Physiographic features

The Baton Rouge Terrace (EPA Level IV Ecoregions 74D) of the Southern Mississippi Valley Loess (MLRA 134) are located in southeast Louisiana, occurs on the Pleistocene Prairie Terraces and is lower in elevation and has flatter topography than Ecoregion 74c to the north. Similar to other parts of Ecoregion 74, loess is thicker to the west.

“Loess” is the geologic term of German origin that refers to widespread deposits of homogeneous layers of friable, porous silt mixed with minor amounts of clay or fine sand (Heinrich, 2008). The loess mantle, created by well-sorted windblown silt, was deposited during the Pleistocene age. Its source was glacial sediment from glacial meltwater that was flowing down an extensive braided stream system depositing large volumes of silt over the floodplain of the Mississippi River (Heinrich, 2008). Glacial meltwater ceased flowing when southern edges of ice sheets stopped melting in fall and winter, thereby creating dry conditions on the previously flooded Mississippi River Valley. Strong seasonal winds blew across dry floodplains and eroded large quantities of silt-sized sediment, and transported it out of the Mississippi alluvial valley and deposited it on adjacent uplands and terraces (Heinrich, 2008). Over thousands of years, the silt accumulations created loess deposits that are many feet thick (Heinrich, 2008).

Where blankets of loess are thicker than 6 feet, the soils formed entirely in loess. Where loess deposits are less than 6 feet thick, soils reflect the nature of the underlying parent material (McDaniel, 2001). Thick loess areas produce intensely dissected terrain with excessively steep slopes and ridge and ravine topography (McDaniel, 2001). The Bluff Hills tend to have deeper, calcareous loess and steeper, much more dissected topography than the Southern Rolling Plains to the east and Baton Rouge Terrace to the Southeast.

This Site occurs mainly on the broad floodplains of creeks and streams and their tributaries draining the Southern Rolling Plains in Louisiana. Smaller areas of this site occur on the narrow drainways and floodplains of the smaller creeks and streams within the Bluff Hills of Louisiana. This site also occurs as "Gallery Forests" in the "Cajun Prairie" Region of MLRA 134, Ecoregion 34j the Lafayette Loess plain. Slopes are level to nearly level (0 to 3 percent).

Table 2. Representative physiographic features

Climatic features

South Louisiana has a warm, humid climate, with fairly long summers and relatively short winters. The result is a long growing season and abundant plant growth. Water is a definitive part of the southern Louisiana landscape, largely due to the combination of low elevation and fairly abundant rainfall in most years. Mean annual precipitation ranges from 51 to 67 inches over this region, and is fairly well distributed throughout the year. There have been very few years when less than 50 inches of precipitation has fallen. Snow is a rarity, and little more than 1 inch typically falls every few years. Growing seasons are long, typically from late February to late November. Along the Gulf Coast, it is not unusual for the lowest winter temperature to be above 30 degrees. Inland, there have been occasional blasts of cold air that have dropped temperatures into the teens and 20s, but these are rare. Hurricanes and tropical storms are an important part of the climate of southern Louisiana, with some impact occurring nearly every year in some part of the region. However, devastating storms do not occur too often, and heavy rain and storm surge are usually the biggest concerns, compared to wind damage. The following climatic data are averages from the five weather stations listed below. Temperature and precipitation may vary considerably from that listed for each month. Site specific weather data should be used for land management decisions. For site specific weather conditions, obtain data from a weather station close to the site. Information can be accessed from specific weather stations at http://www.wrcc.dri.edu/coopmap/ or http://www.wrcc.dri.edu/summary/climsmla.html.

Table 3. Representative climatic features

Climate stations used

• (1) BATON ROUGE RYAN AP [USW00013970], Baton Rouge, LA

• (2) LAFAYETTE RGNL AP [USW00013976], Breaux Bridge, LA

• (3) CLINTON 5 SE [USC00161899], Clinton, LA

• (4) LAFAYETTE [USC00165021], Lafayette, LA

• (5) NEW IBERIA ACADIANA AP [USC00166657], New Iberia, LA

• (6) LSU BEN-HUR FARM [USC00165620], Baton Rouge, LA

• (7) GRAND COTEAU [USC00163800], Opelousas, LA

Influencing water features

This site is influenced by both surface and sub-surface hydrology as part of the flood plain of Streams and creeks. Several inches of standing water can be found in the winter months and soils may be saturated into early spring. Wetness is a dominate driver of this system and in Alternative States it will be a limiting factor.

Soil features

The soils listed in this section of the description may not be all inclusive. There may be other soils that fit this site concept, as well as in some areas where the listed soils are mapped they may not fit the site concept. Some soil map units and soil series included in this Provisional Ecological Site grouping were used as “best fit” for a particular soil-landscape catena during a specific era of soil mapping, regardless of origin of parent material or Major Land Resource Area. Therefore, these soil series may not be typical for MLRA 134, and those soil map units deserve further investigation in a joint ecological-soil survey project. When utilizing this description verify it is the correct site utilizing multiple parameters, the soils, the physiography and the location. If the site does not fit the particular location well utilize the Similar or Associated Sites listed in the Supporting Information section of this description to determine if another site may be a better fit to your location.

Soils are Frequently Flooded Fluventic Dystrudepts (Cascilla) and Aeric Fluvaquents (Falaya). These soils formed in water-reworked loess alluvium derived from streams that drain the loess-mantled uplands of the Southern Mississippi Valley Loess (MLRA 134). Slopes range from 0 to 2 percent. These deep and very deep, moderately to slowly permeable soils are found narrow to broad floodplains.

The water table is at or within 1 to 2 feet of the surface during winter and spring months in normal years. These soils are subject to occasional to frequent flooding of brief to long duration, and can be subject to frequent ponding of long duration.

Table 4. Representative soil features

Animal community

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Hydrological functions

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Recreational uses

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Wood products

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Other products

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Other information

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Other references

Schumacher, B. A., Miller, B. J., & Day, W. J. (1987). A chronotoposequence of soils developed in loess in central Louisiana. Soil Science Society of America Journal, 51(4), 1005-1010.

Autin, W. J., Burns, S. F., Miller, B. J., Saucier, R. T., & Snead, J. I. (1991). Quaternary geology of the lower Mississippi Valley. The Geology of North America, 2, 547-582.

Cowardin, L. M., Carter, V., Golet, F. C., & LaRoe, E. T. (1979). Classification of wetlands and deepwater habitats of the United States. US Fish and Wildlife Service FWS/OBS, 79(31), 131.

Daigle, J.J., Griffith, G.E., Omernik, J.M., Faulkner, P.L., McCulloh, R.P., Handley, L.R., Smith, L.M., and Chapman, S.S., 2006, Ecoregions of Louisiana (color poster with map, descriptive text, summary tables, and photographs): Reston, Virginia, U.S. Geological Survey (map scale 1:1,000,000).

Emerson, F. V. (1918). Loess-depositing winds in Louisiana. The Journal of Geology, 26(6), 532-541.

Ezell, A. W., & Hodges, J. D. (1995). Bottomland hardwood management: Species Site Relationships. MSU Extension Service Publication 2004.

Guyette, R. P., Stambaugh, M. C., Dey, D. C., & Muzika, R. M. (2012). Predicting fire frequency with chemistry and climate. Ecosystems, 15(2), 322-335.

Heinrich, P. V., (2008)_Loess Map of LA, Louisiana Geological Survey

Kochian, L. V., Pineros, M. A., & Hoekenga, O. A. (2005). The physiology, genetics and molecular biology of plant aluminum resistance and toxicity. In Root Physiology: From Gene to Function (pp. 175-195). Springer Netherlands.
Miller, B. J., Lewis, G. C., Alford, J. J. & Day, W. J. (1984) Loesses in Louisiana and at Vicksburg, Mississippi. Guidebook for Friends of the Pleistocene Field Trip.

Miller, B. J., Day, W. J., & Schumacher, B. A. (1986). Loesses and loess-derived soils in the Lower Mississippi Valley. Guidebook for soils-geomorphology tour.

Pettry, D. E., & Switzer, R. E. (1998). Sodium soils in Mississippi.

Rutledge, E.M., M.J. Guccione, H.W. Markewich, D.A. Wysocki, and L.B. Ward. 1996. Loess stratigraphy of the Lower Mississippi Valley. Engineering Geology 45: 167-183.

Saucier, Roger T. 1994. Geomorphology and Quaternary Geologic History of the Lower Mississippi Valley, Volume I & II. U.S. Army Corps of Engineers, Vicksburg, MS.

Theriot, R. F. (1992). Flood tolerance of plant species in bottomland forests of the southeastern United States.

United States Salinity Laboratory Staff, USA, USDA (1954), Diagnosis and improvement of saline and alkali soils, USDA Agriculture Handbook 60,1954, 160 pp.

Contributors

D. Charles Stemmans II