesic environment, totaling 36 

 species in a single plot. They include outlying Rocky 

 Mountain plant species such as small-flowered 

 penstemon (Penstemon procerus) that are of 

 biogeographic interest. [Plot 

 NHMTECRA97SC0002] 



Stipa comata - Bouteloua gracilis - Carex filifoUa 



Herbaceous Vegetation 



[STICOM - BOUGRA - CARHL] 



needle-and-thread - blue grama - threadleaved sedge 



This is one of the most extensive and broadly 

 distributed of upland plant associations within the 

 Northern Great Plains, occurring in Manitoba, 

 Saskatchewan, Nebraska, Wyoming, North and South 

 Dakota and in Montana is a major matrix type from the 

 base of the Rocky Mountain Front eastward. In the 

 Medicine Lake landscape it is restricted to the most 

 xeric exposures, moderate to steep, south- to 

 southwest-facing, mostly convex slopes having shallow 

 soils. ??CompositionaIly the RNA examples of this type 

 are not close to the modal description wherein Stipa 

 comata is the dominant graminoid and Boutebua gracilis 

 has 100% constancy (but cover values not exceeding 

 30 %). Quite possibly past grazing, favoring short- 

 statured rhizomatous species, has influenced the 

 composition of this site. [Plot NHMTECRA97SC0001] 



Stipa curtiseta - Elymus \arvcto\a\m Herbaceous 



Vegetation 



[STICUR-ELYLAN] 



porcupine needle-grass (-) thick-spike wheatgrass 



grassland 



This association is found only on moderate to steep, 

 north-facing slopes with well-developed soils, as 

 restricted to the coulee. It has been described from 

 similar settings in northern Valley and Phillips 

 Counties (DeVelice et al. 1995) and in northwestern 

 North Dakota. However, within the Canadian prairies 

 or prairie parklands it occurs on planar and rolling 

 surfaces as an extensive, prevailing type in mesic 

 settings. In the Tepee Hills representation of this type, 

 porcupine needle-grass (Stipa curtiseta) is mono- 

 dominant (in excess of 50 % canopy cover) and other 

 graminoids, including thickspike wheatgrass (Eijmus 

 \arv:eo\atus) which are said to be dominant or co- 

 dominant in Canadian settings, comprise little more 

 than trace amounts. This suggests the need to further 

 evaluate if not reclassify this plant association. There is 

 a noteworthy and relatively luxuriant diversity of native 



Poscop^TMrn smxAva, - Bouteloua gracilis — Carex fiUfoUa 



Herbaceous Vegetation 



[PASSMl - BOUGRA - CARRL] 



western wheatgrass - blue grama - threadleaved sedge 



grassland 

 This is a broadly distributed type Northern Great Plains 

 plant association, which we have distinguished from 

 ELYLAN - STICOM because it appeared to be present 

 lower in the landscape, on the flats and toeslope 

 positions, than was the ELYLAN - STICOM 

 community type. This distinction may be somewhat 

 artificial but their respective distributions appeared 

 distinct at the time of sampling. This type generally 

 occupies heavier soils and more poorly drained sites 

 than does ELYLAN - STICOM. Western wheatgrass 

 (Pasco/ryrum smithii) is the dominant graminoid with 

 cover usually in excess of 40 %; the cover of blue 

 grama (Bouteloua gracilis) and threadleaved sedge 

 (Carex filifolia) is usually less than that of Pascopyrum 

 smithii. Which species has greater cover seems to vary 

 randomly across the landscape. Within this RNA, 

 crested wheatgrass (Agropyron cristatum) has 

 established significant coverages in this community 

 type, mostly by volunteer seeding from adjacent 

 agricultural lands. [No Plot] 



Pascopyrum smithii Herbaceous Vegetation 

 [PASSMl] 

 western wheatgrass grassland ;„8, 



This association represents, along with westerm 

 smpwberry shrubland, the most mesic sites within the 

 uplands of the refuge. It is a widely distributed across 

 the Northern Great Plains from Montana to Nebraska 

 and south to Colorado. It occupies, as a narrow band, 

 the heaviest alluvium soils of toeslopes and ephemeral 

 drainages; often this type is assumed to be subirrigated 

 and occasionally it can qualify as a jurisdictional 

 wedand (no examples of this on RNA). In its native 

 state, this type is characterized by virtually 



50 



