Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
Major Land Resource Area (MLRA): 134X–Southern Mississippi Valley Loess
The Southern Mississippi Valley Loess (MLRA 134) extends some 500 miles from the southern tip of Illinois to southern Louisiana. This MLRA occurs in Mississippi (39 percent), Tennessee (23 percent), Louisiana (15 percent), Arkansas (11 percent), Kentucky (9 percent), Missouri (2 percent), and Illinois (1 percent). It makes up about 26,520 square miles. Landscapes consist of highly dissected uplands, level to undulating plains, and broad terraces that are covered with a mantle of loess. Underlying the loess are Tertiary deposits of unconsolidated sand, silt, clay, gravel, and lignite. The soils, mainly Alfisols, formed in the loess mantle. Stream systems of the MLRA typically originate as low-gradient drainageways in the upper reaches that broaden rapidly downstream to wide, level floodplains with highly meandering channels. Alluvial soils, mostly Entisols and Inceptisols, are predominantly silty where loess thickness of the uplands are deepest but grade to loamy textures in watersheds covered by thin loess. Crowley’s Ridge, Macon Ridge, and Lafayette Loess Plains are discontinuous, erosional remnants that run north to south in southeastern Missouri - eastern Arkansas, northeastern Louisiana, and south-central Louisiana, respectively. Elevations range from around 100 feet on terraces in southern Louisiana to over 600 feet on uplands in western Kentucky. The steep, dissected uplands are mainly in hardwood forests while less sloping areas are used for crop, pasture, and forage production (USDA-NRCS, 2006).
This site is restricted to the dry to moderately moist (i.e., mesic) backslopes of the northern section of Crowley’s Ridge from about Harrisburg in Poinsett County, Arkansas northward through portions of Stoddard County, Missouri.
All or portions of the geographic range of this site falls within a number of ecological/land classifications including:
-NRCS Major Land Resource Area (MLRA) 134 – Southern Mississippi Valley Loess
-Environmental Protection Agency’s Level IV Ecoregion: Bluff Hills, 74a (Griffith et al., 1998; Woods et al., 2002; Chapman et al., 2002; Chapman et al., 2004; Woods et al., 2004; Daigle et al., 2006)
-231H - Coastal Plains-Loess section of the USDA Forest Service Ecological Subregion (McNab et al., 2005)
-LANDFIRE Biophysical Setting 4515100 and NatureServe Ecological System CES203.072 Northern Crowley’s Ridge Sand Forest and Crowley’s Ridge Sand Forest, respectively (LANDFIRE, 2008; NatureServe, 2011)
-Dry Sand Woodland; Dry-Mesic Sand Woodland; Dry-Mesic Loess Forest; Dry-Mesic Loess Woodland; Dry-Mesic Sand Forest (Nelson, 2005)
-Western Mesophytic Forest Region - Mississippi Embayment Section - Loess Hills (Braun, 1950)
Ecological site concept
The Western Dry Loess Backslope site is restricted to the moderately steep to steep slopes of the northern sections of Crowley’s Ridge. Slopes of this site are greater than 12 percent and are frequently within the range of 12 to 35 percent. Soils of this site are deep and largely comprised of loess and loess over fluviomarine deposits (sand and gravel). Based on the distribution of soils, loess depths vary considerably with deep loess soils (greater than or equal to 4 feet thick), thin loess soils (greater than 20 inches and less than 40 inches thick), and exposed sand and gravel co-occurring in close proximity and within intricate complexes. Upper to mid-slope positions are tend to be quite droughty and this influence is reflected in the local plant community, which is often comprised of drier oaks, hickory, and shortleaf pine, where present. Lower slope positions (i.e., footslopes) often support species indicative of increased moisture such as beech, maple, tuliptree, sweetgum, and occasionally basswood and cucumber tree. This community is largely restricted to moist footslopes within narrow ravines and rarely, if ever, occurs beyond these protected environments. The driest community of this system occurs on local exposures of gravel and sand and on exposed slopes (south- to west-facing slopes). Here, shortleaf pine is often the dominant species with associates of post oak, blackjack oak, black hickory, and a heavy understory component of farkleberry. The contrasting plant communities occurring across this pronounced dry – moist gradient are treated and referenced in this context as dry – mesic forests (the usage of “mesic” in this case refers to moderate moisture and not soil temperature regime).
Western Dry Loess Summit - PROVISIONAL
Northern Loess Sideslope - PROVISIONAL
This site has similar soils and occurs on similar landforms as the Western Dry Loess Backslope site.
Table 1. Dominant plant species
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