Federal Register / Vol. 56. No. 157 / Wednesday. August 14. 1991 / Proposed Rules 40459 



They include sandy soils of riverine 

 ^ islands, bars, and banks and finer- 

 9 textured soils of floodplain terraces. 



Wet entisols have an aquic or peraquic 

 moisture regime and are considered 

 hydric soils, unless effectively drained. 

 Some Entisols are easily recognized as 

 hydric soils such as the Sulfaquents of 

 tidal salt marshes and Hydraquents, 

 whereas others pose problems because 

 they do not possess typical hydric soil 

 field indicators. Wet sandy Entisols 

 (with loamy fine sand and coarser 

 textures in horizons within 20 inches of 

 the surface) may lack sufficient organic 

 matter and clay to develop hydric soil 

 colors. When these soils have a hue 

 between lOYR and lOY and distinct or 

 prominent mottles present, a chroma of 

 3 or less is permitted to identify the soil 

 as hydric (i.e.. an aquic moisture 

 regime). Also, hydrologic data shovmig 

 that the soil is flooded or ponded enough 

 to be wetland are sufficient to verify 

 these soils as hydria Sandy Entisols 

 must have positive indicators of 

 hydrology (see positive indicators for 

 sandy soils for your region) in the upper 

 6 inches and have colors of the loamy 

 fine sand or coarser Aquents. Soils that 

 key to the aerie suborder or have colors 

 of the aerie suborder within 12 inches 

 ^ are not considered hydric soils. Other 

 " Entisols are considered hydric if they 

 classify in the aquic suborder and have 

 the colors as listed for soils that are 

 finer than loamy fine sand in some or all 

 layers to a depth of 12 inches. Soils that 

 key to the aerie subgroup or have aerie 

 colors above 12 inches as listed for 

 Aquent subgroups are not hydric. 



Hydric Mollisols (Prairie and Steppe 

 Soils) 



Mollisols are dark colored, base-rich 

 soils. They are common in the central 

 part of the conterminous U.S. from 

 eastern Illinois to Montana and south to 

 Texas. Natural vegetation is mainly tall 

 and mid grass prairies and short grass 

 steppes. These soils typically have deep, 

 dark-colored surface (mollic epipedons) 

 and subsurface layers that have color 

 values of less than 4 moist and 

 commonly have chromes of 2 or less. 

 The low chroma colors of Mollisols are 

 not necessary due to wetness of periods 

 of saturation. They are rich in organic 

 matter due largely to the vegetation 

 (deep roots) and reworking of the soil 

 and organic matter by earthworms, ants, 

 moles, and rodents. The low chroma 

 colors of Mollisols are not necessarily 

 ^ due to prolonged saturation, so be 



particularly careful in making wetland 

 determinations in these soils. Many 

 Great Groups of aquic Mollisols do not 

 have aerie subgroups. Therefore, if a 

 MoUisol is classified as an AquoU, 



special care is needed to determine if it 

 is hydric. There are two suborders of 

 MoUisols that have aquic moisture 

 regimes: Albolls and AquoUs. AlboUs 

 have an albic horizon that separates the 

 surface layer from an argillic or natric 

 horizon. The albic horizon must have 

 chromas of 2 or less or the albic argillic. 

 or natric horizons must have 

 characteristics associated v/ith wetness 

 such as mottles, iron-manganese 

 concretions larger than 2 mm or both. 

 All Albolls are considered hydric soils. 

 Aquolls exhibiting regional hydrology 

 characteristics for Mollisols in the upper 

 part are considered hydric. 



Hydric Oxisols 



These soils are highly weathered, 

 reddish, yellowish, or grayish soils of 

 tropical and subtropical regions. They 

 are mixtures of quartz, kaolin, free 

 oxides, and organic matter. For the most 

 part they are nearly featureless soils 

 without clearly distinguishable horizons. 

 Oxisols normally occur on stable 

 surfaces and weathering has proceeded 

 to great depths. To be hydric these 

 normally red-colored soils are required 

 to have chromas 2 or less immediately 

 below the surface layer, or if there are 

 distinct or prominent motties, the 

 chroma is 3 or less. They also qualify as 

 hydric if they have continuous plinthite 

 within 12 inches of the surface. 



Hydric Spodosols (Evergreen Forest 

 Soils) 



These soils, usually associated with 

 coniferous forests, are common in 

 northern temperate and boreal regions 

 of the U.S. and along the Gulf-AUantic 

 Coastal Plain. Spodosols have a gray 

 eluvial E-horizon overlying a diagnostic 

 spodic horizon of accumulated 

 (sometimes weakly cemented) organic 

 matter, aluminum, and iron (U.S.DA. 

 Soil Survey Staff 1975). A process called 

 podzolization is responsible for creating 

 these two soil layers. Organic adds 

 from the leaf litter on the soil surface are 

 moved downward through the soil with 

 rainfall, cleaning the sand grains in the 

 first horizon (the E-horizon) then coating 

 the sand grains with organic matter and 

 iron oxides in the second layer (the 

 spodic horizon). Certain vegetation 

 produce organic acids that speed 

 podzolization including eastern hemlock 

 (Tsuga canadensis), spruces (Picea spp.), 

 pine (Pinus spp.), larches (Larix spp.), 

 and oaks (Quercus spp.) (Buol, et al. 

 1980). The E-horizon or Albic horizon by 

 definition has a chroma of 3 or less and 

 is often mistaken for a gleyed layer by 

 the novice. These Spodosols must have 

 one of the positive regional hydrology 

 indicators and meet the color 

 requirement for Aquods listed in "Soil 



Taxonomy." Hydric Spodosols that have 

 a thick (more than 12 inches) sandy 

 epipedon are extremely harder to 

 identify especially in the Gulf-Atlantic 

 Coastal Plain. These soils must also 

 meet the color requirements for the 

 Aquod suborder and meet one of the 

 regional hydrology indicators for sandy 

 soils. 



Hydric Vertisols (Shrink and Swell 

 Soils) 



These soils are dark-colored clayey 

 soils that are extensive in the Great 

 Plains, in the southern U.S., and in parts 

 of California. They develop vnde, deep 

 cracks when dry and swell shut, when 

 wet. Many Vertisols exhibit gilgai 

 microtopography with swells and 

 swales or mounds and hollows. The 

 morphology of these soils may be 

 distinctly different on the mound and in 

 the hollow. They commonly have thick 

 dark-colored surface layers because of 

 the churning action created by the 

 shrinking and swelling clays. During wet 

 periods, they aie very slowly permeable 

 and may pond water on the surface of 

 the micro-hollows, but in dry periods 

 they are rapidly permeable with water 

 travelling along the deep cracks to lower 

 layers. These soils must meet one of the 

 regional hydrology indicators for 

 Vertisols to qualify as hydric 



Hydric Soils Derived From Red Parent 

 Material 



Hydric mineral soils derived from red 

 parent materials (e.g^ weathered clays. 

 Triassic sandstones, and Triassic 

 shales) may lack the low chroma colors 

 characteristic of most hydric mineral 

 soils. In these soils, the hue is redder 

 than lOYR because of parent materials 

 that remain red after dtrate-dithionlte 

 extraction, so the low chroma 

 requirement for hydric soil is waived - 

 (U.S.Dj\. Soil Conservation Service 

 1982). Red soils are most conunon along 

 the Gulf-Atlantic Coastal Plain 

 (Ultisols), but are also found in the 

 Midwest and parts of the Southwest and 

 West (Alfisols). in the tropics, and in 

 glacial areas where older landscapes of 

 red shales and sandstones have been 

 exposed. In southern New England, red 

 parent material hydric soils are derived 

 from reddish sandstone, shale, 

 conglomerate, or basalt These soils 

 include the following series: Meno 

 (Aerie Haplaquepts), Wilbraham (Aquic 

 Dystrochrepts), Lim (Aerie Fluvaquents), 

 and Bash (Fluvaquentic Dystrochrepts). 

 In the absence of diagnostic hydric soil 

 properties, more weight must be placed 

 on the vegetation and hydrology. 



