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Community Field Guide

Scientific Name:
Hesperostipa curtiseta - Elymus lanceolatus Herbaceous Vegetation

Common Name:
Western porcupine grass - thickspike wheatgrass Herbaceous Vegetation

Community Description

The northern porcupine grass - thickspike wheatgrass plant association is a highly productive prairie type of sheltered hillslopes in prairie pothole and prairie parkland regions and also occurs as a matrix community of rolling prairie landscapes of the provinces and adjoining northern Great Plains states. It is quite likely that it occupied some of the richest agricultural land in the northern Great Plains (typified by deep Mollisols) and that virtually all of it has been put under the plow. A few remnant areas in northern Valley County show that given the proper soils it can occur on gently rolling to flat terrain; the same environment, termed the dark-brown soil zone, is occupied by this association, termed the Stipa - Agropyron community in the literature of the Canadian prairies (Coupland 1992). Generally it is rich in species number, particularly forbs, and includes grasses and forbs that are restricted to or reach their peak frequency in this association, compared with surroundings.

This association has been documented as occurring primarily on glacial till on where deep loamy soils have developed on cool, moist north-facing slopes or in swale positions that probably receive in excess of normal precipitation through snow deposition. However, there are a couple of Valley County landscapes where this association occurs on gently rolling to flat terrain, associated with silty loam Mollisols, also a till- and drift-mantled landscape. These occurrences probably represent how the majority of this association was distributed as a matrix type prior to settlement. Regardless of position in the landscape, the soils are well drained and mantled by a deep and continuous litter layer with little or no soil and rock exposed.

Combined graminoid canopy cover of this association frequently exceeds 80% and Hesperostipa curtiseta (northern porcupine grass), the diagnostic graminoid with at least 5% canopy cover, is also usually the herbaceous dominant. However, plots with both Elymus lanceolatus (thick-spike wheatgrass) and Nassella viridula (green needlegrass) dominant have been recorded. The Bitter Creek / Frenchman Creek landscape of north-central Montana differs from some other sampled Montana locations in that Elymus lanceolatus or even Nassella viridula can be dominant and certainly they have higher constancy values here than in the typeís Sheridan County expression. Koeleria macrantha (prairie junegrass), Carex duriuscula (needleleaf sedge), Carex filifolia (threadleaved sedge), Carex inops (sun sedge) and Bouteloua gracilis (blue grama) all have constancy values in excess of 40% and the sedges named may have cover values in excess of 10%. The forb cover is diverse and varies by locality with Pediomelum argophyllum (silver-leaved scurfpea), Achillea millifolium (common yarrow), Geum triflorum (old manís whiskers) and Anemone patens (pasque flower) being particularly constant and occasionally having cover in excess of 5%. Shrub cover may include scattered sprigs of Rosa arkansana (prairie rose) and Symphoricarpos occidentalis (western snowberry) and very limited amounts (< 2%) of Artemisia frigida (fringed sage), ostensibly where grazing has been intensive.

This is one of the few associations where Selaginella densa (compact clubmoss) does not form a nearly continuous mat, in fact, it was absent in over 30% of the plots and averaged only 25% cover in the plots in which it occurred. Redmann (1975) described a unique feature, an abundance of moss in the undergrowth, and this feature has been established by Heidel et al. (2000) to occur, as well in Sheridan County, but the moss was obviously more abundant on north slopes.

This midgrass prairie type is found in the western and northern Great Plains, ranging from Manitoba westward through eastern Alberta and south to North Dakota and Montana.

The Juniperus horizontalis / Hesperostipa curtiseta - (Elymus lanceolatus) association develops on moderate to steep, north-facing slopes and general observation indicates that Juniperus horizontalis, the primary site colonizer and stabilizer, may slowly die out leaving an intact and stable Hesperostipa curtiseta - (Elymus lanceolatus) community.

Global Rank: G? State Rank: S2S3?

Community References


Heidel, B., S. V. Cooper & C. Jean, MTNHP

Cooper and Heidel 1999, Cooper et al. 2001, DeVelice et al. 1995, Heidel et al. 2000, Redman 1975

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This information is from the:
Montana Natural Heritage Program
Montana State Library--Natural Resource Information System
1515 East Sixth Ave., Helena, MT 59620-1800
406 444-5354