Quercus macrocarpa/ Carex inops ssp. heliophila Plant Association 



QUEMAC / CARINO; bur oak / sun sedge 

 MTNHPrank:GlQ/Sl 



Environment: A single stand of QUEMAC/CARINO was sampled on BLM land on north aspect 

 toeslopes of a Mowry Shale ridge just north of the Wyoming border. This is the primary bur oak- 

 dominated community type in the area, encompassing most of Montana's only population of bur oak 

 {Quercus macrocarpa). It is restricted to the two parallel shale ridges that represent the only outcrops 

 of Mowry Shale in the state. The ridges lie within an area that is less than 2 miles x 9 miles in area. 

 Bentonitic shale is extensively exposed, and its high shrink-swell capacity gives the soil surface a 

 fractured appearance through dry summer months. The ridges rise about 50 m (150 ft) above the 

 surrounding plains with variable slopes across the broken topography, and this plant association 

 prevails across the side slopes of the ridges, thinning out on top. 



Vegetation: Except for discrete openings, these woodlands have a fairiy dense canopy of short 

 stature (about 20 ft. tall) trees, including about 60% cover by bur oak {Quercus macrocarpa) and 

 variable cover (average about 20%) by Rocky mountain juniper {Juniperus scopulorum). The shrub 

 layer is depauperate, but Ribes setosum is well represented in patches (10% total cover in the plot) 

 confined to canopy projections of oak trees. Grasses and sedges comprise the well-developed 

 herbaceous layer with about 30% total cover; most abundant are sun sedge {Carex inops ssp. 

 heliophila) a native rhizomatous sedge with about 10% cover, and major but variable cover by 

 Kentucky bluegrass {Poa pratensis), an exotic rhizomatous grass with about 20% cover. Cover by 

 forbs is relatively low (about 10%) while forb diversity is relatively high (18 species in the plot). Of 

 these there is a high proportion of annuals, both native and exotic {Collinsia parvijlora, Collomia 

 linearis, Ellysia nyctelea. Galium aparine, Lotus unifoliatus, Parietaria pennsylvanica. Polygonum 

 convulvulus, Polygonum douglasii, Thlaspi arvense), probably reflecting the cool, wet growing 

 season of 1997. This community type had the highest diversity of ftingi observed in Carter County. 



On the broken ridgetops, there is increased cover of ponderosa pine {Pinus ponder osa) to the point 

 of becoming a codominant tree species. On the more sheltered north-facing slopes. Rocky Mountain 

 juniper {Juniperus scopulorum) approaches codominance. Openings in the toeslope woodlands are 

 alluvial washes dominated by Carex inops ssp. heliophila (syn. C heliophila; C pennsylvanica) and 

 Calamovilfa longifolia (see discussion of CALLON / CARINO). The open ridgetops are similarly 

 dominated by sun sedge, and the widely spaced oaks at the margins presents a savanna-like ecotone. 

 Upland community types in the inter-ridge basins are predominantly sagebrush steppe 

 (ARTTSW/ELYLAN) and wetland bottoms (headwaters of Sheldon Creek) have Spartina pectinata 

 communities (SPAPEC). 



This deciduous woodland type is incompletely documented in the literature and addressed in state 

 classifications. It is reported in South Dakota (Hoffman and Alexander 1987) and in Wyoming 

 (Jones 1992); the Wyoming records are directly contiguous with the study area. Associated species 

 in the Wyoming characterization include, beside the dominants: blue grama {Bouteloua gracilis), 

 buffalograss {Buchloe dactyloides), western wheatgrass {Pascopyrum smithii), native bluegrass 

 (probably Poa secunda and P. ampla), prairie sandreed {Calamovilfa longifolia), sagewort 

 {Artemisia ludoviciana), and prickly pear {Opuntia polyacantha). It is also noted that exotic annual 



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