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Ecoregions of
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| 43c. River Breaks | Level IV Ecoregion |
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43f. Subhumid Pierre Shale Plains |
The Northwestern Great Plains
ecoregion encompasses the Missouri Plateau section of the Great
Plains. It is a semiarid rolling plain of shale, siltstone, and sandstone
punctuated by occasional buttes and badlands. Native grasslands persist
in areas of steep or broken topography, but they have been largely replaced
by spring wheat and alfalfa over most of the ecoregion. Agriculture
is limited by erratic precipitation patterns and limited opportunities
for irrigation.
The River Breaks form broken terraces and uplands that descend to the Missouri River and its major tributaries. They have formed particularly in soft, easily erodible strata, such as Pierre shale. The dissected topography, wooded draws, and uncultivated areas provide a haven for wildlife. Riparian gallery forests of cottonwood and green ash persist along major tributaries such as the Moreau and Cheyenne rivers, but they have largely been eliminated along the Missouri River by impoundments.
Physiography Area (square miles): 10517 Geology Surficial Material and Bedrock Soil Order (Great Groups) Climate Precipitation - Mean annual (inches) Potential Natural Vegetation Blue grama, western wheatgrass, buffalograss, and some bluestem. Juniper and deciduous trees on northfacing slopes. Cottonwood gallery forests on the floodplain. Land Use and Land Cover Steep slopes restrict landuse to cattle grazing. Land cover is mostly rangeland and native grasses. Remnant woodlands in draws and on existing (unimpounded) alluvial flats. |
