stonecrop (Sedum lanceolatum) were noted as the 

 prevalent forbs throughout the drier woodland 

 environments. [Plot NHMTECRN98SC0037] 



Pmus fladlis I Pseudoroegneria spiccaa 



Woodland [PINFLE / PSESPI) 



limber pine / bluebunch wheatgrass woodland 



This plant association was found on a very rocky, thin- 

 soil, limestone ridge with a northwest- and west-facing 

 aspect and stretched up and dowtwlope approximately 

 120 vertical feet from the 8, 160 ft. contour. The 

 ground surface is more than 85% exposed gravel and 

 rock with bare soil constituting another 5-10%. There 

 is no soil profile development and of the upper 10-20 

 cm. more than 50% is rock (gravel size or larger) ; this 

 site verges on being a scree slope. 



In this old growth stand of stunted limber pine (Pinus 

 flexilis) and Douglas fir (Pseiulotsuga merajesii; maximum 

 height of 300 plus yr. old trees 22-24 ft.) all the veteran 

 trees have very battered crowns and boles emblazoned 

 with numerous lightning scars, often having more bare 

 bole and scar tissue than functioning bark. Tree 

 canopy cover ranges between 30 and 50%, composed of 

 only the above named species; there are scattered 

 seedling and samplings but the mid-sized age classes are 

 missing. Shrubs like mountain snowberry 

 (Symphoricarpos oreophilus) and common juniper 

 Quniperus communis) occur in only trace amounts. The 

 herbaceous layer is very sparse (total cover < 10 - 12%) 

 and dominance shifts across the stand, some portions 

 (or patches) being dominated by bluebunch wheatgrass 

 (Pseudoroegneria spicata) others by grayish cymopteris 

 (Cymopterus glaucus) , lanceleaved stonecrop (Sedum 

 lanceolatus), weedy milkvetch (Astragalus miser) and 

 even many-flowered phlox (Phlox multiflora) . Overall 

 Pseureogneria spicata appears to consistently have the 

 highest coverage, though this is generally less than 5%. 



This is among the oldest PINFLE / PSESPI stands that 

 have been inventoried in southwestern Montana; it is 

 so old and lightning struck that none of the trees cored 

 yielded a core that was countable beyond several 

 hundred years, extrapolation yields ages in excess of 

 500 years. Stand structure is rather typical of xeric-site, 

 old-growth with very scattered reproduction and few 

 intermediate-aged trees. This stand represents the 

 moisture stressed extreme of a type that is known as 

 one of the driest of the woodland vegetation types in 

 Montana with exception ofjuniperus spp.-dominated 

 woodlands. [Plot NHMTECRN98SC0036] 



Pseudoroegneria spicata - Poa securuia Herbaceous 



Vegetation 



[PSESPI -POASEC] 



bluebunch wheatgrass - Sandberg's bluegrass grassland 



This association is found as small patches on the very 

 driest of spur-ridges that project to the north from the 

 main east-west trending ridgeline of the Centennials. 

 The combination of thin, rocky, limestone -derived 

 soils, the western exposures of the spur-ridges (having 

 the highest solar insolation values in a landscape with 

 primarily northern exposures) and the prevailing 

 southwesterly winds which scour snow from the 

 windward slopes (west) and crests causes these ridges to 

 be the most moisture-limited of any features in this 

 landscape. Wind deflation causes more than 80% 

 exposed limestone gravels; the depressed interstices are 

 occupied by soil. Litter and basal area together 

 comprise less than 5% of the surface area. 



These ridges are so dry as to be incapbale of supporting 

 much biomass, the total cover approaches the 10 % 

 cutoff of sparsely vegetated communities. Though we 

 have classed the plot as belonging to the bluebunch 

 wheatgrass - Sandberg's bluegrass association 

 (Pseudoroegneria spicata - Poa secunda Herbaceous 

 Vegetation), its position and composition, both in 

 alpha diversity and in the number of cushion plant 

 species prominent, place it closer to the P. spicata I 

 "Cushion Plant" community described by Cooper et al. 

 (1995) for southwestern Montana (not yet recognized 

 in TNC's Western Region Classification) . The shrub 

 component is almost nonexistent; Woods rose (Rosa 

 woodsii) and green rabbitbrush (Chr-jsothamnums 

 viscidiflorus) are so thinly scattered and depauperate as 

 to be obscured by the herbaceous layer. Only two 

 graminoids were present in the plot; the dominant P. 

 spicata and a trace of Idaho fescue (Fetuca idahoerisis) 

 which is virtually ubiquitous in moutain grasslands of 

 southwestern Montana. Low-growing, cushion-like 

 plants or those more typically found in exposed 

 subalpine to alpine environments (e.g. grayish 

 cymopterus [Cymopterus glaucus], lance-leaved 

 stonecrop (Sedum lanceolatum), Rocky Mountain 

 douglasia (Douglasia mantarm) , Cut-leaved daisy 

 (Erigeron compositus), Parry's townsendia (Townsendia 

 panyi) and sheep cinquefoil (Potentdla ovina) are 

 conspicuously reperesented, though individually not 

 exceeding 5% cover. 



OVERALL BIODIVERSITT SIGNIFICANCE: 

 The Sheep Mountain RNA as currently defined is a 

 small, intact sample of predominantly old-growth forest , 

 in the Rocky Mountains biome. It is in the middle of a 



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