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M498 Poa pratensis - Bouteloua dactyloides - Centaurea spp. Great Plains Ruderal Grassland & Shrubland Macrogroup

The U.S. National
Vegetation Classification
Type Concept Sentence: This macrogroup is found on dry to mesic sites in the central and western Great Plains dominated by exotic herbaceous species or deciduous shrubs.
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Common (Translated Scientific) Name: Kentucky Bluegrass - Buffalograss - Knapweed species Great Plains Ruderal Grassland & Shrubland Macrogroup
Colloquial Name: Great Plains Ruderal Grassland & Shrubland
Hierarchy Level: Macrogroup
Type Concept: This macrogroup is found in the Great Plains from north of the U.S.-Canadian border to extreme northern Mexico. It is dominated by exotic, invasive grasses, forbs, or, in the south, deciduous shrubs. These species can become abundant after significant disturbance, often associated with agricultural activities, or a disruption of natural disturbance regimes. Common disturbances which favor establishment of this macrogroup include long-term, heavy grazing, planting exotic species for livestock forage, plowing land and then abandoning it, and a disruption of the natural fire regime. Vegetation cover varies from low to very high. Abundant species vary greatly in this macrogroup, depending on the geographic location, seed sources, and nature of land use. Common species in the north include Agropyron cristatum, Bromus inermis, Bromus arvensis, Bromus tectorum, Elymus repens (on more moist sites), Phleum pratense, Poa pratensis, and Thinopyrum intermedium. In the south, Bothriochloa ischaemum var. songarica, Bouteloua dactyloides (a native but can be dominant on overgrazed rangeland), Dichanthium annulatum, Pennisetum ciliare, and the shrubs Baccharis neglecta, Crataegus mollis, Crataegus viridis, and Rhus lanceolata can be common. Gutierrezia texana and Amphiachyris dracunculoides are often extremely abundant on overgrazed sites in Texas. Across the range the forbs Ambrosia spp., Artemisia absinthium, Carduus nutans, Centaurea spp., Cirsium arvense, Convolvulus arvensis, Dipsacus fullonum, and Euphorbia esula can be common. This macrogroup also includes native upland shortgrass prairie areas dominated by invasive Prosopis glandulosa. This macrogroup can be found on mesic to dry sites on a variety of soils where disturbance regimes have been altered sufficiently to allow the establishment of the exotic species.
Diagnostic Characteristics: This macrogroup is dominated by invasive exotic graminoids, forbs, and (in the south) shrubs. Native species comprise a minor component of the vegetation, except Bouteloua dactyloides, which can be common on overgrazed lands.
Rationale for Nominal Species or Physiognomic Features:
Classification Comments: The geographic and floristic transition to Eastern North American Ruderal Grassland & Shrubland Macrogroup (M123) needs to be defined. Currently it is vaguely described as the "tallgrass region of the Midwestern United States" (possibly Provinces 251 and 255 vs. 332 and 315?). More information is needed on whether succession of this ruderal type could lead to native prairie types.
Similar NVC Types:
M052 Great Plains Sand Grassland & Shrubland, note:
M051 Great Plains Mixedgrass & Fescue Prairie, note:
M123 Eastern North American Ruderal Grassland & Shrubland, note: can be similar where the two distributions meet in the eastern Great Plains.
M307 Southeastern Ruderal Grassland & Shrubland, note:
M493 Western North American Ruderal Grassland & Shrubland, note:
M499 Western North American Cool Semi-Desert Ruderal Scrub & Grassland, note:
M512 North American Warm Desert Ruderal Scrub & Grassland, note:
Physiognomy and Structure: Most sites are dominated by herbaceous species less than 1 m tall. In the northern portion of this macrogroup's range, the grasses are largely C3. Deciduous shrubs are more common in the south and can dominate some stands. Vegetation density can be low, especially on heavily grazed or low-fertility sites, to dense. Some species form near monocultures.
Floristics: Abundant species vary greatly in this macrogroup, depending on the geographic location, seed sources, and nature of land use. Common species in the north include exotic and invasive Agropyron cristatum, Bromus inermis, Bromus arvensis (= Bromus japonicus), Bromus tectorum, Elymus repens (on more moist sites), Phleum pratense, Poa pratensis, and Thinopyrum intermedium. In the south, Bothriochloa ischaemum var. songarica, Dichanthium annulatum, Pennisetum ciliare, and the shrubs Baccharis neglecta, Crataegus mollis, Crataegus viridis, and Rhus lanceolata can be common. Gutierrezia texana and Amphiachyris dracunculoides (= Gutierrezia dracunculoides) are often extremely abundant on overgrazed sites in Texas. Across the range Ambrosia spp., Artemisia absinthium, Carduus nutans, Centaurea spp., Cirsium arvense, Convolvulus arvensis, Dipsacus fullonum, and Euphorbia esula can be common. Bouteloua spp., Bouteloua dactyloides (= Buchloe dactyloides) (which can dominate on overgrazed rangeland), Pascopyrum smithii, Schizachyrium scoparium, and other widespread native grasses can be found in low to moderate amounts. This macrogroup also includes native upland shortgrass prairie areas dominated by invasive Prosopis glandulosa.
Dynamics: This macrogroup tends to replace native prairie through direct planting of exotic species, usually for forage, or through alteration of natural disturbance regimes. Native grasslands are well-adapted to moderate grazing over time or heavy grazing for short periods, but when used as long-term pasture and with high stocking rates, many of the dominant native grasses are reduced or eliminated (Branson and Weaver 1953). Heavy haying or grazing if done consistently during the mid-summer months negatively affect the dominant warm-season grasses by removing their biomass before they have flowered. Cool-season grasses and forbs which set seed earlier are favored by these activities. Native and non-native forbs, woody species, and C3 grasses increase in the absence of fire, especially when combined with grazing by livestock. Drier sites on hilltops or rocky soils persist longer, but mesic sites on lower slopes can be invaded by trees and shrubs after just several years without fire. This macrogroup is typically persistent in the absence of long-term natural disturbance regimes. More information is needed on whether succession of this ruderal type could lead to native prairie types. Annual precipitation in the region where it occurs does not allow rapid tree growth and the new disturbance regime favors the exotic species over most native prairie species.

Historically, mesquite-dominated shrublands and tree savannas probably occurred as a natural component on more fertile soils and along drainages where soils are deep in the short- and midgrass prairie, but mesquite has expanded its range into prairie uplands in recent decades (Sims and Risser 2000). Previously, periodic fire limited the development of woody cover to widely scattered large mesquite trees or possibly denser trees resembling a tree savanna (Archer 1989). Livestock grazing reduces fine fuels that carry fire and disperse seeds away from seed predators in animal dung which provides favorable conditions for germination and establishment (Archer 1989, Brown and Archer 1989). These recent invasive upland mesquite shrublands are considered ruderal or novel in th eshortgrass prairie where it did not occur historically.
Environmental Description: This upland macrogroup occurs on a variety of dry to mesic habitats and is united more by land-use history than by soil properties, slope, or other factors. Sites have a history of significant disturbance, usually for agricultural purposes, though sometimes for infrastructure or other direct development. Sites occur on former crop fields, heavily grazed pastures, and where there was intentional planting of exotic species. Other examples of this macrogroup are created where natural disturbance regimes, especially fire patterns, are altered and the conditions become favorable for the exotic species to grow. Some species can alter soil properties, which may help the exotic species persist (Christian and Wilson 1999, Jordan et al. 2008).
Geographic Range: This macrogroup occurs throughout the western Great Plains from the southern Canadian Prairie Provinces to the U.S.-Mexico border and probably into northern Mexico.
Nations: CA, MX, US
States/Provinces: AB, CO, MT, ND, NE, NM, OK, SD, SK, TX, UT, WY
US Forest Service Ecoregions (2007)
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Plot Analysis Summary:
Confidence Level: High
Confidence Level Comments:
Grank: GNA
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Concept Lineage:
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Obsolete Names:
Poa pratensis - Buchloe dactyloides - Centaurea spp. Great Plains Ruderal Grassland & Shrubland Macrogroup
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Synonomy:
Concept Author(s): Faber-Langendoen et al. (2014)
Author of Description: J. Drake and K.A. Schulz
Acknowledgements:
Version Date: 10Nov2015
References:
  • Archer, S. 1989. Have southern Texas savannas been converted to woodlands in recent history? The American Naturalist 134:545-561.
  • Branson, F. W., and J. E. Weaver. 1953. Quantitative study of degeneration of upland mixed prairie. Botanical Gazette 114: 397-416.
  • Brown, J. R., and S. Archer. 1989. Woody plant invasion of grasslands: Establishment of honey mesquite (Prosopis glandulosa var. glandulosa) on sites differing in herbaceous biomass and grazing history. Oecologia 80:19-26.
  • Christian, J. M., and S. D. Wilson. 1999. Long-term impacts of an introduced grass in the northern Great Plains. Ecology 80(7):2397-2407.
  • Faber-Langendoen, D., J. Drake, S. Gawler, M. Hall, C. Josse, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, L. Sneddon, K. Schulz, J. Teague, M. Russo, K. Snow, and P. Comer, editors. 2010-2019a. Divisions, Macrogroups and Groups for the Revised U.S. National Vegetation Classification. NatureServe, Arlington, VA. plus appendices. [in preparation]
  • Jordan, N. R., D. L. Larson, and S. C. Huerd. 2008. Soil modification by invasive plants: Effects on native and invasive species of mixed-grass prairies. Biological Invasion 10(2):177-190.
  • Sims, P. L., and P. G. Risser. 2000. Grasslands. Pages 325-356 in: M. G. Barbour and W. D. Billings, editors. North American terrestrial vegetation. Second edition. Cambridge University Press, New York. 434 pp.