United States
Environmental Protection
Agency
		
NHEERL
Western Ecology Division
Corvallis OR 97333
EPA/600/R-97/022
February 1997
Research and Development
as EPA
ECOREGIONS OF TENNESSEE

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ECOREGIONS OF TENNESSEE
by
Glenn E. Griffith1, James M. Omernik2, and Sandra H. Azevedo3
EPA/600/R-97/022
February 14, 1997
Western Ecology Division
National Health and Environmental Effects Research Laboratory
U.S. Environmental Protection Agency
200 SW 35th Street, Corvallis, OR 97333
^U.S. Environmental Protection Agency
National Health and Environmental Effects Research Laboratory
200 SW 35th Street, Corvallis, OR 97333
(541) 754-4465; email: glenn@mail.cor.epa.gov
2Project Officer
U.S. Environmental Protection Agency
National Health and Environmental Effects Research Laboratory
200 SW 35th Street, Corvallis, OR 97333
(541) 754-4458; email: omernik@mail.cor.epa.gov
3OAO Corporation
200 SW 35th Street, Corvallis, OR 97333
(541) 754-4361; email: sandi@mail.cor.epa.gov
The information in this document has been funded in part by the U.S. Environmental Protection Agency. It
has been subjected to the Agency's peer and administrative review, and it has been approved for publication
as an EPA document. Mention of trade names or commercial products does not constitute endorsement or
recommendation for use.

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ABSTRACT
Ecoregion frameworks are valuable tools for environmental resource inventory and
assessment, for setting resource management goals, and for developing biological criteria
and water quality standards. In a cooperative project with the Tennessee Department of
Environment and Conservation, the U.S. Environmental Protection Agency, and other
interested state and federal agencies, we have defined ecological regions of Tennessee at
two hierarchical levels that are consistent and compatible with the U.S. EPA ecoregion
framework. Eight level III ecoregions and twenty-five level IV ecoregions have been
mapped for Tennessee. Ecoregions provide a spatial framework within which the quality
and quantity of environmental resources, and ecosystems in general, can be expected to
exhibit a particular pattern. A multi-agency cooperative effort also resulted in the
identification of potential stream reference sites within the Tennessee ecoregions.
Streams that are representative of the ecoregion and are minimally disturbed and least
impacted from point and nonpoint source pollution can serve as suitable reference streams.
The ecoregions and reference sites can be used to better understand regional variations in
stream quality, assess attainable conditions, develop biological criteria, and augment the
watershed management approach.
To obtain a larger, color map (16"x32", 1:1,000,000-scale) of the Level III and IV ecoregions of
Tennessee or for an ARC/INFO export file of the ecoregion boundaries, contact the authors.
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TABLE OF CONTENTS
ABSTRACT			ii
INTRODUCTION			 1
METHODS			 3
RESULTS AND REGIONAL DESCRIPTIONS		 4
65.	Southeastern Plains	 4
65a. Blackland Prairie		 5
65b. Flatwoods/Alluvial Prairie Margins	 6
65e. Southeastern Plains and Hills	 6
65i. Fall Line Hills			 7
65j. Transition Hills	 8
66.	Blue Ridge Mountains	 9
66d. Southern Igneous Ridges and Mountains	 9
66e. Southern Sedimentary Ridges	 10
66f. Limestone Valleys and Coves					 10
66g. Southern Metasedimentary Mountains	11
67.	Ridge and Valley	13
67f. Southern Limestone/Dolomite Valleys and Low Rolling Hills	14
67g. Southern Shale Valleys	14
67h. Southern Sandstone Ridges	15
67i. Southern Dissected Ridges and Knobs	16
68.	Southwestern Appalachians				 16
68a. Cumberland Plateau			17
68b. Sequatchie Valley	18
68c. Plateau Escarpment	18
69.	Central Appalachians	19
69a. Cumberland Mountains			19
71. Interior Plateau		20
71e. Western Pennyroyal Karst	21
7 If. Western Highland Rim	22
71g. Eastern Highland Rim	23
71h. Outer Nashville Basin	:	24
71i. Inner Nashville Basin	25
73.	Mississippi Alluvial Plain			i	26
73a. Northern Mississippi Alluvial Plain	26
74.	Mississippi Valley Loess Plains	27
74a. Bluff Hills	.27
74b. Loess Plains	28
STREAM REFERENCE SITE SELECTION	29
CONCLUSIONS AND RECOMMENDATIONS	31
REFERENCES			34
APPENDIX 1. Summary table of ecoregion characteristics	45
FIGURE 1. Level III Ecoregions of Tennessee and Neighboring States	50
FIGURE 2. Level III and IV Ecoregions of Tennessee	 51
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INTRODUCTION
Spatial frameworks are necessary to structure the research, assessment, monitoring,
and ultimately the management of environmental resources. Ecological region (ecoregion)
frameworks are designed to meet these needs and have been developed in the United
States (Bailey 1976, 1983, 1995; Bailey et al., 1994; Omernik 1987, 1995), Canada (Wiken
1986; Ecological Stratification Working Group 1995), New Zealand (Biggs et al., 1990),
Australia (Thackway and Cresswell 1995), the Netherlands (Klijn 1994), and other
countries. We define ecoregions as areas of relative homogeneity in ecological systems and
their components. Factors associated with spatial differences in the quality and quantity of
ecosystem components, including soils, vegetation, climate, geology, and physiography, are
relatively homogeneous within an ecoregion. These regions separate different patterns in
human stresses on the environment and different patterns in the existing and attainable
quality of environmental resources. Ecoregion classifications are effective for inventorying
and assessing national and regional environmental resources, for setting regional resource
management goals, and for developing biological criteria and water quality standards
(Gallant et al., 1989; Hughes et al., 1990, 1994; Hughes 1989; Environment Canada 1989;
U.S. Environmental Protection Agency, Science Advisory Board 1991; Warry and Hanau
1993).
The development of ecoregion frameworks in North America has evolved considerably
in recent years (Bailey et al., 1985; Omernik and Gallant 1990; Omernik 1995). The U.S.
Environmental Protection Agency's (EPA) first compilation of ecoregions of the
conterminous United States was performed at a relatively cursory scale, 1:3,168,000, and
was published at a smaller scale, 1:7,500,000 (Omernik 1987). The approach recognized
that the combination and relative importance of characteristics that explain ecosystem
regionality vary from one place to another and from one hierarchical level to another. This
is similar to the approach used by Environment Canada (Wiken 1986). In describing
ecoregionalization in Canada, Wiken (1986) stated:
"Ecological land classification is a process of delineating and classifying ecologically
distinctive areas of the earth's surface. Each area can be viewed as a discrete system
which has resulted from the mesh and interplay of the geologic, landform, soil,
vegetative, climatic, wildlife, water and human factors which may be present. The
dominance of any one or a number of these factors varies with the given ecological land
unit. This holistic approach to land classification can be applied incrementally on a
scale-related basis from very site specific ecosystems to very broad ecosystems."
The EPA's ecoregion framework has been revised and made hierarchical. It has been
expanded to include Alaska (Gallant et al., 1995), as well as tie into a North American
ecological region framework (CEC Ecosystem Working Group 1997). A Roman numeral
classification scheme has been adopted for the hierarchical levels to avoid confusion over
different usage of terms such as ecozones, ecodistricts, ecoprovinces, subregions, etc.
Level I is the coarsest level, dividing North America into 15 ecological regions. At level II,
the continent is subdivided into 52 ecoregions, and at level III the continental United States
contains 98 ecoregions (U.S. EPA 1996).
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The level III ecoregions defined initially by Omernik (1987) were shown to be useful for
stratifying streams in Arkansas (Rohm et al., 1987), Nebraska (Bazata 1991), Ohio (Larsen
et al., 1986), Oregon (Hughes et al., 1987; Whittier et al., 1988), Texas (Hornig et al., 1995),
Washington (Plotnikoff 1992), and Wisconsin (Lyons 1989). The 1987 EPA ecoregion map
was used to set water quality standards in Arkansas (Arkansas Department of Pollution
Control and Ecology 1988), identify lake management goals in Minnesota (Heiskary and
Wilson 1989), and develop biological criteria in Ohio (Ohio EPA 1988; Yoder and Rankin
1995). Many state agencies, however, have found that the resolution of the level III
ecoregions does not provide enough detail to meet their needs. This has led to several
collaborative projects, with states, EPA regional offices, and the EPA's National Health and
Environmental Effects Research Laboratory in Corvallis, OR, to refine level III ecoregions
and define level IV ecoregions at a larger (1:250,000) scale. These projects currently cover
Oregon, Washington, North Dakota, South Dakota, Iowa, Indiana, Ohio, Pennsylvania,
Massachusetts, Florida, and parts of Mississippi, Alabama, Virginia, Maryland, and West
Virginia, and are largely in response to requests from EPA regional offices or state water
resource management agencies.
Regional reference sites within an ecoregion can give managers and scientists a better
understanding of attainable water body conditions. Water quality legislation and
regulations, with a mandate to "restore and maintain the chemical, physical, and biological
integrity of the Nation's waters," depend on some model of attainable conditions, that is, on
some measurable objectives towards which cleanup efforts are striving (Hughes et al.,
1986). The biota and physical and chemical habitats characteristic of these regional
reference sites serve as benchmarks for comparison to more disturbed streams, lakes, and
wetlands in the same region (Hughes et al., 1986; Hughes 1995). These sites indicate the
range of conditions that could reasonably be expected in an ecoregion, given natural limits
and present or possible land use practices.
States are adopting biological criteria for surface waters to improve water quality
standards. Biological criteria are defined as numeric values or narrative expressions that
describe the reference biological integrity of aquatic communities inhabiting waters of a
given designated aquatic life use (U.S. EPA 1990). To facilitate the development of
biological criteria for streams and rivers of Tennessee, the Tennessee Department of
Environment and Conservation (TDEC), U.S. EPA Region IV, U.S. EPA-Corvallis, and
other agencies are collaborating to define level III and level IV ecoregions, and to select
stream reference sites. Goals of the project for TDEC's Division of Water Pollution Control
(DWPC) also include identifying high quality waters for application of the state's
Antidegradation Statement in their water quality standards, documenting background
levels of surface water chemical constituents on an ecoregion basis for setting future
permit limits and 305(b) Report water quality assessments, and establishing ecoregion-
specific chemical and biological water quality standards. In this paper, we discuss the
method and materials used to refine level III ecoregions and define level IV ecoregions in
Tennessee, and provide descriptions of the significant characteristics in these regions.
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METHODS
Our regionalization process includes compiling and reviewing relevant materials, maps,
and data; outlining the regional characteristics; drafting the ecoregion boundaries; creating
digital coverages and cartographic products; and revising as needed after review by
national, state, and local experts. In the regionalization process, we used primarily
qualitative methods. That is, expert judgement was applied throughout the selection,
analysis, and classification of data to form the regions, basing judgments on the quantity
and quality of source data and on interpretation of the relationships between the data and
other environmental factors. More detailed descriptions on the U.S. EPA's methods,
materials, rationale, and philosophy for regionalization can be found in Omernik
(1987; 1995), Gallant et al., (1989), and Omernik and Gallant (1990). The regionalization
process used for Tennessee was similar to that of other state-level EPA ecoregion projects
(Griffith et al., 1994a,b,c; Woods et al., 1996).
Maps of environmental characteristics and other documents were collected from the
state of Tennessee, U.S. EPA-Corvallis, and from other sources. The most important of
these are listed in the References section. The most useful map types for our ecoregion
delineation are usually physiography or land surface form, geology, soils, vegetation,
climate, and land cover/land use. There are several different small-scale physiographic
maps of Tennessee that can be found in a variety of publications. Statewide physiographic
and land surface-form descriptions and maps were gathered primarily from Safford (1856),
Glenn (1915), Fenneman (1938), Hardeman et al., (1966), Folmsbee et al., (1969),
Hammond (1970), Fullerton et al., (1977), Miller (1979), and Bayer (1983), as well as the
physiographic coverage from the Tennessee Wildlife Resources Agency's GIS. Landform
subregions and landtype associations delineated by Smalley (1980, 1982, 1983, 1984, 1986)
were useful for our regionalization. Topography and land-form features were also
discerned from 1:100,000 scale topographic maps. Geologic information included maps
such as the 1:250,000-scale state series (Hardeman et al., 1966), and the l:l,000,000-scale
Quaternary geology series (Colquhoun et al., 1987; Gray et al., 1991; Howard et al., 1991;
Miller et al., 1988); state, regional, or local geology descriptions (Safford 1856; King et al.,
1968; Luther 1977; Miller 1979) and national scale maps such as Hunt (1979) and King and
Biekman (1974). Soils information was obtained from the U.S. Department of
Agriculture's (USDA) county soil surveys, the 1:250,000-scale STATSGO soil maps, regional
publications (Edwards et al., 1974), and the state-level 1:750,000-scale general soil map and
descriptions (Springer and Elder 1980). Because soil taxonomy and interpretations are
dynamic, and current soil series names may be different from those in earlier publications,
soil information was also obtained from state soil experts (John Jenkins, Rick Livingston,
USDA Natural Resources Conservation Service). For land use/land cover we used the
1:250,000 scale maps from the U.S. Geological Survey (USGS 1986) and the general
classification of Anderson (1970). Also, for assessing variations in the mix of agriculture
activities as an expression of land potential, many maps from the 1987 and 1992 Census of
Agriculture were analyzed (U.S. Department of Commerce 1990, 1995). Vegetation and
forest cover maps and information were obtained from Braun (1950), Kuchler (1964), the
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forest atlas of the South (USDA, Forest Service 1969), the national atlas (Kuchler 1970;
U.S. Forest Service 1970), and from numerous journal manuscripts cited in the regional
descriptions. In addition, a map produced from composited multi-temporal Advanced Very
High Resolution Radiometer (AVHRR) satellite data was also used to assess boundaries
and regional differences. This AVHRR NDVI (Normalized Difference Vegetation Index)
data is currently being used by the USGS EROS Data Center to characterize land cover of
the conterminous United States (Loveland et al., 1991, 1995).
We used USGS 1:250,000-scale topographic maps as the base for delineating the
ecoregion and subregion boundaries. Although this map series is dated, it does provide
quality in terms of the relative consistency and comparability of the series, in the accuracy
of the topographic information portrayed, and in the locational control. It is also a very
convenient scale. Eight of these quads cover more than 90% of the state and fourteen
maps give complete coverage of Tennessee.
RESULTS AND REGIONAL DESCRIPTIONS
We have divided Tennessee into eight level III ecoregions (Figure 1) and 25 level IV
ecoregions (Figure 2). Although these level IV ecoregions still retain some heterogeneity
in factors that can affect water quality and biotic characteristics, they provide a more
detailed framework and more precise ecoregion boundaries than the national-scale
ecoregions (Omernik 1987). The ecoregion framework also provides more homogeneous
units for inventorying, monitoring, and assessing surface waters than the commonly used
hydrologic unit frameworks or political unit frameworks (Omernik and Griffith 1991).
Most major river basins drain strikingly different ecological regions.
Ecoregion boundaries are often portrayed by a single line, but in reality they are
transition zones of varying widths. In some areas the change is distinct and abrupt, for
example where the Bluff Hills meet the Mississippi Alluvial Plain, or where the
Cumberland Plateau Escarpment meets the limestone valleys of the Ridge and Valley
ecoregion. In other areas, such as the division between the Mississippi Valley Loess Plains
Ecoregion and the Southeastern Plains Ecoregion, the boundary is fuzzy and more difficult
to determine. Fuzzy boundaries are areas of uncertainty or where there may be a
heterogeneous mosaic of characteristics from each of the adjacent areas.
65. Southeastern Plains	Area within TN: 5099 sq. mi.
Percent of state: 12.1%
On Omernik's (1987) ecoregion map, this coastal plain ecoregion boundary ended near
the Mississippi-Tennessee state line, with only a small arm extending north into McNairy
and Hardin counties, TN. A large area of coastal plain west of the Tennessee River was
included with the Interior Plateau ecoregion (71). This area of west Tennessee does have
similar potential natural vegetation as the Interior Plateau, oak-hickory forests rather
than oak-hickory-pine that characterizes the Southeastern Plains (Kuchler 1964). Several
other characteristics, however, suggest that this area is more appropriately included with
the Southeastern Plains. The landforms are irregular plains rather than open hills or
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plains with high hills (Hammond 1970); the geology consists of Cenozoic or Mesozoic-age
sands, silts, and clays rather than Paleozoic limestone, chert, and shale (Hardeman et al.,
1966); the surficial geology is generally sand and clay decomposition residuum rather than
solution residuum (Miller et al., 1988; Gray et al., 1991); and the Tennessee state soils map
shows a distinct coastal plain region (Springer and Elder 1980). According to TDEC
biologists, streams in this area are relatively low-gradient, sandy-bottomed (with occasional
gravel), and are similar to other coastal plain streams of west Tennessee. The Southern
Coastal Plain MLRA also extends over this area to near the Kentucky state line (USDA,
SCS 1981), and the area is within the Upper Gulf Coastal Section of the USFS (Bailey et
al., 1994; Keys et al., 1995).
On our first draft map of Tennessee for this project, the western boundary of the
ecoregion was similar to the coastal plain soil region shown by Springer and Elder (1980)
and the geologic boundary between the Quaternary loess area and the Tertiary-age
Claiborne and Wilcox Formations (Hardeman et al., 1966). During the multi-agency
ecoregion meeting in Murfreesboro (May 9-11, 1995) to discuss the draft map, it was
recommended that the boundary should be further west, as currently depicted, to include
all of the more rolling and hilly areas of the Lexington, Smithdale, and Providence soil
series.
The ecoregion as a whole was characterized by Omernik (1987) as containing smooth to
irregular plains, oak-hickory-pine forests with southern mixed forest in the south,
primarily Ultisol soils, and a mosaic of cropland, pasture, woodland, and forest. Elevations
are generally between 50-900 feet (300-1000 feet in Tennessee), with local relief 100-300
feet. Elevations and relief are greater than the Mississippi Loess Plains (74) to the west,
but generally less than the Interior Plateau (71) to the east. The ecoregion has been
divided into five level IV ecoregions within Tennessee: Blackland Prairie (65a),
Flatwoods/Alluvial Prairie Margins (65b), Southeastern Plains and Hills (65e), Fall Line
Hills (65i), and Transition Hills (65j).
65a. Blackland Prairie	Area within TN: 50 sq. mi.
Percent of state: 0.1%
Extending north from Mississippi, this ecoregion covers only a small portion of McNairy
County, Tennessee. The northern extent of the Blackland Prairie is debatable; even in the
ecoregion in northern Mississippi, the soil mosaic appears to differ from the Blackbelt soils
found in east-central Mississippi and central Alabama. There are, however, continuations
of Blackland Prairie physical factors into Tennessee. The Cretaceous-age Demopolis
Formation (Hardeman et al., 1966) in Tennessee is the geologic base of chalk, marl, and
calcareous clay that characterizes the ecoregion in Mississippi and Alabama. The
Quaternary geology map (Miller et al., 1988) also shows a dark gray clay solution residuum
(rcg) of the Blackland Prairie extending into Tennessee. Although a soil survey for
McNairy County is not yet published, Tennessee soil scientists do concur that there is
Blackland Prairie in this part of the state (John Jenkins, USDA-NRCS, personal
communication). Fenneman (1938, p.69) concludes that, "...the Black Belt gives out a little
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north of the Tennessee boundary." Heineke (1989) suggested a Northeastern Prairie Belt
extended north into Henderson and Carroll counties of Tennessee.
The Blackland Prairie is a flat to undulating lowland, with elevations in Tennessee
between 500-600 feet. The area is mostly in cropland and pasture, with small patches of
mixed hardwoods, generally oaks and hickories. A local botanist suggests that there are
more calciphilic trees, such as sugar maple, in this region than in the rest of ecoregion 65,
as well as some native, calciphilic old-field herbs (Milo Pyne, The Nature Conservancy,
personal communication). On Kuchler's (1964) natural vegetation map, the Blackbelt
vegetation type (sweetgum-oak-cedar) did not extend into Tennessee. Patches of bluestem
prairie are also associated with the ecoregion (DeSelm and Murdock 1993; Kuchler 1964),
although there is evidence that historically these patches were no more extensive in this
area than in the rest of the Southeast, and that the original application of the term
"prairie" to the Black Belt referred to soils and not a unique grassland vegetation type
(Rostlund 1957). Clayey soils from the marly coastal plain clay or silty soils from thin loess
are the most typical soils, generally thermic Alfisols and Ultisols. The primary soil
association for the Tennessee portion of the region is Oktibbeha-Silerton-Dulac
(STATSGO) or Oktibbeha-Boswell-Dulac (Springer and Elder 1980). There are a few
smaller occurrences of Blackland Prairie soils and geology to the north in McNairy and
Henderson counties that were not mapped at this scale. Mean annual precipitation in the
Tennessee portion is approximately 52 inches, with a frost-free period of 210 days.
65b. Flatwoods/Alluvial Prairie Margins	Area within TN: 36 sq. mi.
Percent of state: 0.08%
As with the Blackland Prairie, this narrow ecoregion belt extends north from
Mississippi, but its distinctiveness fades quickly from Ripley, Mississippi north into
Tennessee. The physiographic map by Cushing et al., (1964) extends the Flatwoods north
to the Hardeman/Chester county line in Tennessee. The Tertiary-age Midway group
(Porters Creek Clay and the Clayton Formation) underlie much of the ecoregion, with soils
of montmorillonitic clays or silt loams. The soil associations shown in STATSGO within
Tennessee are Tippah-Luverne-Smithdale and Wilcox-Falkner-Sweatman. In Mississippi
and Alabama, we viewed this ecoregion as a transition region between the Blackland
Prairie and the more forested plains and hills, but it was heterogeneous in terms of
landuse/landcover. Some areas, as the Flatwoods name implies, are heavily forested
(mostly white oak, pignut and mockernut hickories, shortleaf pine, sweetgum, tulip poplar,
with some bottomland hardwoods), but there are prairie and alluvial areas with significant
amounts of cropland and pasture. In Tennessee, the small region stands out as an area of
agriculture between mostly forested land, with slightly lower elevations (400-500 feet) and
less relief than the Southeastern Plains and Hills that surround it. Precipitation and
temperatures are similar to the Blackland Praire (65a).
65e. Southeastern Plains and Hills	Area within TN: 4590 sq. mi.
Percent of state: 10.9%
This ecoregion contains several north-south trending bands of sand and clay formations.
The Tertiary-age Claiborne and Wilcox Formations and Midway Group are to the west, and
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the Cretaceous-age McNairy Sand, the Coon Creek Formation of fossiliferous micaceous
sand, and the Coffee Sand are to the east. With more rolling topography and more relief
than the Loess Plains (74b) to the west (elevations range from 400 feet to over 650 feet),
streams have increased gradient, generally sandy substrates, and distinctive faunal
characteristics (Etnier and Starnes 1993). Potential natural vegetation is oak-hickory,
grading into oak-hickory-pine toward the south into Mississippi (Kuchler 1964). Current
land cover is mostly deciduous and mixed forest with areas of planted pine and pasture;
cropland of soybeans, corn, sorghum, cotton and hay fields occupy the bottoms and
terraces. Common trees of the upland forests include southern red oak, white oak, post
oak, black oak, mockernut and pignut hickory, with some loblolly and shortleaf pine. More
mesic slopes are dominated by white oak, sweetgum, and tulip poplar, with some sugar
maple and American beech (Heineke 1989). Bottomland hardwoods are found in some of
the larger river bottoms such as the Hatchie, and include overcup oak, swamp chestnut
oak, willow oak, water hickory, sweetgum, river birch, tupelo, and bald cypress. Annual
precipitation is 48-52 inches, with a freeze-free period of 200-210 days (Dickson 1974).
Although there are some differences within the ecoregion in the north-south trending
bands of sand and clay formations, we have lumped these at this hierarchical level rather
than split them, as there appears to be mosaics of loess, sand, and clay surficial materials,
as well as varying patterns of silty, sandy, loamy, and clayey soils. The U.S. Forest Service
(Keys et al., 1995) has split several of these bands out, including the Northern Pontotoc
Ridge (222Cf), a term not often seen in the Tennessee literature. According to Fenneman
(1938), the ridge loses its prominence in Tennessee, "...because the adjacent lowlands are
poorly developed." Cushing et al., (1964), however, note that an extension of the Pontotoc
Ridge may form the divide between the Mississippi and Tennessee Rivers in northern
Tennessee and Kentucky.
In the north part of ecoregion 65e, the U.S. Forest Service (Keys et al., 1995) defines a
Clay Hills subsection (222Cd), but the evidence for this boundary placement is not distinct.
There are definite ridge-like, more forested extensions westward from Paris, north and
south of the North Fork Obion River, of Claiborne and Wilcox Formation sand and clay
geology, upland chert-pebble gravel and sand surficial deposits. The forested land cover
rather than a mixed land cover may be due more to land ownership by clay mining
companies than to distinctly different ecological characteristics (John Jenkins, USDA-
NRCS, personal communication).
65i. Fall Line Hills	Area within TN: 9 sq. mi.
Percent of state: 0.02%
The Fall Line Hills level IV ecoregion of Mississippi and Alabama (Alabama DEM and
Mississippi DEQ 1995) was earlier placed within ecoregion 68, the Southwestern
Appalachians. We have revised these boundaries and placed the Fall Line Hills within
ecoregion 65 for several reasons: 1) It is inappropriate to have the Southwestern
Appalachians ecoregion (68) extend into west Tennessee, as shown by the earlier version
of the EPA 1995 Level III Ecoregions of the continental U.S. map; 2) the area known as
the Tennessee or Tombigbee Hills in Mississippi (and the Fall Line Hills in Alabama) is
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composed primarily of coastal plain sediments of the Mississippi Embayment; 3) The
addition of the Transition Hills subregion (65j) within the Southeastern Plains ecoregion
requires the inclusion of the Fall Line Hills in that coastal plain type level III ecoregion; and
4) the resultant framework would more closely resemble and follow the logic of the USFS
and MLRA frameworks.
The ecoregion generally coincides with the Upper Loam Hills and Upper Clay Hills
forest habitat regions (Hodgkins and Cannon 1976) and USFS subsections (Keys et al.,
1995) in Mississippi and Alabama. This is mostly forested terrain of open hills with 200-400
feet of relief. Elevations in the small Tennessee portion, roughly between Chambers
Creek and Pickwick Lake, are 450-685 feet. Medium to coarse sand decomposition
residuum and chert gravel and sand decomposition residuum are the primary surficial
materials in the ecoregion (Miller et al., 1988), covered by Ultisols of the Silerton,
Smithdale, Waynesboro, and Pickwick soil series. The potential natural vegetation is oak-
hickory-pine (Kuchler 1964). In Tennessee, the Fall Line Hills average 53 inches of annual
precipitation with a frost-free period of 207 days.
65j. Transition Hills	Area within TN: 413 sq. mi.
Percent of state: 1.0%
The U.S. Forest Service names these the Transition Loam Hills (Keys et al., 1995;
Hodgkins and Cannon 1976), but clay soils occur here as well as loam soils. The ecoregion
includes the Paleozoic Bottom physiographic region in Mississippi (Pike et al., 1969) and
part of the Fall Line Hills physiographic region in Alabama (Sapp and Emplaincourt 1975).
As a transition area, arguments could be made that this ecoregion belongs with the
Interior Plateau Ecoregion (Omernik 1987). The region includes much of the
Southwestern Clastic Rock District defined by R. Paul Terrel (Fullerton et al., 1977) that
was considered part of the Highland Rim. Many streams have cut down into the
Mississippian and Silurian-age rocks and may look similar to those of the Interior Plateau.
Cretaceous-age coastal plain sediments, however, overlie the older limestone, shale and
chert (Fort Payne and Silurian Formations). The topography may be determined by the
older underlying formations (Hodgkins and Cannon 1976), but the soils are mostly
governed by the overlying coastal plain deposits. The Tuscaloosa Formation consists of
gravel in a matrix of silt and sand, and the Eutaw Formation consists of fine-grained
glauconitic, micaceous sand with interbedded clays (Hardeman 1966). Soils and MLRA
maps generally include the southwest part of Wayne County, TN with the Coastal Plain
(Springer and Elder 1980; USDA-SCS 1981). Soils are primarily thermic Paleudults,
Hapludults, and Fragiudults, including the Silerton, Savannah, Dickson, Lax, Saffell, and
Brandon series.
The Transition Hills ecoregion is a mostly forested region with oak-hickory-pine natural
vegetation (Kuchler 1964). White oak, southern red oak, black oak and post oak are
common, along with the hickories and shortleaf pine. Pine plantations associated with pulp
and paper operations are a common land cover. Elevations in the Tennessee portion range
from 400-1000 feet, the highest of ecoregion 65. Annual precipitation averages 50-56
inches, with a fireeze-free period of 200-210 days.
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66. Blue Ridge Mountains	Area within TN: 2510sq.ini.
Percent of state: 6.0%
The Blue Ridge Mountains level III ecoregion extends from southern Pennsylvania to
northern Georgia, varying from narrow ridges to hilly plateaus to more massive
mountainous areas with high peaks. In Tennessee, the Blue Ridge region is often called
the Unaka Mountains, and the term Great Smoky Mountains generally refers to those in
the vicinity of the national park. The ecoregion within the state is characterized by
forested slopes, high gradient, cool, clear streams, and rugged terrain on a mix of igneous,
metamorphic, and sedimentary geology. Soils are mostly mesic, udic Dystrochrepts,
Hapludults and Haplumbrepts. Elevations generally range from 1000-6000 feet, with
Clingmans Dome, the highest point in Tennessee, reaching 6643 feet. Annual precipitation
ranges from 45-60 inches, but can be 80 inches or more on the well-exposed high peaks of
the Smoky Mountains (Dickson 1974). The freeze-free period within Tennessee is variable
depending on elevation and latitude, ranging from less than 150 days to more than 200
days.
The Blue Ridge is the most floristically diverse region of the state (Wofford 1989). From
a national scale, the potential natural vegetation consists of Appalachian oak forests,
northern hardwoods, and Southeastern spruce-fir forests (Kuchler 1964), but shrub, grass
and heath balds, hemlock, cove hardwoods, and oak-pine communities are also significant
(Clebsch 1989). High elevation balds provide grassy habitat for birds and mammals that
would not otherwise occupy these areas where spruce-fir forest dominate (DeSelm and
Murdock 1993). A distinctive breeding bird community was detected in high elevation
areas in the Blue Ridge (Nicholson 1991; Kendeigh and Fawver 1981). A distinct fish
fauna, less diverse than the Ridge and Valley, is associated with streams and rivers of the
region (Etnier and Starnes 1993; Bivens et al., 1985).
The ecoregion in Tennessee has been divided into four level IV ecoregions: Southern
Igneous Ridges and Mountains (66d), Southern Sedimentary Ridges (66e), Limestone
Valleys and Coves (66f), and Southern Metasedimentary Mountains (66g).
66d. Southern Igneous Ridges and Mountains	Area within TN: 235 sq. mi.
Percent of state: 0.6%
This ecoregion occurs in Tennessee's northeastern Blue Ridge near the North Carolina
border, primarily on Precambrian-age igneous and some high-grade metamorphic rocks.
Although igneous describes the initial origin of the rocks, some of them underwent various
degreees of metamorphism, and the term crystalline might be a better general descriptor
for these ridges and mountains. The typical rock types include Cranberry granite, Roan
gneiss, Beech granite, and Mt. Rogers Group metavolcanics (Hardeman 1966). Elevations
range from 2000-6000 feet, with Roan Mountain at 6286 feet. Unaka-Ashe soils are a
typical association found on the steep slopes of the higher mountains, while Ashe-Evard
soils are on side slopes and lower mountains. These tend to be loamy, well-drained, acid
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soils (Dystrochrepts and Haplumbrepts). Annual precipitation for the ecoregion is
approximately 50-60 inches, and the freeze-free period is 150-170 days.
Although there are a few small areas of pasture and apple orchards, the region is mostly
forested. Appalachian oak forest and northern hardwoods forest are Kuchler's (1964)
general potential natural vegetation types. The mixed oaks and hickories (and the
chestnut, before the blight) occupy the lower slopes, along with various pine and oak-pine
communities on drier sites. Cove hardwoods, dominated by yellow poplar and yellow
poplar-oak types, along with hemlock-white pine and hemlock-hardwood types are found
on the more sheltered and moist northern slopes, coves, and ravines, up to about 4000-
4500 feet. The northern hardwoods of the sugar maple-beech-yellow birch cover type
occur above 3500 feet to about 5000 feet, and also include red maple, basswood, buckeye,
hemlock, sweet birch, red oak, and black cherry. Above about 5400 feet, the red spruce
and Fraser fir are found in small areas of the ecoregion, along with some yellow birch,
mountain ash, and sugar maple. Rhododendron balds, grass balds, and alder balds can be
found on Roan Mountain.
66e. Southern Sedimentary Ridges	Area within TN: 799 sq. mi.
Percent of state: 1.9%
This ecoregion in Tennessee includes some of the westernmost foothill areas of the
Blue Ridge Mountains ecoregion, such as the Bean, Starr, Chilhowee, English, Stone, Bald
and Iron Mountain areas. Elevations are in the 1000-4000 feet range. The geology is
primarily Cambrian-age sedimentary rocks (shale, sandstone, siltstone, quartzite,
conglomerate). Some streams in this ecoregion occur on limestone. In the north, there is
a correlation of the ecoregion with the Ditney-Tate-Maymead soil association (STATSGO
208). These are found on the quartzites, shales, sandstones of the Erwin, Unicoi, and
Hampton formations. To the south, the soil associations include Jefferson-Wallen-Gilpin
(STATSGO 139) or Wallen-Jefferson-Ramsey (Springer and Elder 1980), predominantly
friable loams and fine sandy loams (Dystrochrepts and Hapludults) with variable amounts
of sandstone rock fragments. On Chilhowee Mountain, mixed oak forests on northern and
eastern slopes and oak-pine forests on south and southwest slopes comprise about 60% of
the forest cover, with second growth pine, yellow poplar, scrub oak, and oak-hickory cover
types comprising approximately another 30% of the area (Thomas 1989). Virginia pine-
pitch pine, along with some Table Mountain pine, occupies thin soil areas on exposed
ridges, and hemlock-white pine, with abundant rhododendron, is found in the deeper
ravines and moist coves. Annual precipitation for the Tennessee portion of the ecoregion
is 44-48 inches in the north and 52-56 inches in the south. The frost-free period ranges
from 150 to 200 days depending on latitude and elevation.
66f. Limestone Valleys and Coves	Area within TN: 139 sq. mi.
Percent of state: 0.3%
The Blue Ridge overthrust belt forced rocks to the east up and over younger rocks to
the west. In places, the Precambrian rocks have eroded through to Ordovician limestones,
as seen especially in deep cove areas that are surrounded by steep mountains. We have
mapped eleven of the main limestone valley and cove areas in the Blue Ridge of
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Tennessee; other limestone stream and river valleys occur in the ecoregion, but could not
be delineated at this scale and level of resolution. The small but distinct limestone areas
include the Mountain City lowland area and Shady Valley in the north, to Wear Cove,
Tuckaleechee Cove, and Cades Cove in the south. The geology in the northern areas is
primarily the Cambrian-age Shady dolomite, while the coves in Great Smoky Mountains
National Park are on the Cambrian and Ordovician Knox Group limestones and dolomites
with some areas of Blockhouse shale (Hardeman 1966; King et al., 1968). Quaternary
geology is mostly cherty clay solution residuum. Typical Ultisol and Alfisol series found in
the valleys and coves include Keener, Lonon, Northcove, Statler, and Bledsoe (Richard
Livingstone, NRCS, personal communication). Elevations are generally 1500-2500 feet.
The frost-free period is 160-190 days, and precipitation ranges from 45-55 inches.
Most of these limestone valleys and coves were originally forested, but have been
cleared for agriculture. Hay and pasture, with some tobacco patches on small farms, are
typical land uses. Knolls and slopes are dominated by oaks, with some white pine,
hemlock, tulip poplar, sourwood, and dogwood. Virginia pine and pitch pine are found on
drier sites and old field successional areas. The resource management of Cades Cove as a
historic district has had multiple ecological effects and tradeoffs regarding changes to
terrestrial flora and fauna, as well as the aquatic ecosystem (Bratton et al., 1980). The
open fields of Cades Cove tend to be dominated by exotic plant species and grasses such as
fescue and witch grass. In northeast Tennessee, Shady Valley historically had extensive
wetlands, and its soils still have a residual histic component (Milo Pyne, The Nature
Conservancy, personal communication). Vegetation changes for Shady Valley and
Johnson County have been described by Barclay (1957).
66g. Southern Metasedimentary Mountains	Area within TN: 1338 sq. mi.
Percent of state: 3.2%
The name of this ecoregion follows that of the U.S. Forest Service subsection (Keys et
al., 1995). It is a region of low mountains, elevations 1000-6000 feet, with local relief 1000-
3000 feet. The geologic materials are generally older and more metamorphosed than the
Southern Sedimentary Ridges (66e) found at the western margins and northern part of
the Blue Ridge ecoregion in Tennessee. The geology consists of metamorphic and
sedimentary rocks of the Pre-Cambrian age Ocoee Supergroup: mostly siltstone,
sandstone, shale, conglomerate, graywacke, arkose, phyllite, slate, schist, and quartzite of
the Walden Creek, Great Smoky, and Snowbird Groups (Hardeman 1966; King et al.,
1968). The slate and phyllite of the Anakeesta Formation in the Great Smoky Group
contain iron sulfides that can locally acidify small streams, especially when slumps or road
cuts expose the sulfide materials to air and water (Huckabee et al., 1975). Surficial geology
in the ecoregion consists of bouldery colluvium (Miller et al., 1988; Howard et al., 1991).
Soils are generally Dystrochrepts and Hapludults, with Haplumbrepts and Spodosols at the
highest elevations (Springer and Elder 1980). Soil associations are shown as Sylco-Ranger-
Citico and Ditney-Jeffrey-Brookshire on the state map; Ramsey-rock outcrop-Barbourville
and Junaluska-Spivey-Tsali in the STATSGO database. Other common soil series include
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Cataska, Keener, Lostcove, and Unicoi.) Average annual precipitation in the ecoregion is
55-75 inches, with a freeze-free period 170-200 days (Dickson 1974; Mundy and Gray 1986).
These mountains support extremely complex and numerous plant communities and a
great diversity of plant species. The potential natural vegetation of the ecoregion had
three general classes defined by Kuchler (1964), Appalachian oak forest, northern
hardwoods, and Southeastern spruce-fir forest. The low to intermediate elevation areas
are dominated by mixtures of oaks, pines, and various combinations. Pines such as
Virginia pine, pitch pine, shortleaf pine, white pine, and Table Mountain pine can occur in
pure stands or mixed with oaks on a variety of drier, exposed, or shallow-soil sites. Oaks in
the drier areas include post oak, blackjack oak, southern red oak, scarlet oak, and black
oak. White oak and chestnut oak are widespread at intermediate elevations, and the more
mesic northern red oak extends to higher elevations, and is also found in the cove
hardwoods (Clebsch 1989). The mixed mesophytic or cove hardwoods forest is rich in tree
species, occurring in the more moist and sheltered coves, ravines, and northerly slopes, up
to about 4000-4500 feet in elevation (Whittaker 1956). Yellow poplar, hemlock, oaks,
basswood, sugar maple, ash, beech, basswood and other hardwoods are typical. Hemlock
forests occur in slightly more-exposed sites than the cove hardwoods, up to similar
elevations. The northern hardwoods forests are found from about 3500 feet in elevation to
over 5000 feet, and are dominated by sugar maple, beech, yellow birch, hemlock, red oak,
buckeye, basswood, and wild black cherry. Spruce-fir forests, found generally above 5500
feet, have been affected greatly over the past twenty-five years by the balsam wooly aphid,
as well as by a growth decline in red spruce (Ramseur 1989; Clebsch 1989). Shrub and
grass balds at the highest elevations are dynamic, ecologically significant, oft-debated, and
celebrated areas (Mark 1958; Gersmehl 1970; Lindsay and Bratton 1979).
A special area of management concern in this ecoregion is the Copper Basin or
Ducktown District. Located in the southeast corner of Tennessee and extending into
North Carolina and Georgia, the bowl-like basin was the site of copper mining and
smelting from the 1850's to 1987. By the early 1900's, sulfur dioxide fumes and intensive
lumbering left a severely eroded expanse of bare earth devoid of plant life. Surrounding
zones included areas of grasses, stunted shrubs, and dead-topped trees with gullied
subsoils. Erosion has contributed large loads of sediment and metals to the Ocoee River,
and has caused the loss of approximately 98% of the storage capacity of Ocoee No. 3
Reservoir (Denton et al., 1994). Revegetation efforts in the Copper Basin have occurred on
and off since the 1930's (Quinn 1988). A map of the extent of three forest injury zones
(Quinn 1993), based on a 1906 U.S. Forest Service map, covers an area about 540 square
miles in the three states. The extent of the underlying Copperhill Formation of the Great
Smoky Group is not shown on the state geology map (Hardeman 1966), and it is difficult to
determine if pre-mining ecological conditions were different from other areas of ecoregion
66g. Natural vegetation was thought to be similar to the mixed forest of surrounding areas
(Quinn 1991).
The Conasauga watershed area also exhibits some ecological differences from the rest
of ecoregion 66g, primarily in its different fish species and benthic macroinvertebrates.
This is most likely due to its drainage connection with the Gulf of Mexico.
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67. Ridge and Valley	Area within TN: 7668 sq. mi.
Percent of state: 18.2%
"If anything is evident from this discussion of the geology of the Great Valley, it should be the fact that it is
complicated," (Luther 1977).
In Tennessee, this northeast to southwest trending ecoregion is also known as the
Great Valley of East Tennessee. It is a relatively low-lying region between the Blue Ridge
Mountains to the east and the Cumberland Plateau on the west, but elevations range from
a low of about 700 feet in Hamilton County to over 3000 feet on Chimneytop Mountain in
northern Greene County. The roughly parallel northeast-to-southwest trending ridges
and valleys come in a variety of widths, heights, and geologic materials, a result of extreme
folding, thrusting, and faulting events. Silurian, Ordovician, and Cambrian-age limestone,
dolomite, shale, siltstone, sandstone, chert, mudstone, and marble are found in the
ecoregion in Tennessee. Springs and caves are relatively numerous.
The land-surface form has been classed as open hills with 300-500 feet of local relief,
and more than 75% of the gentle slope in the lowland (Hammond 1970). Case (1925) found
four types of topography in the region and noted that they were so intermingled that it was
difficult to classify them regionally. The types he noted were: 1) short broken ridges or
rounded hills, locally known as knobs, 2) long, straight, narrow, sharp-crested ridges with
narrow intervening valleys, 3) uniformly fluted ridge and valley land, with long, narrow,
rounded ridges separated by narrow, flattish valleys, and 4) broad, rolling uplands
separated by canyon-like valleys or in places by broader valleys. Much of the drainage is in
a trellised pattern, with small streams draining the ridge slopes, joining at right angles with
larger, lower-gradient stream courses that meander along the parallel valley floors. The
larger rivers that come out of the Blue Ridge Mountains often transect the ridges and
valleys. The ecoregion has great aquatic habitat diversity in Tennessee and supports a
diverse fish fauna rivaled only by that of the Highland Rim (Etnier and Starnes 1993).
The frost-free period in the Tennessee portion is 190-220 days. Annual precipitation
ranges from the state low of near 40 inches in the north, where moisture-laden clouds are
intercepted by the Cumberland Plateau/Mountains and the Blue Ridge Mountains, to 54
inches in the south (Dickson 1974). Potential natural vegetation was mapped as
Appalachian oak forest (Kuchler 1964), and this grades into Oak-Pine towards the Georgia
border (Shanks 1958). Present-day forests cover about 50% of the region, and vary in
composition and structure due to the diversity of physical environments and human uses
(Martin 1989).
To be consistent with the Ridge and Valley ecoregion classification in states to the north
(Woods et al., 1996), the ecoregion in Tennessee has been subdivided into the following
regions: Southern Limestone/Dolomite Valleys and Low Rolling Hills (67f), Southern Shale
Valleys (67g), Southern Sandstone Ridges (67h), and Southern Dissected Ridges and Knobs
(671).
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67f. Southern Limestone/Dolomite Valleys and Low Rolling Hills
Area within TN: 5324 sq. mi.
Percent of state: 12.6%
This is a heterogeneous ecoregion composed predominantly of limestone and dolomite,
but there are other rock formations and strata with varying characteristics. Landforms
include undulating valleys as well as low rolling hills and ridges, with elevations ranging
from 700 feet in the south to 2000 feet on the highest hills in the north. The soils are
primarily Paleudults (Fullerton, Dewey, Decatur, Bodine, Waynesboro series) that are
variable in their productivity, and landcover ranges from areas of intensive agriculture to
other areas of thick forest. Most of the Ridge and Valley's urban areas are located in 67f.
White oak forests, bottomland oak forests, and sycamore-ash-elm riparian forests are
the most common forest types (Martin 1989). Loblolly pine plantations occur in several
areas in the southern part of the ecoregion. Grassland barrens, dominated by little
bluestem, are one type of non-forest vegetation that occurs in the Ridge and Valley. These
often occur on shallow, clayey soils usually over the Chickamauga group limestone, and
may have cedar-pine glades intermixed. (DeSelm et al., 1969; De Selm and Murdock 1993).
The climate is slightly more mild compared to the higher elevation ridges and mountains of
East Tennessee. The frost-free period ranges from 190-220 days, and average annual
precipitation is 40 inches in the north to 54 inches in the south.
67g. Southern Shale Valleys	Area within TN: 1433 sq. mi.
Percent of state: 3.4%
The Southern Shale Valleys consist of lowlands, rolling valleys, and some slopes and
hilly areas, that are dominated by fine-grained rock, primarily shale. Local relief is
generally 100-400 feet. In the north, two areas of the ecoregion are associated with the
Ordovician-age Sevier shale, which tends to be calcareous. The largest area extends from
northern Blount County, past Douglas Lake, parts of the Lick Creek and Holston River
valleys, the Kingsport area, and into Virginia. The second area is more dissected, hilly and
steep, extending from near Johnson City, around South Holston Lake and into Virginia, at
the foot of the Blue Ridge Mountains ecoregion. Soil associations in these areas are mostly
Bays-Dandridge-Montevallo (STATSGO) or Dandridge-Needmore-Whitesburg soil
associations (Springer and Elder 1980). These are slightly acid or neutral, well drained or
excessively drained soils, primarily Eutrochrepts and Hapludalfs.
The shale valleys to the south are associated with Cambrian-age shale, limestone, and
siltstone, and what was previously called the Litz-Sequoia-Talbott soil association. As
Springer and Elder (1980, p.52) noted for these mostly acid soils, "Except for a few narrow
bands of limestone, shale underlies the unit. Nearly all of the soils formed in residuum
from this tilted shale." Townley and Montevallo soils are now used in place of the Litz and
Sequoia series in the southern Ridge and Valley (Rick Livingston, NRCS, personal
communication).
The steeper slopes in the ecoregion are used for pasture or have reverted to brush and
forested land, while hay, corn, tobacco, and garden crops are grown on the foot slopes and
bottom land (Springer and Elder 1980). The forested sections are mostly white oak
communities and some white oak-hickory, along with successional cedar and pine types
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(Martin 1989). Virginia pine and shortleaf pine forests occur here, and plantations of
loblolly and white pine are extensive in some areas, especially toward the south. Annual
precipitation is 40-48 inches in the north, with a freeze-free period of 180-200 days, while
the southern areas near the Georgia border receive 50-54 inches of precipitation and 220
frost-free days.
67h. Southern Sandstone Ridges	Area within TN: 326 sq. mi.
Percent of state: 0.8%
The Southern Sandstone Ridges are high, steep, forested ridges with narrow crests, and
have typically stony, sandy soils of low fertility. Elevations can reach over 3000 feet, and
precipitation averages 44-54 inches. Although most all of the ridges were once logged, a
variety of forest types of different ages and composition occurs here. The natural
vegetation consists primarily of Appalachian oak forest (Kuchler 1964). White oak
communities are common, some mixed mesophytic and tulip poplar forests are found in
depressions and on lower slopes, and chestnut oak forests occupy some of the drier upland
sites (Martin 1989). Pitch pine can be found on the higher, exposed ridges.
This ecoregion encompasses the major sandstone ridges, but the map delineations often
enclose some associated areas of shale and siltstone. Some of these areas are not
separated because of the map scale and the generalized geologic information. Wallen
Ridge and Powell Mountain in Hancock and Claiborne counties are composed primarily of
the Silurian-age Clinch Sandstone and Rockwood Formation (shale, siltstone, sandstone).
The soil associations are shown as Wallen-Jefferson in the county soil survey and
Armuchee-Collegedale-Montevallo by STATSGO. East of Powell Mountain, parts of
Newman Ridge (Chattanooga Shale, Newman Limestone, and the Pennington Formation
shales, siltstones and sandstones) could be similar to ridges of ecoregion 67i. Soils,
however, are shown as Jefferson-Wallen-Gilpin, similar to other sandstone ridge areas.
The polygon enclosing the Clinch Mountain sandstone ridge area in the northern part of
the ecoregion has areas of shale as well. It appears that the west side has more sandstone
(Silurian-age Clinch Sandstone) as does Short Mountain and Pine Mountain on the east,
while the central and southeast areas have more shale (Mississippian and Devonian-age
Chattanooga Shale and the Grainger Formation of shale, siltstone, sandstone and
conglomerate). Armuchee-Collegedale-Montevallo soils are on the west, and Jefferson-
Wallen-Gilpin soils are to the east.
White Oak Mountain, in Hamilton County in the southern part of the ecoregion, has
some sandstone on the west side, but abundant shale and limestone as well (shale,
siltstone and sandstone of the Rockwood Formation, Ft. Payne chert and shale, and
Newman Limestone). The delineated ridge polygon also encompasses Grindstone
Mountain, capped by the Gizzard Group sandstone, the only preservation of
Pennsylvanian-age strata in the Valley and Ridge of Tennessee (Tennessee Division of
Geology 1979).
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67i. Southern Dissected Ridges and Knobs	Area within TN: 585 sq. mi.
Percent of state: 1.4%
The ridges delineated for this ecoregion are primarily those with abundant shale that
have a prominant topographic expression. They are lower and more dissected than ridges
of ecoregion 67h. On topographic maps, one can often see the distinctly different contour
patterns of these dissected ridges compared to the sandstone ridges of 67h. The shale ridge
contour lines show a more crenulated pattern reflecting the more broken, almost
hummocky ridges, compared to the smoother, more parallel contour patterns of the more
sharply pointed sandstone ridges. In states to the north of Tennessee, streams of this
ecoregion tend to be less acidic than on the sandstone ridges (67h), and have storm
hydrographs with higher peaks (Woods et al., 1996).
In Tennessee, the ridges on the east side of the ecoregion tend to be associated with the
Ordovician-age Sevier shale, Athens shale, and Holston and Lenoir limestones. These
formations can include calcareous shale, limestone, siltstone, sandstone, and conglomerate
(Hardeman 1966). In the central and western part of the ecoregion, the dissected ridges
are associated with the Cambrian-age Rome Formation: shale and siltstone with beds of
sandstone. Again, this mixture of geologic materials illustrates the difficulty of separating
shale ridges from sandstone ridges, and it is the resistant sandstone beds that most often
form the ridge.
An effort was made to obtain supporting information for the geological distinctions from
soils classifications, either from the county soil surveys, the state soil map (Springer and
Elder 1980), or from soils and geology explanations from Tennessee Division of Geology
(1973; 1979) publications and Martin (1989). Dystrochrepts and Eutrochrepts are the
primary soil great groups of the ecoregion. Soils that appeared to be associated with the
Rome Formation shale ridges included the Lehew, Litz, Muskingum, and Montevallo
series. Soils over the Sevier and Athens shale and the Holston and Lenoir formations
include the Dandridge, Whitesburg, Wallen, Calvin, Montevallo, Tellico, and Alcoa series.
Chestnut oak forests and pine forests are typical for the higher elevations of the ridges,
with areas of white oak, mixed mesophytic, and tulip poplar on the middle and lower
slopes, knobs, and in draws (Martin 1989). Some pasture and cropland is found on the less
sloping land. The frost-free period is generally 180-210 days. Precipitation increases from
44 inches in the north to 54 inches in the south or at higher elevations.
68. Southwestern Appalachians	Area within TN: 4813 sq. mi.
Percent of state: 11.4%
The ecoregion defined by Omernik (1987) contained two separate areas of the
Southwestern Appalachians: the Cumberland Plateau area of Tennessee, southern
Kentucky, northwest Georgia, and northeast Alabama; and the forested area of the
southern Plateau plus the Fall Line Hills in north-central Alabama. We have recently
modified the ecoregion boundary in the Sand Mountain area of northern Alabama to join
these two areas (U.S. EPA 1996). The ecoregion's land-surface form was characterized as
open low to high hills and open mountains, with natural vegetation of oak-hickory-pine
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and mixed mesophytic forests, and Hapludults as the dominant soil great group. Land use
was characterized as a mosaic of cropland, pasture, woodland, and forest (Omernik 1987).
In Tennessee, the eastern boundary of the ecoregion, along the more abrupt escarpment
of the Cumberland Front where it meets the Ridge and Valley (67), is relatively smooth
and only slightly notched by small eastward flowing stream drainages. The western
boundary, where it meets the Interior Plateau's Eastern Highland Rim (71g), is more
crenulated with a rougher escarpment that is more deeply incised. The deeper gorges
provide wet and cool environments that can harbor distinct plant communities (Caplenor
1979). Hinkle (1989) concluded that the mixed mesophytic forest was mostly restricted to
these deeper ravines and escarpment slopes, and the upland forests were better
characterized as mixed oak forests. Streams have cut down into the limestone but the
gorge taluses are composed of sandstone boulders. Many waterfalls occur where the
sandstone is undercut.
We have divided the Southwestern Appalachians of Tennessee into three level IV
ecoregions: the Cumberland Plateau (68a), the Sequatchie Valley (68b), and the Plateau
Escarpment (68c).
68a. Cumberland Plateau	Area within TN: 3184 sq. mi.
Percent of state: 7.6%
This area is generally considered the Mid-Cumberland Plateau (e.g., Smalley 1982)
consisting of open low mountains and tablelands of considerable relief. The ecoregion is
about 1000 feet higher than the Eastern Highland Rim (71g) to the west, and receives
slightly more precipitation with cooler annual temperatures than the surrounding lower-
elevation ecoregions. The plateau surface is less dissected with lower relief compared to
the Cumberland Mountains (69d) or the Plateau Escarpment (68c). The plateau surface is
generally 1200-2000 feet in elevation, with the Crab Orchard Mountains reaching over
3000 feet. Annual precipitation averages 48-60 inches from north to south, and the freeze-
free period is 180-200 days.
The geology of the Cumberland Plateau is Pennsylvanian-age conglomerate, sandstone,
siltstone, and shale: the Crab Orchard Mountains Group in the south, and Rockcastle
Conglomerate and Crooked Fork Group in the north (Hardeman et al., 1966). In two small
areas north of the Sequatchie Valley, the Pennsylvanian-age sandstone has eroded down
to the Mississippian carbonate rocks to form the uvalas or sinks of Grassy Cove and Crab
Orchard Cove. The most common soil series on the Cumberland Plateau are Lily (formerly
Hartsells), Ramsey, Lonewood, and Gilpin; generally loamy, silicious, mesic Hapludults and
Dystrochrepts. The region is mostly forested, with minor areas of agriculture, pine
plantations, and coal mining activities.
Kuchler (1964, 1970) suggests a small area of northern hardwoods vegetation on the
higher peaks of the Crab Orchard Mountains, but the majority of the plateau surface is
dominated by mixed oak and oak-hickory communities (Hinkle 1989). White oak is
generally the most frequent species, but scarlet oak and black oak are also common. Some
red maple dominated stands are found in poorly drained lowland sites, and shortleaf pine
and Virginia pine are associated with oak species on upper slopes, old fields, and cliff edges.
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Many mesophytic tree species found in the ravines and gorges of the Plateau Escarpment
(68c), such as sugar maple, sweet birch, cucumber tree, and white basswood, are mostly
absent from the Cumberland Plateau upland (Hinkle 1989).
The western boundary of the ecoregion is distinct in the southern and central part of
the state, with general accordance of soil, geology, and physiography. North of the Caney
Fork and Sparta, however, there is less distinction, and more outliers of the Plateau
characteristics occur on the Eastern Highland Rim. R. Paul Terrel mapped that area of the
Highland Rim as the "Cumberland Plateau Transition and Outlyers" (sic) (Fullerton et al.,
1977).
68b. Sequatchie Valley	Area within TN: 250 sq. mi.
Percent of state: 0.6%
Structurally associated with an anticline, of which the Crab Orchard Mountains are the
topographic high, erosion of broken rock to the south scooped out the linear Sequatchie
Valley. The Sequatchie River rises from springs associated with interior drainage of coves
or sinkholes (Grassy, Swaggerty, and Crab Orchard Coves) further north in 68a and 68c
(Milici 1967). The open, rolling, predominantly limestone valley floor, generally 600-1000
feet in elevation, is usually at least 1000 feet below the top of the Cumberland Plateau
(68a). Cherty clay solution residuum overlies the Knox Group limestone and dolomite, with
a low central ridge separating west and east valleys of Mississippian and Ordovician
limestone and shales. Pailo-Fullerton-Barger soils are typical of the low hills and ridges of
the valley (Paleudults and Hapludults), with Waynesboro-Etowah-Sullivan soils on the
stream terraces and floodplains (primarily Eutrochrepts). The freeze-free period is
approximately 190-210 days, with annual precipitation of 52-60 inches. The potential
natural vegetation is Appalachian oak forest and mixed mesophytic forest (Kuchler 1964),
but the valley is an agriculturally productive region, with most land in pasture, hay,
soybeans, small grain, corn, and tobacco. Southern red oak, white oak, post oak, and
hickories are common in the wooded areas. The region is sometimes considered as a part
of the Ridge and Valley (67).
68c. Plateau Escarpment	Area within TN: 1379 sq. mi.
Percent of state: 3.3%
The delineation of this ecoregion at this hierarchical level was debated by those
attending the multi-agency ecoregion meeting in Murfreesboro, but there are distinct
differences in geology, land form, soils, and vegetation from the Cumberland Plateau (68a).
TDEC Chattanooga Field Office personnel also recommended that the Plateau Escarpment
was an important region to distinguish for this framework. It is a transition area between
the plateau (68a) and the valley areas (68b, 67f) or the Eastern Highland Rim (71g),
characterized by steep slopes and high velocity, high gradient streams. Elevations are
generally between 800-2100 feet and local relief is often 1000 feet or more. General
climate characteristics are similar to the Cumberland Plateau (68a), although the cliffs,
ravines, and gorges can have a variety of micro-climates. More eroded outliers and
remnants of the Plateau Escarpment can be found on the Eastern Highland Rim (71g).
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From low to high elevation, the geology includes Mississippian-age Monteagle and
Bangor Limestone, the Hartselle Formation sandstone, shale, and limestone, the
Pennington Formation shale, siltstone, and dolomite, and the Pennsylvanian-age Gizzard
Group of shale, siltstone, sandstone, and conglomerate (Hardeman 1966). Many waterfalls
occur near the boundary of 68c and 68a where the sandstone cap is undercut by the
erosion of softer underlying rocks. Surficial geology is classified as colluvium with huge
angular, slabby blocks of sandstone. Common soil series include Bouldin, Ramsey, Gilpin,
Allen, Jefferson, and Varilla.
The rugged topography inspired Braun (1950) to designate much of this portion of the
Cumberland Plateau as the "Cliff Section." The wet and cool environments in the gorges
have provided a refugia for forest communities that are generally better known to the
north or at higher elevations in the Blue Ridge Mountains (Caplenor 1979). Twelve
vegetation community types in the Plateau ravines and gorges were identified by Hinkle
(1989), ranging from mixed oak and chestnut oak on the upper slopes, mixed mesophytic
forests on the middle and lower slopes (beech-tulip tree, sugar maple-basswood-ash-
buckeye), with hemlock along rocky streamsides and river birch along floodplain terraces.
In the gorges of Fall Creek Falls State Park, the forest communities were classified as
mixed mesophytic, hemlock, hemlock-basswood, hemlock-yellow birch, oak-hickory, and
chestnut oak (Caplenor 1965).
69. Central Appalachians	Area within TN: 896 sq. mi.
Percent of state: 2.1%
The Central Appalachians ecoregion stretches from northern Tennessee to central
Pennsylvania, consisting of high hills and low mountains, with mixed mesophytic forests,
Appalachian oak forests, and small areas of northern hardwoods forests (Omernik 1987).
The dissected, rugged terrain is composed of sandstone, shale, conglomerate and coal.
Soils developed from the interbedded rock are primarily Dystrochrepts and Hapludults.
Bituminous coal mines are common, and have caused the siltation and acidification of
streams. In Tennessee, we have defined one level IV ecoregion, the Cumberland
Mountains (69d).
69d. Cumberland Mountains	Area within TN: 896 sq. mi.
Percent of state: 2.1%
In contrast to the more plateau-like area dominated by sandstone geology to the west
and southwest in ecoregion 68, this is a highly dissected mountainous ecoregion of high
relief with more shale. From low to high elevations, the geology includes the Slatestone,
Indian Bluff, Graves Gap, Red Oak Mountain, Vowell Mountain, and Cross Mountain
Formations (Wilson and Stearns 1958; Hardeman 1966). These are some of the younger
Pennsylvanian-age shales, sandstones, siltstones, and coal. There are also sandstone-
dominated ridges, such as Pine Mountain and Cumberland Mountain in Campbell County
(associated with the Cumberland Block or Pine Mountain Thrust Plate), and Walden Ridge
in Anderson County. These are the Strike Ridges defined by Smalley (1984). The
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mountainous area to the west and southwest of the Cumberland Block is referred to as the
Wartburg Basin (Smalley 1984; Hinkle 1989). The ecoregion contains steep mountain
slopes with narrow crests, with elevations generally 1200-3000 feet. Cross Mountain west
of Lake City reaches 3534 feet in elevation. Narrow winding valleys separate the
mountain ridges, and relief can range from 1800-2000 feet. Annual precipitation is
approximately 50-55 inches and the frost-free period is 180 days.
Soils of the Cumberland Mountains are generally well-drained, loamy, acidic, with low
fertility and mesic soil temeratures (Dystrochrepts and Hapludults). The primary soil
association is Muskingum-Gilpin-Jefferson, shown on the state general soil map (Springer
and Elder 1980), or the Kimper-Shelocta-Hazleton association shown by the STATSGO
database. Other common soil series include Ramsey, Lily, and Alticrest. Most of the land
cover is deciduous and mixed forest. Large tracts of land are owned by lumber and coal
companies, and there are many areas of stripmining.
The potential natural vegetation is a mixed mesophytic forest (Kuchler 1964), although
composition and abundance would vary greatly from place to place depending on aspect,
slope position, and degree of shading from adjacent land masses. Braun (1950) thought
that the mixed mesophytic forest reached its best development in this area, and her
Cumberland Mountain section of the Mixed Mesophytic Forest region generally coincides
with Fenneman's (1938) Cumberland Mountain physiographic section. The current forests
have been altered by logging, coal mining, chestnut blight, and fire since Braun's
descriptions were made. White oak, chestnut oak, and black oak forests are common, with
northern red oak forests on north slopes. Sugar maple-yellow poplar-basswood-buckeye
forests, or some combination, occur in coves and north-facing drainages. Other important
tree species in the mixed mesophytic forest include red maple, yellow birch, black walnut,
cucumber tree, eastern hemlock, black cherry, sweetgum, and bitternut hickory.
American beech is found on middle to lower slopes, generally below 2000 feet, and
shortleaf, pitch, and Virginia pines occur on some shallow-soil ridges and exposed slopes.
71. Interior Plateau	Area within TN: 15,735 sq. mi.
Percent of state: 37.4%
The Interior Plateau is a diverse ecoregion extending from southern Indiana and Ohio
to northern Alabama. The geology is a mix of Paleozoic limestone, chert, sandstone,
siltstone and shale, distinctly different from the coastal plain sands of western Tennessee
ecoregions 65 and 74. The landforms include open hills, plains with hills, irregular plains,
and tablelands of moderate relief (Hammond 1970). Elevations are lower than the
"Appalachian" ecoregions (66, 67, 68, 69) to the east. Oak-hickory forest, with some areas
of bluestem prairie and cedar glades are Kuchler's (1964) natural vegetation type. The
ecoregion has the most diverse fish fauna in Tennessee (Etnier and Starnes 1993).
In Tennessee, we have divided the Interior Plateau into five level IV ecoregions:
Western Pennyroyal Karst (71e), Western Highland Rim (71f), Eastern Highland Rim
(71g), Outer Nashville Basin (71h), and Inner Nashville Basin (71i).
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71e. Western Pennyroyal Karst	Area within TN: 857 sq. mi.
Percent of state: 2.0%
There are many sources of evidence supporting the delineation of this ecoregion as
distinct from the Western Highland Rim (71f). In comparison to other regional
frameworks of Tennessee, our boundaries of the region are most similar to those of the
Southern Pennyroyal region defined by R. Paul Terrell in Fullerton et al., (1977). The
ecoregion is also similar to Smalley's (1980) Weakly Dissected Karst Plain region, and
extends slightly farther south than Shanks' (1958) Kentucky Prairie Barrens floristic
region. As seen on topographic maps and Hammond's (1970) land form map, it is a flatter
area of irregular plains rather than the open hills of the Western Highland Rim, with
elevations in the Tennessee portion generally ranging from 500-750 feet. Underground
drainage and small sinkholes are common in some areas.
Soils are mostly of the Pembroke, Crider, and Baxter series that formed from a thin
loess mantle over residuum of Mississippian-age St. Genevieve and St. Louis limestones.
The productive soils have made this a notable agricultural area, and most of the ecoregion
is cultivated or in pasture. Annual precipitation averages 49 inches and the freeze-free
period in the Tennessee area is about 200 days. Many areas have soils with fragipans
(Dickson, Taft, and Guthrie series) creating imperfectly drained soils, and the wetter areas
have usually been drained for agriculture. Cedar Hill Swamp in Robertson County was at
one time one of the best remaining examples of an oak swamp in the ecoregion (Ellis and
Chester 1989).
The vegetation of this part of Tennessee has been characterized as transitional between
Braun's (1950) mixed mesophytic forest region and the more xeric oak-hickory region
(Chester and Ellis 1989; Duncan and Ellis 1969). From a national scale, oak-hickory
dominates the potential natural forest matrix, but the region was once also characterized
by mosaics of bluestem prairie (Kuchler 1970). The barrens of Kentucky that extended
south into Stewart, Montgomery, and Robertson counties, were once some of the largest
natural grasslands in Tennessee (Chester and Ellis 1989). These prairies were earlier
considered floristically similar to the prairies of the Middle West (Transeau 1935; Shanks
1958), but there is abundant evidence to suggest that the barrens are not an outlier of the
Midwestern tallgrass prairie (Baskin et al., 1994). Barrens flora included big bluestem,
little bluestem, Indian grass, switch grass, and herbs and forbs such as blue sage,
milkweed, and white prairie clover (Baskin et al., 1994; Chester 1993). Where not cleared
for agriculture, forests on the broad uplands and slopes contain various combinations white
oak, black oak, southern red oak, scarlet oak, eastern red cedar, hickories, red maple,
northern red oak, and elms depending on slope aspect (Smalley 1980). Present-day forests
on upland flats and depressions of the Pennyroyal plain are dominated by blackgum,
sweetgum, red maple, slippery elm, black oak, willow oak, and pignut hickory (Chester et
al., 1995). Similar species can be found in the lower terraces and streambottoms (Smalley
1980).
The eastern boundary of the region is not distinct, although there is a definite change in
the land cover mosaic east of Portland in Sumner County, with more patches of forest.
Our boundary between this ecoregion and the Eastern Highland Rim (71g) did not follow
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exactly a soil association line, but generally placed it where the Baxter-Mountview-
Pembroke (Dickson) soils of the Western Pennyroyal Karst met the Sugar grove-Sulphura-
Dickson soils (STATSGO #55) and the more forested patches of the Eastern Highland Rim.
Our placement was also influenced by information on Kentucky soils, physiography, and
geology (Bailey and Winsor 1964; Agricultural and Industrial Development Board of
Kentucky 1953; USDA-SCS 1975; Noger 1988). This break is also near the USFS division
between the Eastern and Western Higland Rim (Smalley 1983; 1980; Keys et al., 1995).
The southern boundary of the ecoregion differs from the USFS Penneroyal (sic) Karst
Plain subsection 222Eh that extends further south (Keys et al., 1995). Their boundary
follows the cherty clay solution residuum (rcc) Quaternary geology class (Gray et al., 1991;
Miller et al., 1988), and the hilly and rolling (D2) vs. hilly and steep (Dl) areas from the
state soil map (Springer and Elder 1980). We believe the boundary is more distinct further
north, and thus avoid lumping flat, karst, "barrens" and agricultural terrain of 71e, with
hilly, forested, well dissected terrain that is more typical of 71f.
71f. Western Highland Rim	Area within TN: 5871 sq. mi.
Percent of state: 13.9%
This ecoregion is part of a broad, tilted plateau, with landforms characterized as open
hills with 50-75% of the gentle slope in the lowlands (Hammond 1970). Elevations are 400-
1000 feet, with local relief 300-500 feet. The geologic base is limestone, chert, and shale of
Mississippian age. Surficial geology is chert-fragment solution residuum; cherty silty clay,
locally phosphatic, solution residuum; and cherty clay solution residuum. In the western
portion of the region near the Tennessee River, older Silurian-age limestone and shale is
exposed, and barrens occur here on shallow, clayey soils (Milo Pyne, The Nature
Conservancy, personal communication). Soils of the Western Highland Rim tend to be
cherty, acid, and low in fertility, mostly Paleudults and Fragiudults. Common soils series
include Mountview, Dickson, Baxter, Brandon, Bodine, Hawthorne, Sulphura, Lax, and
Saffell. Streams of the Western Highland Rim are characterized by coarse chert gravel
and sand substrates with areas of bedrock, moderate gradients, and relatively clear water
(Etnier and Starnes 1993). The freeze-free period in the Tennessee portion of the region is
185-205 days, and annual precipitation is approximately 50-56 inches.
The oak-hickory natural vegetation was mostly deforested in the mid to late 1800's, in
conjunction with the iron-ore related mining and smelting of the mineral limonite, but now
the region is again heavily forested. Drier ridges and slopes are dominated by scarlet oak,
chestnut oak, black oak, and post oak, with abundant white oak on the broader uplands.
The more moist north slopes have beech-maple or beech-tulip poplar-white oak
communites (Duncan and Ellis 1969; Chester et al., 1995). Ravines and streambanks may
contain red elm, silver maple, red maple, boxelder, sweetgum, black willow, and sycamore.
In addition to the limestone barrens near the Tennessee River, barrens are also found on
some upland loess soils of the Western Highland Rim, and these can have different
vasuclar taxa from the limestone barrens (DeSelm 1988).
Some agriculture occurs on the flatter interfluves and in the stream and river valleys:
mostly hay, pasture, and cattle, with some cultivation of corn and tobacco. The flatter area
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around Lawrenceburg contains more extensive cropland and pasture, and some
geographers suggest this district resembles the southern part of the Eastern Highland Rim
(R.Paul Terrel in Fullerton et al., 1977). There is some merit to the idea of a Southern
Highland Rim to cover these areas of less relief and more agriculture, especially as it
extends south into Alabama. As Smalley (1980) noted, in Alabama it is an "arbitrary
division between the Eastern and Western Highland Rims."
71g. Eastern Highland Rim	Area within TN: 2923 sq. mi.
Percent of state: 6.9%
In many places, the Eastern Highland Rim of Tennessee has more level terrain than the
Western Highland Rim (7If), with landforms generally characterized as tablelands of
moderate relief, irregular plains, and some open high hills (Hammond 1970). Elevations
are 800-1300 feet with local relief 100-500 feet, therefore lower and flatter than ecoregion
68 to the east. In Kentucky, the ecoregion is often called the Eastern Pennyroyal. The
boundary between the Eastern Highland Rim and the Western Pennyroyal Karst
ecoregion (71e) was discussed in the section on 71e. The western boundary of the
ecoregion in Tennessee, where it meets the Outer Nashville Basin (71h), tends to remain
on the rim or plateau area, putting the dissected escarpment within the Nashville Basin.
In northern Tennessee, the ecoregion includes more strongly dissected areas near the
Cumberland River and Dale Hollow Lake. There is a hilly, knobby transition to the
Nashville Basin around the Cumberland River area (Smalley 1983; Fullerton et al., 1977),
and the division between 71g and 71h in this area is not easily made.
Geologic materials in the region consist of Mississippian-age limestone, chert, shale, and
dolomite. The surficial geology is mostly cherty clay or chert-fragment solution residuum.
Soils are mostly Paleudults and Fragiudults, with common soil series on the smoother
areas including Dickson, Mountview, Baxter, Waynesboro and Decatur. The ecoregion
contains some hilly outliers from the Cumberland Plateau, and there is also karst terrain
sinkholes and depressions, especially noticeable between Sparta and McMinnville in
Warren and White Counties. Numerous springs and spring-associated fish fauna are also
found in the region (Etnier and Starnes 1993).
Kuchler's (1964) natural vegetation for the region is primarily oak-hickory forest, but
the region is transitional between the oak-hickory type to the west and the mixed
mesophytic forests of the Cumberland Plateau and Cumberland Mountains to the east.
McKinney (1989) summarized the forest communities of the Eastern Highland Rim as
xeric and sub-xeric oak-hickory forests; mesic upland forests of sugar maple, beech, tulip
poplar and white oak; mixed mesophytic forests of sugar maple, beech, tulip poplar, white
oak, black walnut, yellow buckeye, and white basswood; swamp forests of overcup oak,
sweetgum, willow oak, river birch, and red maple; bottomland forests of silver maple, box
elder, red maple, sycamore, and slippery elm; and rare hemlock forests that have a mixed
mesophytic or a mixed oak component. Shanks (1958) showed a strong representation of
bottomland hardwoods in Lincoln and Coffee counties, reflecting a floristic peninsula
extending northward into his barrens region of the southeastern Highland Rim, and
known for its plants of coastal plain affinities. Extensive areas of the original bottomland
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forest in the ecoregion have been inundated by the large impoundments. The barrens
areas formed over chert rock and soils that often limited tree life but supported grasses
such as switchgrass, Indiangrass, and little bluestem. These former prairie areas are now
mostly oak thickets or pasture and cropland. Cropland, pasture, and an extensive
ornamental nursery industry occupy much of the more level land throughout the
ecoregion. In Tennessee, the freeze-free period for the ecoregion is 190-210 days, and
annual precipitation is 52-56 inches.
71h. Outer Nashville Basin	Area within TN: 4414 sq. mi.
Percent of state: 10.5%
This is a more heterogeneous ecoregion than the Inner Nashville Basin (71i), with more
rolling and hilly topography. As DeSelm (1959) wrote, "It is into this region that remnants
of the dissected rim extend...". Some regional frameworks of Tennessee separate the
Outer Nashville Basin from the strongly dissected escarpment, but these hills and knobs
are usually labeled as transition areas (Smalley 1980,1983; Fullerton 1977). Our Outer
Nashville Basin ecoregion encompasses more of the topographic basin and attempts to
include most all of the areas of Ordovician limestone bedrock. It thus includes some of the
Mississippian-age Fort Payne Formation (characteristic of the Highland Rim) among the
higher hills and knobs. This formation, however, is characteristic of this ecoregion as well,
occurring throughout the Outer Nashville Basin on the higher hills. From a stream
ecosystem perspective, this more encompassing regional delineation includes most of those
systems that have substrates on the Ordovician geology.
The limestone geology is generally non-cherty, except on hills in the south, and the
rocks and soils are high in phosphorus. The Quaternary geology consists of phosphatic
sandy solution residuum and cherty silty clay, locally phosphatic, solution residuum. In
places such as the Columbia/Mt. Pleasant area, the limestone yields commercial phosphate.
On the west side of the ecoregion, the boundary tends to follow the line dividing the
Dellrose-Mimosa-Bodine soil association (STATSGO #66) and the Bodine-Sulfura-Dellrose
association (STATSGO #54) of the Western Highland Rim (7If). On the east side,
however, the ecoregion boundary keeps to the top of the plateau or rim, and some of the
Bodine-Sulfura-Dellrose soils of the escarpment are included within the Outer Nashville
Basin. In the south, the boundary follows the Ordovician-age limestone into Limestone
County, Alabama in the area around the lower Elk River to Wheeler Lake. In addition to
Dellrose, Mimosa, and Bodine, other soils series common to the outer basin include
Stiversville, Hampshire, Armour, Maury, Barfield, Hawthorne and Sulphura.
Elevations are generally 500-1200 feet, although the unique Short Mountain is over
2000 feet. The freeze-free period is 190-210 days, and annual precipitation is 48-54 inches.
Deciduous forest with pasture and cropland are the dominant land covers. Oak-hickory is
the dominant forest type, but some transitional mixed mesophytic also occurs. White oak,
southern red oak, northern red oak, black oak, scarlet oak, shagbark hickory and pignut
hickory are common. On more northerly and mesic slopes, oaks and hickories with yellow
poplar, elms, red maple, American beech, sugar maple, black walnut, white ash, or black
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cherry can be found. Poorly drained terraces and stream bottoms contain willow oak,
sweetgum, red maple, blackgum, green ash, and American sycamore.
Streams are low to moderate gradient, with productive, nutrient-rich waters, resulting
in algae, rooted vegetation, and occasionally high densities offish. The Nashville Basin as
a whole has a distinctive fish fauna, notable for fish that avoid the region, as well as those
that are present (Etnier and Starnes 1993).
71i. Inner Nashville Basin	Area within TN: 1670 sq. mi.
Percent of state: 4.0%
This ecoregion is generally less hilly and lower in elevation than the Outer Nashville
Basin (71h). Outcrops of limestone are common, and soils are generally shallow (a few
inches deep in the once large tracts of cedar glades) and are redder and lower in
phosphorus than those in the outer basin (Springer and Elder 1980). Talbott, Bradyville,
and Mimosa (Hapludalfs) are typical soil series, along with Gladeville (Rendolls) and
Barfield (Hapludolls) soils. Elevations are mostly 500-900 feet, with some higher hills. The
geology consists of the Ordovician-age Ridley, Lebanon, and Carters limestone formations
(Hardeman et al., 1966), with a surficial layer of thin clayey solution residuum (Gray et al.,
1991; Miller et al., 1988). Streams are lower gradient than surrounding regions, often
flowing over large expanses of limestone bedrock.
The major plant communities of the Inner Nashville Basin include cedar glades, cedar
thickets, cedar-hardwood forests, and deciduous forests. This unique mixed
grassland/forest cedar glades vegetation type is apparent at a national scale (Kuchler 1964;
1970), and has been described by Harper (1926), Freeman (1933), and Quarterman
(1950a,b; 1989) among others. Cedar glades have Eastern red-cedar associated with the
ecological complex, but are defined as the open areas of rock, gravel, or shallow soil that
remain bare or are occupied by low-growing herbaceous plant communities (Quarterman
1989). Glades have been distinguished from the more prairie-like barrens as having less
than 50% cover of perennial grasses (Quarterman 1989). Glades in the Southeast are
customarily identified by their substrate (Quarterman et al., 1993), and the limestone
glades of Tennessee, with their many endemic species, are primarily located on the
Lebanon and Ridley limestones of the Inner Nashville Basin. The most characteristic
hardwoods within the Inner Nashville Basin are a maple-oak-hickory-ash association
(McKinney and Hemmerly 1984).
The more xeric, open characteristics and shallow soils of the cedar glades affect the
distribution of amphibians and reptiles (Jordan et al., 1968). Species associated with the
deciduous forests of middle Tennessee, such as aquatic turtles, salamanders, and certain
snakes, are mostly absent from cedar glade habitats. Zigzag salamanders are common in
the cedar glades because the larval stages and hatchlings are terrestrial. Lizards such as
the northern fence lizard, the six-lined racerunner, the five-lined skink and the
southeastern five-lined skink, are generally more abundant than in surrounding habitats,
and are prey for cedar glade snakes such as the midwest worm snake, black king snake,
eastern milk snake, and southeastern crowned snake (Jordan et al., 1968).
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Urban, suburban, and industrial land use in the Inner Nashville Basin has increased
rapidly in recent years. Due to the generally shallow soils, productive cropland is generally
in small tracts on terraces or narrow bottoms. Pasture and hay are common, with small
areas of row crops. The freeze-free period is 190-210 days, and annual precipitation ranges
from 48 to 53 inches. Similar to most of Tennessee, the precipitation is well-distributed
throughout the year, although slightly higher amounts fall December through March.
73. Mississippi Alluvial Plain	Area within TN: 854 sq. mi.
Percent of state: 2.0%
This riverine ecoregion extends from southern Illinois, at the confluence of the Ohio
and Mississippi Rivers, south to the Gulf of Mexico. It is mostly a flat, broad floodplain with
river terraces and levees providing the main elements of relief. Regionally, the soils tend
to be poorly drained, although locally some sandy soils are well-drained. Winters are mild
and summers are hot, with temperatures and precipitation increasing from north to south.
Bottomland deciduous forest vegetation covered the region before clearance for
cultivation. The Tennessee portion of this ecoregion is within one level IV ecoregion, the
Northern Mississippi Alluvial Plain (73a).
73a. Northern Mississippi Alluvial Plain	Area within TN: 854 sq. mi.
Percent of state: 2.0%
Within the state, this is a relatively homogenous region of Quaternary alluvial deposits
of sand, silt, clay, and gravel. It is bounded distinctly on the east by the Jackson Formation
bluffs of Tertiary age, and on the west by the Mississippi River. Average elevations are
around 250 feet, ranging from near 300 feet in the north near Reelfoot Lake to 215 feet
near Memphis in the south. The two main distinctions in the Tennessee portion of the
ecoregion are between areas of loamy, silty, and sandy soils with better drainage, and
areas of more clayey soils of poor drainage that may contain wooded swamp land and
oxbow lakes. Robinsonville (Udifluvents) and Commerce (Fluvaquents) are well-drained to
somewhat poorly drained Entisols of the region, Sharkey and Tunica soils are poorly-
drained Haplaquepts, and Reelfoot (Argiudolls) and Bowdre (Hapludolls) soils are
somewhat poorly-drained Mollisols. Annual precipitation is 48-50 inches, with a freeze-free
period around 220-230 days.
Most of the region is in cropland, with some areas of deciduous forest. Soybeans,
cotton, corn, sorghum, and vegetables are the main crops. The potential natural
vegetation (Kuchler 1964) consists of Southern floodplain forest (oak-tupelo-baldcypress).
The oaks are mostly southern red oak, overcup oak, swamp chestnut oak, Nuttall oak,
water oak, and black oak. In addition to tupelo and bald cypress, other common trees
include red maple, sugarberry, pecan, elm, eastern cottonwood, and sweetgum. The
bottomland hardwood communities around Reelfoot Lake include a bald cypress
community with black willow; a swamp red maple-green ash-black willow community; a
sugarberry-soft maple-green ash community; a water oak-sweetgum-bitternut hickory
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community; and an upland forest community containing tulip poplar, black walnut, black
cherry, and sassafras (Guthrie 1989).
Reelfoot Lake, in Lake and Obion counties, was created by a series of strong
earthquakes in 1811 and 1812 and provides important habitat for fish, birds, and other
wildlife. Although the size of the lake has been reduced greatly due to soil erosion from
surrounding land, more than 56 species of fish inhabit its waters, the richest assemblage of
swamp-dwelling fishes in Tennessee (Etnier and Starnes 1993). Waterfowl, raptors, and
migratory songbirds are also often seen in the region. Open Lake in Lauderdale County is
another tectonic lake in this ecoregion (Rick Livingston, NRCS, personal communication).
74. Mississippi Valley Loess Plains	Area within TN: 4509 sq. mi.
Percent of state: 10.7%
This ecoregion stretches from near the Ohio River in western Kentucky to Louisiana.
It consists primarily of irregular plains, with oak-hickory and oak-hickory-pine natural
vegetation. Thick loess tends to be the distinguishing characteristic. With flatter
topography than the Southeastern Plains ecoregion (65) to the east, streams tend to have
less gradient and more silty substrates. Agriculture is the dominant land use in the
Tennessee portion of the ecoregion.
We have divided the ecoregion into two level IV ecoregions: the Bluff Hills (74a) and the
Loess Plains (74b). The possibility of including a third region, Alluvial Floodplains, was
debated by the authors and collaborators at several of the ecoregion meetings in
Tennessee, but the consensus was not to delineate these river bottoms at this hierarchical
level.
74a. Bluff Hills	Area within TN: 486 sq. mi.
Percent of state: 1.1%
Along the western edge of the ecoregion, bordering the Mississippi Alluvial Plain, are
deep loess hilly areas, often called bluff hills (Cross et al., 1974). In Tennessee, the steep
parts of these bluffs nearest the river occur on geology that Hardeman (1966) calls the
Jackson Formation. Mississippi River boatmen called the high bluffs that edged the river
at four points in Tennessee the Chickasaw Bluffs (Safford 1856). Consisting of sand, clay,
silt, and lignite (Hardeman 1966), the bluffs are capped by loess greater than 60 feet deep
(Miller et al., 1988; Gray et al., 1991). The disjunct ecoregion in Tennessee encompasses
those thick loess areas that are generally the steepest, most dissected, and forested.
The soils of the region are generally deep, steep, silty, and erosive. Upland soils, mostly
Hapludalfs, Fragiudalfs, or Eutrochrepts, include the Memphis, Loring, and Natchez series.
Adler soils (Udifluvents) are common in the floodplains. Gravels are sometimes exposed at
the base of the bluffs. Several locations have deep excavations through the loess cap to
quarry sand and gravel. The landcover of the ecoregion is primarily forest and pasture,
with small fields of crops on the more level rolling hilltops or in the narrow valley bottoms.
Annual precipitation averages 50 to 52 inches, with a frost-free period of 200-230 days.
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As the ecoregion extends south through Mississippi, oak-hickory forests characterize
this hilly portion of the ecoregion, rather than the oak-pine mix on the plains to the east
(USDA, Forest Service 1969; Kuchler 1970; U.S. Forest Service 1970). A mosaic of
microenvironments is found in the carved loess due to variations in slope aspect and
different exposures to sun, moisture, and wind. On the ridges and dry slopes of the Third
Chickasaw Bluff in Shelby County, sweetgum, white oak, tulip poplar, sugar maple,
hophornbeam, and black oak were dominant (Miller and Neiswender 1989). The moist
slopes were dominated by American beech, sweetgum, tulip poplar, sugar maple, and
northern red oak. Streambeds, ravines, and bottomland forests contained sycamore,
eastern cottonwood, American beech, sweetgum, tulip poplar, sugarberry, northern red
oak, green ash, and hackberry. Small cypress swamps had, in addition to the cypress,
minor components of sugarberry, boxelder, green ash, and water hickory. Vegetation on
some of these Chickasaw bluffs in Tennessee appear to be more similar to forests of the
cove hardwoods communities of the Blue Ridge and Cumberland Plateau areas than to
other forests of the Mississippi Embayment (Miller and Nieswender 1989). Shanks (1958)
defined a relatively narrow Mississippi River Bluffs subregion that is rich in mesophytes,
noting that some woody species had Appalachian and Central Basin affinities. The
abundance of mesophytes such as beech and sugar maple in the Bluff Hills forests may
rest as importantly on lack of human disturbance of the stand being studied as on
particularly mesic habitat conditions (Mark Cowell, Indiana State University, personal
communication).
Smaller streams of the Bluff Hills have localized reaches of increased gradient and small
areas of gravel substrate that create aquatic habitats that are distinct from those of
ecoregion 74 as a whole. Unique, isolated fish assemblages more typical of upland habitats
can be found in these stream reaches (Etnier and Starnes 1993).
74b. Loess Plains	Area within TN: 4023 sq. mi.
Percent of state: 9.6%
The Loess Plains ecoregion within Tennessee consists of gently rolling, irregular plains,
250-500 feet in elevation, with 100-200 feet of local relief. The loess can be over 50 feet
thick, and soils are primarily Fragiudalfs and Hapludalfs, with Fluvaquents and Udifluvents
in the bottoms. Common soil series are Grenada, Loring, Memphis, Collins, Waverly,
Falaya, and Routon. Oak-hickory and southern flooplain forests are Kuchler's (1964)
potential natural vegetation types. Habitats in the Haywood County portion of 74b were
classified as upland forest, bottomland forest, cypress-gum swamp, beaver marsh, old field,
wet field, and disturbed (Lewis and Browne 1991). Most of the forest cover has been
removed for cropland. The remaining upland forest is characterized by canopy species
such as white oak, southern red oak, blackjack oak, black oak, post oak, mockernut
hickory, and pignut hickory (Lewis and Browne 1991; Heineke 1989). The ecoregion in
Tennessee is a productive agricultural area of soybeans, cotton, corn, milo, and sorghum
crops, along with livestock and, historically, some poultry. The freeze-free period is 200-
230 days north to south, and annual precipitation is 50-52 inches.
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Several large river systems and their tributaries, the Obion, Forked Deer, Hatchie,
Loosahatchie, and Wolf, cross the ecoregion with wide flood plains that are distinct from
the adjacent uplands. The Hatchie River mainstem is one of the least disturbed and
supports populations of deer, wild turkeys, beavers, otters, waterfowl, and migratory birds.
The bottomland forests contain overcup oak, water oak, willow oak, swamp chestnut oak,
water hickory, silver maple, sweetgum, sycamore, river birch, green ash, tupelo, and
cypress. Streams of the ecoregion are low-gradient and murky, with silt and sand bottoms.
Many of the streams have been deforested and channelized, and much of the once-
abundant forested wetland habitat has been lost. Valley plugs or channel blockages, where
channel aggradation and driftwood accumulation combine to change flow patterns, are
common along the low-gradient alluvial streams in this region (Diehl 1994).
STREAM REFERENCE SITE SELECTION
To develop biological criteria and evaluate impaired water bodies, it is important to
establish reference conditions that are suitable for comparison. A key function of an
ecoregion framework is its use in selecting regional reference sites and facilitating the
assessment of regionally attainable conditions. Ideally, control sites for estimating
attainable conditions should be as minimally disturbed as possible yet representative of the
streams for which they are to be controls (Hughes et al., 1986). Although no two streams
are alike, we hypothesize that streams within an ecoregion will have generally similar
characteristics as compared to all streams within a state, major basin, or larger area. If an
ecoregion has a variety of stream types, it might also be important to classify these types
and to consider groundwater influences, as these may tend to mask regional differences.
Additional classifications or hierarchical levels may be needed to sort out differing stream
segments and habitat types.
General guidelines for selecting reference sites have been given in Hughes et al., (1986)
Gallant et al., (1989), and by Hughes (1995). The process continues to be refined, however,
as experience is gained in current and ongoing ecoregion/reference site projects. For any
given project it may be necessary to modify or expand general procedures; due to varying
characteristics or objectives in different areas, it is difficult to follow strictly a detailed rule-
based approach that will be applicable to all regions. Our process of selecting candidate
reference sites in Tennessee is outlined below:
1).	We defined level III and level IV ecoregions within which there is apparent
homogeneity in a combination of geographic characteristics that are likely to be associated
with resource quality, quantity, and types of stresses and biological responses.
2).	We characterized disturbance generally (such as areal or nonpoint source pollution,
and local or point sources of pollution) in each ecoregion and analyzed geographic
characteristics to better understand representative or typical conditions. What comprises
disturbance may vary considerably from one region to another. In regions with nutrient-
rich soils, poor drainage, but great agricultural potential, all streams may have been
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channelized at one time or another, and all watersheds may have a high percentage of
agricultural land use. Reference streams in such a region comprise those with few if any
point sources, lack of recent channelization activity, and riparian zones with a relatively
large percentage of woody vegetation. Regions with nutrient-poor soils, lacking
agricultural potential, and containing a different set of identifying landscape characteristics
such as steep forested mountains and cool, clear, high-gradient streams, are likely to be
affected by different types of stressors. Relative lack of silvicultural activities, mining, or
heavy recreational usage may be important criteria in selecting minimally-impacted,
representative reference streams in these regions.
3). We chose a set of stream sites that appeared relatively undisturbed and completely
within the ecoregion, and approximated the area of the surface watersheds. The list of
candidate reference sites was compiled from suggestions made by personnel from the
TDEC Division of Water Pollution Control, USFS, Tennessee Valley Authority, and
Tennessee Department of Health, from previous surveys of "pristine" streams (Etnier et
al., 1983), as well as from examination of maps to find streams that appeared to be
relatively undisturbed yet representative of the ecoregion. The actual number of
sites/watersheds selected was a function of the apparent homogeneity or heterogeneity of
the region, the size of the region, hydrologic characteristics, and simply how many stream
sites/watersheds were available for selection. The point of diminishing returns, regarding
the number of streams necessary to address regional attainable quality and within-region
variability, may be reached with only a few sites in ecoregions that are relatively
homogeneous and/or small. Complex regions, on the other hand, are likely to require a
large number of sites. Another consideration was access, that is, did roads or trails allow
the biologists to get near the stream section for sampling? Although sampling locations
should be as far from bridges as possible, access across private property or other cultural
and natural hazards can reduce the number of candidate sites for consideration as final
reference sites to be sampled.
Disturbance and typicalness were interpreted from information shown on 1:250,000-
scale and 1:100,000-scale USGS topographic maps, land use and land cover maps, county
soil surveys, and local expert judgement. The existence of populated areas, industry,
agricultural land use, forestry, mining, fish hatcheries, transportation routes, etc., were
interpreted from mapped information and other sources. The 1993 Tennessee Water
Quality Assessment 305(b) report (Denton et al., 1994) was also consulted for each
potential site to assess water chemistry/quality, and point- or non-point source pollution
impacts. The number of preliminary candidate sites per ecoregion varied, ranging from
none in some of the smallest ecoregions (65a,b), to more than twenty sites in ecoregions
68a and 71f. We developed a list of the candidate sites that included the ecoregion, site
number, stream name and location, estimated watershed area, major basin, county,
1:100,000-scale and 1:250,000-scale map names, TDEC Field Office, and additional
comments. This was given to the state biologists along with maps of the site locations.
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4).	Each set of sites was reviewed by state biologists, and sites were visited during ground
reconnaissance to evaluate the usefulness of the ecoregions, the characteristics that
comprise reference sites in each ecoregion, the range of characteristics and types of
disturbances in each region, and the way in which site characteristics and stream types
vary between regions. In this process, sites found to be unsuitable were dropped (because
of disturbances not apparent on the maps or due to anomalous situations) and other sites
were added. TDEC biologists assessed nearly 300 streams statewide in the initial screening
of candidate reference sites (Linda Cartwright, TDEC-DWPC, personal communication).
5)	Some aerial reconnaissance was conducted to identify disturbances not observable from
the ground, to get a better sense for the spatial patterns of disturbances and geographic
characteristics in each region, and to photograph typical characteristics, site locations, or
disturbances for use in briefings and publications.
It should be remembered that all reference sites have some level of disturbance. There
are no pristine, unimpacted watersheds in Tennessee, or, considering atmospheric
deposition of contaminants, anywhere else in the U.S. We searched for the least or
minimally impacted sites, but levels of impact are relative on a regional basis. The
characteristics of appropriate reference sites will be different in different ecoregions and
for different waterbody and habitat types. It is desirable, therefore, to have a large
number of candidate reference sites for each region to help define the different types of
streams, to illustrate the natural variability within similar stream types, and to clarify the
factors that characterize the best sites from factors present in the lower quality sites.
A set of current reference stream sites should be just one part in determining reference
stream condition. Other aids such as historical data, laboratory data, quantitative models,
and best professional judgement can also be helpful (Hughes 1995).
CONCLUSIONS AND RECOMMENDATIONS
This general ecoregion framework developed for Tennessee appears to be a useful
framework for environmental resource assessment and management. It is a formalization
of some commonly recognized regions in Tennessee and has similarities to other
frameworks of the area. The interest in such a multi-purpose regional framework should
be in its potential usefulness, rather than the absolute truth of boundary line placement on
the ground, or the correspondence of any one ecological component. Modifications of the
framework might be warranted, however, as more information and understanding is
gained. Our intent was to make the ecoregion framework compatible and consistent with
the EPA ecoregion framework in surrounding states. This consistency allows biologists,
ecologists, and resource managers to share and compare environmental data across
political boundaries. We encourage TDEC and other Tennessee agencies and organizations
to consider the analysis of compatible data from these neighboring states that share
ecological regions to help clarify regional conditions and characteristics.
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The hypothesis that a regional framework and sets of regional reference sites can give
managers and scientists a better understanding of the spatial variations in the chemical,
physical, and biological components of water bodies in Tennessee is intuitive but must be
tested. We believe that these tools can help build a foundation for assessing attainable
conditions. A preliminary assessment of stream chemistry values from the sampled
reference sites in Tennessee does indicate some distinct regional differences. Significant
time and effort will be required for the collection and creative analysis of data to develop
biological criteria and regional water quality standards, and to more fully understand
attainable water conditions. The process of selecting regional reference sites requires
considerable time, conscientious map analysis, and thorough.field reconnaissance. Enough
reference^sites must be selected to account for the natural variability within the
ecoregions. If the selected reference sites show a high range of variability, additional
stratification may be necessary. Developing or modifying multimetric indices for fish,
macroinvertebrate, and habitat evaluations at reference sites also requires significant time
and experimentation. Part of the challenge will be to analyze and integrate environmental
data in meaningful ways, with the desirable longer-term goal of developing potential
indexes of ecological integrity to assess more holistically the health of Tennessee's
ecosystems.
The goal of TDEC's Division of Water Pollution Control is to reclaim polluted waters, to
prevent future pollution, and to plan for the future use of the waters of the state (Denton
et al. 1994). The ecoregion framework is one tool to help implement the requirements of
the Tennessee Water Quality Control Act and develop water quality criteria that will
protect designated uses of water bodies. It is a tool that allows for the recognition of
natural differences in different areas of the state, and, together with the reference sites,
clarifies the regional definition of high quality waters. Avenues for maintaining or even
improving the quality of identified reference streams should be explored, since these are
some of the best quality streams remaining. The Antidegradation Statement in
Tennessee's water quality standards appears to offer one way of protecting these high
quality waters.
Water cannot be viewed in isolation from its watershed and that is why holistic
perspectives are important. Although watersheds are useful study units for understanding
the quantity and quality of water at any given point on a stream, it must be recognized that
the spatial distribution of factors that affect water quantity and quality (such as vegetation,
land cover, soils, geology, etc.), does not coincide with topographic watershed boundaries
(Omernik and Griffith 1991). Because there are an infinite number of points on a stream
from which watersheds can be defined, watershed management or ecosystem
management requires a spatial framework that considers the regional tolerances and
capacities of landscapes. That is why the ecoregion framework can complement TDEC's
watershed management approach. When ecoregions and watersheds are used together
correctly, they provide a powerful mechanism for developing resource management
strategies.
While the ecoregion framework may be useful for developing regionalized chemical and
biological criteria for streams, other uses of such a framework in different parts of the
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country have included: lake classification and development of eutrophication criteria;
development of nonpoint-source pollution management goals; reporting on the status or
attainment of water quality; assisting programs addressing wetland classification and
management; analyzing types and distributions of protected areas or ecological reserves;
and developing regional indicators of forest disturbance and biodiversity. Scott et al.,
(1993) suggested that identifying management areas for biological diversity requires an
analysis of the distribution of biodiversity from the perspective of ecoregions rather than
political units.
Improving the quality of aquatic and terrestrial ecosystems in Tennessee will require
the cooperation and coordination of federal, state, and local interests. It is our hope that a
consistent hierarchical ecoregion framework will help improve communication and
assessment within and among different agencies. Although pollution of water bodies,
fragmentation or loss of habitat, and alteration of landscapes have many causes, regional
assessment tools can be valuable to both resource managers and researchers for
stratifying natural variability and addressing the nature of these issues.
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44

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Appendixl
Summary Table of Ecoregion Characteristics
45

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Appendix 1.
Summary Table of Ecoregion Characteristics
		
| Level IV Ecoregion
Physiography

Geology
Soil
Climate
Potential Natural
Vegetation
Land Use and Land Cover |

Area
(Mim
mBa)

Ehntitn
/
Local Rdkf
fifc«0
Sarfldal and bedrock
Ordtr (Great Gmps)
Com mo a Sofl Series
Tempera! in /
Mabtora Reghats
Prdpltitlw
m»«i maaJ
(tubes)
FratFMt
(diyi)
Mesa
Ttmpsstar*
JuJf nrfoteo. (7)


63>.
Bbckland Prairis
SO
Ttr^pntiw pi*m« unH undulating
Lowland; low gradient streams with
clay, gmrf wrvH rill SUbStTBtES
500-600
/
50-100
Quaternary dark gray clay or day
loam over Cretaceous-age chalk,
marl, and calcareous day
Ultisols (Hapludalts);
Alfi
-------
67 RIDGE AND VALLEY









Level IV Ecoregion
Physiography

Geology
Soil
Climate
Potential Natural
Vegetation
Land Use and Land Cover

Area
(•quire
miles)

Elevation
/
Local Relic!
(Tea}
SarOciaJ and bedrock
Order (Great Grcopi)
Common SoD Series
Temperature /
MobUre Regime)
PredpiUUon
Metu ¦•m"1
(isfbet)
Krtfl Free
Me«a
(d*y»)
Mean
Tempcntnre
January in infamy
Jul>' min.4nax (F)


67f.
Southern
Limestone /
Dolomite Valleys
and Low Rolling
Hill*
5324
Undulating to rolling valleys with
rounded hilts, some steep ridges in
the north; caves and springs;
moderate to low gradient streams
with bedrock, cobble, gravel, and
sandy substrain
700-2000
/
100-700
Quaternary cbeny clay solution
residuum; Ordovician dolomite and
limestone, cherty in places
Uliisols (Paleudults)
Fullerton, Dewey, Decatur,
Bodine, Waynesboro
Thermic / Udic
40-54
190-220
24-25/43-47
64-6S/85-S9
Appalachian oak fcrest
(mixed oaks, hickory, pine,
poplar, birch, maple);
bottomland oak and
mesophytic forests; cedar
barrens
Cropland and pasture, mixed
forest, some pine plantations,
run! residential, tntan and
industrial
67g
Southern Shale
Valleys
1433
Undulating ic rolling valleys,
some low, rounded h ilia and knobj;
moderate to low gradient streams
with bedrock, cobble, growl, and
sandv substrates
800-1500
/
100-400
Quaternary sandy shaly
decomposition residuum;
Ordovician and Cambrian shale,
limestone, siltsionc
Incepusols (Hutrochrepts,
Dystrochrepts); Ultisols
(Haptudulta); Alfisols
(Hapludalfs)
Dandridge, Bays, Needmorc,
Moctevallo, Townley
Thennic, mesic
/Udic
40-54
190-220
25-2S/45-47
64-65/87-89
Appalachian oak forest
(mixed oaks, hickory, pine,
poplar, birch, maple)
Pasture with small fields of
hay, com, tobacco; small
farms and rural residential;
minor patches of mixed
forest, some nine olantaiions
67h.
Southern
Sandstone Ridges
326
Tall, steep ridges, some narrow
intervening valleys; high to
moderate gradient streams with
mostly rock)* substrates
900-3000
/
800-1200
Quaternary quartzite-block loamy
colluvium; Ordovician, Silurian,
Devonian and Mi&sissippian
sandstone, shale, siltsionc,
conglomerate
Inccpiisols (D>-suochrepts);
Ultisols (Hapludults)
Wallen, JcfTcrson, Gilpin
Mesic/Udic
44-54
1S0-200
22-26/41-45
62-66/83-87
Appalachian oak forest
(mixed oaks, hickory, pine,
poplar, birch, maple); some
mixed mesophytic forest
(beech, tulip poplar, oaks,
buckeve. basswood")
Deciduous and some mixed
forest; minor pasture and
cropland ic narrow valley
bottoms
671-
Southern
Dissected Ridges
and Knobs
5S5
Ridges, hills, and knobs, lower and
mare dissected than 67h; small,
moderate to high gradient streams
with rock, cobble, and gravel
substrates
800-2000
i
300-600
Quaternary sandy shaly
decomposition residuum; Cambrian
and Ordovician shale, siltsionc,
sandstone, quart2ose limestone
Incepusols (Dystrochrepts,
Eutrochrepts); Ultisols
(Hapludults)
Lebew, Liiz, Muskingum,
Montevallo, Wallen,
Dandridge, Tellico, Steekee,
Mesic / Udic
44-54
1S0-210
23-27/42-46
63-67/84-8S
Appalachian oak forest
(mixed oaks, hickory, pine,
poplar, birch, maple); some
mixed mesophytic forest
(beech, tulip poplar, oaks,
buckeye, basswoodl
Mostly mixed forest, some
pasture and cropland on leas
sloping Land
|68^^^^^SOUTlIWESTJERN APPALACHIANS \
§ Level IV Ecoregion
Physiography

Geology
Soil
Climate
Potential NaturoJ
Vegetation
Land Use and Land Cover g
J
Area
(tquare
mi] a)

Elevation
/
Local Relief
fleet)
SotQcIjU and bedrock
Order (Great Groopj)
Common Sofl Scries
Temperature /
Molxtare Regimes
Precipitation
Mean >jtnni1
Cinches)
Frost Free
Mean tinmil
(dtyi)
Mean
Temperature
Tamii-y niinAimf;
Juhymhitau. (F)
|68a.
1 Cumberland
1 Plateau
3,1S4
Undulating and rolling tableland
and some open low mountains;
somewhat weakly dissected
1200-2000
/
3QQ-S00
Quaternary sandy decomposition
residuum; Pennsytvanian
conglomerate, sandstone, sillstone,
shale
Ultisols (Hapludulta);
Incepusols (Dystrochrepts)
Lily, Ramsey, Lonewood,
Gilpin
Mesic/Udic
48-60
LS0-200
21-27/42-47
61-66/83-SS
Mixed oak foresi on
uplands; mixed mesophytic
forest (maple, buckeye,
beech, tulip poplar, oak) in
ravines and gorees
Mostly forested; limber and §
coal mining activities; some g
cropland and pasture; tourism; S
public recreation and wildlife \
areas s
iSequatcbie Valley
250
Undulating to hilly 4 mile wide
linear valley, some level
bottomland and low terraces;
small alluvial fans; moderate to
low gradient streams and several
serines
600-1000
/
100-300
Quaternary cherty clay solution
residuum; Ordovician limestone and
dolomite, Mississippian and
Ordovician cherty limestone and
shale
Ultisols (Palcudulu,
Hapludulta)
Waynesboro, Etowah,
Sequatchie, Pailo, Fullerton
Thermic / Udic
52-60
190-210
25/45
65/SS
Appalachian oak forest
(mixed oaks, hickory, piae,
poplar, birch, maple)
Cropland and pasture, with \
bay, soybeans, small grain, |
corn, and tobacco; mostly \
mixed forest on central ridge §
| Plateau
I Escarpment
1,379
Long, steep mountainsides, some
nearly vertical cliffs near top of
escarpment; ravines and gorges;
high velocity, high gradient
streams and many waterfalls
500-2 LOO
/
900-1500
Quaternary colluvium with huge
blocks; Pennsylvania!! sandstone,
siitstooe, shale, conglomerate;
Mississippiaa limestone, sandstone,
shale
Ultisols (Palcudulu,
Hapludulta); Incepusols
(Dystrochrepts)
Bouldin, Ramsey, Gilpin,
Allen, Jefferson, Varilla
Mesic/Udic
52-60
L80-200
21-27/42-47
61-66/S3-SS
Mixed oak and chestnut
oak on upper slopes; mixed
mesophytic forest (beech,
tulip poplar, maple,
basswood, buckeye,
hemlock) on lower slopes
Forested; steep slopes limit §
road building and forestry; |
minor cropland and pasture in §
lower stream bottoms 1
47
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CENTRAL A^PAf .A rHI ANS
Level IV Eco region
Physiography

Geology
Soil
Climate
Potential Natural
Vegetation '
Land Use and Land Cover g

Am
mik>)

Ehntfos
/
tooIBtfitf
(TeeO
Sarfldd aad b«drock
Order (Great Greupi)
f-ommwa SoD Scries
Ten pen tar* /
Mototun Regimes
Precipitation
fcrtcha)
Fred Fra
Moa tssul
(d«y«)
Mean
Temperature
My rnkten, (F)


59 d.
Cumberland
Mountains
896
Low mountains with long, steep
slopes, narrow to rounded uneven
f and narrow, wtsdinj
valleys; highly dissected by
moderate to high gradient,
bedrock- dominated, clear-water
stre»TTn
1200-3500
/.
1500-2000
Quaternary sandstone- and shale-
dast loamy colluvium;
Pesnsylvanian shale, sandstone,
siltstone, and coal
Inceptisols (Dystrochrepts);
Uhisols (Hap hi delta)
Jefferson, Shelocta,
Gilpin, Petros, Ramsey,
Lily, A1 tier est,
Muskingum
Mesic/Udic
50-55
180
21/43
61/85
Mixed mcsophytic forest
(maple, buckeye, beech,
tulip poplar, oak)
Deciduous and mixed forest;
extensive coal mining; forestry
71	INTERIOR PLATEAU			%
Level IV Ecoregkm
I
Am
(iqutt
nika)
Physiography
Ekratfea
/
Local Bifid
ffto)
Geology
Sufltbl ud bedrock
Soli
Order (Great Groapi)
Soil Series
Temperature /
Mabtar* Rcgtmo
Climate
Pr«dptUtioa
(tubes)
Frost Free
(dayi)
Mean
Timpcntin
MjrmhAia^^
Potential Natural
Vegetation
Land Use and Land Cover
:S
Sgru.
%
ji Pennyroyal Kant
S| Western
Irregular plains, mostly gently
rolling and weakly dissected; kazst
sinkholes *tw4 depressions; few
permanent	mostly gravel
and bedrock substrata
500-750
/
60-200
Quaternary cherty day solution
residuum; Miasissippian limestone
Alfisols (Paleudalfs);
Uhisols (Paleudults,
Fmgruduhs)
Pembroke, Cridcr,
Baxter, Mountvicw,
Dickson
Thermic / Udic
23/43
/
66/88
Oak-hickory forest and
blucstcm prairie
5*71f.
Western Highland
1 Rim
Mostly cropland and pasture: ig
tobacco, livestock, whh some £•
f(wi soybeans, and wtmll
grains; small patdies of mixed 'x|
and deciduous forest; large 3
military reservatioa
Highly dissected open hills, rolling
to steep; nanow winding to
moderately broad ridges; some
level bottom land along major
and rivers; moderate
gradient streams with gravel, sand,
and bedrock substrates
400-1000
/
300-500
Quaternary cherty clay and chen
fragment solution residuum;
Mississipptan chert and cherty
limestone, calcareous sUicastonc,
some shale
Ultisols (Paleodults,
Fragiudults, Hapluduhs);
Alfisols (Paleudalfs);
Inceptisols (Dystrochrepts,
Eutrochrepts)
Xlotmtview, Dickson,
Baxter, Brandon,
Hawthorne, Sulphura,
Lax, Saffell
Thermic / Udic
23-26/45-48
I
63-67/88-90
Oak-hickory forest;
somewhat transitional
between the more xeric
oak-hickory forest to the
west and the mere mesie
mixed mesophytic forest to
jhisa.
Mostly deciduous forest; some g
pasture and cropland on flatter^
stream and river valley |
terraces, primarily hay, canle, g
and some com and tobacco g
if. Eastern Highland
I Rim
2,923
Weakly dissected plateau or
tablelands; moderately dissected
open hills iwwt knobs to the north;
some sinkholes and depressions;
low to moderate gradient gravel-
and bedrock-bottomed streams;
800-1300
/ •
100-500
Quaternary cherty clay and chert
fragment solution rriiihifin^
Mississippian chert and cherty
ihwwinw( calcareous silicastone,
minor shale, some sandstone on
knobs in north
Ultisols (Fragruduhs,
Paleudults); Alfisols
(Paleudalfs)
Dickson, Mountvicw,
Baxter, Waynesboro,
Cumberland, Decatur
Thermic 7 Udic
24-27/44-47
/
63-68/87-89
Mostly oak-hickory, but
transitional between the
more xeric oak-hickory
forest to (he west and the
more mesic
mcsophytic forest to the
east; several areas of
bottomland hardwoods
Cropland and pasture, with
nurseries, hay, tt»hII
acreages of com, cotton,
soybeans, *w*n grains,
tobacco; farm woodlots and
deciduous forest; urban
§71h.
ij| Outer Nashville
% Basin
Open hills, gently rolling to steep;
some plains with hills; highly
dissected escarpments; moderate
gradient bedrock- and gravel-
bottomed streams
500-1200
/
300-500
Quaternary phosphatic sand
solution residuum and cherty cilty
clay, locally phosphatic, solution
residuum; Ordovician limestone wH
shaly limestone; Mississippian chert
and cherty limestone on higher hills
and knobs; some Devonian
(Chattanooga) shale
Ultisols (Paleudults,
Haptudults); Alfisols
(Haptudalfs); Inceptisols
(Dystrochrepts,
Eutrochrepts)
Ddlrose, Mimosa,
Stiversville, Hampshire,
Armour, Maury, Barfield,
Hawthorne, Sulphura
Thermic f Udic
48-54
190-210
25/47
/
66/89
Mostly oak-hickory, but
transitional between the
more xeric oak-hickory
forest to the west and the
more mesic mixed
mcsophytic forest to the
east
Mosaic of urban, pasture,	$
forest, cropland;	^
generally deciduous forest on	Q
ridge caps, pasture and red	j:|!
on hillsides, ""«n jiji
fields of com, tobacco, hay,
and garden crops on foot	g
slopes and bottom land	S
1,670
Inner NashvfDe
Basin
Smooth to rolling plain, with
«nm> rmMl knobs	low
gradient dear water	on
bedrock substrate
500-900
/
60-400
Quaternary thin clayey solution
residuum; Ordovician limestone, low
in phosphates
Alfisols (Haptudalfs);
MoUisols (Ratdolls);
Inceptisols (Eutrochrepts)
Talbott, Bradyville,
Gladeville, Inman,
Mimosa
Thermic / Udic
190-210
25/46
/
66/90
Oak-hickory forest; cedar
glades (poverty grass, red
cedar, winged elm,
hackbetry, oaks)

Urban and residential; pasture &
and cropland of hay, with jy
tnrn>	«m«n grains; iv
beef cattle and dairying; |j
patches of mixed woodland g
and stands of red cedar j?
			 'jv/.vavavm'}
48
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•73 MISSISSIPPI ALLUVIAL PLAIN
Level IV Ecorogion
Physiography

Geology
Soil
Climate
Potential Natural
Vegetation
Land Use and Land Cover

Aru
(iquare
mQ(f)

Elevation
/
Local Relie:
I'fec)
Snrfkial tad bedrock
Order (Great Groopi)
Common So3 Series
Temperature /
Moisture Regimes
Precipitation
Mean
(iachet)
Frost Free
Mean ¦timni
(day»)
Mean
Tempera tare
January nuo^nci,'
Aihy airraxi, (F)
|73a
Northern
Mississippi
Alluvial Plain
S54
Flat plains and Levees of the
Mississippi River floodplain. A
few low-gradient streams, mostly
channelized; oxbow lakes, ponds,
swamps, tectonic lakes (Rcelfoot,
Open)
215-300
/
25-50
Quaternary alluvial sand, silt, clay,
gravel
Hntisols (Fluvaqucnts,
Udifluvents); tnccptisols
(Haplaquepts); Mollisols
(Argiudolls, Hapludolls);
Alfisols (Endoaqualfs)
Commerce,
Robinsonville, Sharkey,
Tunica, Reelfoot,
Bowdre, Forestdale
Thermic / Udic,
Aquic
49-52
200-230
25-30/43-48
6S-73/S9-91
Southern floodplain /
bottomland hardwood
forests (oak-tupelo-bald
cypress)
Extensive cropland of I
soybeans, cotton, com,
sorghum, vegetables, hay;
some deciduous forest and
forested wetlands








$74 MISSISSIPPI VALLEY LOESS PLAINS
i Level IV Ecoregion
Physiography

Geology
Soil
Climate
Potential Natural
Vegetation
Land Use and Land Cover

Ares
(iquare
miles)

Elevation
/
Local Reiki
(Tee)
SorOdaJ and bedrock
Order (Great Gronps)
Common Soil Series
Temperatore /
Moisture Regimes
Precipitation
Mean
(iache*)
Frost Free
Mean annual
(day.)
Mean
Temperature
January ni
July mrp/mfiT, (F)
74a.
Bluff 11 ills
436
Irregular plains with dissected hills
and ridges; steeper hillsides and
narrow hollows to the west,
smoother terrain to the east.
Moderate to low gradient silt and
sand bottomed streams, some with
occassional travel
250-500
/
100-200
Quaternary loess more than 60 ft.
deep; Tertiary sand, silt, clay and
lignite of the Jackson Formation
along western bluffs; Coastal plain
gravel exposed at base of bhifls
Alfisols (Hsptudalfs,
Fragiudaifs); Hntisols
(Udifluvents, Fluvaqueots);
Inceptisols (Eutrochrepts)
Memphis, Loring. Adler.
Natchez
Thermic / Udic
50-52
200-230
25-30/43-4S
6S-73/89-91
Oak-hickory forests, with
some areas richer in
mesophytes such as beech
and sugar maple
Deciduous forest; pasture and
cropland (hay, soybeans,
cotton, com, wheat) on small
farms on gentler slopes
74b.
Loess Plains
4,023
Irregular plains, level to gently
rolling, with wide, flat
bottomlands and floodplains; low
gradient sill and sand bottomed
streams, most have been
channelized
250-500
/
50-100
Quaternary loess with alluvial silt
and sand in bottomlands
Alfisols (Fragiudaifs,
Hapludalfs, Epiaqualfs);
Eotisols (Fluvaquents,
Udifluvents)
Grenada, Loring.
Memphis, Collins,
Waveriy, Falaya, Routon
Thermic / Udic
and Aquic
50-52
200-230
25-30/43-4S
6S-73/89-91
Oak-hickory forests,
southern floodplain /
bottomland hardwood forests
(oak-tupelo-bald cypress)
Cropland of soybeans, cotton,
corn, grain sorghum, and
some pasture; deciduous forest
and forested wetlands on
larger bottomlands
49
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~
39
Ozark Highlands
iH
45
Piedmont
¦
63
Middle Atlantic Coastal


Plain
liii
65
Southeastern Plains
~
66
Blue Ridge Mountains
Hi
67
Ridge and Valley
Q
68
Southwestern Appalachians
¦
69
Central Appalachians
H
70
Western Allegheny Plateau
¦
71
Interior Plateau

72
Interior River Lowland

73
Mississippi Alluvial Plain
¦
74
Mississippi Valley Loess


Plains
Figure 1. Level in Ecoregions of Tennessee and Neighboring States.
-------
Level III and IV Ecoregions of Tennessee
65 Southeastern Plains
65a Blackland Prairie
65b Ratwoods/Alia vial Prairie Margins
I I 65e Southeastern Plains and Hills
¦1 65i Fall Line Hills
ED 65j Transition Hills
66 Blue Ridge Mountains
¦1 66d Southern Igneous Ridges and Mountains
¦¦ 66c Southern Sedimentary Ridges
1 I 66f Limestone Valleys and Coves
[ 1 66g Southern Metasedimentary Mountains
	 Level III ecoregions
	 Level IV ecoregions
67 Ridge and Valley
I I 67 f Southern Limestone/Dolomite
V alleys and Low Rolling Hills
I 1 67g Southern Shale Valleys
I I 67h Southern Sandstone Ridges
Hi| 67i Southern Dissected Ridges and Knobs
68	Southwestern Appalachians
t: : I 68a Cumberland Plateau
I I 68b Sequatchie Valley
IB 68c Plateau Escarpment
69	Central Appalachians
¦I 69d Cumberland Mountains
71 Interior Plateau
t—J 7 le Western Pennyroyal Karst
Si 71 f Western Highland Rim
¦I 7 lg Eastern Highland Rim
F I 7 lh Outer Nashville Basin
I I 7 ii Inner Nashville Basin
73	Missisippi Alluvial Plain
I i 73a Northern Mississippi Alluvial Plain
74	Mississippi Valley Loess Plains
H 74a Bluff Hills
BMi 74b Loess Plains
-------