Native Vegetation of the Northern Plains

The Northern Plains are part of the NorthAmerican Interior Plains that extend from the foot ofthe Rocky Mountains eastward to the CanadianShield and Appalachian Provinces and extend fromthe Athabasca River on the Alberta Plateausouthward to the Gulf Coastal Plains (Fenneman1931, 1946; Hunt 1974; Goodin and Northington1985). The Interior Plains are divided east and westinto the Great Plains and the Central LowlandPhysiographic Provinces (Fenneman 1931, 1946). The Northern Plains are separated from the SouthernPlains by the North Platte-Platte-Missouri RiverValleys (Raisz 1957). The portions of the GreatPlains and Central Lowland Provinces that exist inthe Northern Plains are separated in North and SouthDakota and Saskatchewan by an eroded east facingescarpment at the eastern extent of the Tertiarysedimentary deposits of material eroded from theRocky Mountains that form a fluvial plain overlayingthe Cretaceous bedrock (Hunt 1974). The surfacelandform feature that shows the location of thisboundary is the east escarpment of the MissouriCoteau (Finneman 1931). In eastern Nebraska, theseparation of the Great Plains and Central LowlandProvinces is the western limit of older pre-Wisconsinglacial drift which has a mantle of loess (winddeposited silt) (Fenneman 1931).

The Northern Plains has a continentalclimate with cold winters and hot summers. Mean airtemperatures increase from north to south changingfrom about 35E - 40E F (1.7E - 4.4E C) in the north toabout 48E - 51E F (8.9E - 10.6E C) in the south. Mostof the precipitation occurs during the early portion ofthe growing season. Total annual precipitationfluctuates greatly from year to year. Periods of waterdeficiency during the growing season occur morefrequently than growing seasons without deficiencies. Drought conditions are common. Mean annualprecipitation increases from west to east and increasesfrom north to south. In the northern portion,precipitation ranges from about 12 inches (304.8 mm)in the west to about 24 inches (609.6 mm) in the east. In the southern portion, precipitation ranges fromabout 14 inches (355.6 mm) in the west to about 32inches (812.8 mm) in the east.

Evapotranspiration affects the quantity ofmoisture in the soil and the duration infiltrated waterremains available for plant growth. The potentialevapotranspiration for most of the Northern Plains isgreater than annual precipitation. Potentialevapotranspiration demand increases from north tosouth, and increases from east to west. Along the

eastern edge of the Northern Plains, the precipitationis greater than potential evapotranspiration duringmost years. The region also has several local areaswhere the combination of stored soil water,precipitation, plus water runin is greater thanevapotranspiration. Subirrigated soils where therooting zone is moist for most of the growing seasonwould be comparable to conditions with greaterprecipitation than evapotranspiration.

Soil development is effected by climate,parent material, topography, living organisms, andtime (Brady 1974). The main climatic factors thataffect soil development are temperature andprecipitation. Climate determines the type and rate ofweathering that occurs. The rates of biogeochemicalprocesses in soil are effected by soil temperature andsoil moisture. Climate determines the type of nativevegetation and the quantity of biomass production. There is a relationship between the type of nativevegetation and the kind of soil that develops. Increases in soil moisture, increase the biomassproduction and tend to increase organic content ofsoils. Increases in soil temperature, increase the rateof decomposition and tend to decrease organiccontent of soils (Brady 1974).

Classification of soils into principalsuborders is based on differences caused by climateand associated native vegetation. The biologicalprocesses in soil are effected by soil temperature andsoil moisture. The different climatic characteristicsimportant in soil development are separated intospecific soil temperature regimes and soil moistureregimes.

The Northern Plains has two soiltemperature regimes based on mean annual soiltemperature. The mean annual soil temperature isconsidered to be the mean annual air temperature plus1.8E F (1E C ) (Soil Survey Staff 1975). The Frigidsoil temperature regime has mean annual soiltemperatures of less than 47E F (8E C). The Mesicsoil temperature regime has mean annual soiltemperatures higher than 47E F (8E C) and lower than59E F (15E C) (Soil Survey Staff 1975). Theseparation between the Frigid and Mesic soiltemperature regimes occurs along a wide irregularbelt that extends eastward from central Wyomingalong its north border with Montana and continues tonorth central South Dakota just south of its northborder with North Dakota, then extends at asoutheasterly diagonal to about the center of SouthDakota’s east border with Minnesota, and then

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extends at a northeasterly angle to the boundary of theOak Forest.

Soil moisture regimes are based on the soilmoisture conditions in the soil. The Northern Plainshas four north-south zones of soil moisture regimesthat increase in soil moisture from west to east. Thesoils in the Aridic and Torric soil moisture regime,typically of arid climates, are dry in all parts for morethan half the time and the soils are never moist for aslong as 90 days during the growing season (SoilSurvey Staff 1975). The soils in the Ustic soilmoisture regime, typically of semi arid climates, aredry in some or all parts for 90 or more days in mostyears, but not dry in all parts for more than half thetime, and are not dry for as long as 45 days during the4 months that follow the summer solstice in 6 or moreyears out of 10 years (Soil Survey Staff 1975). Thesoils in the Udic soil moisture regime, typically of subhumid climates, are not dry for as long as 90 days. During the summer, the amount of stored moistureplus rainfall is approximately equal to or exceeds theamount of evapotranspiration (Soil Survey Staff1975). The soils in the Perudic soil moisture regime,typically of humid climates, are rarely dry. Duringthe summer, the precipitation is greater than theevapotranspiration (Soil Survey Staff 1975).

The combination of four soil moistureregimes (Aridic, Ustic, Udic, and Perudic) and twosoil temperature regimes (Frigid and Mesic) results ineight distinct soil moisture-temperature regimes in theNorthern Plains. The soils in the Aridic-Frigid soilmoisture-temperature regime are primarily AridicBorolls (arid cool Mollisols) and Torriorthents (hotdry recently eroded medium to fine textured Entisols)and support vegetation of short grasses with somemid grasses. The soils in the Ustic-Frigid soilmoisture-temperature regime are primarily TypicBorolls (semi arid cool Mollisols) and supportvegetation of mid and short grasses. The soils in theUdic-Frigid soil moisture-temperature regime areprimarily Udic Borolls (sub humid cool Mollisols)and support vegetation of mid grasses with some tallgrasses. The soils in the Perudic-Frigid soil moisture-temperature regime are primarily Aquolls (humidcool Mollisols that are saturated and absent of oxygenat times for unknown lengths) and support vegetationof tall grasses. The soils in the Aridic-Mesic soilmoisture-temperature regime are primarily Argids(arid warm Aridisols with thin horizons, dry for longperiods, and have a clay layer) and Aridic Ustolls(arid warm Mollisols) and support vegetation of shortgrasses. The soils in the Ustic-Mesic soil moisture-temperature regime are primarily Ustipsamments(semi arid warm Entisols that are well sorted wind

deposited sands) and Typic Ustolls (semi arid warmMollisols) and support vegetation of mid and shortgrasses with lower topographic slopes supporting tallgrasses. The soils in the Udic-Mesic soil moisture-temperature regime are primarily Udic Ustolls (subhumid warm Mollisols) and support vegetation of midgrasses and tall grasses. The soils in the Perudic-Mesic soil moisture-temperature regime are primarilyUdolls (humid warm Mollisols that do not have acalcium carbonate layer) and support vegetation oftall grasses.

Development of plant communities andvegetation types is effected by the climaticcharacteristics of temperature, precipitation, andevapotranspiration demand; the soil characteristics oftexture, structure, and chemical and mineralcomposition; and the landform topographiccharacteristics of slope, aspect, and elevation. Vegetation of the Northern Plains separates into 10grassland vegetation types and 7 grassland withwoodland or forest vegetation types. The vegetationof the Northern Plains map (figure 1) developed byDr. W.C. Whitman (Barker and Whitman 1989) is acompilation of information from several sourcessupplementary to the basic map of potential naturalvegetation by Kuchler (1964). Modifications tovegetation type designations, distributions, andboundaries were conflated into the base map fromstate vegetation maps for Montana (Ross and Hunter1976, Hacker and Sparks 1977), Nebraska (Kaul1975, Bose 1977), North Dakota (Shaver 1977),South Dakota (Baumberger 1977), and Wyoming(Shrader 1977). Vegetation type designations anddistributions from scientific papers were added forCanada (Clarke, Campbell, and Campbell 1942;Moss and Campbell 1947; Coupland and Brayshaw1953; Coupland 1950, 1961). A new concept of aplains rough fescue mixture along a portion of thenorthern border of North Dakota was introduced tothe map details by Whitman and Barker (1989).

No living plant species are known to haveoriginated in the Northern Plains. All plant speciesconsidered to be native to the Northern Plainsoriginated and developed in other regions andsometime later migrated into the Northern Plains. The plant communities and vegetation types,however, are relatively young and began developmentin place about 5,000 years ago when the currentclimate with cycles of wet and dry periods began.

The Tall Grass Prairie, Bluestem-Switchgrass-Indiangrass Type, exists on the easternmargin of the Northern Plains Grasslands and extendsfrom southern Manitoba through eastern North and

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South Dakota and western Minnesota southward intonorthwestern Iowa and northeastern Nebraska to thePlatte River. The physiography of the region consistsof the Manitoba Plain and the Red River Valley Plainof the Small Lakes Section and extends into theDissected Till Plains Section of the Central LowlandProvince. The climate is humid withevapotranspiration lower than precipitation. The soilmoisture regime is Perudic and the soil temperatureregime is Frigid in the north and Mesic in the south. The soils are primarily Aquolls in the north andUdolls in the south.

The Transition Mixed Grass Prairie,Wheatgrass-Bluestem-Needlegrass Type (figure 1),exists between the Tall Grass Prairie on the east andthe Mixed Grass Prairie on the west and extends fromeast central Saskatchewan and southwesternManitoba through east central North and SouthDakota and east central Nebraska to the Platte River. The physiography of the region consists of theSaskatchewan Plain and the Glaciated Plains (DriftPrairie) of the Small Lakes Section of the CentralLowland Province and extends into the easternportion of the High Plains Section of the Great PlainsProvince. The climate is sub humid withevapotranspiration greater than precipitation overmost of the area except for subirrigated soils andtopographic slope positions with water runin. Thesoil moisture regime is Udic and the soil temperatureregime is Frigid in the north and Mesic in the south. The soils are primarily Udic Borolls in the north andUdic Ustolls in the south.

The Mixed Grass Prairie has a high midgrass component with some short grasses and sometall grasses present and is separated into threevegetation types based on differences resulting fromsoil texture and soil temperature regime.

The Mixed Grass Prairie, Wheatgrass-Needlegrass Type (figure 1), exists on semi arid coolsoils between the Transition Mixed Grass Prairie onthe east and the Short Grass Prairie on the west andextends from mid Saskatchewan through westernNorth Dakota and eastern Montana to north centraland northwestern South Dakota. The physiography ofthe region consists of the eastern portions of theGlaciated and Unglaciated sections of the MissouriPlateau Section, including the Alberta Plain, of theGreat Plains Province. The climate is semi arid withevapotranspiration greater than precipitation. Thesoil moisture regime is Ustic and the soil temperatureregime is Frigid. The soils are primarily TypicBorolls.

The Mixed Grass Prairie, Wheatgrass-Grama Type (figure 1), exists on semi arid warm claysoils south of the Wheatgrass-Needlegrass Type andis in southwestern South Dakota. The physiographyof the region consists of the southeastern portion ofthe Unglaciated section of the Missouri PlateauSection of the Great Plains Province. The climate issemi arid with evapotranspiration greater thanprecipitation. The soil moisture regime is Ustic andthe soil temperature regime is Mesic. The soils areprimarily clay textured Typic Ustolls.

The Mixed Grass Prairie, Wheatgrass Type(figure 1), exists on semi arid warm dense clay soilssouth of the Wheatgrass-Needlegrass Type and is innorthwestern South Dakota. The physiography of theregion consists of the central portion of theUnglaciated section of the Missouri Plateau Sectionof the Great Plains Province. The climate is semi aridwith evapotranspiration greater than precipitation. The soil moisture regime is Ustic and the soiltemperature regime is Mesic. The soils are primarilydense clay textured Typic Ustolls.

The Northern Short Grass Prairie, Grama-Needlegrass-Wheatgrass Type (figure 1), exists onthe western side of the Northern Plains Grasslandsand extends from southeastern Alberta andsouthwestern Saskatchewan through central Montanaand southward into northeastern Wyoming. Thephysiography of the region consists of the westernportions of the Glaciated and Unglaciated sections ofthe Missouri Plateau Section of the Great PlainsProvince. The climate is arid with evapotranspirationgreater than precipitation. The soil moisture regimeis Aridic and the soil temperature regime is Frigid inthe north and Mesic in the south. The soils areprimarily Aridic Borolls and Torriorthents in thenorth and Argids and Aridic Ustolls in the south.

Dr. Whitman (Barker and Whitman 1989)continued the separation of this vegetation type fromthe Wheatgrass-Needlegrass Type because of thenotable increase in the shortgrass component and therelative decrease of western wheatgrass and needleand thread. Cool-season grass species increasetowards the northern portions and warm-season grassspecies increase towards the southern portions. Theneedlegrasses increase in the north. Blue grama andbuffalograss increase in the south. Because of thepresence of mid cool-season grasses, the NorthernShortgrass Prairie has sometimes been combined withthe Northern Mixed Grass Prairie. However, thesetwo vegetation types are distinct and should remainseparated. The Grama-Needlegrass-Wheatgrass Typehas the appearance of a shortgrass prairie and has an

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arid soil moisture regime, less soil horizondevelopment, shallower soil depth to theaccumulating soluble salts and developing argillic(clay) layer, shallower rooting depth, lower soil waterholding capacity, greater evapotranspiration potential,and generally more xeric than the Wheatgrass-Needlegrass Type.

The Northern Short Grass Prairie, SaltgrassType, exists on salt affected soils distributed in localareas across the Northern Short Grass Prairie region. Few plant species can tolerate the harshenvironmental conditions of salt-affected areas. Thetolerant species have mechanisms to exclude uptakeof salts, or physiologically separate and discharge theundesired salts.

The Southern Short Grass Prairie, Bluegrama-Buffalograss Type (figure 1), exists innorthwestern Nebraska and extends into east centralWyoming north of the North Platte River. Thephysiography of the region consists of a smallwestern portion of the High Plains Section of theGreat Plains Province. The climate is arid withevapotranspiration greater than precipitation. Thesoil moisture regime is Aridic and the soiltemperature regime is Mesic. The soils are primarilyArgids and Aridic Ustolls.

The Sandhills Prairie, Bluestem-Sandreed-Grama-Needlegrass Type (figure 1), exists in thenorth central portion of Nebraska south of theNiobrara River and north of the Platte River. OtherSandhills Prairie areas exist scattered throughout theNorthern Plains. Many areas are too small to map. Alarge area of Sandhills Prairie exists along theSheyenne River in southeastern North Dakota andanother large area exists near Swift Current,Saskatchewan. The physiography of the NebraskaSandhills consists of the Sand Hills region of theHigh Plains Section of the Great Plains Province. The climate is semi arid with evapotranspirationgreater than precipitation. The soil moisture regimeis Ustic and the soil temperature regime is Mesic. The soils are primarily Ustipsamments.

The Foothills Prairie, Plains Rough FescueType (figure 1), exists as a fringe along the montaneforest of the Rocky Mountain foothills from Albertato south central Montana and along the aspengroveland and aspen parkland bordering the borealforest zone in Alberta and Saskatchewan and the typemingles with the Wheatgrass-Bluestem-NeedlegrassType extending across Saskatchewan andsouthwestern Manitoba and into northern NorthDakota. Plains Rough Fescue has continued to move

south in the Transition Mixed Grass Prairie and theMixed Grass Prairie of North Dakota. Thephysiography of the region consists of the northernportion of the Glaciated section of the MissouriPlateau Section of the Great Plains Province and thenorthern portion of the Small Lakes Section of theCentral Lowland Province.

The Pacific Bunchgrass Prairie, Bluebunch-Fescue Type (figure 1), exists in the south centralportion of Montana. Numerous other areas too smallto map exist within the Great Plains. Thephysiography of the region consists of theUnglaciated section of the Missouri Plateau Sectionof the Great Plains Province.

The Badlands and River Breaks, WoodyDraw and Savanna Types (figure 1), exist in centralMontana along the Missouri and Musselshell Rivers,in western North Dakota along the Little MissouriRiver, and in southwestern South Dakota along theWhite River. The physiography of the region consistsof the Unglaciated section of the Missouri PlateauSection of the Great Plains Province.

The Pine Savanna, Pine-Juniper-BluebunchType (figure 1), exists on rough uplands in southcentral and southeastern Montana, north centralWyoming, western South Dakota, and southwesternNorth Dakota. The physiography of the region is theUnglaciated section of the Missouri Plateau Sectionof the Great Plains Province.

The Black Hills Pine Forest, Pine-Spruce-Aspen Type (figure 1), exists in southwestern SouthDakota and northeastern Wyoming. Thephysiography of the region consists of the Black Hillssection of the Missouri Plateau Section of the GreatPlains Province.

The Montane Forest, Pine-Fir-Spruce Type(figure 1), exists on the Sweetgrass Hills, and theHighwood, Bearpaw, Little Rocky, Moccasin, Judith,and Big Snowy mountains in Montana and theCypress Hills in Saskatchewan. The physiography ofthe region consists of the laccolithic domedmountains in the Unglaciated section and theerosional upland remnant in the Glaciated section ofthe Missouri Plateau Section of the Great PlainsProvince.

The Upland Woodlands, Aspen-Ash-Oak-Juniper Types (figure 1), exist as scattered areas withvarious types of trees, shrubs, and grasses in NorthDakota, Manitoba, and Saskatchewan. Thephysiography of the region consists of upland

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positions of the Small Lakes Section of the CentralLowland Province and of upland positions of theUnglaciated section of the Missouri Plateau Sectionof the Great Plains Province.

The Riparian Woodlands, Cottonwood-Ash-Elm Type (figure 1), exists along the floodplains ofthe larger rivers and streams and as small grovesalong minor drainage ways located throughout theNorthern Plains.

The environmental and biological factorsthat affect development of plant communities andvegetation types are the same factors that affect soildevelopment. The current climate with wet and dryperiods, and the current soil moisture and soiltemperature regimes have been operational for about5,000 years. Soil moisture regimes affect distributionof plant species affiliations. The species affiliationsthat are the major vegetation types in the Northern

Plains; Tall Grass Prairie, Transition Mixed GrassPrairie, Mixed Grass Prairie, and Short Grass Prairie;coincide with the four soil moisture regimes; Perudic,Udic, Ustic, and Aridic; respectively. The four soilmoisture regimes are further separated into two soiltemperature regimes; Frigid in the northern portionsand Mesic in the southern portions. Soil temperatureregimes affect composition and distribution of cool-season and warm-season grasses within the vegetationtypes. In the northern Frigid temperature regime,warm-season grass species decrease and cool-seasongrass species increase. In the southern Mesictemperature regime, cool-season grass speciesdecrease and warm-season grass species increase.

Acknowledgment

I am grateful to Sheri Schneider forassistance in production of this manuscript.

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