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

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CLIMATE OF EAST TEXAS/INTRODUCTION 65 are less useful for agriculture than are Vertisols, and at present they tend to be used as pastures or home sites. Shrink-swell phenomena, while still occurring on Mollisols, are less problematic than on Vertisols (Diamond & Smeins 1993; Hallmark 1993). Mollisols are more common to the west of East Texas on the Grand Prairie (made up of the Fort Worth Prairie and Lampasas Cut Plain). The soils of that region are often developed on layers of relatively hard limestone, and the area has sometimes been called the “hard lime rock region” (Hill 1901). Laws (1962) and Brawand (1984) have studied the characteristics of soils formed from the Austin Chalk in the Dallas area. Alfisols, which develop principally on bedrocks which are higher in sand and lower in calcium carbonate, are found in the Blacklands mainly on the eastern and northern margins of the main belt of the Blackland Prairie (Hallmark 1993) (Fig. 30), on the western margin of the Fayette Prairie, and in places on the San Antonio Prairie. These soils, which develop under forests as well as prairies, are less fertile than either Vertisols or Mollisols (Hallmark 1993). Mima mounds (also called pimple mounds or prairie mounds), another microtopographical feature (Fig. 31), were once found on many Alfisols within the Blackland Prairie region and can still be observed on certain unplowed prairie remnants (e.g., northern Grayson County (Fig. 34) and the Nature Conservancy’s Tridens Prairie in Lamar County). Mima mounds are circular, saucer-shaped hills ranging from about 1 to 15 meters in diameter and up to approximately 1.5 meters in height. While numerous hypotheses have been proposed, the specific cause of these structures is not known with certainty and they are possibly of multiple origins (Collins et al. 1975; Diamond & Smeins 1993). Though wind (erosion/deposition) appears to be a widely accepted explanation, other possibilities are that the mounds formed by wave action, are the products of past drainage patterns (e.g., runoff erosion combined with vegetation anchoring soil in place), are formed by fossorial (= burrowing) rodents (such as pocket gophers), or are the result of seismic activity (Diamond & Smeins 1985; Cox & Hunt 1990; Sletten et al. 1994; Ganse 2003). What is known is that some process operating in the past (but not presently in the area) is responsible for mima mound formation—this seems clear since, once destroyed, mima mounds do not reform under current conditions (unlike gilgai which will reestablish). Both gilgai and mima mounds increase microhabitat diversity and thus contribute to vegetational differences over small distances. The overall biological diversity of the prairie is therefore greatly increased by this variation in microtopography (Miller & Smeins 1988; Diamond & Smeins 1993). Due to the variation in vegetation associated with the different microhabitats produced by both gilgai and mima mounds, these features are often easily discernible in the field at certain seasons of the year (Figs. 33, 34). Sometimes a particularly conspicuous species will be quite obviously associated with a microtopographical high or low (e.g., Helianthus mollis, ashy sunflower, on mima mounds) and allow these areas to be spotted from long distances. CLIMATE AND WEATHER OF EAST TEXAS East Texas, like the state as a whole, is a region of dramatic climate transition. The striking vegetational change from the swampy tropical-like forests of Caddo Lake and the Big Thicket on the eastern margin of East Texas to the grasslands of the Blackland Prairie just to the west is a vivid reflection of this climatic transition (Stahle & Cleaveland 1995). The climate of East Texas is considered subtropical (Jordan et al. 1984; Yelderman 1993; Norwine et al. 1995; Peterson 1995), but a wide range of extremes can be found. Detailed climatic information about one East Texas site, Nacogdoches, can be found in Chang et al. (1996). Like the rest of the state, East Texas can be referred to climatically as a “land of contrasts” (Bomar 1995). This results in part from two major competing factors which dominate the climate of Texas— frontal systems from the north and west, and moist air moving inland from the Gulf of Mexico. As these influences interact, dramatic weather often results (North et al. 1995b). There is ample reason why locals say, “If you don’t like the weather, just wait a few minutes.”
66 INTRODUCTION/CLIMATE OF EAST TEXAS “Blue northers,” cold fronts swinging down from the north and accompanied by rapid drops in temperature of dozens of degrees, are common (Bomar 1995). An example was the “frigid blast of bitterly cold Arctic air” that in January of 1973 “knifed through Texas and far into the Gulf of Mexico, leaving a blanket of snow as deep as nearly a half foot in the piney woods of East Texas” (Bomar 1995). One of the most important factors causing such extremes is East Texas’ geographic position. The North American continent is uniquely shaped—like a giant funnel or inverted wedge with a 6,500 km (4,040 mile) wide base in the sub-Arctic. From there it narrows to the south eventually ending in the tiny Isthmus of Panama. The central part of the continent has two north-south mountain ranges, the eastern Appalachians and the western Rockies, which act like the sides of a funnel. An old saying is that “there ain’t nothin’ between Texas and the North Pole but an old barbed-wire fence and it’s down most of the time” (Girhard 2003). During winter, super-chilled Arctic air from the vast northern part of the continent can surge uninhibited far to the south, to East Texas and beyond (e.g., “blue northers” can even reach Guatemala, causing freezing temperatures and damage to plants in mountainous areas of the tropics—G. Diggs, pers. obs.). This phenomenon is sometimes referred to as a “climatic trumpet,” presumably because it magnifies or amplifies seasonality and long-term climate—the exaggerated seasons and weather extremes of North America are thus a function of geography (Flannery 2001). Conversely, warm air from the Gulf of Mexico can move far to the north during summer. An important consequence of the unimpeded movement of these air masses is that for much of the eastern U.S., including southern areas like East Texas, temperatures during the coldest month often approach freezing or below, while summers are virtually tropical. Such conditions are perfect for deciduous forests, and it is no accident that in presettlement times a vast deciduous forest spread all across the eastern U.S. as far west as East Texas (Flannery 2001). FIG.35/MEAN ANNUAL TEMPERATURE (˚F) FOR TEXAS (ADAPTED FROM GRIFFITHS & ORTON [1968] BY HATCH ET AL.[1990]).
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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
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4 INTRODUCTION/GEOGRAPHIC AREA OF E
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10 INTRODUCTION/MAJOR RIVERS OF EAS
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12 INTRODUCTION/PLANTS TREATED The
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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 and 64: 46 INTRODUCTION/SOILS SOIL ORDER DE
Page 65 and 66: 48 INTRODUCTION/SOILS, EAST TEXAS B
Page 67 and 68: 50 INTRODUCTION/SOIL-RELATED GEOLOG
Page 77 and 78: 60 INTRODUCTION/SOILS OF BLACKLAND
Page 79 and 80: 62 INTRODUCTION/SOILS OF BLACKLAND
Page 81: 64 INTRODUCTION/SOILS OF BLACKLAND
Page 85 and 86: 68 INTRODUCTION/CLIMATE OF EAST TEX
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Page 95 and 96: 78 INTRODUCTION/GEOLOGY OF PINEYWOO
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Page 105 and 106: 88 INTRODUCTION/PRESETTLEMENT VEGET
Page 107 and 108: 90 INTRODUCTION/CURRENT VEGETATION
Page 123 and 124: 106 INTRODUCTION/POST OAK SAVANNAH
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Page 127 and 128: 110 INTRODUCTION/GEOLOGY AND SOILS
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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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126 INTRODUCTION/POST OAK SAVANNAH
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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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