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

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vegetation or small areas <strong>of</strong> woodland growing on north-facing slopes.There is some evidence that grassland once covered the lower slopes <strong>of</strong> the Guadalupe Mountains as wellas the higher elevations up to 7500 feet, and that desert shrubs invaded the area after it was overgrazed in thelate 19th century (Gehlbach 1979, Northington and Burgess 1979, Schmidley 2002). Today, yucca (Yucca spp.),sotol (Dasylirion spp.), lechuguilla (Agave lechuguilla), ocotillo (Fouquieria splendens) and cacti (Opuntiaspp.) dominate rocky slopes below 5500 feet, but up to 6500 feet on exposed southern exposures and on thesteeper western escarpment. These shrub species are sometimes called succulent desert shrubs to distinguishthem from woody desert shrubs, such as creosotebush (Larrea tridentata) and tarbush (Flourensia cernua),typically found in the drier Chihuahuan Basins and Playas (24a) (Gehlbach 1979). Grasslands dominated bythreeawns (Aristida spp.), muhly (Muhlenbergia spp.), and gramas (Bouteloua spp.) persist near alluvial fansand on benches and gentle slopes with deeper soils (Northington and Burgess 1979).Several lizard species that are adapted to the exposed, sun-baked landscape <strong>of</strong> west <strong>Texas</strong> are indicative<strong>of</strong> the succulent desert shrubland: the round-tailed horned lizard (Phrynosoma modestum), the checkeredwhiptail (Cnemidophorus tesselatus), and the greater earless lizard (Cophosaurus texanus) (Gehlbach 1979).Other characteristic desert fauna are common, such as rattlesnake (Crotalusspp.), kangaroo rat (Dipodomys spp.), tarantula (Aphonopelma spp.),roadrunner (Geococcyx californianus), and, perhaps unexpectedly, muledeer (Odocoileus hemionus), a large mammal that is also well-adaptedto desert life. In fact, in 1905 Vernon Bailey reported in his BiologicalSurvey <strong>of</strong> <strong>Texas</strong> that the mule deer was more numerous in the dry foothills<strong>of</strong> the western Guadalupe Mountains than it was in the wooded regions athigher elevations (Schmidley 2002). The mule deer can survive withoutwater for extended periods by getting moisture from the plants that it eats,such as the pulpy heart <strong>of</strong> the sotol plant. The heart <strong>of</strong> the sotol, or mescal,was also a staple in the diet <strong>of</strong> the Mescalero Apaches, who mastered theart <strong>of</strong> survival in the desert (Phelan 1976).The round-tailed horned lizard (Phrynosomamodestum) is a reptilian indicator <strong>of</strong> the succulentdesert shrubland in the Chihuahuan Desert.Photo: Erik Enderson, Tucson Herpetological SocietyLevel IV Ecoregion23a. Chihuahuan Desert SlopesArea (sq. mi.) 69Lower slopes <strong>of</strong> Guadalupe Mountains; very steep on west and south sides <strong>of</strong>Physiographyrange, more gradual on the east; cut by steep canyons. Moderate gradient ephemeralstreams that carry water only after periodic storms.Elevation /4500-6500 /Local Relief (feet)800-2000Pleistocene to Holocene clay loam colluvium and residuum mixed with limestoneSurficial Geology;and sandstone fragments, gypsum deposits; Pleistocene to Holocene gravels andBedrock Geologysands in drainages.Permian limestones, sandstones, and claystones.Mollisols (Calciustolls), Aridisols (Haplocalcids, Petrocalcids), EntisolsSoil Order (Great Groups)(Torriorthents)Limestone foothills, flat benches, and erosional slopes: Ector, Lozier, Rock outcrop.Common Soil SeriesAlluvial terraces and fans: Tencee, Tome.Soil Temperature /Thermic /Soil Moisture Regimes Ustic, AridicMean Annual Precipitation (in.) 15-18Mean Annual Frost Free Days 180-210Mean Temperature (F) 29/52;(Jan. min/max; July min/max) 62/85On benches and slopes with deeper soil: grasses such as blue, black, and sideoatsgramas, purple threeawn, mourning lovegrass, curlyleaf muhly. On rocky slopes andVegetationin disturbed grasslands: succulent desert shrubs such as sotol, lechuguilla, yucca,ocotillo, and cacti.Shrubland and grassland. Rangeland where not protected in Guadalupe MountainsLand Cover and Land UseNational Park.<strong>Ecoregions</strong> <strong>of</strong> <strong>Texas</strong> 5
Perennial streams are rare in the GuadalupeMountains <strong>of</strong> Ecoregion 23; stream channelsgenerally carry water only after storm events.Sparse vegetation, typical <strong>of</strong> the ChihuahuanDesert, grows on lower mountain slopes.Photo Phil Gavenda.23b Montane WoodlandsThe Montane Woodlands ecoregion occurs above 5000 feet on the GuadalupeMountains on north slopes and in stream riparian zones and above 6500 feet on southfacing slopes and on the steep western escarpment. This portion <strong>of</strong> Ecoregion 23b isat the southernmost tip <strong>of</strong> the Arizona/New Mexico Mountains (23), surrounded bydesert on three sides. Compared to other mountain ranges in Ecoregion 23, the extent<strong>of</strong> pinyon-juniper woodland, oak woodland, and coniferous forest is much reduced(Johnston 1979). The mapped polygon for Ecoregion 23b is generalized and does not convey the patchynature <strong>of</strong> the woodland cover. Densities <strong>of</strong> juniper (Juniperus spp.), pinyon pine (Pinus edulis), and oak(Quercus spp.) vary according to aspect. At middle elevations, a chaparral community occurs beneath thetrees, composed <strong>of</strong> shrubs such as desert ceanothus (Ceanothus greggii), alderleaf mountain mahogany(Cercocarpus montanus), and catclaw mimosa (Mimosa aculeaticarpa). The top <strong>of</strong> the plateau is grassy andpark-like with scattered juniper, pinyon pine, and oak. Douglas-fir (Pseudotsuga menziesii), southwesternwhite pine (Pinus strobiformis), and ponderosa pine (Pinus ponderosa) grow in limited areas at the highestelevations (above 7000 feet) where more moisture is available (Northington and Burgess 1979). These areas<strong>of</strong> high elevation conifers form a distinct level IV ecoregion elsewhere in the Arizona/New Mexico Mountains(23), but in the Guadalupe Mountains the coniferous area is too small to map at the 1:250,000 scale.The east and west faces <strong>of</strong> the Guadalupe Mountains are cut by a series <strong>of</strong> canyons. Surface water isscarce; infiltrating rainfall percolates through the limestone, creating caverns throughout the range and a fewsprings that emerge from sandstone layers at 6000 feet or below. In the canyons, Chihuahuan desert shrubs andhigher elevation conifers mix with deciduous riparian trees such as chinkapin oak (Quercus muehlenbergii),wavyleaf oak (Quercus pauciloba), and bigtooth maple (Acer grandidentatum). The canyons support a highnumber <strong>of</strong> endemic plant species due in part to their isolation as relics <strong>of</strong> a wetter climate; they also providevaluable habitat for songbirds that are characteristic <strong>of</strong> more northerly regions.McKittrick Creek Canyon is a center <strong>of</strong> biotic diversity and a focal point for visitors in Guadalupe MountainsNational Park. Several ice-age era woodland species are found here due to water and high, sheltering walls<strong>of</strong> the canyon. McKittrick Creek is considered a perennial stream, although it <strong>of</strong>ten runs underground andends at the mouth <strong>of</strong> its canyon. Stream temperatures vary between 59°F near springs to 77°F in open shallowsections. Two species <strong>of</strong> sunfish (Lepomis spp.) and rainbow trout (Salmo gairdneri), stocked in McKittrickCreek by previous landowners, are still present. The trout are able to survive and reproduce in the uppersections <strong>of</strong> the creek at cooler spring sources (Lind 1979). Hanging terraces, or limestone seeps, on the walls<strong>of</strong> McKittrick Canyon, support maidenhair fern (Adiantium capillus-veneris), sawgrass (Cladium mariscus),and the rare Chapline columbine (Aquilegia chrysantha var. chaplinei), mountain deathcamas (Zigadenuselegans), and mountain ninebark (Physocarpus monogynus) (Northington and Burgess 1979). The canyonecosystems are vulnerable communities, even with National Park protection; they are vulnerable to flashflood and drought, browsing and trampling by elk and deer, and trampling by human visitors.Mule deer (Odocoileus hemionus), black bear (Ursus americanus), mountain lion (Puma concolor), and6<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 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 and 50: Level IV Ecoregion29c. Western Cros
Page 51 and 52: than the limestone of</stro
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
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31d Rio Grande Floodplain and Terra
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62shrink when dry and swell when we
Page 73 and 74:
32b Southern Blackland PrairieThe S
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33 EAST CENTRAL TE
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and need some patchy distubances an
Page 79 and 80:
33d Northern Prairie OutliersThe sm
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Level IV Ecoregion33e. Bastrop Lost
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34a Northern Humid Gulf Coastal Pra
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34b Southern Subhumid Gulf Coastal
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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
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live oak trees (Quercus virginiana)
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Shoal grass (Halodule wrightii) mea
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Upland oak-pine forest in Ecoregion
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35c Pleistocene Fluvial TerracesThe
Page 101 and 102:
35f FlatwoodsMostly flat to gently
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pasture, although some woodland sti
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invariant definition of</st
Page 107 and 108:
how many stream sites/watersheds ar
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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
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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
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Hickory, BlackHickory, WaterHollyHu
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