40458 Federal Register / Vol. 58, No. 157 / Wednesday. August 14, 1991 / Proposed Rules 



gray layers (E-horizons) immediately 

 below the surface layer that are gray for 

 reasons other than saturation, such as 

 leaching due to organic acids (see 

 Spodosols below). 



Mineral soils that are alternately 

 saturated and oxidized (aerated) during 

 the year are usually mottled in the part 

 of the soil that is seasonally weL 

 Mottles are spots or blotches of different 

 colors or shades of colors interspersed 

 with the dominant (matrix) color. The 

 abundance, size, and color of the 

 mottles usually reflect the hydrology — 

 the duration of the satiu-adon period, 

 and indicate whether or not the soil is 

 satuj-ated for long periods. Mineral soils 

 that are predominantly grayish with 

 common or many, distinct or prominent 

 brown or yellow mottles are usually 

 saturated for long periods during the 

 growing season and are hydric soils. 

 Soils that are predominantly brown or 

 yellow with gray mottles are saturated 

 for shorter periods and may be hydric 

 depending on the depth to the gray 

 mottles and the color of the overlying 

 layer. Mineral soils that are never 

 saturated are usually bright-colored and 

 are not mottled; they are nonhydric soils 

 (Tiner and Veneman 1987). Realize, 

 however, that in some hydric soils, 

 mottles may not be visible due to 

 masking by organic matter (Parker, et aJ. 

 1984). 



It is important to note that the 

 gleization and mottle formation 

 processes are strongly influenced by the 

 activity of certain soil microorganisms. 

 These microorganisms reduce iron when 

 the soil environment is anaerobic that 

 is, when virtually no free oxygen is 

 present, and when the soil contains 

 organic matter. If the soil conditions are 

 such that free oxygen is present, organic 

 matter is absent, or temperatures are too 

 low (below 41 degrees Fahrenheit) to 

 sustain microbial activity, gleization vriH 

 not proceed and mottles vriil not form, 

 even though the soil may be saturated 

 for prolonged periods of time (Diers and 

 Anderson 1984). Soil colors as discussed 

 above often reveal much about a soil's 

 historical wetness over the long term. 

 Scientists and others examining the soil 

 can determine the approximate soil 

 color by comparing the soil s£unple with 

 a Munsell soil color chart. The 

 standardized Munsell soil colors are 

 identified by three components: Hue, 

 value, and chroma. The hue is related to 

 one of the main spectral colors: red, 

 yellow, green, blue, or purple, or various 

 mixtiu'es of these principal colors. The 

 value refers to the degree of lightness, 

 while the chroma notation indicates the 

 color strength or purity. In the Munsell 

 soil color book, each individual hue has 



its ov^ page, each of which is further 

 subdivided into imits for value (on the 

 vertical axis) and chroma (horizontal 

 axis). Although theoretically each soil 

 color represents a unique combination 

 of hues, values, and chromas, the 

 number of combinations common in the 

 soil environment usuedly is limited. 

 Because of this situation and the fact 

 that accurate reproduction of each soil 

 color is expensive, the Munsell soil color 

 book contains a limited number of 

 combinations of hues, values, and 

 chromas. The color of the soil matrix or 

 a motUe is determined by comparing a 

 soil sample with the individual color 

 chips in the soil color book. The 

 appropriate Munsell color name can be 

 read from the facing page in the 

 "Munsell Soil Color Charts" 

 (Kollmorgen Corporation 1975). Chromas 

 of 2 or less are considered low chromas 

 and are often diagnostic of hydric soils. 

 Low chroma colors include black, 

 various shades of gray, and the darker 

 shades of brown and red. 



Gleying (bluish, greenish, or grayish 

 colors) in or immediately below the A- 

 horizon is an indication of a markedly 

 reduced hydric soil and an area that 

 should meet wetland hydrology in the 

 absence of significant hydrologic 

 modification. Gleying can occiu- in both 

 mottled and unmottied soils. Gleyed soil 

 conditions can be determined by using 

 the gley page of the "Munsell Soil Color 

 Charts" (Kollmorgen Corporation 1975). 

 Note: gleyed conditions normally extend 

 throughout saturated soils. Beware of 

 soils with gray subsoils due to parent 

 materials, soils with gray e-horizons or 

 albic horizons due to leaching and not to 

 saturation; these latter soils can often be 

 recognized by bright-colored layers 

 below the e-horizon. (See "Atypical 

 Hydric Soils" below.) 



Mineral soils that are saturated for 

 substantial periods of the grov/ing 

 season, but are unsaturated for some 

 time, commonly develop mottles. Soils 

 that have brightly colored mottles and a 

 low chroma matrix are indicative of a 

 fluctuating water table. 



The following color features in the 

 horizon immediately below the A- 

 horizon (or E-horizon. albic horizon) 

 provide evidence of soil saturation 

 sufficient to be hydric soils and should 

 also meet the weUand hydrology 

 criterioru 



(1) Matrix chroma of 2 or less in 

 mottled soils, or 



(2) Matrix chroma of 1 or less in 

 unmottied soils. 



Note: Mollisols have value requirements of 

 4 or more as well as chroma requirements for 

 aquic suborders. (See "Atypical Hydric Soils" 

 below.) 



The chroma requirements above are 

 for soils in a moistened condition. 

 Colors noted for dry (unmoistened) soils 

 should be clearly stated as such. The 

 colors of the topsoil (A-horizon) are 

 often not indicative of the hydrologic 

 situation because cultivation and soil 

 enrichment affect the original soil color. 

 Hence, the soil colors below the A- 

 horizon (and E-horizon. if present) 

 usually must be examined. 



Note: Beware of hydric soils that have 

 colors other than those described above. [See 

 "Atypical Hydric Soils" below.) 



Diuing the oxidation-reduction 

 process, the iron and manganese in 

 solution in saturated soils are 

 sometimes precipitated as oxides into 

 concretions or soft masses upon 

 exposure to air as the soil dries. 

 Concretions are local concretions of 

 chemical compounds (e.g., iron oxide) in 

 the form of a grain or nodule of varying 

 size, shape, hardness, and color 

 (Buckman and Brady 1969). Manganese 

 concretions are also usually black or 

 dark brown, while iron concentrations 

 are usually yellow, orange or reddish 

 brown. In weUands, these concretions 

 are also usually accompanied by soil 

 colors as described above. 



Atypical Hydric Soils 



Some hydric soils are soils lacking 

 diagnostic hydric soil properties or soils 

 that may look like hydric soils in terms 

 of soil color, but whose color is not the 

 result of excess wetness. 



Presumably, the area in question has 

 been located on a soil survey map that 

 identified it as a hydric component of a 

 map unit on the coimty list of hydric soil 

 map units or if no maps are available, 

 soil properties (matrix colors) that 

 appear to contradict landscape position 

 (e.g., red-colored soils in obvious 

 depressions or gray-colored soils in 

 obvious uplands) have been observed. 

 Atypical Hydric soils are discussed 

 below. 



To determine whether the area in 

 question is weUand, emphasis will be 

 placed on vegetation and signs of 

 hydrology, yet always consider 

 landscape position in assessing the 

 likelihood of wetland in these situations. 



Hydric Entisols (Floodplain and Sandy 

 Soils) 



Entisols are usually young or recenUy 

 formed soils that have litUe or no 

 evidence of pedogenically developed 

 horizons (U.SJD.A. Soil Survey Staff 

 1975). These soils are typical of 

 floodplains throughout the U.S., but are 

 also found in glacial outwash plains, 

 along tidal waters, and in other areas. 



