ECOREGIONS OF TEXAS Glenn Griffith, Sandy Bryce, James Omernik, and Anne Rogers ECOREGIONS OF TEXAS Glenn Griffith1, Sandy Bryce2, James Omernik3, and Anne Rogers4 December 27, 2007 1Dynamac Corporation 200 SW 35th Street, Corvallis, OR 97333 (541) 754-4465; email: [email protected] 2Dynamac Corporation 200 SW 35th Street, Corvallis, OR 97333 (541) 754-4788; email: [email protected] 3U.S. Geological Survey c/o U.S. Environmental Protection Agency National Health and Environmental Effects Research Laboratory 200 SW 35th Street, Corvallis, OR 97333 (541) 754-4458; email: [email protected] 4Texas Commission on Environmental Quality Surface Water Quality Monitoring Program 12100 Park 35 Circle, Building B, Austin, TX 78753 (512) 239-4597; email [email protected] Project report to Texas Commission on Environmental Quality The preparation of this report and map was financed in part by funds from the U.S. Environmental Protection Agency Region VI, Regional Applied Research Effort (RARE) and Total Maximum Daily Load (TMDL) programs. ABSTRACT Ecoregions denote areas of general similarity in ecosystems and in the type, quality, and quantity of environmental resources. Ecoregion frameworks are valuable tools for environmental research, assessment, management, and monitoring of ecosystems and ecosystem components. They have been used for setting resource management goals, developing biological criteria and establishing water quality standards. In a cooperative project with the Texas Commission on Environmental Quality, the U.S. Environmental Protection Agency, the U.S. Department of Agriculture, and other interested state and federal agencies, we have defined ecological regions of Texas at two hierarchical levels that are consistent and compatible with the U.S. EPA ecoregion framework. Twelve level III ecoregions and 56 level IV ecoregions have been mapped for Texas. These general purpose regions are useful to help structure and implement ecosystem management strategies across federal agencies, state agencies, and nongovernmental organizations that are responsible for different types of resources within the same geographical areas. Aquatic biologists in Texas have a long history of analyzing streams and potential reference conditions within a variety of Texas regional frameworks. This ecoregion framework was the result of input from a variety of disciplines, both terrestrial and aquatic based, and takes a broader ecological perspective than just water quality or aquatic macroinvertebrates. We believe that this new ecoregion framework still provides a valuable tool for the State’s water quality assessments. Streams that are representative of an ecoregion and are minimally disturbed and least impacted from point and nonpoint source pollution can serve as suitable reference streams. Ecoregions and reference watersheds can be used together to better understand regional variations in stream quality, assess attainable conditions, develop biological criteria, and augment the watershed management approach. ACKNOWLEDGEMENTS Many people contributed to the organization of this project and to the development of the Texas ecoregion framework. For their collaboration and contributions, special thanks are given to Anne Rogers (TCEQ), Bill Harrison (TCEQ), Stephen Hatch (Texas A&M University), David Bezanson (Natural Area Preservation Association), Jeffrey Comstock (Indus Corporation), Philip Crocker (USEPA), Art Crowe (TCEQ), Michael Golden (NRCS), Susan Casby-Horton (NRCS), James Greenwade (NRCS), Conrad Neitsch (NRCS), Shannen Chapman (Dynamac Corporation), Augie De La Cruz (TCEQ), Kevin Wagner (Texas State Soil and Water Conservation Board [TSSWCB]), Richard Egg (TSSWCB), Alan Woods (Oregon State University), Clark Hubbs (University of Texas), David Certain (The Nature Conservancy) and Thomas Loveland (USGS). These people were authors or collaborators of the multi-agency Texas ecoregion poster published by the USGS (Griffith et al., 2004). Thanks are also given to the reviewers of the ecoregion poster, including Charles Hallmark (Texas A&M University), Gordon Linam (TPWD), Milo Pyne (NatureServe), and Raymond Telfair, II (TPWD). To obtain larger, color maps of the Level III and IV ecoregions of Texas or for an ARC/INFO export file of the ecoregion boundaries, contact the authors or see www.epa.gov/wed/pages/ecoregions/tx_eco.htm. ii Ecoregions of Texas TABLE OF CONTENTS ABSTRACT................................................................................................……………………...…... ii ACKNOWLEDGEMENTS……………………………………………………………………....….. ii LIST OF FIGURES............................................................................................................................... iv LEVEL III ECOREGIONS OF TEXAS MAP...................................................................................... v LEVEL III AND IV ECOREGIONS OF TEXAS MAP....................................................................... vi INTRODUCTION........................................................................................……………………...….. 1 METHODS...............................................................................................………….…………….…... 2 RESULTS AND REGIONAL DESCRIPTIONS......................................………………………….... 4 23. Arizona/New Mexico Mountains.................................................................................................... 4 23a. Chihuahuan Desert Slopes.………................................................................................... 4 23b. Montane Woodlands..........……………..................................….…................................ 6 24. Chihuahuan Deserts...........................................……………………….…..................................... 8 24a. Chihuahuan Basins and Playas....................................………………...………..…….... 8 24b. Chihuahuan Desert Grasslands....................................………………...……………..... 10 24c. Low Mountains and Bajadas........................................………………...………….….... 12 24d. Chihuahuan Montane Woodlands.................................................................................... 14 24e. Stockton Plateau............................................................................................................... 16 25. High Plains...................................................................................................................................... 18 25b. Rolling Sand Plains.......................................................................................................... 18 25e. Canadian/Cimarron High Plains....................................................................................... 19 25i. Llano Estacado.................................................................................................................. 20 25j. Shinnery Sands.................................................................................................................. 22 25k. Arid Llano Estacado......................................................................................................... 24 26. Southwestern Tablelands................................................................................................................. 25 26a. Canadian/Cimarron Breaks.............................................................................................. 25 26b. Flat Tablelands and Valleys.............................................................................................. 28 26c. Caprock Canyons, Badlands, and Breaks......................................................................... 29 26d. Semiarid Canadian Breaks............................................................................................... 31 27. Central Great Plains........................................................................................................................ 32 27h. Red Prairie........................................................................................................................ 32 27i. Broken Red Plains............................................................................................................. 34 27j. Limestone Plains............................................................................................................... 36 29. Cross Timbers.................................................................................................................................. 37 29b. Eastern Cross Timbers...................................................................................................... 37 29c. Western Cross Timbers..................................................................................................... 39 29d. Grand Prairie.................................................................................................................... 40 29e. Limestone Cut Plain......................................................................................................... 41 29f. Carbonate Cross Timbers.................................................................................................. 43 30. Edwards Plateau.............................................................................................................................. 44 30a. Edwards Plateau Woodland.............................................................................................. 45 30b. Llano Uplift...................................................................................................................... 47