the peculiar growth form is genetically- or 

 environmentally-induced. Its sporadic distribution 

 challenges accurate estimates of canopy cover, which 

 range from 15-30 %, placing these stands, according to 

 the parameters of the National Vegetation 

 Classification Standard, in both the woodland and 

 grassland categories. The relatively species diverse 

 shrub layer is dominated by Wyoming big sagebrush 

 {Artemisia tridemaia ssp. wjiommgensis) , whose variable 

 canopy cover appears to be a function of competition 

 with neighboring trees. Graminoid and forb cover vary 

 depending on aridity, with western wheatgrass 

 {Pascopr^rum smxthii), prairie junegrass {Koeleria 

 macrantha) and yarrow (AchiUea millejoUum) in the 

 widespread, less arid conditions, and little bluestem 

 {Schizachrjium scoparium), sun sedge (Carex inops), and 

 few-flowered wild buckwheat {Eriogonum pauciflorum) 

 in driest places. 



PitccmeOia nuttktUUma Sparse Vegetation 



[PUCNUT] 



Nuttall's alkaligrass barrens 



This association is sparsely-vegetated with Nuttall's 

 alkaligrass (PuccinnelUa nuttallii) as dominant, occurring 

 as a broken stringer along an intermittent drainage that 

 feeds into Third Coulee. It constitutes the vegetation 

 band closest to the incised charmel on a floodplain 

 position with silty loam alluvial soils; salt efflorescence 

 was not observed but this community is known to occur 

 on salt-affected soils that have a slightly wetter, 

 temporarily inundated, moisture regime. Within the 

 TNC tracking system this community type has been 

 reported only from Colorado as Gl ? but Heidel and 

 Cooper (1996) have documented it from western plains 

 of Montana near the Rocky Mountain Front, noted it 

 in field reconnaissance, and cited it from the Canadian 

 literature (synonym: PucdnnelUa airoides, Dodd and 

 Coupland 1966). 



The Fourth Ridge example of this type has low diversity 

 and is compositionally very similar to other observed 

 Montana occurrences with PucdmWia matalliana 

 dominant at around 40 % canopy cover; inland 

 saltgrass (^^tkUis spicata) and povertyweed (Iva 

 coaMris) are the ordy other forbs exhibiting more than 

 trace coverages. This community grades to Distichilis 

 spicata-dominated sites on drier positions. Wyoming 

 big sagebrush (Artemisia tridentata ssp. wyomingensis) in 

 trace amounts was the only shrub noted within the 

 plot. Within the channelway, yellow sweetclover 

 QAelilotus officinalis) was noted as forming extensive, 

 virtually unbroken swathes in the same position as 



PUCNUT and extending to the drier Distichilis stricta 

 association positions £is well. 



Downstream from the PUCNUT sampling site a 

 comparable landscape position was occupied by what 

 has been described as western wheatgrass - irJand 

 saltgrass grassland {Pascopyrum smithii - Distichlis spicata 

 Herbaceous Vegetation; 04; WY, ND). This type has 

 not been formally described from MT, but probably has 

 been subsumed to date within the Distichilis stricta or 

 Pascopyrum smithii community types of Hansen et al. 

 (1995). [Plot NHMTECFR97SC0004] 



Calamovilfa longifolia - Carex inops 



Herbaceous Vegetation 



(CALLON- CARING] 

 prairie sandreed - sun sedge grassland 



There are sites occurring as tiny woodland openings at 

 higher positions in the landscape that appear to be 

 developed on a more erosive shale member that 

 weathers to a fissile texture (functions as sandy soil 

 analogue) and may be acidic in its reaction. These sites 

 have a high percent of exposed soil (in excess of 80 %), 

 a much reduced vegetation cover and the composition 

 in dominant vegetation is highly variable across the 

 landscape. They are in erodible settings, which 

 complicates interpretation. The sample plot appears to 

 be most similar in site and vegetation parameters to the 

 prairie sandreed - sun sedge grassland (Calamovilfa 

 km^folia - Carex inops Herbaceous Vegetation) that has 

 been identified for southeastern Montana (Hansen and 

 Hoffman 1988). 



The vegetative aspect is dominated by rhizomatous 

 graminoids, sun sedge (Carex inops) and Calamovilfa 

 longifolia (prairie sandreed) with plains reedgrass 

 (Calamagrostis mcmtar\ensis) and Pascopyrum smithii just 

 exceeding trace amounts. We hypothesize that an 

 acidic reaction of the substrate is reflected in the forb 

 component dominance by few-flowered buckwheat 

 (Eriogonum pauciflorum). Shrubs like prairie rose (Rosa 

 arfeansana) and trees like Rocky Mountain juniper 

 (Juniperus scopulorum) constitute less than 3 % canopy 

 cover and their population structure does not indicate a 

 change in their contribution. (Plot 

 NHMTECFR97SC0005] 



OVERALL BIODIVERSITY SIGNIFICANCE: 

 Fourth Ridge RNA features a woodland community 

 dominated by Rocky Mountain juniper (Juniperus 

 scopulorum) in good condition. It is part of one of the 

 most extensive Rocky Mountain juniper woodland 

 stands in the Great Plains portion of the state, and near 



16 



