Natural Resources
Conservation Service
Ecological site NX118A01Y007
Seasonally Wet Terraces and Footslopes
Last updated: 9/22/2023
Accessed: 11/13/2024
General information
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.
MLRA notes
Major Land Resource Area (MLRA): 118A–Arkansas Valley and Ridges, Eastern Part
Major Land Resource Area 118A, Arkansas Valley and Ridges Eastern Part, is in Arkansas and Oklahoma. This MLRA is about 6,755 square miles (17,495 square kilometers). The Ozark National Forest and the northern portion of the Ouachita National Forest occur in this MLRA.
This area is mostly in the Arkansas Valley Section of the Ouachita Province of the Interior Highlands. Small areas in the southeast corner and the south-central part of the MLRA are in the Ouachita Mountains. This MLRA consists of long, narrow ridges and high flat-topped mountains capped with sandstone that trend northeastward. Crests are narrow and rolling on ridges, while broad and flat on mountaintops. The intervening valleys are broad and smooth. Elevations generally range from 310 feet (90 meters) to 760 feet (230 meters) with higher and lower elevations on the valleys and ridgetops.
The ridgetops and valleys in this MLRA are underlain by slightly folded to level beds of sandstone and shale of the Pennsylvanian age. The terrace deposits along the Arkansas River include a complex sequence of unconsolidated gravel, sandy gravel, sands, silty sands, silts, clayey silts, and clays. The individual deposits are commonly lenticular and discontinuous. At least three terrace levels are recognized with the lowest being the youngest.
The dominant soil orders in this MLRA are Ultisols. The soils in the area have a thermic soil temperature regime, a udic soil moisture regime, and mixed or siliceous mineralogy.
Ecological site concept
The Seasonally Wet Terraces and Footslopes ecological site is on hills and valleys along hillslopes, flood plains, and paleoterraces. This site has slopes between 0 and 5 percent with elevations ranging from 190 to 1,970 feet (57 to 600 meters). The soils associated with this site are deep to very deep and formed in alluvium derived from sandstone, siltstone, and shale. Important abiotic characteristics associated with this site are a greater than 18 percent clay content in the particle size control section, a root restrictive layer (clay) within 20 inches (50 cm) of the soil surface, redox reactions below 20 inches (50 cm), and an acidic pH decreasing in strength down the soil profile. A perched water table is present during winter and spring.
Associated sites
NX118A01Y008 |
Fluventic Flood Plain This ecological site is differentiated from the Seasonally Wet Terraces and Footslopes by landscape position and less than 18 percent clay in the particle size control section. |
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Similar sites
NX118A01Y003 |
Rarely Flooded Terrace This ecological site is differentiated from the Seasonally Wet Terraces and Footslopes by less than 18 percent clay in the particle size control section. |
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Table 1. Dominant plant species
Tree |
(1) Quercus |
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Shrub |
Not specified |
Herbaceous |
(1) Panicum virgatum |
Legacy ID
F118AY007AR
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Ecosystem states
T1A | - | Tree removal, brush management, plantation tree establishment and management. |
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T1B | - | Tree removal, mechanical and chemical woody vegetation suppression, tillage, introduce annual or perennial forage species. |
T2A | - | Woody species removal, prescribed fire, seeding, and grazing. |
T3A | - | Forage species suppression, brush management, plantation tree establishment and management. |
State 1 submodel, plant communities
1.1A | - | Less water during vegetation establishment. |
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1.2B | - | More water during vegetation establishment. |
1.2A | - | Less water during vegetation establishment. |
1.3A | - | More water during vegetation establishment. |
1.3B | - | More water during vegetation establishment. |