fairy-candelabra (Androsace septentrionalis) , and 

 Nuttall's pussy-toes (Antennaria parviflora). 



Yellow sweetclover (Melilotus officinalis) is uncommon 

 in the sampled stand but widespread; other expressions 

 of this association are densely carpeted with this 

 introduced species and it has high potential for 

 expansion. Other introduced species such as goat's 

 beard (Tragopogan dubius) and Japanese brome (Bromus 

 japonicus) generally have insignificant populations. 

 [Plot NHMTECRN98SC0001] 



Artemisia tridermta ssp. wyomingensis I Pseudoroegneria 



spicata Shrubland 



[ARTTSW/PSESPI] 



Wyoming big sagebrush / bluebunch wheatgrass 



shrubland 



This association is typical of the mid- to upper-slope 

 positions of steeper slopes of all aspects, associated with 

 glacial drift soils, both coarser-textured (mosdy sandy 

 loams) and having greater amounts of gravel than the 

 ARTTSW / PASSMl p.a. It grades to ARTTSW / 

 PASSMl both at downslope positions and at slope 

 shoulders. Generally both the amount of bare soil and 

 the exposed gravel/rock comprise upwards of 70% of 

 the substrate; the erodible surface probably accounts 

 for the lack of a microbiotic soil crust. Wyoming big 

 sagebrush {Artemisia tridentata ssp. Wyomingensis) 

 ranges in cover from 10% to upwards of 35 % but 

 generally exceeds 20%. Fringed sage (Artemisia frigida) , 

 broom snakeweed (Gutierrezia sarothrae) , soapweed 

 yucca (Yucca glauca) and aromatic sumac (Rhus 

 trilobata) are the shrubs consistently present in trace 

 amounts. Bluebunch wheatgrass (Pseudoroegneria 

 spicata) is the dominant graminoid, though its cover 

 does not much exceed 30%. Graminoids consistently 

 present with low covers and associated with coarser- 

 textured substrates, or well-drained xeric sites include, 

 plains muhly (Muhknbergia cuspidata), prairie sandreed 

 (Calamovilfa langifoUa), and sand dropseed (Sporobolus 

 cryptandrus) . Little bluestem (Schizachyrium scoparium) 

 is often present. The forb component is very weakly 

 represented; no one species can be said to be abundant 

 but scarlet globemallow (Sphaeralcea coccinea), brittle 

 prickly-pear (Opuntia fragilis) , Hood's phlox (Phlox 

 hoodii) and American vetch (Vicia americarui) are 

 consistently present. [Plot NHMTECRN98SC00021 



Chrysothamnus ruiuseosus I Eriogormm pauciflorum 



Sparse Vegetation 



[CHRNAU/ERIPAUl 



common rabbitbrush / few-flowered wild buckwheat 



barrens 



This localized and small patch association is found on 

 the island's uppermost outcrops and has been 

 previously described in the Limber Pine RNA, in Valley 

 County (Branson et al. 1970) and in Carter County 

 (Vanderhorst et al. 1998). Soils of this site possess no 

 horizons and are weathered from a very dark grey, 

 possibly acidic, shale and bentonite. Though the 

 ultimate result of weathering is clay-sized particles, 

 much of the substrate has just been broken down to 

 sand-size particles and thus has better drainage than 

 would be expected of a soil high in clay; it is also highly 

 erosive, rills and gullies abound. This association 

 mostly occupies upper hill slopes or crests and has 

 depauperate vegetation (< 10% canopy cover). There is 

 a suite of species adapted to these sites including long- 

 leaved sage wort (Artemisia longifolia), common 

 rabbitbrush (Chrysothamnus ruiuseosus), few-flowered 

 wild buckwheat (Eriogonum pauciflorum; E. brevicauk 

 var. brevicauk in southeast Montana), Indian ricegrass 

 (Oryzopsis hymenoides) and western wheatgrass 

 (Pascopyrum smithii) that regularly appear in various 

 mixes and quantities. On York Island, Eriogonum 

 pauciflorum has greater cover than associated species, 

 and Chrysothamnus ruiuseosus cover is less than 3%. 

 The 19 species of the sample plot is an unusually high 

 number; normally species richness does not exceed 5- 

 10 for this type. [Plot NHMTECRN98SC0003] 



Other Vegetation: Other patchy or restricted plant 

 associations were noted on York Island. The 

 southemeastem point had the best development of the 

 Rocky Mountain juniper / indian ricegrass woodland 

 (Juniperus scopulorum /Oryzopsis micrantha 

 Woodland; JUNSCO/ORYMIC) on the steep, north- 

 facing slope of a small hill. Small patches of western 

 snowberry shrubland (Symphoricarpos occidentalis 

 Shrubland) are confined to swales and drainage 

 courses. Sandy ridgetops at the north end have prairie 

 sandreed - sun sedge (Calamagrostis longifolia - Carex 

 inops), and the drainage courses graded in places into 

 the western wheatgrass - green needlegrass grassland 

 (Pascopyrum smithii - Nasella viridula Herbaceous 

 Vegetation). 



Most of the perimeter was ringed by sparsely-vegetated 

 shoreline flats of shale fragments colonized by yellow 

 sweetclover (Melilotus officiruilis) , pummeled by the 

 waves and pounded into rack lines that set off 

 backwater wetlands in what were previously bays. 

 These backwater wetlands are colonized and variably 

 dominated by advenrive and exotic species like 

 common sunflower (Helianthus annuus), tumbleweed 

 (Amaranthus albus), (Powell's amaranth (Amaranthus 

 powellii), redorache (Atriplex rosea) , slimleaf goosefoot 



37 



