Hole, Francis Doan, 1913-2002 / Soils of Wisconsin
Chapter 6 introduction to the soil associations of Wisconsin, pp. 49-50
A soil association is a geographic assemblage of soils. Any ac- count of the soil associations (i.e., soilscapes, page 4; see Buol, Hole, and McCracken, 1973) of a region must take the soil series of that region into consideration. The list of kinds of soils present in Wisconsin is still incomplete, for several reasons: First, detailed observations have not been made in many areas, particularly in northern counties; second, the process of classify- ing the soils and correlating them with those of adjacent states is still in progress; finally, changes in soils brought about by land use have not been adequately observed, recorded, and eval- uated. Even so, the current list of soil series is impressive, as rep- resented in Part III. A soil association name, such as Tama, Ashdale, Downs, and Muscatine silt loam (Al), tells what kinds of soils are grouped in a repeating pattern in a particular land- scape. In this discussion several soil terms that are somewhat analogous to plant ecological terms are used. Some Analogous Terms Pertaining to plant ecology botany (plant science) phytosphere vegetation of a region flora of a region sequence of plant communities down-slope xeric I mesic hydric Pertaining to soil ecology pedology (soil science) pedosphere soil continuum of a region total list of soil series, types, and phases ('pedota) of a region excessively drained soil association well drained (soilscape) poorly or very poorly drained The pedosphere is the continuum of soils on the land portions of the lithosphere. Within a particular region the soil continuum is a mosaic of soilseapes in which the soil species, called soil series, types, and phases, are present in certain proportions and arrangements. We might coin a new collective term, pedota, for the soil species of a region. Soil continuum and pedota differ from each other in a quantitative way. The pedota is the total list of soil species present, regardless of the numerical abundance of each.' The soil continuum, on the other hand, has to do with combinations of species present in a given region and with the relative abundance of each species (Hole, 1953). For this pur- pose, the common species are far more important than the rare ones. The presence or absence of the latter may be of little sig- nificance in the functioning of the landscape, though it may be highly significant as a record of past environments. The basic task of identifying and describing the soil series is arduous, and is still in progress. 1. One body of a rare species can contribute as much to the pedotal list as thousands of bodies of a common species. In actual practice, soil species are not listed in county soil survey reports unless they occupy more than 500 to 1,000 acres. Therefore, considerable information about unusual soils is not generally available. For example, in soil association G25, in Sec. 16, T.37N., R.1OE. in Oneida County, a small body of a red (2.5YR 4/4, moist) silt loam 50 cm thick over a sandy loam fragipan resting on acid outwash sand was observed along Gude- gast Creek. The soil map (Hole and Schmude, 1959) includes the area in Peat-Au Gres soils, nearly level. The red soil remains unnamed and is not described in the soil survey report. CHAPTER 6 Introduction to the Soil Associations of Wisconsin Most soilscapes in Wisconsin include soils of both good and poor natural drainage status, and were originally covered by a vegetative sequence from a mesic or even xeric plant community toahydric one, i.e., afen, wet meadow, orbog. Hence, soils that are very different occur side by side on the land. Fig. 5-1 was de- signed to indicate this. Crop production is known to vary from one soil member of a soil association to another. Natural plant communities are so rare, particularly in well-drained uplands, that correlation of properties of soil profiles and native vegeta- tion has been difficult. A serious attempt to do this was made in the forests of the Menominee Indian lands (Milfred, Olson, and Hole, 1967). The soil map (Plate 1) is cartographically generalized, but with a legend that is detailed to the soil series level. This map shows the major broad pedological features of the state and serves as an introduction to detailed soil maps (see list, Appen- dix 5) and to the actual soil bodies themselves. The 190 associations (Al through JiS) listed in the legend of the soil map are distinctive, though in varying degrees. Several examples will illustrate this. The level landscape of the Antigo Flats in Langlade County is occupied by an association of soils, the principal three of which are named Antigo silt loam, Brill silt loam, and Onamia loam. This grouping is labeled F25 on the soil map, not only in Langlade County, but wherever it occurs in northern Wisconsin (Figs. 12-2, 13-3, 13-5). The Baraboo silt loam and Skillet silt loam soil association (A 10) is extensive in portions of the Baraboo Hills of Sauk County. The Horicon Marsh in Dodge County is a large body of peat rimmed with wet mineral soils. This soil association (slightly acid to alkaline sedge and woody peat and muck soils; Pella, Poygan, and Brookston silt loam and silty clay loam) is labeled 115 on the soil map. In the drumlin field of Dodge County, well-drained soils of drum- lins are associated in the landscape with linear bodies of wet soils between the hills. This is soil association B13, Miami, Dodge, and Pella silt loam association. The exact proportions of soils present in each soil association are, with few exceptions, un- known at present and therefore cannot be tabulated in this report. Each soilscape has a characteristic fabric. Soilscape fabric analysis is under study by the author and coworkers, and results will be reported elsewhere. In brief, the study concerns soil body patterns as they occur in loops, whirls, and stripes in the land- scape. Many of the soilseapes, like the four examples just given, are recognizable from the window of a vehicle during a trip across 49
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