Schizachyrium scoparium - Carex filifolia Plant Association 



(syn. Andropogon scoparius - Carex filifolia) 



SCHSCO / CARFIL; little bluestem / thread- leafed sedge 



MTNHP rank: G4/S3 



Environment: SCHSCO/CARFIL was sampled twice on BLM land in the northern part of the 

 county east of Mill Iron and in southwest comer south of Hammond. Both sites have sandstone 

 derived soils and the communities are small patches in mosaics with ponderosa pine (PFNPON / 

 JUNHOR, PINPON / PSESPI, and PINPON / SCHSCO) and grassland (STICOM / CARFIL, 

 CALLON / CARINO) communities. Stands of little bluestem observed in Carter County were 

 usually small in size and limited to specialized topographic positions or disturbance regimes, 

 primarily on substrates derived from sandstone. It was seen both on ridge shoulders above slumping 

 escarpments, and on the toeslope deposits below, part of thin hilly range sites. Hansen and Whitman 

 (1938) described how S. scoparium is capable of colonizing areas of step-erosion on northerly slopes 

 and is an effective competitor that, once established, shows no sign of being replaced on these sites. 

 Similar observations have been made on coarse-textured substrates throughout extreme eastern 

 Montana in the course of other studies, which establishes SCHSCO - CARFIL as a topoedaphic 

 climax type. This type is usually associated with outcrops and escarpments, which support 

 ponderosa pine; some stands appear to be serai to ponderosa pine communities (see discussion of 

 PFNPON/SCHSCO). Just west of Alzada (on what appeared to be a shale-derived soil) a fallow field 

 was observed with little bluestem, an apparent primary successor on abandoned fields. 



Vegetation: Large bunches of the warm season grass Schizachyrium scoparium are the distinctive 

 visual indicator of this community type, taller than the codominant low, clump forming sedge Carex 

 filifolia. Either species may be dominant; cover of Schizachyrium scoparium was around 30% and 

 40% and cover of Carex filifolia was around 10% and 50% in the two respective plots. The plots 

 have a high diversity of grasses and forbs. In addition to the dominants, grasses in both plots include 

 Calamovilfa longifolia, Koeleria macrantha, Stipa comata, and Vulpia octofiora. There is a total of 

 28 species of forbs in the 2 plots but only Lygodesmia juncea, Polygala alba, and Psoralea 

 argophylla are in both. Pinus ponderosa and the shrubs Artemisia frigida and Yucca glauca are 

 present in trace amounts in both plots. 



Soils: In the study area, we found SCHSCO - CARFIL exclusively on coarse textured soils derived 

 from sandstone parent materials, consistent with Hansen and Hoffman (1988). A grassland 

 community dominated by little bluestem is also documented on shale derived substrate in the 

 Thompson Creek drainage west of Alzada (Ecological Consulting Service 1975). DeVelice et al. 

 (1995) noted that these non-sandstone occurrences can be explained by the fact that fissile shale can 

 mimic sandstone in effective soil texture and water-holding capacity. In western North Dakota, 

 Jensen et al. (1992) have found this type in the same topographic positions (primarily steep, upper 

 slopes of all aspects) but with parent materials varying from sandstone to mixed sedimentary rock 

 and glacial till. White (1970) states that S. scoparius will grow on substrates (shale) that should 

 ostensibly weather to fine-textured soils, if rock (shale) fragments are present. 



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