The Cumberland Plateau is an extremely varied landscape that consists of mountains, deeply incised stream valleys, broad floodplains, steep to rolling hills, and a tableland surface with minimal relief. Each of these land types is inhabited by different forest communities. Forest composition is largely a function of slope position, aspect, and form (Hinkle and others 1993) and disturbance history. On the Cumberland Plateau, true mixed mesophytic forests are restricted to protected mesic sites such as gorges and coves (Martin 1992). The entire Cumberland Plateau does not support true mixed mesophytic forests, and the forests on the Cumberland Plateau, while still a component of the Mixed Mesophytic Forest Region, support lower quality forests relative to the Cumberland Mountains because of extreme relief and nutrient-poor soils (Braun 1942). Best examples of true mixed mesophytic forests appear in the Cumberland Mountains (Braun 1942).

In general, forests of the Cumberland Plateau proper exhibit greater dominance of American beech and white oak and reduced dominance of yellow buckeye, white basswood, sugar maple, yellow-poplar, and northern red oak compared to the Cumberland Mountains (Muller 1982). Because of these variations within the Mixed Mesophytic Forest Region, Braun (1950) further subdivided the classifications into sections, subsections, and districts. The majority of the Cumberland Plateau in Tennessee was classified into the Cliff Section subdivision of the Cumberland and Allegheny Plateaus section (the Cliff Section extends from southern Kentucky to northern Alabama). Braun (1950) named this section for the rugged terrain or “bold cliffs” that characterize the Plateau through much of Tennessee and Braun (1950) subdivided the Cliff Section into Northern and Southern districts, with the Cumberland Plateau of Tennessee largely within the Southern district.

The complex topography and variations in substrates create a wide range of microclimatic and edaphic conditions on the Cumberland Plateau. However, the vegetation of the region can be classed into one of two broad categories: the flat to rolling plateau uplands and the plateau ravines and gorges (Hinkle 1989). The most spatially comprehensive study on Cumberland Plateau forest communities was conducted by Hinkle (1978) and summarized in Hinkle (1989). Hinkle documented 12 community types through the flat to rolling plateau uplands that ranged from stands dominated by red maple, river birch, and American holly on floodplain terraces to stands dominated by red maple, white oak, and blackgum on poorly drained swales to stands dominated by blackjack oak and Virginia pine on xeric ridge tops (Hinkle 1978; Hinkle 1989). Slope forests are generally dominated by mixed oak species with white oak being the most abundant followed by scarlet oak and black oak. Other common canopy dominants on the Plateau tabletop include shortleaf pine, post oak, chestnut oak, and mixed hickory species (Hinkle 1989). On upland sites, species composition is controlled by topography, factors related to soil water availability (such as depth to bedrock and surface stone cover), and disturbance history (Hinkle 1978). Aspect has little influence on the Plateau surface, but is significant on the slopes of higher ridges and mountains and on the steep escarpment slopes (Clatterbuck and others 2006).

Ravines and gorges occur throughout the Plateau but become more common near the eastern and western escarpments. In these areas, erosion of the caprock has created steep and often very deep gorges. These gorges were the inspiration for Braun (1950) to name this region the Cliff Section. Hinkle (1978) identified 12 community types in the ravines that ranged from communities dominated by chestnut oak, white oak, or black oak at upper slope positions to rich white oak, northern red oak, and sugar maple stands at middle and lower slope positions (Hinkle 1989). Hinkle (1978) noted that the common mixed mesophytic indicator species (yellow buckeye and white basswood) were present but not important in most of the sugar maple-white oak, northern red oak-sugar maple, and white oak-northern red oak communities sampled. Hinkle noted, however, that many stands seemed successional to mixed mesophytic types. Stands dominated by eastern hemlock are restricted to headwaters and along bedrock streams where they occur as ribbon forests (Hart and Shankman 2005). The only other common conifer in ravines is white pine, which usually occurs in association with eastern hemlock (Hinkle 1989). Factors related to soil moisture and nutrient availability control community composition in ravine communities (Hinkle 1978). Forest communities on the Cumberland Plateau can be classified as evergreen coves, mixed mesophytic, mixed hardwoods, or xeric pine-hardwoods.

Eastern hemlock dominates on small isolated locations on the Cumberland Plateau and occurs in almost pure stands on specific sites. These evergreen cove forests are largely restricted to narrow gorges and riparian areas along bedrock streams (Hinkle 1989) and on lower, north facing slopes (Martin 1975; Encyclopedia of Southern Appalachian Forest Ecosystems; Shankman and Hart 2007). These stands often have discrete boundaries (Caplenor 1979). Cove forests occupy concave landforms and the sheltered topography provides some protection from high wind and other disturbance events. Coves dominated by eastern hemlock are often called "acid coves" because of low soil pH. The bark and litter of eastern hemlock contain high concentrations of tannins. Tannins slow the rate of litter decomposition and contribute to a thick and highly acidic forest floor in mature stands (Finzi and others 1998). Because eastern hemlock occurs mostly on acidic soils, it is usually absent from gorges and coves that contain soil from limestone parent material. Other common canopy trees include sugar maple, red maple, white basswood, yellow-poplar, American beech, umbrella magnolia, and yellow birch. White pine is the only other conifer that occurs in the canopy of eastern hemlock stands. Rosebay rhododendron often dominates the shrub layer of evergreen coves and may form dense thickets. As gorges widen, forests transition from eastern hemlock to eastern hemlock-mixed deciduous stands (Quarterman and others 1972; Caplenor 1979). Eastern hemlock does occur in mesic forests throughout the region, but only dominates on specific sites (Martin 1975).

Mixed mesophytic forests develop on moist, well-drained sites (Runkle 1996) and dominate these habitats on the unglaciated Plateaus province in Ohio, West Virginia, Kentucky, Tennessee, and Alabama. Both Braun (1950) and Kuchler (1964) placed the Cumberland Plateau almost wholly within the Mixed Mesophytic Forest Region (with the exception being the southern end of the Plateau and specific local areas). The best examples of mixed mesophytic forests occur in the Cumberland Mountains (Braun 1942). These forests are noted for their compositional and structural diversity (Muller 1982). Mesophytic forests are characterized by a lack of dominance by any one species, but common canopy species include white oak, northern red oak, white ash, American beech, sugar maple, yellow-poplar, and eastern hemlock (Martin 1992). They also contain specific indicator species, e.g., yellow buckeye and white basswood, in the canopy and possess high species richness in all forest layers. In general, forest communities of this region are characterized by high plant diversity at the community level and contain over 30 canopy species (Hinkle and others 1993). The plant diversity of the region has been attributed in part to the great variety of site conditions (Sampson 1930; Braun 1942; Braun 1950), which results in high beta (different sites) and gamma (regional) diversity (Muller 1982). Common species in mixed mesophytic stands include sugar maple, white basswood, yellow-poplar, American beech, eastern hemlock, yellow birch, northern red oak, chestnut oak, cucumber tree, umbrella magnolia, yellow buckeye, white ash, and pignut hickory (Martin 1975).

Although, Braun (1950) and Kuchler (1964) considered the Cumberland Plateau a component of the Mixed Mesophytic Forest Region, true mesophytic forests are restricted to protected mesic sites such as coves, gorges, and along rocky streams (Martin 1992). The majority of the Plateau is composed of mixed hardwoods species (Smalley 1982; Hinkle 1989). Interestingly, most vegetation studies on the Cumberland Plateau have focused on mixed mesophytic stands (e.g., Caplenor 1965; Quarterman and others 1972; Martin 1975; Muller 1982; Schmalzer 1988; McEwan and others 2005; McEwan and Muller 2006).

The majority of the Cumberland Plateau supports mixed hardwood species (exceptions being moist gorges and coves and xeric ridgetops). On the Plateau uplands, oaks are the most widespread genus, with white oak, scarlet oak, black oak, post oak, and chestnut oak the most common (Hinkle 1989). Of the oak species, white oak is most common in upland communities (Martin 1975). Hickories are generally of limited importance, but dominate some stands probably as a result of past disturbance (especially selective logging and high grading). The most common hickories in the region are shagbark, mockernut, and pignut. Hinkle (1989) concluded that hickory species were not common canopy components and the Cumberland Plateau should not be considered a component of the oak-hickory forest.

In general, mixed oak species dominate slope forests of the undulating Cumberland Plateau. Chestnut oak, white oak, and black oak dominate upper slopes, while middle and lower slope positions are dominated by white oak, northern red oak, and sugar maple (Hinkle 1989). Middle and lower slope positions support mesic communities composed of American beech, red maple, yellow-poplar, white basswood, white ash, and yellow buckeye. Composition of slope forests on the Cumberland Plateau is influenced by soil moisture and nutrient conditions (Hinkle 1978). Species composition shifts are projected for some mesic oak forests of the Plateau as shade-tolerant species in the understory, e.g., red maple, sugar maple, and American beech are recruited to larger size classes after small-scale disturbance events (Hinkle 1989; Kuddes-Fischer and Arthur 2002; Gilbert and others 2003; Hart 2007; Hart and Grissino-Mayer 2008).

Xeric pine-hardwood stands on the Cumberland Plateau occur on south-facing slopes, ridgetops, and sites on the undulating Plateau surface (Smalley 1982; Hinkle 1989). Sites that support this forest type have shallow soils with low moisture holding capacity and are exposed to high intensity solar radiation. Thus, these sites support forests that tolerate dry conditions (Clatterbuck and others 2006). These xeric forests are largely composed of oak, shortleaf pine, Virginia pine, and loblolly pine. The driest sites are dominated by Virginia pine (Hinkle 1989), but Virginia pine also occurs as early old-field succession on moderate to deep soils. The range of pitch pine extends onto the northern section of the Cumberland Plateau and longleaf pine occurs on the southern portion of the Plateau in Alabama. Major oak species include blackjack, shingle, chestnut, scarlet, southern red, post, and black. Mesophytes are not important contributors to these pine–hardwood stands (Martin 1975). Other hardwood species include red maple, dogwood, blackgum, sourwood, and sassafras (Kuddes-Fischer and Arthur 2002). In general, these forests occur on sites that are not productive and moisture limited (Clatterbuck and others 2006).

Aspect and slope position strongly influence soil and surface moisture conditions in these xeric stands and, in turn, fire behavior. The Plateau surface, upper slopes, and those facing south to west dry more rapidly and burn with greater frequency and intensity, thus maintaining disturbance dependent species such as the yellow pines (Buckner 1995).

In the absence of disturbance, especially fire, pine-hardwood stands on the Cumberland Plateau are largely successional to hardwood (Gilbert and others 2003). In mature stands on xeric sites, the pine species often exist only as large scattered individuals (Martin 1975). Archaeological, paleoecological, and historical studies have found that anthropogenic disturbance, including fire, occurred in the region during the last 17,000 years (Stewart 1956; Delcourt 1979; Wilson and Finch 1980; Kline and others 1982; Delcourt and others 1986; Welch 1999; Delcourt and Delcourt 2004). Fire exclusion on the Cumberland Plateau has allowed for the development of an understory of fire-intolerant species, e.g., red maple, sugar maple, American beech. Composition in some stands has shifted to a support a higher density of fire-sensitive species, while fire-tolerant species have not regenerated (Arthur and others 1998; Kuddes-Fischer and Arthur 2002). Fires may be especially important in the pine-hardwood stands to favor the regeneration of disturbance dependent species.