U.S. National Vegetation Classification By Thomas Foti, September, 1999
When the Arkansas Gap Analysis Project began in 1992, a uniform classification of plant communities for the United States did not exist, and previous state GAP’s did not use consistent vegetation units. There were several vegetation classifications in use in Arkansas, but no standard classification, and the units classified varied widely in concept and definition. Since some AR-GAP cooperators were working closely with The Nature Conservancy on its national classification effort, we decided to create a new classification that was crosswalked to the existing state classifications and that had a conceptual base that allowed it to be crosswalked into the emerging national classification. Like the national classification, its higher levels were based on physiognomy and lower levels on floristic composition. It was published as “A classification system for the natural vegetation of Arkansas” by Thomas Foti, Xiaojun Li, Martin Blaney and Kimberly G. Smith, Proceedings of the Arkansas Academy of Science, Vol. 48, 1994 pp. 50-62. It is appended to this crosswalk with the narrative explanation unchanged and the classification itself updated to 1997, as it was actually used by AR-GAP.
The Arkansas classification system was comprised of 8 levels with levels 6-8 being floristic units. The classification includes 58 units at level 6, 90 units at level 7 and over 200 units at level 8. Level 6 was selected as the mapping level, with the exception of one level 7/8 unit, Cypress Swamp. Of these, it was possible to distinguish 31 units based on plot data used for image classification. Even though these map units are given the designation of one level 6 unit, in some cases they stand for two or more units that could not be separated.
This analysis crosswalks the 31 vegetation mapping units of the AR-GAP to the U.S. National Classification as of mid-1999. In total the 31 mapping units correlate to 64 Alliances in the national classification. These Alliances include 97 Associations in Arkansas. The Alliances per AR-GAP mapping unit range from 1 (16 mapping units) to 7 (1 mapping unit):
Alliances/Mapping unit Frequency
AR-GAP level 6 mapping units are equivalent to or coarser than the U.S. National Classification Alliance level; no U.S. Classification Alliance corresponds to more than one AR-GAP level 6 unit.
In the list that follows, each AR-GAP mapping unit is followed by the corresponding U.S. National Classification Alliances and Associations. Each Alliance includes the description that is presented in the National Classification. It is followed by the list of Associations that exist in Arkansas, without a description.
oligantha, Piptochaetium avenaceum, and Tephrosia virginiana. Some associations can result from natural or anthropogenic
disturbances such as fire or windstorms, while others occur naturally on the landscape, maintained by edaphic situations, and
may even be "climax" on these sites. Soils of these forests are acidic and are derived from sandstone, chert or granitic rock situated on ravines, ridges, and steep, often south-facing, slopes; the surface is often rocky. In the coastal plain, this alliance is particularly typical of clay soils, on hillsides, ridges, flats, and low hills. In the Ouachita Mountains and Ozarks, forests of this alliance typically occur on south-facing slopes and saddles, and rocky outcrops and bluffs, but may also occur on lower, north-facing slopes. This is a wide-ranging alliance and currently is known to occur in the Cumberland Plateau and Mountains, Southern Blue Ridge, Arkansas Valley, Ouachita Mountains and Ozarks, and Gulf Coastal Plain, and is likely in the Piedmont.
RANGE: This alliance is found in southern Missouri, Alabama, Arkansas, Georgia, Kentucky, Louisiana, Mississippi, North
Carolina, Oklahoma, South Carolina, Tennessee, Texas, and West Virginia. This is a wide-ranging alliance and currently is known
to occur in the Cumberland Plateau and Mountains, Southern Blue Ridge, Arkansas Valley, Ouachita Mountains and Ozarks, and
Gulf Coastal Plain, and is likely in the Piedmont.
FEDERAL LANDS: DOD (Fort Benning); NPS (Hot Springs, Kennesaw Mountain, Shiloh?); USFS (Angelina, Bankhead?,
Chattahoochee, Daniel Boone, Davy Crockett, Kisatchie, Oconee, Ouachita, Ozark, Sabine, Sam Houston, St. Francis, Sumter,
SYNONYMY: IA6a. Dry Shortleaf Pine - Oak - Hickory Forest, in part (Allard 1990); Dry Shortleaf Pine - Oak Forest (Foti
1994); Dry Oak--Hickory Forest, in part (Schafale and Weakley 1990); Pinus echinata - Quercus alba - Quercus velutina
forest association (Hoagland 1997); Shortleaf Pine-White Oak CUPL (Pyne 1994); Mixed Oaks-Shortleaf Pine HR (Pyne 1994);
Shortleaf Pine-Oak Series, in part (Diamond 1993); T1B3aII3b. Quercus alba - Pinus echinata - Quercus (velutina, falcata)
(Foti et al. 1994); Shortleaf Pine - Oak: 76, in part (Eyre 1980).
REFERENCES: Allard 1990, Campbell et al. 1996, Diamond 1993, Eyre 1980, Faber-Langendoen et al. 1996, Foti and Guldin
1994, Foti et al. 1994, Fountain and Sweeney 1985, Fountain and Sweeney 1987, Hoagland 1997, Johnson 1986, Kennedy 1973, Martin and Smith 1991, Martin and Smith 1993, Rice and Penfound 1959, Schafale and Weakley 1990, United States Forest Service 1990