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

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ORIGIN AND DIVERSITY OF EAST TEXAS FLORA/INTRODUCTION 221 February 1999 directed several federal agencies ‘to prevent the introduction of invasive species and provide for their control and to minimize the economic, ecological, and human health impacts that invasive species cause’; (Fed. Regist. 64(25):6183–86).” Thus, the National Invasive Species Council, an inter-departmental council that coordinates effective federal governmental activities regarding invasive species, was formed (Invasivespecies.gov 2004). Unfortunately, more nonindigenous species are being introduced each year, and the problem of invasives is “clearly worsening” (Wilcove et al. 2000). Despite the seriousness of the problem, Texas was until recently one of only 16 states without a noxious plant program (USDA Natural Resources Conservation Service 2002). This lack of an official policy has hindered effective control efforts. In 2003, a state bill authorizing the publication of a list of noxious plants was passed (Hibbs 2003; Texas Parks & Wildlife 2003) and that list is now available on-line (Texas Administrative Code 2005). However, Texas still has no single authority in charge of addressing invasive species issues and detailed policies for effective and coordinated control efforts are still lacking. Fortunately, attention is now focused on the problem and a major collaborative conference addressing the issue, the statewide Texas Invasive Plant Conference (The Pulling Together Initiative), is scheduled for November 2005 (TexasInvasives.org 2005). While usually not discussed in detail, the interaction of invasions with various aspects of human-caused global environmental change (e.g., climate change, modified nutrient cycles including carbon and nitrogen, changes in fire regimes, and land use changes) deserves significant attention (Mooney & Hobbs 2000; Simberloff 2004). Without some of these changes, many invasions would simply not be able to occur. Invasive exotics are an example of the phenomenon of ecological release—an introduced species is released from the ecological constraints of its native area (e.g., diseases, parasites, pests, predators, nutrient deficiencies, competition, etc.) and is consequently able to undergo explosive population growth in its new home. Elton (1958), one of the founders of the field of invasion ecology, used the term “ecological explosion” for this phenomenon, because the invasions display a “bursting out from control of forces that were previously held in restraint by other forces.” Unfortunately, ecological release is well known in East Texas. For example, Pueraria montana var. lobata, kudzu, an aggressive vine which can completely cover native forests, is already well-established in a number of East Texas counties (e.g., Colorado, Grayson, and Lamar). This species, which has taken over more than 7 million acres of land in the southern U.S. (Lembke 2001), is one of the most notorious examples of an invasive exotic plant. Festuca arundinacea, tall fescue, is capable of invading intact native tall grass prairies and is considered by some (e.g., Fred Smeins, pers. comm.) to be the most serious invasive threat to tall grass Blackland Prairie remnants such as the Nature Conservancy’s Clymer Meadow in Hunt County. The eastern Asian Sapium sebiferum, usually known as Chinese tallow tree or as popcorn tree, has been widely used in landscaping in East Texas, in part because of its brilliant fall color. However, this species is now widely recognized as one of the most serious invasive exotics in East Texas and in the adjacent Gulf Prairies and Marshes (e.g., Barrilleaux & Grace 2000; Keay et al. 2000; Loos 2002). It is particularly problematic in invading and destroying native Coastal Prairie habitats and is showing a rapid increase in sapling populations in some floodplain forests of the Big Thicket National Preserve (Harcombe et al. 1998; Keay et al. 2000). There are numerous other examples in East Texas of ecological release. Some of the most serious or potentially serious include Bothriochloa ischaemum var. songarica (King Ranch bluestem), Cuscuta japonica (Japanese dodder), Hydrilla verticillata (hydrilla), Imperata cylindrica (cogon grass), Lespedeza cuneata (sericea lespedeza or Chinese bush-clover), Ligustrum sinense (Chinese privet), Lonicera japonica (Japanese honeysuckle), Orobanche ramosa (branched broom-rape), Salvinia molesta (giant salvinia), Solanum viarum (tropical sodaapple) and Sorghum halapense (Johnson grass). It should be pointed out that while this discussion focuses on plants, there are numerous problematic invasive animals, fungi, microorganisms, and viruses that have
222 INTRODUCTION/ORIGIN AND DIVERSITY OF EAST TEXAS FLORA tremendous negative impacts in the U.S. (e.g., European zebra mussels, fire ants, Africanized (killer) bees, gypsy moths, chestnut blight, Dutch elm disease, West Nile virus). Unfortunately, a number of these are currently affecting East Texas. Of particular importance for many plant communities is the direct negative impact caused by feral hogs (Sus scrofa). This species causes various types of damage ranging from exposing soil to erosion to general destruction of vegetation, hindering longleaf pine restoration efforts (by uprooting plants while searching for longleaf seedlings), disturbing habitats in and around small streams where they wallow, changing successional patterns, affecting water infiltration rates (Synatzske 1997; Halstead 2002), and damaging populations of herbaceous species with underground storage structures. CHARACTERISTICS OF INVASIVE EXOTICS Most introduced plants do not become problematic invaders because they face a variety of environmental hazards in their new surroundings, and most are unable to persist and naturalize (Williamson 1996; Williamson & Fitter 1996; Mack & Erneberg 2002). Of the more than 30,000 introduced plant taxa commercially available in the U.S. today, it is estimated that fewer than 3,000 (10%) have become naturalized (Mack & Erneberg 2002), and even fewer have become problematic invaders. Whether or not a particular species becomes invasive depends upon complex interactions between several factors: 1) the characteristics of the invading species (i.e., invasion potential—including competitive ability, reproductive rate, persistence of seeds, disease and herbivore resistance, climatic compatibility, ecological distinctiveness, genetic variability, etc.); 2) propagule pressure (how many seeds or other propagules are introduced); and 3) the properties of the ecosystem that is being invaded (e.g., level of disturbance, resistance to invasion, vacancy of niches, etc.) (Williamson 1996; Lonsdale 1999; Lambrinos 2002). One of the most important ecosystem factors is disturbance—disturbance reduces the ability of native species to compete with potential invaders (Lonsdale 1999). Unfortunately, most habitats worldwide—and virtually all in East Texas— are now disturbed. Because so many interacting factors are involved, it is very difficult to predict with certainty whether a species will become invasive or not. This low level of predictability has long been noted (e.g., Elton 1958) and is a serious problem. The literature of invasion ecology is full of examples of presumed-harmless species intentionally introduced for specific purposes (e.g., erosion prevention, forage, biological control) but which become horrible pests as the result of unanticipated consequences. Some species, because of frost sensitivity, sterility, or similar known limiting factors, can be assumed to be relatively safe. Others (e.g., species known to be problematic in other parts of the world) may have a much greater probability of becoming invasive. However, for many species, the invasion potential is uncertain. Thus, individuals intentionally introducing plants (i.e., those in the horticultural trade) should take precautions and be alert for evidence of high invasion potential. A useful, albeit rough, rule of thumb regarding the frequency of invasion has been called the “tens rule” (e.g., Williamson 1996). By this it is meant that roughly 10% of plant species imported become feral (found in the wild), 10% of these become established (naturalized, with self-sustaining populations), and 10% of these become pests (invasive). Given the many thousands of species that have been introduced into the U.S., it is fortunate that the percentage is not higher. One curious aspect of invasive species is that there often appears to be a time lag between their actual introduction and their widespread impact (J. Taylor, pers. comm.; Simberloff 2000a, 2004). Sometimes a species is seen only rarely and appears innocuous for a significant period of time, after which its spread appears rapid—the invader seems to undergo a population explosion. These species are sometimes referred to as “sleepers” (Simberloff 2004). The cause of this phenomenon is not clear, but possibilities include adaptation to the local environment or quirks of dispersal (e.g., getting into roadside environments where highway mowing equipment can result in extremely rapid and widespread dispersal). Insight on
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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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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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ILLUSTRATED FLORA OF EAST TEXAS - Brit - Botanical Research ...

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