Ecoregions of Texas, AS-199 - Texas Commission on Environmental ...

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The red wolf once inhabited the Grand Prairie (29d). It is intermediate insize between the gray wolf and the coyote. Photo: Greg Koch, USFWSSome common Great Plains animals, such as black-tailed jackrabbits (Lepuscalifornicus) and the scissortail flycatcher (Tyrannus forficatus), range farther eastthrough the Grand Prairie, creating an overlap in Great Plains and eastern forestspecies. The Grand Prairie was once also the home <strong>of</strong> bison (Bison bison), red wolf(Canis rufus), and black bear (Ursus americanus). Red wolf numbers were decimatedalong with gray wolves (Canis lupus monstrabilis) under predator control programsin the late 19 th and early 20 th centuries; the last <strong>of</strong> the red wolves in the wild in <strong>Texas</strong>hybridized with coyotes (Schmidley 2002).Level IV EcoregionArea (sq. mi.) 3298PhysiographyElevation /Local Relief (feet)Surficial Geology;Bedrock GeologySoil Order (Great Groups)Common Soil SeriesSoil Temperature /Soil Moisture RegimesMean Annual Precipitation (in.) 33-37Mean Annual Frost Free Days 220-245Mean Temperature (F)(Jan. min/max; July min/max)VegetationLand Cover and Land Use29d. Grand PrairieRolling plains with some bedrock exposure. Meandering, incised streams.450-1170 /50-300Quaternary and Tertiary stony calcareous clay solution residuum and silty claydecomposition residuum;Lower Cretaceous limestone, marl, and claystone.Mollisols (Calciustolls, Haplustolls), Inceptisols (Haplustepts), Entisols(Ustorthents), Alfisols (Paleustalfs, Haplustalfs), Vertisols (Haplusterts)Convex uplands and slopes: Aledo, Bolar, Eckrant, Purves, Dugout, Maloterre.Level uplands: Denton, Crockett. Erosional footslopes: Cranfill. Stream terraces:Wilson, Burleson.Thermic /Ustic, Udic Ustic31/55;72/96Upland tall to midgrass prairie. Minimally disturbed grasslands: big bluestem,yellow Indiangrass, sideoats grama, little bluestem, switchgrass, tall dropseed,<strong>Texas</strong> cupgrass. Grazed grasslands: silver bluestem, grama grasses, <strong>Texas</strong>wintergrass, purple threeawn, seep muhly, buffalograss, mesquite, introducedbermudagrass and Kleingrass. Escarpments: plateau live oak, juniper, sumac, <strong>Texas</strong>persimmon. Riparian woodland: elm, hackberry, bur oak, pecan.Pasture, grassland, shrubland, urban. Grazing, dairy farming, some cropland <strong>of</strong>corn, grain sorghum, and wheat.29e Limestone Cut PlainThe Limestone Cut Plain is similar to the Edwards Plateau (30) in its woodlandvegetation, but the Edwards Limestone substrate preferred by this vegetation type ismore restricted in the Limestone Cut Plain. Ecoregion 29e has a more varied geologythan Ecoregion 30, and it is more highly eroded. It has higher precipitation amounts thanthe Edwards Plateau, and its grasslands have elements <strong>of</strong> the eastern tallgrass prairie.The Limestone Cut Plain is bounded on the west by the sandstones and clays that supportCross Timbers oak woodland, on the east by the remnant Balcones Escarpment marking the boundary withthe Blackland Prairie (32), and on the north by the transition to the smoother topography <strong>of</strong> the Grand Prairie.The southern boundary is a transition to the Balcones Canyonlands (30c), with its characteristic oak motte/Ashe juniper woodland, dissected canyon topography, and spring-fed streams.Mesas alternate with broad intervening valleys in the stairstep topography <strong>of</strong> the Limestone Cut Plainecoregion. Although Edwards Limestone caps the highest buttes, the Limestone Cut Plain is distinguished byother Lower Cretaceous limestones, predominately the Glen Rose Formation and Walnut Clay, that are older<strong>Ecoregions</strong> <strong>of</strong> <strong>Texas</strong> 41
than the limestone <strong>of</strong> the Edwards Plateau (30). The Glen Rose Formation has alternating layers <strong>of</strong> limestone,chert, and marl that erode differentially and generally more easily than the Edwards Limestone. The effects <strong>of</strong>increased precipitation and run<strong>of</strong>f are also apparent in the increased erosion and dissolution <strong>of</strong> the limestonelayer. The Limestone Cut Plain has flatter topography, lower drainage density, and a more open woodlandcharacter than the Balcones Canyonlands (30c).The soils over the limestone substrate are shallow. The broad lowlands generally contain grasslandsgrowing on the Walnut Clay. The narrow mesa divides, capped by Edwards Limestone, support oak savanna,and uncapped mesas may also support prairie. The woodland vegetation <strong>of</strong> Ecoregion 29e is similar tothat <strong>of</strong> the Balcones Canyonlands, but less diverse; it includes plateau live oak (Q. fusiformis), cedar elm(Ulmus crassifolia), <strong>Texas</strong> ash (Fraxinus texensis), big tooth maple (Acer grandidentatum), and bur oak (Q.macrocarpa). Other endemic Edwards Plateau (30) floral species are prevalent. The dry rocky slopes havelittle soil, but they may have a sparse cover <strong>of</strong> white shin oak (Q. sinuata var. breviloba), sumac (Rhus spp.),and Ashe juniper (Juniperus asheii). Although the grasslands <strong>of</strong> the Limestone Cut Plain are a mix <strong>of</strong> tall, mid,and short grasses, some consider it a westernmost extension <strong>of</strong> the tallgrass prairie, which distinguishes thisecoregion from the Edwards Plateau Woodland (30a). Presettlement grasslands included species such as bigbluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), yellow Indiangrass (Sorghastrumnutans), tall dropseed (Sporobolus asper var. asper), and sideoats grama (Bouteloua curtipendula). Thesetallgrass prairies once supported herds <strong>of</strong> bison. With concentrated grazing these grasses have been replacedby species such as silver bluestem (Bothriochloa laguroides ssp. torreyana), <strong>Texas</strong> wintergrass (Stipaleucotricha), and purple threeawn (Aristida purpurea). As in some other limestone regions (e.g., <strong>Ecoregions</strong>30a, 30c, 29f), fire suppression and grazing have changed the nature <strong>of</strong> the oak savanna and grassland throughthe expansion <strong>of</strong> shrubs such as Ashe juniper and mesquite. Where they are present, mature Ashe juniperstands have value as nesting habitat for the endangered golden-cheeked warbler (Dendroica chrysoparia) thatnests in low numbers in this ecoregion.The Cross Timbers ecoregion is a “crossroads” <strong>of</strong>landscapes and vegetation types with its prairiesand woodlands. The pale yucca (Yucca pallida)in bloom here is endemic to a six-county area<strong>of</strong> central <strong>Texas</strong> where the southern part <strong>of</strong> theCross Timbers (29) meets <strong>Ecoregions</strong> 30 and 32.Photo: Clarence RechenthinThe Paluxy River is deeply incised into the soluble Lower Cretaceous limestones<strong>of</strong> Ecoregion 29e. Photo: John CrossleyThe Glen Rose Formation, exposed at thesurface <strong>of</strong> the Limestone Cut Plain (29e),contains dinosaur tracks <strong>of</strong> both carnivoroustheropods (pictured here) and herbivoroussauropods. Photo: Keith Minor42<strong>Ecoregions</strong> <strong>of</strong> <strong>Texas</strong>
Page 1: Below is an Electronic Version <str
Page 4 and 5: ECOREGIONS OF TEXAS</strong
Page 6 and 7: TABLE OF CONTENTSABSTRACT..........
Page 8 and 9: 2526272526272330293235332430323423
Page 10 and 11: INTRODUCTIONSpatial frameworks are
Page 12 and 13: Maps of environmen
Page 14 and 15: vegetation or small areas o
Page 16 and 17: the only chipmunk in Texas<
Page 18 and 19: to the north. There is a high deman
Page 20 and 21: taller, coarser tobosa grass (Pleur
Page 22 and 23: the fractured rock. The Bof
Page 24 and 25: hollows, moving upslope to create c
Page 26 and 27: The headwater catfish (Ictalurus lu
Page 28 and 29: streams. Two sand plains streams, C
Page 30 and 31: Several caliche horizons (calcium c
Page 32 and 33: winds (Spearing 199</strong
Page 34 and 35: Geology is an important geographica
Page 36 and 37: the villages of Pa
Page 38 and 39: Area (sq. mi.) 5569PhysiographyFlat
Page 40 and 41: Tableland topography of</st
Page 42: y the Brazos and Colorado rivers ha
Page 45 and 46: Level IV Ecoregion27i. Broken Red P
Page 47 and 48: Post oaks (Quercus stellata) and bl
Page 49: Level IV Ecoregion29c. Western Cros
Page 53 and 54: underlying the sandstone. This has
Page 55 and 56: Since settlement, many wildlife spe
Page 57 and 58: (Pellaeae spp.), Nuttall’s stonec
Page 59 and 60: Trinity-Edwards aquifer, discharges
Page 61 and 62: Edwards Plateau to savanna-like con
Page 63 and 64: species list, prefers fast moving w
Page 65 and 66: Level IV Ecoregion31a. Northern Nue
Page 67 and 68: 31c Texas-Tamaulip
Page 69 and 70: 31d Rio Grande Floodplain and Terra
Page 71 and 72: 62shrink when dry and swell when we
Page 73 and 74: 32b Southern Blackland PrairieThe S
Page 75 and 76: 33 EAST CENTRAL TE
Page 77 and 78: and need some patchy distubances an
Page 79 and 80: 33d Northern Prairie OutliersThe sm
Page 81 and 82: Level IV Ecoregion33e. Bastrop Lost
Page 83 and 84: 34a Northern Humid Gulf Coastal Pra
Page 85 and 86: 34b Southern Subhumid Gulf Coastal
Page 87 and 88: occasional discontinuous drainage r
Page 89 and 90: oundary was the ability to match th
Page 91 and 92: Level IV Ecoregion34f. Lower Rio Gr
Page 93 and 94: live oak trees (Quercus virginiana)
Page 95 and 96: Shoal grass (Halodule wrightii) mea
Page 97 and 98: Upland oak-pine forest in Ecoregion
Page 99 and 100: 35c Pleistocene Fluvial TerracesThe
Page 101 and 102:
35f FlatwoodsMostly flat to gently
Page 103 and 104:
pasture, although some woodland sti
Page 105 and 106:
invariant definition of</st
Page 107 and 108:
how many stream sites/watersheds ar
Page 109 and 110:
commonly believed. Typically, about
Page 111 and 112:
CONCLUSIONS AND RECOMMENDATIONSThis
Page 113 and 114:
104Ecoregions <str
Page 115 and 116:
Biggs, B.J.F., M.J. Duncan, I.G. Jo
Page 117 and 118:
Diggs, G.M., Jr., and P.C. Schulze.
Page 119 and 120:
Graves, J. 2002. Texas</str
Page 121 and 122:
Hunt, C.B. 1967. Physiography <stro
Page 123 and 124:
Maxwell, T.C. 1979. Avifauna <stron
Page 125 and 126:
Richmond, G.M., D.L. Weide, and D.W
Page 127 and 128:
U.S. Department of
Page 129 and 130:
Woods, A.J., J.M. Omernik, D.R. But
Page 131 and 132:
Herbaceous Plants(Forbs, Grasses, a
Page 133 and 134:
Hickory, BlackHickory, WaterHollyHu
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