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

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■ abundant lianas (= large woody vines) extending high into the canopy, ■ the presence of epiphytes (e.g., Spanish moss, resurrection fern), ■ the presence of abundant individuals of the palm family (Sabal minor,dwarf palmetto, sometimes dominating the forest floor—e.g., palmetto-hardwood flats), ■ many species of orchids, ■ numerous and often conspicuous ferns and fern allies, ■ a conspicuous bamboo (Arundinaria gigantea,giant cane, historically forming large canebrakes), ■ numerous representatives of many characteristically tropical plant families such as Annonaceae (including pawpaw), Araliaceae (e.g., hercules’-club), Bignoniaceae (e.g., crossvine), Lauraceae (e.g., red bay), Marantaceae (e.g., powdery thalia), Mayacaceae (e.g., bog-moss), Melastomataceae (e.g., meadow-beauty), and Symplocaceae (e.g., sweet-leaf ), ■ high species richness, ■ areas with standing water for long periods of time (e.g. Neches River bottoms), and ■ animal links to the tropics including the presence of leaf-cutting ants (Fig. 95), large crocodilians (American alligator), and even (until the early 1900s) jaguars (Bailey 1905). Clearly these similarities to the tropics reflect the humid subtropical climate of the area—nonetheless, they make the Big Thicket interesting and unusual in a state mostly characterized by quite different types of vegetation. WHAT IS UNIQUE ABOUT THE BIG THICKET ?—As MacRoberts and MacRoberts (2004a) pointed out, the Big Thicket shares a great deal with the rest of the southeastern U.S. It has similar levels of habitat diversity, appears to be comparable in terms of species richness, and is perhaps not a biological crossroads. Given these similarities, is there anything unique or special about the Big Thicket? The answer to this question is yes. While clearly part of NATURAL HISTORY OF BIG THICKET/INTRODUCTION 171 FIG.95/LEAFCUTTER ANTS (FROM COOKE & COOKE 1995, USED WITH PERMISSION OF LOIS LEONARD STOCK). the southeastern U.S., the Big Thicket represents the southwestern extreme of the Southeastern Mixed Forest Province and the Outer Coastal Plain Mixed Forest Province (Keys et al. 1995; Turner et al. 1999). Hundreds of species that occur in an arc from Virginia or North Carolina south to Florida and west to Texas reach the southern or southwestern limit of their ranges in the Big Thicket, or are confined or largely confined in Texas to the Big Thicket area. The reasons for their occurrence in the Big Thicket include the high rainfall and overall mesic conditions and the presence of specialized habitats (e.g., hillside seepage bogs, pine flatlands, etc.). A few of the hundreds of examples include Bartonia texana (Texas screwstem), Ctenium aromaticum (toothache grass), Dryopteris ludoviciana (southern wood fern), Lachnocaulon digynum (pineland bogbutton), Magnolia pyramidata (pyramid magnolia), Palhinhaea cernua (nodding club-moss), Rhynchospora tracyi (Tracy’s beak sedge), Sabatia dodecandra (marsh rose-gentian), Stewartia malacodendron (silky-camellia), and several Xyris (yellow-eyed-grass) species. In addition to widespread species reaching their distributional limit, a number of taxa in the Big Thicket are either rare, endangered, endemic to the West Gulf Coastal Plain, or endemic to the Big Thicket itself (e.g., Yucca cernua).
172 INTRODUCTION/SUMMARY DEFINITION OF BIG THICKET The Big Thicket thus represents a biological boundary and is therefore important for a variety of reasons. For one thing, populations at the extreme margin of a species’ range are often unique genetically and represent an irreplaceable genetic resource. Second, peripheral populations are often more sensitive to environmental change and can act as ecological indicators, serving as an early warning system against changes that may possibly have broader implications. In the modern world, with humans having the capacity to influence global climatic processes, such indicators may be vital. From the Texas perspective, the Big Thicket is important because it represents a unique area within the state—it is only in this relatively small corner of Texas that numerous plant communities and hundreds of species can be found. From a slightly broader perspective, the Big Thicket is valuable since it contains one of the only relatively large protected areas in the entire West Gulf Coastal Plain, an important regional center of endemism (MacRoberts et al. 2002c). As such, it is critical in protecting representative samples of numerous unique West Gulf Coastal Plain plant communities and species. Exemplifying this importance is the fact that two areas within the Big Thicket (Longleaf Ridge and the Big Thicket-Sandylands Complex) are among the top ten richest conservation areas in the West Gulf Coastal Plain ecoregion, with Longleaf Ridge considered to be the richest (Nature Conservancy 2003). The Big Thicket is also unique within Texas from the standpoint of ecosystem services. Given its position just north of one of the largest population centers in the state, the role of the Big Thicket in terms of hydrology (flood control, water purification, etc.) and other ecosystem services makes it uniquely important to Texas, not only ecologically, but economically as well. SUMMARY DEFINITION OF THE BIG THICKET Based on all of the preceding material, how then can one define the Big Thicket? While linked with the West Gulf Coastal Plain and the rest of the southeastern U.S., we suggest that several highly interrelated factors when combined can give a reasonable way of defining and delineating the Big Thicket: ■ Ecological definition of the area as a loblolly pine-white oak-beech-magnolia forest, with a rich understory of evergreen and deciduous shrubs, numerous climbing vines, and varied herbs, plus included vegetation types (e.g., xeric sandylands, baygalls, etc.). ■ Biological boundary as the southwestern extreme of the Southeastern Mixed Forest and Outer Coastal Plain Mixed Forest provinces. ■ Humid subtropical climate—Mild temperatures and high, rather evenly distributed rainfall— approximately 48 to nearly 60 inches (122 to 152 cm) per year. ■ Geological, hydrological, and edaphic complexity. ■ High levels of habitat diversity and species richness. In concise terms, the Big Thicket is thus the biological boundary area at the southwestern extreme of the southeastern U.S., humid subtropical in climate, geologically and hydrologically complex, rich in species, and characterized by a loblolly pine-white oak-beech-magnolia forest with many associated and often very distinct vegetation types. While the Big Thicket is a meaningful and useful concept, its exact boundaries will continue to be imprecise. Individual species have ranges that can be determined with precision, but the ranges of different species rarely correspond. As a result, vegetational areas usually cannot be clearly delimited. Ultimately, it is clear that virtually any vegetational area is a human concept without precise boundaries. However, an artificial delineation of the Big Thicket, such as the one presented here (page 167; also see Fig. 94), can provide a practical approximation. This imprecision does not make the region any less interesting, valuable, or worthy of conservation. The Big Thicket by any definition is a rich and unique part of Texas and North America, and one which warrants long-term protection and preservation.
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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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108 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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222 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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