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

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ORIGIN AND DIVERSITY OF EAST TEXAS FLORA/INTRODUCTION 199 presents both an unparalleled conservation opportunity and the potential for widespread loss of forest land through various types of development. As a result of these concerns, the National Parks Conservation Association recently named the Big Thicket National Preserve as one of its “Ten Most Endangered Parks” (National Parks Conservation Association 2003; Warchut 2003). A longer-term concern is the effect rising atmospheric CO2 levels and possible global climate change will have on the Big Thicket and its species. The local consequences of such climate change are particularly difficult to predict, but the Big Thicket and East Texas as a whole could see substantial effects. As noted by Cameron et al. (1997), the boundaries of the Big Thicket National Preserve are static, while many of the habitats and species being protected may face significant shifts in their ranges in response to climate change (e.g., northern movement of climatic zones). In an area such as the Big Thicket, where most areas outside the Preserve have been highly modified by human activities, the ability of species to move and thus survive changes in climate is highly limited. Emphasizing this point, Cameron et al. (1997) noted that while global climate change “is a serious threat to the integrity of all natural systems and nature preserves, natural habitats in east Texas along with their associated fauna are particularly vulnerable to environmental change because of their extreme fragmentation.…” Faced with these challenges, conservationists are actively working in a variety of ways. Numerous individuals, both inside and outside of government, are involved in efforts to secure the remainder of the funding for the previously approved “additions” to the national preserve. Because of the large amount of timber company land now for sale, efforts are being made at this critical juncture to purchase some of the available acreage to increase the area permanently protected. For example, organizations such as the Conservation Fund are attempting to buy areas adjacent to the preserve, including a 1,000 acre (405 hectare) plot which will provide a buffer zone around the new visitor center. The Big Thicket Association (www.btatx.org) still actively engages in conservation activities, including publication of the Big Thicket Reporter (through which information on preservation and related efforts can be obtained), co-hosting Big Thicket Science Conferences, and supporting efforts to expand the national preserve. Numerous other organizations and individuals are involved in various activities to focus attention on the preserve and the larger ecosystem, with the goal ultimately being to protect the Big Thicket. These activities range from creating and managing small preserves (e.g., Watson Pineland Preserve), to research (e.g., Paul Harcombe), writing and publishing (e.g., James Cozine, Pete Gunter, Maxine Johnston), fund-raising, and political action—all are important. One specific example is Lamar University’s Center for the Study of the Big Thicket (http://dept.lamar.edu/artssciences/BIGTHICKET/home.htm), which is promoting the study of the natural and cultural history of the Big Thicket. Such varied conservation approaches are essential, since what is done now and in the next few years will forever determine the fate of the ecosystem, and future generations will look back to this time as a turning point in efforts to save the Big Thicket of East Texas. ORIGIN AND DIVERSITY OF THE EAST TEXAS FLORA INTRODUCTION TO THE EAST TEXAS FLORA The flora of East Texas, like that of any relatively large region, has a complex and varied origin. Ultimately, it is the result of the evolutionary and distributional history of each of the component species, as well as a reflection of past and present climate and soil conditions. However, several influences can be observed which together allow at least a broad understanding of how the present flora originated. East Texas contains components of four major floristic provinces as defined by Thorne (1993d): the Appalachian Province, the Atlantic and Gulf Coastal Plain Province, the North American Prairies Province, and the Sonoran Province.
200 INTRODUCTION/ORIGIN AND DIVERSITY OF EAST TEXAS FLORA There are also considerable numbers of Texas endemics. In addition, the modern flora contains 18% introduced species, these having come from various parts of the world. It should be noted that this book is a snapshot of the flora as it currently exists and that the flora will continue to change. Natural causes—glacial cycles, shifts in weather patterns, etc.—have had and will continue to have an effect. For example, studies of bogs at various Texas localities (e.g., Patschke Bog, Lee County; Boriack Bog, near Austin; Gause Bog, Milam County), as well as larger scale studies and analyses, indicate that near the end of the last glacial maximum, species currently present only much further north (e.g., white spruce) were present in Texas, suggesting a very different climate (Potzger & Tharp 1943, 1947, 1954; Bryant 1977; Bryant & Holloway 1985b; Delcourt & Delcourt 1993; Stahle & Cleaveland 1995). Certain present-day plant distributions may thus be relicts of these past climatic conditions (Kral 1966c). The current occurrence of the predominantly northern American beech (Fagus grandifolia) in the eastern part of the Pineywoods or the unusual occurrence of plants normally found in Eastern Texas in microhabitats of the Edwards Plateau, the Trans-Pecos, or the Cross Timbers and Prairies are examples of this pattern. Human activities (e.g., habitat alteration, human-induced climate changes, introduction of exotic species, etc.) will also cause the flora to change. For example, some of the introduced species are currently having significant adverse impacts on the native ecosystems. Specific cases include hydrilla (Hydrilla verticillata), which now chokes many miles of Texas waterways, and Chinese tallow tree (Sapium sebiferum), which is invading extensive areas in the Big Thicket. In general, with the exception of the wetter extreme eastern portion, much of East Texas can be considered ecotonal—a transition zone. When looking back over thousands of years, the “history of this ecotonal region involved introduction of Picea [spruce] and mesic deciduous vegetation from the north during cool moist intervals, the establishment of oak savannah or an oak–hickory (Carya illinoinensis) association in warmer drier times, and possibly the incursion of arid elements from the west during periods of maximum temperature and dryness” (Graham 1999). In other words, the region has had a varied climate and complex floristic influences. A number of these influences will be described below. INFLUENCE OF THE EASTERN DECIDUOUS FOREST ON THE EAST TEXAS FLORA The eastern deciduous forest, which covers only approximately 11% of the North American continent, “is the most diverse and species-rich component of the North American vegetation” (Graham 1999). This forest extends as far west as East Texas, where a number of temperate genera reach the southwestern limit of their present distribution in the continental U.S. (Graham 1999). In East Texas, the influence of the eastern deciduous forest is represented by plants from two floristic provinces, the Appalachian Province and the Atlantic and Gulf Coastal Plain Province (Thorne 1993d). This component of the flora is particularly important in the Pineywoods, the Post Oak Savannah, and the Red River drainage, but eastern deciduous forest elements occur across all of East and adjacent North Central Texas and even make up an important component of the flora of the Edwards Plateau to the south and west (Amos & Gehlbach 1988). The vast deciduous forest biome of eastern North America is composed of a number of plant communities, and the various forests and savannahs of East Texas represent a diversity of these community types. They range from wet and mesic communities dominated by species such as bald-cypress and water tupelo or beech and magnolia in the eastern part of East Texas, to drier pine-dominated ones (e.g., Arenic Longleaf Pine Uplands), to various oak-hickory or oak communities further west in the Post Oak Savannah. The latter, in combination with the Cross Timbers just to the west, represent the relatively dry western fringe of the eastern deciduous forest (Thorne 1993d). From the historical biogeography standpoint, eastern deciduous forest elements are one of the most fascinating components of the East Texas flora. Since the breakup of the supercontinent Pangaea, extensive dispersal of plants and animals between the Eurasian and North American continents has occurred, and the combined area (previously the northern part 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
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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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14 INTRODUCTION/GUIDE TO ARRANGEMEN
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16 INTRODUCTION/GUIDE TO SOURCES OF
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18 INTRODUCTION/GUIDE TO GEOGRAPHIC
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20 INTRODUCTION/GUIDE TO ENDANGERED
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22 INTRODUCTION/GUIDE TO GLOSSARY,
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24 INTRODUCTION/GUIDE TO ABBREVIATI
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26 INTRODUCTION/SUMMARY DATA ON FLO
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28 INTRODUCTION/ACKNOWLEDGMENTS Kar
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30 INTRODUCTION/AUTHORS’ NOTE Pre
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32 INTRODUCTION/GENERAL GEOLOGY OF
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46 INTRODUCTION/SOILS SOIL ORDER DE
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48 INTRODUCTION/SOILS, EAST TEXAS B
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50 INTRODUCTION/SOIL-RELATED GEOLOG
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60 INTRODUCTION/SOILS OF BLACKLAND
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66 INTRODUCTION/CLIMATE OF EAST TEX
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Forests define East Texas, and to a
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78 INTRODUCTION/GEOLOGY OF PINEYWOO
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80 INTRODUCTION/PRESETTLEMENT, EARL
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88 INTRODUCTION/PRESETTLEMENT VEGET
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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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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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