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

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FUTURE OF BLACKLAND PRAIRIE/INTRODUCTION 147 crops.” Three specific Blackland communities, (Schizachyrium scoparium-Paspalum plicatulum, Schizachyrium scoparium-Sorghastrum nutans, and Tripsacum dactyloides-Panicum virgatum), are considered “threatened natural communities” by the Texas Organization for Endangered Species (TOES 1992). Conversion of the Blackland Prairie for agriculture was the most important cause of the destruction of this ecosystem, with only marginal, often steeply sloped land not rapidly brought under cultivation. High prices for cotton and grains eventually resulted in the cultivation of even these marginal areas, “…with disastrous effects. Blackland soils on steep slopes, stripped of their protective grass, eroded rapidly. Gullying was everywhere, and in a few years, over much of the marginal slope-lands, as much as three feet of soil had been eroded, exposing barren rock where once was prairie soil” (Hayward & Yelderman 1991). Today, extensive eroded areas and large sections that have been contoured to remedy erosion can be seen in many places throughout the Blacklands. More recently, urbanization became a significant cause of prairie loss, particularly around the larger metropolitan areas. In places such as Dallas, it is all too common to see the rich black soil of areas formerly covered by blackland prairie being covered by more highways, strip malls, shopping centers, and residential areas. Even putting aside issues of prairie destruction, it is interesting to contemplate the long-term consequences of using large amounts of our richest farm land for non-agricultural purposes. In addition to direct destruction of prairie through cultivation or other uses (e.g., urbanization), existing isolated small prairie remnants are currently being lost through invasion by woody vegetation and introduced species. Recurrent fire and grazing by bison were natural processes that maintained the Blackland ecosystem; the removal of these processes causes changes in the vegetation (Smeins 1984; Smeins & Diamond 1986; Diamond & Smeins 1993). Given the relatively high rainfall over most of the Blacklands and with the suppression of fire by humans, native trees and shrubs (e.g., Juniperus virginiana—eastern red-cedar, Ulmus crassifolia—cedar elm), as well as introduced species, are able to invade and eventually take over areas that were formerly prairie. Similar encroachment by Juniperus spp. is known in adjacent Oklahoma and is widely recognized as a “threat to the ecological integrity of grassland ecosystems” (Hoagland 2000). In this relatively high rainfall, ecotonal region, periodic appropriate disturbance (e.g., fire, enlightened grazing regime, mowing) is essential for the maintenance of prairie— without some type of disturbance, brush encroachment/thicketization rapidly occurs. However, even native hay meadows, which are routinely disturbed, are often markedly different from the original vegetation because of the substitution of mowing and herbicide use (particularly in the past) in place of fire and grazing. The results include a reduction in broadleaved prairie species and an increased abundance of grasses (Diamond & Smeins 1993). While grazing was a natural component of the Blacklands and many other Texas ecosystems, overstocking with and overgrazing by domesticated animals has caused a dramatic decline and even near elimination of numerous plants from many areas (Cory 1949). The cumulative effect of all these human-induced changes is that the Blackland Prairie communities have been largely destroyed. Large areas that were once tall grass prairie are now covered by crops or other introduced and now naturalized species such as Bothriochloa ischaemum (King Ranch bluestem), Cynodon dactylon (Bermuda grass), and Sorghum halepense (Johnson grass). Roadsides and pastures are particularly obvious examples; in many cases, hardly any native grasses can be found. In these areas, there has also been an accompanying dramatic reduction in native forb diversity. In striking contrast to the loss of natural terrestrial communities of the Blackland Prairie, there has been a tremendous increase in aquatic habitats. Most native wetlands, including prairie “pothole-like” wetlands, have been lost. However, with the construction of
148 INTRODUCTION/FUTURE OF BLACKLAND PRAIRIE FIG. 81/ PHOTOGRAPH OF PRESCRIBED BURN DURING JANUARY 2002 ON AUSTIN COLLEGE’S CLINTON AND EDITH SNEED ENVIRONMENTAL RESEARCH AREA IN GRAYSON CO.(PHOTO BY PETER SCHULZE). numerous reservoirs and ponds, there is vastly more habitat for aquatic vegetation than in presettlement days. With the exception of oxbow lakes along some of the larger streams, the only permanent surface water prior to human intervention was in rivers, streams, swampy or marshy areas, beaver ponds, and springs. Introduced, and native, aquatic plants are now widespread and in some cases so abundant as to be problematic weeds. Many aquatic plants probably have populations several orders of magnitude greater than in the relatively recent past. This same pattern holds not just for the Blackland Prairie, but for all vegetational areas within East Texas. Because, as mentioned earlier, only a tiny amount of Blackland Prairie remains (5,000 acres or 0.04% of the original—Appleton 2000), a vigorous and varied conservation strategy will be necessary to preserve meaningful representatives of its constituent communities. Preserving as many of the remaining native fragments as possible is obviously critical, and this approach is being pursued by organizations such as the Nature Conservancy (e.g., Clymer Meadow in Hunt County, Tridens Prairie in Lamar County), Texas Parks and Wildlife Department, local governments (e.g., Collin County—Parkhill Prairie), Austin College (Garnett Prairie in Grayson County), Texas A&M University-Commerce (Cowleach Prairie Preserve in Hunt County), and private landowners (e.g., Matthews-Cartwright-Roberts Prairie in Kaufman County and the approximately 2,000 acre/800 hectare Smiley-Woodfin Prairie in Lamar County). Prairie restoration efforts are also being undertaken by a variety of organizations. Examples include The Heard Natural Science Museum and Wildlife Sanctuary (a tall grass prairie restoration project) and Austin College (Sneed Prairie Restoration Project). Such preserves and restoration sites require active management to prevent brush encroachment and invasion by native species, and a variety of techniques are being employed, including enlightened grazing regimes, mowing, and fire. Prescribed fire (controlled burning) is perhaps the most important tool used in Texas in prairie management at the present time. Fire is routinely used by a number of agencies/organizations in maintaining and restoring prairies in East Texas—examples include the Texas Parks and Wildlife Department, the U.S. Fish and Wildlife Service, the Nature Conservancy of Texas, and Austin College (Fig. 81). B
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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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198 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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