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Large parts of the upper Midwest, USA were impacted by permafrost during the Last Glacial Maximum (LGM). Even though permafrost persisted as the Laurentide Ice Sheet began to recede, direct age control of this interval is largely lacking. To better temporally constrain the permafrost interval in western Wisconsin, we identified two sites, outside the Late Wisconsin (MIS 2) glacial limit, that contain relict, ice‐wedge pseudomorphs, initially interpreted to be sand wedges, hosted within well‐drained outwash deposits. The pre‐Wisconsin (>MIS 5) host material commonly displays up‐turned bedding near the contact with the wedges, indicative of well‐formed features. The wedges are filled with well‐sorted, gravel‐free, medium and fine sands, and lack evidence of post‐formational disturbance, pointing to an aeolian sand infill and confirming them as sand wedges. Ventifacts on nearby uplands attest to windy conditions here in the past. Optically stimulated luminescence (OSL) ages on five sand wedges indicate that they filled with sand between c. 19.3 and 18.3 ka at the southerly site and between c. 15.1 and 14.7 ka at the northerly site, which is closer to the LGM margin. Sand wedges at the latter site were wider and had more complex morphologies, possibly suggesting a longer interval of formation and/or more intense permafrost. We also examined a site along a ridge crest, between the two wedge sites, which displayed interbedded loess and sand, dated by OSL to 12.7 ka. Together, these results point to dry, cold, windy conditions in west‐central Wisconsin, within 100 km of the LGM limit. At this time, aeolian sands were being transported across a landscape with (at least scattered) permafrost. The OSL results suggest multiple phases, or perhaps time‐transgressive, sand‐wedge formation, associated with permafrost between c. 19 and 15 ka, with dry, windy (and likely, cold) conditions persisting until at least 12.7 ka. [ABSTRACT FROM AUTHOR]

Although glossic horizons are widespread throughout the Great Lakes region (USA), any type of detailed empirical investigation of their genesis has not been conducted for decades. In this study, we investigated a well‐drained Haplic Glossudalf formed in calcareous till in northern Michigan and examined its glossic features across five stages of development, from nondegraded to completely degraded. Along this sequence, the glossic horizon is formed from a Bt horizon, then destroyed, evolving into an E horizon. Argillic horizon degradation is initiated from the top downward, along discrete percolation pathways. Here, temporary, highly localized, anoxic conditions favor the reduction and eluviation of Fe oxides associated with argillans. After Fe removal, clay, and to lesser extent fine silt, in the argillans become mobilized. This process results in bleached, E horizon interfingerings that penetrate the upper Bt horizon. Although eluviation of clay and fine silt is required for glossic horizon formation, their removal follows a distinct pathway from fine clay through coarse clay, and finally fine silt. This research documents the importance of redox processes at microsites in the upper Bt horizon as the destabilizing trigger for glossic horizon formation. Redox processes and microerosion may be more important than the traditionally accepted view of destabilization of clay floccules by loss of basic cations from the exchange complex. We also note that lessivage, as traditionally defined, in these soils is associated with not just clay translocation, but also fine silt. Core Ideas: The glossic horizon in this study has formed by degradation of an argillic horizon.Degradation is initiated by localized redox processes which facilitate loss of Fe oxides.Eluviation of Fe destabilizes materials in illuviation cutans, facilitating further translocation.Translocation can occur even if the exchange complex is saturated by basic cations.Temporally, the loss of materials follows the pathway fine clay–coarse clay–fine silt. [ABSTRACT FROM AUTHOR]

We examined the impact of three different sample preparation methods on bulk soil geochemistry data obtained from a hand‐held, portable X‐ray fluorescence (pXRF) spectrometer. We generated data from a soil core recovered from the surface, downward into unaltered loess, and into a buried soil at a site in eastern Iowa. Samples were scanned (i) directly from field‐moist soil cores; (ii) after drying, grinding, and being loosely massed in plastic cups; and (iii) as pressed‐powder pellets. Data derived using these methods were compared with data obtained from a standard benchtop X‐ray fluorescence (XRF) unit. Generally, the results indicated that data from pressed powder pellets often provide the best correlation to benchtop XRF data, although the results were sometimes element or compound specific. Calcium oxide, Fe2O3, and K2O generally provided the strongest correlations between pXRF‐ and XRF‐reported values; SiO2 data were more problematic. Field‐moist pXRF scans generally underestimated element concentrations, but the correlations between pXRF and benchtop XRF measurements were greatly improved after applying pXRF‐derived calibration standards. In summary, although element/compound data provided by pXRF showed significant relationships to benchtop XRF data, the results are improved with proper sample preparation (i.e., drying, grinding, pressing) and usually by calibrating the pXRF data against known standards. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) translocated from O horizons has been viewed as the main source of subsoil carbon (C) in Spodosols. However, recent studies in other soil types have concluded that little O horizon DOM reaches the subsoil directly. We investigated whether C derived from O horizons contributes to deep-soil C stores in six Spodosol profiles under coniferous (red pine) or deciduous (sugar maple) forests. We used spectroscopic, stable-isotope and pyrolysis-gas chromatography/mass spectroscopy analysis of DOM and solid phase soil samples to assess whether O horizon C was transported directly to deep soil horizons or had been exchanged with mineral soil organic matter (SOM) pools. All three approaches indicated that O horizons are the source of the majority of DOM entering B horizons, with little contribution from desorbed SOM. Despite a greater stock of O horizon C in red pine stands, there was no difference between forest types in the quantity of C delivered to B horizons (18 g C m-2 y-1). However, C derived from O horizons accounted for ~95% of the C entering B horizons in sugar maple stands, but only ~80% in red pine stands. Molecular analysis of DOM and SOM also showed a greater resemblance of B horizon SOM to DOM in sugar maple stands; however, it also clearly indicated the importance of microbial processing of input C in the formation of B horizon SOM. Our results demonstrate the strong connection between O horizons and deep soil C stocks in these sandy Spodosols and indicate that future changes in the quantity or quality of DOM entering the mineral soil have the potential to alter the delivery of surface C to depth. [ABSTRACT FROM AUTHOR]

This study was performed in the eastern Upper Peninsula of Michigan, where Spodosols are extremely well developed. We instrumented a Typic Durorthod with zero-tension lysimeters to capture water leaving the O, E, and B horizons and with sensors to determine volumetric water contents with depth. We also occasionally measured snowpack depths and determined snow water equivalents. These field data were used to validate a hydrologic model that was run for the site using nearby National Weather Service (NWS) data. Good agreement between the modeled output and field data from the site enabled us to apply 1961 to 2013 NWS data from three additional stations along a transect that spans the range of podzolization strength in Michigan as inputs to the model. Soils remain dry throughout the summer and slowly wet up in fall. The more strongly developed soils in the north are slightly wetter in fall, facilitating breakdown of fresh litter and enhancing production of soluble organic materials. Their translocation into the mineral soil is presumably deepest and most pronounced during snowmelt, facilitated by a strong "pulse" of cold snowmelt water. This pulse comprises well over half of the annual flux of water at 100-cm depth, even though its timespan is short. Snowmelt fluxes are larger and of shorter duration in the north, where podzolization is strongest. By storing precipitation in a thick snowpack, the pedogenic system compresses inputs of water, creating deeper, more concentrated pulses of percolation when soluble organic materials are readily available; this is the essence of podzolization in this region. [ABSTRACT FROM AUTHOR]

Hillslope position has long been important in soil geomorphology. At the scale of county-level soil maps, more soil boundaries are based on topography than any other soil-forming factor. However, the inability to accurately delineate topographic breaks across hillslope--either due to lack of sufficient topographic resolution or the proper technology to develop and/or model them--hinders soil mapping efforts. In this research, we developed a decision tree model for classifying hillslope position, which was calibrated and validated using the observations of soil scientists in the field. Different decision tree structures were tested with classification breaks based on calibration groups' mean midpoints, median midpoints, and fuzzy membership. The final model objectively and quantitatively classifies the five major hillslope positions and performs well on different landscapes, making it suitable for efficient application to large areal extents. The resulting maps of hillslope position represent base maps that can be used to (i) improve research on toposequences by providing explicit definitions of each hillslope element's location, (ii) facilitate the disaggregation of soil map unit complexes, and (iii) identify map unit inclusions that occur due to subtle topographic variation. Base maps developed by the model can also help identify areas of possible inaccuracies in soil maps, especially where soil boundaries cross topographic breaks. Predictions from the model enable the mapper to better place soil map unit boundaries at locations where defendable landscape breaks exist. [ABSTRACT FROM AUTHOR]

Precision, particularly in terms of repeatability in particle size analysis (PSA), has recently resurfaced as an issue due to the increased use of laser PSA for PSA. Because laser diffractometry produces much more detailed data than does traditional pipette analysis, and because a much smaller sample is used in the analysis, precision or repeatability of laser-produced PSA data is a legitimate concern. For example, of the 1485 soil samples analyzed in our study, most of which are silty or loamy and each of which was analyzed at least twice, 11.5% changed texture class, from the first to the second PSA measurement. Statistical analysis of these paired, subsample data was therefore used to establish a standard for normal variance among the subsamples, as a test of precision. Subsample pairs with an absolute cumulative bin difference (CBD) of <1 SD above the population's mean CBD were determined to have acceptable precision. This approach provides both a simple method for assessing the variation in PSA data sets and establishes a comparable standard for determining when additional measurements are needed to find a more precise result. Researchers may be tempted to simply use mean PSA data for samples that have been run multiple times. However, we found that using the per bin mean for only the two best matching subsamples was the optimal approach. Our analysis also indicates that, as particle size gets coarser (at least within silty/loamy samples), the precision of laser-generated particle size data generally decreases. [ABSTRACT FROM AUTHOR]

Understanding the spatial and temporal variation in soil temperatures is important to classification, land use, and management. To that end, mean annual soil temperature (MAST) data for Wisconsin and Michigan were modeled to (i) determine the effects of the Great Lakes and their snowbelts on soil temperatures, and (ii) better estimate the location of the boundary between the mesic and frigid soil temperature regimes in this region. The location of the mesic-frigid (M-F) line is particularly difficult to determine where east-west gradients in air temperature cross north-south trends in snowfall due to Lake Michigan. Additionally, the soil temperature regime of several Great Lakes' peninsulas near the M-F line is in question. To determine the accuracy of our soil temperature model, soil temperature data output from it were compared with data derived from thermocouples implanted in soils at 39 sites in northern Michigan that bad been collecting data several times daily for more than 6 yr. Error statistics for the model show that it has essentially no mean bias when examined on an annual basis or for winter, and only a bias of 0.1°C for the warm season. The M-F line in Wisconsin and Michigan is slightly north of most previously estimated locations, and is strongly influenced by the snowbelt in southern Michigan. Soils in deep snow areas stay warmer in winter than do soils inland, increasing their MAST and forcing the M-F line north of where air temperatures alone might have placed it. Lake-effect areas also stay cold longer into the spring season, and cool down more slowly in fall. Soil temperatures in these areas are, therefore, more moderated on an annual basis, as indicated by coefficients of variation. [ABSTRACT FROM AUTHOR]

The evolution of fragipans in the Great Lakes region is poorly understood despite the common occurrence of fragipans in the region. To help resolve this problem, three soils with fragipans in northern Michigan were studied to evaluate the pedogenic pathways for fragipan evolution, and the results extended in soils forming under similar conditions. Soil characterizations were made via field, physical, chemical, and micromorphological observations and analyses and were evaluated in terms of the major models of fragipan genesis. Because it appears that a combination of pedogenic models best explains many of the fragipan properties of our soils, while also allowing for their variable expression, we developed a new model—one that integrates and synthesizes existing models and our findings—to explain fragipan evolution for many soils in Michigan and the Great Lakes region. The Michigan Model of Frugipan Evolution (MMFE) is therefore a synthesizing rondel that involves the self-weight collapse of a wet soil or parent material, followed by physical ripening of the collapsed zone. Ripening helps to retain the closely packed fabric and intergrain bridging in the collapsed zone, creating a protofragipan. Later, amorphous bonding agents precipitate in the protofragipan due to its position near a weathering-front discontinuity. The resulting fragipan develops progressively and becomes better expressed with further pedogenesis. Fragipan degradation is eventually initiated by an in- creasingly prominent, perched zone of saturation that forms seasonally above the fragipan. With time, processes associated with fragipan degradation and translocation of materials to lower paris of the profile exceed processes associated with progressive development, and the fragipan is destroyed. [ABSTRACT FROM AUTHOR]

Many of Michigan's loamy soils exhibit varying degrees of fragipan expression, which may be variously influenced by their parent materials. We examined three soils in northern Michigan with varying degrees of fragipan expression to assess development of fragipans formed in acidic and calcareous glacial drift. To accomplish this, soil characterizations were made through field, physical, chemical, and micromorphological observations and analyses. The soils have bisequal horizonation: an upper sequum associated with podzolization processes and lower sequum associated with lessivage. Protofragipans and fragipans are found only in the lower sequum. The soils experience periodic episaturation and contain at least one lithologic discontinuity, often near the protofragipan or fragipan. The protofragipan and fragipans have loamy sand to loam textures, weak platy to subangular blocky structure, higher bulk densities (1.5–1.9 g cm-3) and lower pH values (4.8–6.8) than adjacent horizons, brittle failure, and fine vesicular pores. Eluvial protofragipan and fragipan horizons contain albic materials that tongue into underlying argillic horizons, Illuvial fragipans exhibit clay coats, flows, and bridging. Thin-section characterizations confirm the presence of closely packed fabrics, intergrain bridging by clays, and void pedofeatures. Scanning electron microscopy (SEM) provides evidence of eluviation, reorganization of silt and clay, fluctuating redox conditions, degraded void pedofeatures, and the presence of surficially amorphous (bonding) materials in the protofragipan and fragipans. Soil extraction data do not preclude the presence of a fragic- property (brittleness) agent. Results, therefore, indicate that these protofragipans and fragipans are pedogenic and can form, with vari- able expression, in both acidic and calcareous glacial parent materials. [ABSTRACT FROM AUTHOR]

Investigates the patterns of soil development in Michigan. Effects of vegetation and fire frequency on soil development; Association of soil development with climatic parameters and vegetation; Importance of snowmelt infiltration on podzolization.

Focuses on a study conducted on soil development in Baraga County, Michigan to identify the influence of geomorphic aspects as a means of explaining within-landform variability. Reference to the Baraga County Soil Survey; Effects of slope gradient on soil development; How soil is affected by slope aspect; Results of the survey.

Discusses the characterization of secondary carbonates in three alfisols in Michigan. Relation of secondary carbonates to ustic soil moisture regimes; Possible genetic explanations; Determination of the presence of calcic horizons.

BSTRACT: Soil water was monitored by neutron scattering in six soils, three each within two drainage catenas in east-central Illinois, over a 15-month time span. The prairie soils have formed in: (1) 76-152 cm of silt loam, eolian sediments (bess) over glacial till (Catlin-Flanagan-Drummer catena), and (2) bess greater than 152 cm in thickness (Tama-Ipava-Sable catena). We characterized the water content of these soils over the total time span and for wet and dry climatic subsets, as an aid to potential irrigation decisions. Soils of the thin bess, C-F-D catena dried out to lower water contents and had greater soil water variability than did the thick bess soils. Under wet conditions, soil water contents in the two catenas were quite similar. Alleviation of surface and subsurface drying via irrigation would thus be more advantageous to yields on the C-F-D soils than on the T-I-S soils. [ABSTRACT FROM AUTHOR]