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

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SOILS/INTRODUCTION 47 These are low fertility, acidic, forest soils, which form in areas of sandy parent material. They are highly leached and defined by a dark colored subsurface layer (humus complexed with aluminum and sometimes iron) underlying a bleached layer of light-colored sand. ULTISOLS—are deeply weathered, somewhat infertile, acidic soils that form in areas of relatively high precipitation and subtropical temperatures, and thus substantial weathering. In fact, they are considered the most weathered of all midlatitude soils, hence the derivation of their name (Latin: ultimus, ultimate) (Steila 1993). They are common on geologically old landscapes in warm climates where soil weathering processes such as the leaching of clays and other minerals out of the topsoil by abundant rainfall have occurred over a long period of time. Due to both chemical and physical weathering, Ultisols tend to be deep and leached of most soluble bases such as calcium, resulting in their acidic nature and low fertility (lower than Alfisols). Extensive weathering also results in a highly developed soil profile and a subsurface horizon enriched in clay. Under good drainage conditions, Ultisols are frequently reddish or yellowish in color due to the oxidation of iron and manganese compounds (e.g., Fe-Mn oxides). They are the dominant soil order on the Wilcox, Reklaw, Queen City, and Sparta formations generally north of Nacogdoches and Crockett, as well as the Willis Formation north of Jasper and Woodville, and they support much of the forest vegetation in those areas. While capable of supporting productive forest, Ultisols are not well-suited for continuous agriculture without the input of commercial fertilizers (McDaniel 2002). VERTISOLS—(self-swallowing or churning, from Latin: verto, turn upward) are high shrink/swell soils that are clayey throughout and that crack to the surface when dry. Because of the shrinking and swelling characteristic of Vertisols and the resulting continuous cycle of overturning or self-plowing (Steila 1993), they generally have less well-developed horizons than many other soil orders. The microtopographical features known as gilgai are usually present (see page 63 for details). Soils that crack to the surface have such a profound effect on the vegetation and land use that this governs their classification. Vertisols occur mainly on the Cook Mt., Manning, Fleming, and Beaumont Formations and on the Blackland Prairie. PRIMARY SOIL CHARACTERISTICS AFFECTING PLANT COMMUNITIES There are several primary soil characteristics which affect plant communities: soil texture, available water-holding capacity, soil reaction (pH), fragipans (compacted layers below the soil surface), and surface slope or gradient. Of particular importance in determining the properties of a soil is its texture, resulting from the proportion of mineral particles in three different size categories. The smallest soils particles are referred to as clay (particle size of 0.0001 to 0.002 mm), somewhat larger particles as silt (0.002 to 0.05 mm), and the largest as sand (0.05 to 2 mm). Soil texture and available water-holding capacity are related. Clayey soils, with their greater surface area, hold more water than sandy soils. As the clay content increases the water-holding capacity increases. However, when the clay content of a soil exceeds 30 to 35 percent, the available water-holding capacity does not necessarily increase (and may in fact decrease). This is because clay particles have such a strong attachment to soil moisture that it is not available to plant roots. In contrast to clay soils, some upland sandy soils are so excessively drained that even in areas of high rainfall, plants living on these soils are adapted to quite dry conditions. Highly acidic (low pH) soils can also greatly affect vegetation by limiting nutrients, including nitrogen. In such cases, plants adapted to low nutrient conditions (e.g., carnivorous plants) are sometimes common. In soils with a high pH (alkaline), iron becomes less available, causing some plants (especially pines) to become chlorotic (= yellow or bleached due to the loss of chlorophyll or failure of chlorophyll synthesis). Although other factors are important, possibly the greatest natural influences on pine tree growth and density may be the available water in a soil and the soil acidity.
48 INTRODUCTION/SOILS, EAST TEXAS BOTTOMLANDS, STREAM TERRACES Because of the sedimentary nature of East Texas parent materials, and because of the typically shallow slope of many of the strata, very thin layers of one material (e.g., sand) can sometimes overlay a different type (e.g., clay). Thus, a superficial examination of the surface material may not be sufficient to determine what is actually influencing the plant cover at a particular location. An excellent example can be found in some areas of the Post Oak Savannah, where various arrangements of sand and clay layers result in a complex mosaic of woodland/savannah and prairie vegetation. Soil surfaces with a nearly level gradient, clayey texture, and compacted or impermeable layers can become supersaturated or have standing water over the soil surface. This can result in characteristic plant communities (e.g., wet pine savannahs). Another example can be seen in certain small seepage areas, commonly referred to (depending on type and classification system) as “Wet Herbaceous Seeps” (see page 96), “hanging bogs,” “hillside bogs,” “acid seeps,” “muck bogs,” or “possum haw bogs.” These occur where a layer of permeable sand at the surface is underlain by a relatively impermeable clay or sandstone. Water percolating downward through the sand encounters the impermeable layer and moves laterally, sometimes forming small areas at the surface that are saturated with water—and which are typically highly acidic and nutrient-poor. Unusual plant assemblages occur in these habitats and include a number of rare species (e.g., Palhinhaea cernua, nodding club-moss—MacRoberts & MacRoberts 1995b). Species typically present in Wet Herbaceous Seeps include carnivorous plants (Drosera spp., Pinguicula pumila, Sarracenia alata), Xyris spp. (yellow-eyed-grass), Eriocaulaceae (pipeworts), orchids (e.g., Pogonia ophioglossoides), club-mosses (Lycopodiaceae), and cinnamon and royal ferns (Osmunda cinnamomea, O. regalis) (Bezanson 2000). Fire suppression, resulting in the encroachment of woody vegetation, is a serious threat to the longterm survival of many of these communities (Keith & Carrie 2002). SOILS OF EAST TEXAS BOTTOMLANDS The Entisols and Inceptisols typical of bottomlands receive new sediments during each flood occurrence and vary greatly in texture, acidity, wetness, and drainage. Colors range from gray to red depending on the state of iron oxidation. Highly oxidized iron is reddish to yellowish in color, while reduced iron is generally gray. Texture and relative productivity of these soils is strongly determined by the source of the deposited sediment. In the smaller streams where the slope gradient is higher (i.e., more rapid water flow), only the coarser material is deposited. This gives rise to better-drained, loamy soils. As streams get larger and the slope gradient decreases, they become relatively more sluggish, especially during floods. This allows the finer clayey particles to be deposited. The resulting soils are generally more clayey and wetter. The soils in the bottomlands of smaller streams, where the soils are better drained, support a predominance of pines. In the central and northern parts of East Texas, the large stream bottomland soils are generally poorly or very poorly drained and support vegetation often referred to as “bottomland hardwoods.” In the southern part of East Texas, the extremely poor drainage results in many swamps and isolated marshes. The swamps may have a predominance of Taxodium distichum (bald-cypress), Nyssa aquatica (water tupelo), or Acer rubrum (red maple). SOILS OF EAST TEXAS STREAM TERRACES Stream terrace soils are mostly Alfisols and occur as nearly level to gently sloping benches or plains adjacent to larger streams throughout East Texas. Landscapes of the terraces may be three-tiered and are generally accepted to be older alluvial depositions that have been modified by wind. Poorly drained depressions, flats, and mounds may occur in sequence. Such a landscape, ranging from poorly drained depressions to well-drained mounds, tends to give rise to varied plant communities. The wetter depressions are covered with hardwoods while pines dominate the loamy mounds.
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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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Page 15 and 16: TABLE OFCONTENTS/ PAGE APPENDICES A
Page 17 and 18: Hymenocallis liriosme
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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
Page 63: 46 INTRODUCTION/SOILS SOIL ORDER DE
Page 67 and 68: 50 INTRODUCTION/SOIL-RELATED GEOLOG
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
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Page 107 and 108: 90 INTRODUCTION/CURRENT VEGETATION
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98 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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