PLANT SPECIES ADAPTED TO THE SOUTHERNPRAIRIES AND GREAT PLAINS

W. T. CARTERBureau of Chemistry and Soils

As experimental work Is under way byresearch agencies of the Soil Conserva-tion Service to determine the suitabilityof plant species for soil erosion con-trol, and as values have not as yet beendefinitely established, I will confinethis discussion to a brief outline of themajor plant communities and the importantspecies of the native vegetation of thevarious soil groups of the southern prai-ries and plains.

Broadly considered, there are but afew general plant associations In theseunforested areas of the south and south-west, these being closely related intheir distribution to moisture, tempera-ture, soils and relief. These consist,for the most part, of relatively fewgenera and not a very large number ofspecies, though associated with the com-munities of plants most commonly foundthere are many species of but slight dis-tribution as to numbers and therefore arerelatively unimportant.

On the prairies (pedalferic soilarea) the coarse grasses largely predom-inate even on the heavy dark soils.

On the plains (pedocalic soil areas)the short grasses predominate on thesoils of heavy texture, and coarse bunchgrasses are by far the most abundant onthe sandy soils. The short grasses ofthe extreme southern part of the plainsis dominated by the curly mesquite grass,but north of about parallel of latitude32 degrees the buffalo grass and gramagrasses take the place of curly mesquiteas the dominant members of the plant com-munities on the heavy soils. Small treeand shrub growth of many species occur inthe southern pedocalic area on soils ofboth heavy and of light texture, theseconsisting mainly of several species ofoaks, and thorny small trees and shrubs,northward these coarse plants thin outgreatly and consist mostly of some smalloak and mesquite trees.

The general relationships of nativeplants to the several great treeless soilbelts Indicated on the accompanyingsketch map will be briefly outlined. InTexas the southern limits of tho plainsand prairies occur, these north-southbelts comprising broad soil groups whichdiffer in general characteristics largelyIn proportion to differences in moistureconditions and ranging from soils devel-oped under humid conditions on the east,the pedalfers (prairies and forests) and,going westward, the several belts of ped-ocals which make up the soils the plains

consisting of (1) the southern Chernozem-Chestnut belt; (2) the Brown Soil Belt;and (3) the extreme western belt of Sier-osem or desert.

Plants on Soils of the Pedalferic Area

Broadly considered, the humid areawherein the soils of pedalferic develop-ment occur, comprise here two great soiland plant divisions, that is, the soilsof somewhat podzolic development withtimber vegetation, and soils (largelyRendzinas) which have been developed un-der grass cover—the prairies. Rainfallhere ranges from an average annual ofabout 25 or 30 Inches in the westernpart, to 50 inches in the eastern sec-tions.

The native vegetation of the timber-ed areas comprises pine, pine and hardwoods mixed, and on the western forestfringe only hardwoods, mainly oaks. Thesoils here are somewhat podzolio in char-acter, though they are not true podzolssuch as are developed typically in morenortherly latitudes. They are for themost part highly siliceous, light color-ed, acid, rather thoroughly leached, lowin organic, matter and of low to only mod-erate inherent fertility. Only verysmall amounts of native grasses occur inthe timbered sections, and though grassgrowth increases greatly when the timberis cleared away, lt is largely of coarsebunch grasses of such types as speciesof Andropogons panicums and Paspalums.

Native Plants on the Soilsof the Prairies

On the prairies the soils for themost part are heavy dark soils developedfrom calcareous formations and the nativevegetation is very largely of coarsebunch grasses, though the more westerlyareas have in places considerable of theshort grasses.

The prairies are of 3 distinct divi-sions, each characterized by definitecommunities of native grasses, soils andrelief. Locally these are known as theGrand Prairie, Blackland Prairie, andCoast Prairie.

The Grand Prairie comprises highundulating and rolling to hilly reliefwith deeply cut valleys in the hardlimestone from which the dark heavysoils have been developed.. The grasscover on the deep soils consists largelyof coarse bunch grasses (largely of

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Andropogon sp.) with a considerable ad-mixture of other species, and some buffa-lo grass (Buchloe dactyloides) and sever-al species of grama grass, though prob-ably Bouteloua gracills and B. Curtipen-dula are the most abundant. Practicallyall of the soils are heavy clays or clayloams and in many places the short grass-es mentioned predominate. On the stony,rough or shallow soils, of which there isa large proportion on this prairie, thegrass growth is thin and some small treesgrow thinly, these consisting principallyof shin oak, live oak, and various others.The soils here are largely of the Denton,San Saba, Crawford and Brackett series.

On the Blackland Prairie, a largewell-drained undulating area of darkheavy .soils deeply developed over marlsand chalk, the proportion of coarse bunchgrasses (largely Andropogon sp.) is larg-er and the buffalo and grama grasses oc-cupy a smaller proportion of the landthan they do on the Grand Prairie. Thesoils for the most part are highly cal-careous, deep, and very fertile, thusproviding a favorable environment for thethick grass cover. A very large propor-tion of the original growth has been de-stroyed by cultivation. '.Where the slopesare steep the cultivated soil has inplaces been thinned and gullied by ero-sion. Erosion Is checked by reintroduc-tion of the native grasses and by bermu-da and other grasses. At the Soil Con-servation Station at Temple, Texas, manygrasses and other plants are being testedas means for preventing or checking ero-sion on typical Blackland soils. A num-ber of plants show promise though re-sults are as yet incomplete. At presentit appears that, the valuable grasses forchecking erosion here are bermuda grass,St. Lucie grass and buffalo, curly mes-quite, grama, Dallis, and other grassesincluding species of the Andropogons areof considerable value. Some of thesewithstand well the extreme of heat andcold, moisture and dryness of the region,though some (such as the bermuda) may betoo difficult to keep out of crops incultivated fields If used" In proximity tocropland. The soils of this prairie arelargely of the Houston series, with somealso of the Wilson and Crockett series.

The moat southern prairie—the CoastPrairie, is a nearly flat smooth landhaving very slow drainage. Soil erosionis not a great problem, and agriculturaldevelopment is retarded by Inadequatedrainage over large areas. Due to thesmooth deep soils, the large amount ofmoisture, and to the long growing season,the grass growth is abundant and luxuri-ant. Two general kinds of soils occurhere. These are the dark generally heavyand highly productive soils, largely ofthe Lake Charles series; and the sandylight colored soils of low to moderate

fertility. On the dark soils the An-dropogons and Bouteloua species abound,though some species of Paspalum, Agros-tis, Panicum, and other genera are alsoabundant.

On the sandy soils, largely of theHockley and Katy series, the rank growthof grasses comprise chiefly species ofAndropogon (considerable Ascoparius) andPaspalum, Panicum and Sporobolus speciesare also abundant. This, the only largearea of light colored prairie soils inTexas, is being gradually encroached onby post oak from the bordering forestlands on the north.

The Subhumid Plains(Chernozem-Chestnut Section)

This great area comprises a broadnorth-south belt of soils of pedocalicdevelopment occupied by a native vegeta-tion of many species of grasses, shrubs,and herbaceous plants. The surfaceranges from flat and undulating tostrongly rolling and elevation rangesfrom sea level to an extreme of about14.000 feet above. The growing season ofabout 173 days a year in extreme north-west Texas Increases gradually southwardto about 318 days a year at the southerntip of the state. The average annualrainfall in the eastern edge of the beltis about 25 to 30 inches and decreaseswestward to about 20 inches in the west-ern part. This section of the plains isoccupied by parts of several geographicsubdivisions, each characterized by cer-tain groups of soils and communities ofnative plants.

The Rio Grande Plain:

This is the most southerly divisionwherein subtropical plants are readilygrown. Here the land is covered with aheavy growth of grasses and also in manyplaces by a large amount of small treesand shrubs. The dark soils of this sec-tion, deep and smooth and highly fertile,have a heavy native growth of shortgrasses—chiefly both buffalo grass(Buchloe dactyloides) and curly mesquite(Hilarla belangeri) and considerableamounts of several species of the gramagrasses (Bouteloua species). In addi-tion to many other less abundant species,this type of land supports a large amountof small mesquite trees, and variousthorny shrubs such as chaparral, huajil-lo, catclaw, huisache and others. Ero-sion on the smooth dark soils is not agreat problem here. These soils arelargely of the Victoria, Goliad and Ore-lia series.

On the sandy soils of the Rio GrandePlain, there is less of the brush growthbut a thick growth of coarse bunch grass-es occurs with several species of grama

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and Aristida quite abundant. The sandysoils are chiefly of the Duval, Vebb,Brennon and Nueces series.

The Edwards Plateau:

Just north of the Rio Grande Plain,the Edwards Plateau, a rolling, deeplydissected limestone plain with shallowdark heavy soils mostly of Valera series,lies around 2000 feet above sea level.Soils are of very thin layers mostly.The grass community here Is thin in manyplaces but consists largely of curly mes-qulte and buffalo grasses with several ofthe grama grasses. On the generally thinstony and rough lands many small treesand shrubs grow, these consisting chieflyof mesquite, shin oak, live oak, cedar,sumac, and species of thorny shrubs suchas species of mimosa, acacia, condalia,colubrina, odostemon, and others. Manyof these trees and shrubs, though ofscattered growth, afford valuable browsefor the range livestock.

The Rolling Plains:

Just north of Edwards' Plateau ex-tending northward through Oklahoma andKansas is the great area which physiogra-phically is' known as the Central Lowland.In Texas that part occupying the sectionwhere the soils are of pedocalic develop-ment is referred to here as the RollingPlains. This division of the plains isoccupied by several broad groups of soilseries which for the most part are of(1) smooth heavy dark soils (2) red un-dulating to rolling sandy soils, and (5)some light colored loose sandy soils.

The dark smooth soils, especiallythose of heavy texture support a nativegrowth consisting largely of short g r a s s - e s — c h i e f l y the buffalo and grama grass-

es—and here the northerly latitude ap-pears unsuitable to the curly mesquitegrass so abundant farther south and itsplace northward is taken by the buffalograss. On the sandy soils of the RollingPlains section, though some species ofgrama grasses are abundant, the principalgrowth, especially on the lighter textur-ed, sandy soils consists largely of thebluestems Andropogan scoparius, A. furca-tes, and A. succharoides and variousother bunch grasses, and especially spe-cies of Aristida on overgrazed pastures.Shin oak, a very small shrub-like treegrows abundantly on some of the veryloose light sandy soils of the RollingPlains. All of these grasses and otherplants are invaluable in checking soilerosion, both by water or by wind ero-sion. Mechanical barriers designed tohold rainwater on the land enormously in-creased the grass cover in some pasturesby causing a large proportion of the wa-ter to penetrate into the soil. The dark

soils are largely of the Abilene andHollister and Roscoe series and the sandysoils of the Vernon and Miles series.

The High Plains:

This large area, largely of darkbrown soils and red soils constitutes ahigh smooth plateau of deep highly fer-tile soils. In the northern half ofthis plains division, the clay loam tex-ture predominates and here the nativegrowth is very largely buffalo grass withan admixture of other grasses but mostlyof blue grama (B. gracills) which makesup 10 to 20 per cent of the grass cover.Here erosion is not generally severe,though where the grass cover has been de-stroyed, gullies and sheet erosion startin a short time. The native grass cover,however, encroaches rapidly to stop sucherosion where it can possibly gain a "foothold. The heavy soils are mostly ofthe Pullman, Richfield and Zita series.In the southern half of the High PlainsPlateau, the soils are largely sandy—though large areas are of moderatelyheavy red fine sandy loams having a grasscover largely of some species of gramagrass with a small amount of buffalograss and in places much of three-awnedgrasses (Aristida sp.). On this redsandy soil (Amarillo fine sandy loam cat-claw shrubs abound, in places. Some areasof very loose sands occur in the south-western part of the High Plains and themost characteristic growth here is verylow small shin oak trees (Q. havardi) andsome of the very coarse bunch grasseslargely of the Andropogon Species.

The sandy soils of this section aresubject to severe drifting in hard windswhere the native vegetation has been re-moved. This blowing and drifting of thesoil is retarded by allowing the coarsegrasses and small shin oak trees to re-capture the land and drifting places.These sandy soils are mostly of the Amarillo and Springer series.

The Semi-Arid Plains(Brown Soils)

This division of soils occupies anarrow north-south belt just west of theSubhumid Plains of dark brown and redsoils. The vegetation is somewhat simi-lar to the belt on the east in that vari-ous species are common, though of consid-erably less abundance on the more wester-ly and drier semi-arid plains. The nor-mal soils here are lighter in color, con-tain less organic matter and largeramounts of calcium carbonate and in fact,are less well-developed than the darkersoils of the Subhumid Plains. The tran-sition of soils and vegetation occurabout at the point where a drawn lineindicates the western limit of system

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atlc dry farming.The southern part of this belt lies

at the extreme west side of the RioGrande Plains and the native vegetationhere comprises chiefly buffalo, and curlymesquite grasses with some species ofgrama grass on the heavy soils, with gra-ma and bluestems (Andropogon species)more abundant on the sandy soils. Thesoil series here are largely of Uvaldeand Maverick series.

Northward, the Edwards' Plateau di-vision comprising a rough broken and gen-erally shallow soil section of lightbrown soils chiefly of Ector and Reaganseries has a thin growth of the grama,buffalo and mesquite grasses with manyof the small trees and shrubs similarto those on the plateau to the east, butof thin scattered growth. A few desertand semi-desert shrubs occur in places,these being largely of the Flourensiaand Govillea species with some lechuguil-la, yucca, and sotol, and others. Inthe west this division occurs on the highridges and mountain areas? where in addi-

tion to various grasses there are sootswith a considerable growth of pine andoak trees. " The principal soils on thesmoother areas of this division in andaround the rough lands are of the Reaganseries, and the shallow and stony soilsof the Ector, Brewster and other series.

The Arid Land Plains(Sierosetn)

This is a desert to semi-desert sec-tion of extreme western Texas in theTrans-Pecos country. Here the averagerainfall is only about 10 or 12 inches ayear. The chief native vegetation is oflow green shrubs mostly Creosote bush(Covillea tridentata) and black brush ortar brush (Flourensia cernua). The grassgrowth is extremely.light though in pla-ces on flats a considerable amount oftobosa grass (Hilaria mutica) is present,and a scattering of burro grass, yeso andother grasses grow in spots. The chiefsoils of this dry land country are of theReeves series.

See next page

for

Sketch Hap and Legend

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Plant species adapted to the Southern Prairies and Great Plains

Legend to Sketch map,

F — Forest t Humid regionP — Prairiest Humid region

SH - Subhumid Plains (Chernozem-Chestnut soils Belt)SA - Semiarid Plains (Brown soils belt)A - Arid and desert plains (Sierosem soils belts)

Physiographic subdivisions and main plant communities

I - Coast Prairie Coarse bunch grasses s Andropogons, Paspalum, PanicumII - Blackland Prairie: Andropogon-Bouteloua-BuchloeIII - Grand Prairie Andropogon-Buchloe-Bouteloua; shin oakIV - Rio Grande Plain* Hilaria-Buchloe; Andropogon-Bouteloua; Many shrubsV - Edwards Plateau Hilaria-Buchloe-Boutelouai Many small tree and shrubsVI - Rolling Plains* Hilaria-Bouteloua} Andropogon-BoutelouaVII - High Plains* Buchloe-B.gracilis; Bouteloua-Aristida; Coarse bunch

grasses, shin oak.VIII - Trans-Pecos Mountains and Roughlands* Bouteloua hirsuta-bunch grasses;

pine, oaks* Lechuguilla-SotolIX - Trans-Pecos Basins* Desert shrubs (Covillea-Flourensia); Bouteloua

' ramosa B. breviseta, Sporobolus, Scleropogon.

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