ILLUSTRATED FLORA OF EAST TEXAS - Brit - Botanical Research ...

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SOIL-RELATED GEOLOGY, PINEYWOODS, POST OAK SAVANNAH/INTRODUCTION 55 FIG.26/CLOSEUP <strong>OF</strong> WECHES FORMATION OUTCROP SHOWING CALCAREOUS MARINE FOSSILS.SAN AUGUSTINE CO.(PHOTO BY RJG). & Diamond 1983; Miller & Smeins 1988). Soils of the Cook Mountain Formation are Vertisols or vertic Alfisols. These soils are very clayey. The clay, known as “montmorillonite” or “smectite,” has a high shrink/swell ratio and exerts immense pressure on the roots of all vegetation. This condition is extremely stressful to pines. The soils derived from the Cook Mountain support prairie vegetation (Jackson & Garner 1982) and underlie the southwestern tip of the Fayette Prairie and part of the San Antonio Prairie (Smeins & Diamond 1983). Further east, where moisture is more abundant and the soils more leached, the Cook Mountain supports vegetation characteristic of the Pineywoods. SPARTA FORMATION—This Eocene layer of primarily loose, unconsolidated, fine to coarse, light-colored quartz sand (with some fragments of fossil wood) is a continental deposit laid down approximately 50 million years ago as the Gulf of Mexico transgressed inland (Sellards et al. 1932; Maxwell 1970; Goodwin 2002; C. Miller Drilling 2001). The sandy soils derived from the Sparta underlie portions of the Post Oak Savannah and Pineywoods. High, dry habitats on the porous soils of the Sparta are similar to those found on the Carrizo (see below) and Queen City formations, and are typically Ultisols with a sandy surface layer over a loamy subsoil. They are characterized by such species as Quercus stellata (post oak), Q. incana (bluejack or sandjack oak), Yucca louisianensis (Louisiana yucca), Pinus echinata (shortleaf pine), and Schizachyrium scoparium (little bluestem). WECHES FORMATION—The Middle Eocene, shallow marine-deposited Weches Formation is characterized by the mineral glauconite (a green-colored iron potassium silicate related to micas and clays), as well as glauconitic clays, calcareous marls, rich marine fossil deposits (Fig. 26), and mudstone (Sellards et al. 1932; George 1988; George & Nixon 1990). In some areas, where the soluble ingredients of the glauconite have leached out and iron has concentrated, iron-bearing limonite (iron-stone) is found. This ore was mined in the nineteenth century—e.g., near Jefferson in Marion County and near Rusk in Cherokee County
56 INTRODUCTION/SOIL-RELATED GEOLOGY, PINEYWOODS, POST OAK SAVANNAH (Sellards et al. 1932; Brown et al. 1969). The average width of the outcrop of the Weches is two to five miles (3.2 to 8 km) (Sellards et al. 1932). Surface exposures usually occur on slopes (due to erosion) and are typically small, ranging from only 5 to 20 m wide and usually not more than 100 m in length (George & Nixon 1990). Where freshly exposed, the glauconitic strata have an olive green cast, but upon weathering become reddish brown (Fig. 27) (George & Nixon 1990). Soils of the Weches Formation range from shallow and rocky (which apparently limits voody vegetation) on the steeper slopes to deep on the flatter slopes (generally less than 5 to 8 percent), are characterized by a basic pH, and have a layer of glauconitic clay. They are typically Alfisols with a distinctive red clayey subsoil. Outcrops of the Weches are often waterlogged during the spring because of the clay stratum, since “downwardly percolating water reaching the impermeable clay layer moves laterally until it exits on hillsides where the outcrops occur” (George 1988). However, due to their shallowness, Weches outcrop soils can become quite dry in summer and fall (George & Nixon 1990). The basic pH (7.1–8.2) is in striking contrast to that of the mostly acidic soils of East Texas (pH 4.4–6.2) and is probably of major importance in determining the unusual plant community occupying the outcrops. The unique conditions provided by the Weches Formation result in the development of “Glauconite shale glades” (Bezanson 2000), also known as Weches outcrop communities (Fig. 28). These are usually small, isolated, natural opening or glade communities typically having sparse woody growth and an unusual herbaceous assemblage, including two endemics: Texas golden glade cress (Leavenworthia aurea var. texana) (Mahler 1987; Poole et al. 2002) and the federally endangered white bladderpod (Lesquerella pallida) (George & Nixon 1990). Interest in this habitat increased dramatically when Lesquerella pallida, now recognized as endemic to Weches outcrops, was rediscovered in 1981 after having not been seen since its initial collection in the 1830s (Nixon et al. 1983; George & Nixon 1990). This species is currently known from only seven localities, all in San Augustine County (Texas Parks and Wildlife 1999). A number of other species (e.g., Liatris mucronata, Paronychia virginica, Petalostemum pulcherrimum) found on Weches outcrops are disjunct from much further west in Texas. Similarities exist between the Weches outcrop communities and those of the “cedar glades” well known in the southeastern U.S. and adjacent areas (see e.g., Baskin & Baskin 1985, 2000; George & Nixon 1990). Another interesting phenomenon is the occurrence of the somewhat calciphilic Thaspium barbinode (Apiaceae), whose only known Texas location is in Houston County on sand over the Weches. The nearest other locations of this species are in the Ouachita Mountains of McCurtain County, Oklahoma, and in deep ravines west of the Ouachita River in Caldwell Parish, Louisiana—disjunctions of approximately 300 km (186 miles) (Bridges & Orzell 1989a). The Weches can also significantly affect local topography (and thus vegetation). For example, where erosion-resistant ironstone layers occur they cap hills and escarpments— maximum local elevations are found in Anderson and Cherokee counties (Fogg & Kreitler 1982). The result can be “a picturesque, rugged topography of steep, high, flat-topped hills dissected by deep V-shaped valleys” (Sellards et al. 1932). In areas without ironstone, the topography can merely be rolling. Outcrops of the Weches are sometimes mined for road material, gravel, or the fertilizer/soil additive greensand (though it is of low quality for this use), while others are overgrazed or destroyed by various types of development. Unfortunately, the unusual plant community on the Weches currently has virtually no protection in Texas. QUEEN CITY FORMATION—The Eocene Queen City Formation represents delta deposits and marginal marine sand shoals (Kreitler et al. 1980) and “consists mostly of thick bedded to massive cross-bedded very fine to fine quartz sand that is interbedded with silt and clay. Stringers of lignite and clay are present in the upper portions of the formation and layers of shale are found deeper in the formation” (C. Miller Drilling 2001). Where porous sands of
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ILLUSTRATED FLORA OF EAST TEXAS
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ALLDREDGE, LINDA & JACK BATTERBAE,
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We would like to recognize and expr
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ISSN 0833-1475 ISBN 1-889878-12-X S
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“DEEP EAST TEXAS IS AN OLD, QUIET
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Elray S. Nixon E lray Nixon was bor
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ILLUSTRATED FLORA OF EAST TEXAS TAB
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TABLE OFCONTENTS/ PAGE APPENDICES A
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Hymenocallis liriosme
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ILLUSTRATED FLORA OF EAST TEXAS OVE
Page 21 and 22: 4 INTRODUCTION/GEOGRAPHIC AREA OF E
Page 27 and 28: 10 INTRODUCTION/MAJOR RIVERS OF EAS
Page 29 and 30: 12 INTRODUCTION/PLANTS TREATED The
Page 31 and 32: 14 INTRODUCTION/GUIDE TO ARRANGEMEN
Page 33 and 34: 16 INTRODUCTION/GUIDE TO SOURCES OF
Page 35 and 36: 18 INTRODUCTION/GUIDE TO GEOGRAPHIC
Page 37 and 38: 20 INTRODUCTION/GUIDE TO ENDANGERED
Page 39 and 40: 22 INTRODUCTION/GUIDE TO GLOSSARY,
Page 41 and 42: 24 INTRODUCTION/GUIDE TO ABBREVIATI
Page 43 and 44: 26 INTRODUCTION/SUMMARY DATA ON FLO
Page 45 and 46: 28 INTRODUCTION/ACKNOWLEDGMENTS Kar
Page 47 and 48: 30 INTRODUCTION/AUTHORS’ NOTE Pre
Page 49 and 50: 32 INTRODUCTION/GENERAL GEOLOGY OF
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Page 65 and 66: 48 INTRODUCTION/SOILS, EAST TEXAS B
Page 67 and 68: 50 INTRODUCTION/SOIL-RELATED GEOLOG
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Page 77 and 78: 60 INTRODUCTION/SOILS OF BLACKLAND
Page 83 and 84: 66 INTRODUCTION/CLIMATE OF EAST TEX
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Page 95 and 96: 78 INTRODUCTION/GEOLOGY OF PINEYWOO
Page 97 and 98: 80 INTRODUCTION/PRESETTLEMENT, EARL
Page 105 and 106: 88 INTRODUCTION/PRESETTLEMENT VEGET
Page 107 and 108: 90 INTRODUCTION/CURRENT VEGETATION
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106 INTRODUCTION/POST OAK SAVANNAH
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110 INTRODUCTION/GEOLOGY AND SOILS
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112 INTRODUCTION/SOILS, FIRE, AND T
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114 INTRODUCTION/SOILS, FIRE, AND T
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116 INTRODUCTION/ PRESETTLEMENT, EA
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118 INTRODUCTION/VEGETATION OF POST
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124 INTRODUCTION/CONDITIONS TODAY O
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128 INTRODUCTION/RED RIVER AREA are
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130 INTRODUCTION/BLACKLAND PRAIRIE
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132 INTRODUCTION/GEOLOGY OF BLACKLA
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134 INTRODUCTION/PRESETTLEMENT AND
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144 INTRODUCTION/VEGETATION OF BLAC
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146 INTRODUCTION/FUTURE OF BLACKLAN
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148 INTRODUCTION/FUTURE OF BLACKLAN
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150 INTRODUCTION/CADDO LAKE LOCATIO
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152 INTRODUCTION/CADDO LAKE FIG.84/
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154 INTRODUCTION/PRESENT AND FUTURE
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156 INTRODUCTION/BIG THICKET THE BI
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158 INTRODUCTION/BIG THICKET GEOGRA
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160 INTRODUCTION/NATURAL HISTORY OF
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172 INTRODUCTION/SUMMARY DEFINITION
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184 INTRODUCTION/HISTORY OF BIG THI
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190 INTRODUCTION/CONSERVATION IN BI
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200 INTRODUCTION/ORIGIN AND DIVERSI
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228 INTRODUCTION/CONSERVATION IN EA
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234 INTRODUCTION/HISTORY OF BOTANY
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244 INTRODUCTION/BOTANY IN NORTH CE
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246 INTRODUCTION/BOTANY IN NORTH CE
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248 INTRODUCTION/BOTANY AT UNIVERSI
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250 INTRODUCTION/BOTANY AT TEXAS A&
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252 INTRODUCTION/BOTANY AT TEXAS A&
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254 INTRODUCTION/OTHER CONTRIBUTION
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256 INTRODUCTION/CURRENT BOTANICAL
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258 INTRODUCTION/BOTANICAL ART IN E
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