The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Michael J. Vepraskas - One of the best experts on this subject based on the ideXlab platform.
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Interpreting morphological features in wetland Soils with a hydrologic model
CATENA, 2008Co-Authors: Michael J. Vepraskas, Peter V. CaldwellAbstract:Abstract Wetlands in the United States are protected by law and are identified by their Hydric Soils, wetland hydrology, and vegetation. Hydric Soils are easily identified by color characteristics termed Hydric Soil field indicators, that form under saturated and anaerobic conditions, but wetland hydrology is difficult to assess. This study determines how often seven Hydric Soil field indicators met wetland hydrology requirements which require a water table be within 30 cm of the surface for 14 days or more during the growing season in over half the years. Studies were conducted at five sites in North Carolina in both wetland and upland plots. Soils ranged from Aquic Paleudults to Typic Haplosaprists across all sites. The water-table simulation model DRAINMOD was calibrated to Soil conditions in individual plots. Long-term rainfall data were used with the calibrated models to compute 40 years of daily water table data to represent both wet and dry years. It was found that the Hydric Soils with field indicators composed of organic materials in layers over 20 cm thick (Histosol and Histic epipedon field indicators) met wetland hydrology requirements each year, and in addition were ponded with water for periods between 67 to 139 days on average each year during the growing season. Plots in mineral Soils having the Dark Surface (S7) indicator as well as the Sandy Mucky Mineral (S1) indicator also met the saturation requirements for wetland hydrology every year, and were ponded for only 3 days per year on average. Other mineral Soils with an Umbric Surface (F13) or a Depleted Matrix (F3) field indicator met wetland hydrology requirements in approximately 95% of the years, and had water tables within 30 cm of the surface for 40 days per year on average. The Redox Depressions (F8) field indicator occurred in a small depression that was saturated for 87% of the year for periods averaging approximately 30 days. These results showed that Hydric Soil field indicators can be calibrated to long-term water table data that will allow precise assessments of wetland hydrology on-site.
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DYNAMICS OF REDOXIMORPHIC FEATURE FORMATION UNDER CONTROLLED PONDING IN A CREATED RIVERINE WETLAND
Wetlands, 2006Co-Authors: Michael J. Vepraskas, Jimmie L. Richardson, John P. TandarichAbstract:Abstract Hydric Soils are identified on-site using morphological features called “field indicators”. It is not known how long it takes for these indicators to form, nor whether they occur in created wetlands inundated for approximately 5% of the growing season, which is the minimum duration needed to meet wetland hydrology requirements. This study evaluated formation of redoximorphic features and Hydric Soil field indicators under field conditions following controlled, short-term floods that produced ponding events. A flood plain was constructed along an artificial stream channel (100-m long) where flooding was controlled by dams at each end of the channel. Floodwaters inundated Soils on the flood plain nine times over a 3-year period. Ponded water was kept on the Soils for periods ranging from 4 to 44 days. During ponding events, Fe2+ concentrations were approximately 1 to 4 mg/L, which indicated that the Soils were anaerobic and undergoing Fe reduction. Redox depletions formed in A horizons following a ...
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Calibrating Hydric Soil Field Indicators to Long-Term Wetland Hydrology
Soil Science Society of America Journal, 2004Co-Authors: Michael J. Vepraskas, David Lindbo, R. W. SkaggsAbstract:Jurisdictional wetlands are required to be saturated to the surface for 5% or more of the growing season in 5 out of 10 yr, but practical field methods for confirming this are lacking. This study determined whether Hydric Soil field indicators were related to wetland hydrology requirements. Water table levels were monitored daily for 2.5 yr in a toposequence of nine Soil plots that included well to poorly drained members (Oxyaquic Paleudults and Typic Albaqualfs). Monitoring data were used to calibrate a hydrologic model that simulated water table levels from inputs of hourly rainfall data. Forty years of rainfall data were then used with the model to compute long-term daily watertable levels in each plot. These data were summarized as saturation events, which are the frequency that water tables were at or above preselected depths for at least 21 d. Twenty-one days was the average period needed for Fe reduction to begin in these saturated Soils. This condition must occur for Hydric Soil field indicators to form. Regression equations were developed to relate saturation events to percentages of redoximorphic features. The r 2 values for relationships between percentages of redoximorphic features and saturation events were >0.80 for depths of 15 cm, and >0.90 for depths between 30 and 90 cm. Results showed that the depleted matrix field indicator, in which redox depletions occupy >60% of the horizon, occurred in Soils that were saturated for 21 d or longer at least 9 yr out of 10. This indicated the depleted matrix indicator occurred in Soils that were saturated nearly twice as long, and more frequently, than the minimum requirements needed to meet wetland hydrology requirements.
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Predicting Long-Term Wetland Hydrology From Hydric Soil Field Indicators
2002Co-Authors: Michael J. Vepraskas, David Lindbo, R. Wayne SkaggsAbstract:Frequency and duration of saturation data are used to evaluate a Soil's suitability for on-site waste disposal as well as to determine whether a site is in a jurisdictional wetland. Such data can be acquired from hydrologic models if the models are calibrated for individual sites. The principal objective of this study was to calibrate Soil color patterns, specifically percentages of redoximorphic features, to long-term water table fluctuations in two toposequences in the NC Coastal Plain. Water table levels were monitored for up to 3 yrs. in 22 Soil plots of the two toposequences. Plots were arranged in transects that extended from well (Typic Paleudults) or moderately well (Aquic Paleudults) to very poorly drained Soils (Umbric Paleaquults). Percentages of redoximorphic features were estimated in 15 cm depth increments to a depth of 90 cm in each plot. The hydrologic model, DRAINMOD was calibrated for each Soil plot using the record of daily water table levels, in situ saturated hydraulic conductivity, Soil water characteristic, depth to impermeable layer, depth of rooting, and rainfall. The calibrated DRAINMOD models were used along with historic rainfall data to estimate the number of times each Soil plot experienced saturation events lasting 21 days or longer for a 40-yr. period. Percentages of redoximorphic features (i.e. gray and red colors) were significantly correlated (r2 > 0.80) with average number of saturation events across all Soils for individual depths of 45, 60, 75 and 90 cm. Highest correlations (r2 values > 0.87) were found for relationships between redox depletions and saturation events during the growing season. The Hydric Soil field indicator the "depleted matrix" occurred in layers that were saturated for 2 1 to 4 1 days every year during the 40-yr. period considered.
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A field method for determing percentage of coated sand grains
Soil Science Society of America Journal, 2001Co-Authors: David Lindbo, Michael J. Vepraskas, F. E. RhotonAbstract:Several USDA-NRCS Hydric Soil field indicators require estimation of the percentage of organic-coated sand grains (black grains). For example, to meet the Dark Surface field indicator the Soil layer must contain at least 70% coated (black) grains. Field experience has shown that the estimation of the percentage of coated sand grains is often subjective and highly variable from one Soil scientist to another. In order to overcome this variability a set of standards was created using a mixture of black and light gray (representing uncoated grains) sand grains. Weighing out each component for the desired ratio and mixing them in a 47-mm-diam. petri dish we made a set of three standards consisting of 50, 70, and 90% black grains. To test the effectiveness of these standards, Soil scientists estimated the percentage of coated grains from similarly prepared samples first without the use of the standards and then with the use of the standards for comparison. Individuals improved the accuracy of their estimates by 10 to 60% and their Hydric Soil identification by 16%. The standards are easily prepared, easy to use, and portable.
Peter V. Caldwell - One of the best experts on this subject based on the ideXlab platform.
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Interpreting morphological features in wetland Soils with a hydrologic model
CATENA, 2008Co-Authors: Michael J. Vepraskas, Peter V. CaldwellAbstract:Abstract Wetlands in the United States are protected by law and are identified by their Hydric Soils, wetland hydrology, and vegetation. Hydric Soils are easily identified by color characteristics termed Hydric Soil field indicators, that form under saturated and anaerobic conditions, but wetland hydrology is difficult to assess. This study determines how often seven Hydric Soil field indicators met wetland hydrology requirements which require a water table be within 30 cm of the surface for 14 days or more during the growing season in over half the years. Studies were conducted at five sites in North Carolina in both wetland and upland plots. Soils ranged from Aquic Paleudults to Typic Haplosaprists across all sites. The water-table simulation model DRAINMOD was calibrated to Soil conditions in individual plots. Long-term rainfall data were used with the calibrated models to compute 40 years of daily water table data to represent both wet and dry years. It was found that the Hydric Soils with field indicators composed of organic materials in layers over 20 cm thick (Histosol and Histic epipedon field indicators) met wetland hydrology requirements each year, and in addition were ponded with water for periods between 67 to 139 days on average each year during the growing season. Plots in mineral Soils having the Dark Surface (S7) indicator as well as the Sandy Mucky Mineral (S1) indicator also met the saturation requirements for wetland hydrology every year, and were ponded for only 3 days per year on average. Other mineral Soils with an Umbric Surface (F13) or a Depleted Matrix (F3) field indicator met wetland hydrology requirements in approximately 95% of the years, and had water tables within 30 cm of the surface for 40 days per year on average. The Redox Depressions (F8) field indicator occurred in a small depression that was saturated for 87% of the year for periods averaging approximately 30 days. These results showed that Hydric Soil field indicators can be calibrated to long-term water table data that will allow precise assessments of wetland hydrology on-site.
David B. Kelley - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of Soil Properties and Hydric Soil Indicators for Vernal Pool Catenas in California
Soil Science Society of America Journal, 2008Co-Authors: Anthony T. O'geen, William A. Hobson, Randy A. Dahlgren, David B. KelleyAbstract:Vernal pool Soils in California's Mediterranean climate experience extremes in pedogenesis driven by prolonged saturation to extended desiccation. Four northern California vernal pool Soil catenas (summit, rim, and basin) were assessed to determine how Soil properties and Hydric Soil indicators vary in response to duration of standing water and landscape position. Each catena had differences in parent material or degree of Soil development. Soil properties differed subtly across each microtopographic sequence. In the well-developed Soils, the geochemical signature of horizons overlying the duripans changed sharply compared with horizons below the restrictive layers, suggesting polygenic origins of the Soil profiles. The presence and abundance of redoximorphic features (RMFs) in profiles corresponded poorly with the duration of standing water at the four sites. Instead, the abundance of RMFs coincided better with the thickness of the Soil above the restrictive horizons in all settings with duripans. Hydric Soils were identified in the basin positions of each catena. Most rim positions contained Hydric Soils and most summit positions had Soils that were not Hydric. Indicators F8 (redox depressions) and TF2 (test indicator for red parent materials) were most commonly applied. None of the vernal pool catena Soils met F9 (vernal pools Hydric Soil indicator), thus the Hydric Soil criteria for vernal pools may need to be revised.
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evaluation of Soil properties and Hydric Soil indicators for vernal pool catenas in california erratum 2010 mar apr v 74 no 2 p 696
Soil Science Society of America Journal, 2008Co-Authors: A T Ogreen, William A. Hobson, R A Dahlren, David B. KelleyAbstract:Vernal pool Soils in California's Mediterranean climate experience extremes in pedogenesis driven by prolonged saturation to extended desiccation. Four northern California vernal pool Soil catenas (summit, rim, and basin) were assessed to determine how Soil properties and Hydric Soil indicators vary in response to duration of standing water and landscape position. Each catena had differences in parent material or degree of Soil development. Soil properties differed subtly across each microtopographic sequence. In the well-developed Soils, the geochemical signature of horizons overlying the duripans changed sharply compared with horizons below the restrictive layers, suggesting polygenic origins of the Soil profiles. The presence and abundance of redoximorphic features (RMFs) in profiles corresponded poorly with the duration of standing water at the four sites. Instead, the abundance of RMFs coincided better with the thickness of the Soil above the restrictive horizons in all settings with duripans. Hydric Soils were identified in the basin positions of each catena. Most rim positions contained Hydric Soils and most summit positions had Soils that were not Hydric. Indicators F8 (redox depressions) and TF2 (test indicator for red parent materials) were most commonly applied. None of the vernal pool catena Soils met F9 (vernal pools Hydric Soil indicator), thus the Hydric Soil criteria for vernal pools may need to be revised.
James S. Wakeley - One of the best experts on this subject based on the ideXlab platform.
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Preliminary Investigations of Hydric Soil Hydrology and Morphology in the United States
1996Co-Authors: James S. Wakeley, Steven W. Sprecher, Warren C. LynnAbstract:Abstract : Preliminary results based on 2 years of monitoring at most sites indicate that time lags between saturation and iron reduction range from several days to several weeks, depending upon temperature and other factors. Growing seasons based on measured Soil temperatures often differed considerably from approximations based on air temperatures and Soil temperature regime regions. Due to annual variability, longer monitoring periods are needed to identify reliable Hydric Soil indicators.
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Relationships among wetland indicators in Hawaiian rain forest
Wetlands, 1996Co-Authors: James S. Wakeley, Steven W. Sprecher, Robert W LichvarAbstract:We applied established methods for wetland identification in lowland and montane wet forests (rain forests) on the island of Hawaii to determine whether rain forests exhibited wetland indicators specified in delineation manuals and to examine relationships among indicators of hydrophytic vegetation, Hydric Soils, and wetland hydrology. Morphological characteristics and ferrous iron tests indicated pockets of Hydric organic Soils within areas mapped as Folists. Hydrophytic vegetation decisions based on prevalence values agreed with Hydric Soil determinations more often than did decisions based on dominant plant species. None of the rain forest types we studied exhibited wetland indicators throughout, but some sites contained scattered small wetlands occupying microtopographic lows created by cracks, folds, and undulating flow patterns in the lava bedrock. Further work is needed to identify reliable wetland indicators that can be used during drier portions of the year and to distinguish Hydric from nonHydric organic rain forest Soils.
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Environmental gradients and identification of wetlands in north-central Florida
Wetlands, 1996Co-Authors: Mary M. Davis, James S. Wakeley, Steven W. Sprecher, G. Ronnie BestAbstract:Vegetation composition, Soil morphology, and hydrology were characterized along wetland-to-upland gradients at six forested sites in north-central Florida to compare results of Federal wetland delineation methods with 3–5 yr of hydrologic data. Wetland and non-wetland identifications were supported by hydrology data in eight of nine plant communities. Lack of Hydric Soil indicators and hydrophytic vegetation in two upland communities (scrub and mixed mesic hardwoods) agreed with a deep water table. Six wetland communities (cypress dome, cypress strand, bayhead, cypress/bayhead, red maple/oak swamp, and cedar swamp) with field indicators of wetland hydrology, hydrophytic vegetation, and Hydric Soils were inundated or had water tables at or near the ground surface at least 5% of the growing season in most years., Flatwoods communities, however, occurred at intermediate positions on the moisture gradient and could not be consistently identified as wetland or upland communities. Identification of flatwoods as wetlands depended on wetland delineation method and was not usually supported by hydrologic measurements. In the flatwoods community, Soil properties and vegetation composition were correlated with the mean and standard deviation of water-table depths, as well as the depth continuously exceeded by the water table at least 5% of the growing season in most years. Various hydrologic parameters need to be considered in addition to the 5% exceedence level currently used in Federal wetland delineation guidance when characterizing wetland conditions in low-gradient areas such as flatwoods.
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Identification of wetlands in the Southern Appalachian Region and the certification of wetland delineators
Water Air and Soil Pollution, 1994Co-Authors: James S. WakeleyAbstract:According to the Corps of Engineers Wetlands Delineation Manual, wetlands are identified by the presence of field indicators of hydrophytic vegetation, Hydric Soils, and wetland hydrology. In the southern Appalachian region, situations that present problems for wetland delineators include (1) wetlands developed on recently deposited alluvial Soils that may show little evidence of Hydric conditions, (2) areas occupied by FAC-dominated plant communities, (3) wetlands affected by past or present drainage practices, (4) man-induced wetlands that may lack certain wetland field indicators, and (5) Hydric Soil units that are too small or narrow to be delineated separately on Soil survey map sheets. In March 1993, under direction of Section 307(e) of the Water Resources Development Act of 1990, the Corps of Engineers initiated a Wetland Delineator Certification Program. A 1-year demonstration program has recently ended in Maryland, Florida, and Washington, with nationwide implementation scheduled for later in 1994. This voluntary program is designed to increase the quality of wetland delineations submitted with Section 404 permit applications, and reduce processing time by reducing the need for extensive field verification of wetland boundaries.
Martin C Rabenhorst - One of the best experts on this subject based on the ideXlab platform.
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Improving Hydric Soil Identification in Areas Containing Problematic Red Parent Materials: a Nationwide Collaborative Mapping Approach
Wetlands, 2019Co-Authors: Sara C. Mack, Jacob F. Berkowitz, Martin C RabenhorstAbstract:Hydric Soil identification utilizes diagnostic morphologic features, including iron transformations, resulting from anaerobic conditions. However, Soils derived from some red parent materials (RPM) fail to develop characteristic Hydric Soils morphologies, confounding Hydric Soil and wetland delineation. Laboratory and field methods addressing resistant RPM Soils exist, but application remains limited by uncertainty regarding problematic RPM distribution. In response, a collaborative effort (>50 participants) documented problematic RPM distribution across the contiguous United States. Specifically, >1100 samples from >450 locations underwent laboratory analysis using the Color Change Propensity Index to identify problematic RPM Soils. Geospatial analysis linked verified problematic Soils with associated geologic units and Soil series, generating maps of RPM distribution. Potential problematic RPM was identified in the Northeast and Mid-Atlantic, Great Lakes, South-central, and Desert Southwest-Western Mountains (problematic RPM regions herein), encompassing diverse groups of Soils and parent materials. Despite the observed variability in Soil characteristics, results suggest that problematic RPM was consistently derived from sedimentary, hematite-rich red bed formations developed where deposition of terrestrial sediments occurred in near-shore, marginal-marine environments. Understanding problematic RPM Soils distribution promotes the appropriate application of existing Hydric Soil field indicators, including F21 – Red Parent Material, thus improving approaches to Hydric Soil identification and wetland management.
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Understanding the Inhibition of Color Change in Problematic Red Parent Material Hydric Soils
Soil Science Society of America Journal, 2019Co-Authors: Sara C. Mack, Martin C Rabenhorst, Jacob F. BerkowitzAbstract:Problematic red parent material (PRPM) Soils resist redox-induced color changes and development of redoximorphic features, posing a challenge to Hydric Soil and wetland identification. Previous studies suggested that color change resistance was a function of the mineralogical properties of hematite inherited from Soil parent materials, but the underlying cause of the phenomenon has remained uncertain. In this study, several hypotheses (i.e., physical occlusion, Al substitution, and crystal size) were investigated to explore the mechanism of PRPM Soil color change resistance. The physical occlusion hypothesis was assessed by comparing Color Change Propensity Index (CCPI) values between size fractions for both PRPM and non-PRPM Soils. Persistence of color change resistance (low CCPI) in the finest (clay) fractions of all PRPM Soils resulted in removing the physical occlusion hypothesis from consideration. Substitution of Al for Fe in hematite was compared between PRPM and non-PRPM clay fractions by observing X-ray diffraction (XRD) peak shifts. Substitution of Al in hematite remained low for the PRPM samples (mean 0.8 mol%), compared with the non-PRPM (mean 6.8 mol%) suggesting that Al substitution is not the cause of observed color change resistance. Finally, mean hematite crystallite size was evaluated using Scherrer equation calculations. Mean hematite crystallite size in PRPM Soils was significantly larger than non-PRPM Soils (P = 0.0039), suggesting that color change resistance and the PRPM Soil phenomenon are derived from the large size of hematite crystals.
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Soil color and us northeast aquods
Soil Science Society of America Journal, 2016Co-Authors: Mark H Stolt, Martin C Rabenhorst, Elham A. Ghabbour, Geoffrey DaviesAbstract:Aquods commonly occur in wetland settings across a range of temperature regimes. Understanding their morphologies is critical to developing effective Hydric Soil indicators. In this study, we examined a range of wet Spodosols of the northeastern United States. We tested whether the red hues associated with wet spodic horizons are a function of humic (HA) and fulvic acids (FA) or Fe, and addressed questions related to Hydric Soil indicators, horizon designation, and Soil classification. Only two of the 11 seasonally saturated Spodosols met current criteria for Aquods. Almost all of the 24 Bh, Bhs, or Bhsm horizons had 3 to 10 times more ammonium oxalate extractable Al than Fe (mean Fe was <0.15%), yet only three pedons met the current criteria for “Al” great groups. We found no consistently applied color or sesquioxide content criteria for separating Bh from Bhs horizons. These results suggest that criteria for horizon designation and classification of Aquods need to be reconsidered. There were no relationships between extractable Fe and hue (p = 0.50). Weak correlation coefficients (−0.40 and −0.39; p = 0.051 and 0.057) between hue and FA and HA suggest little support for red hues being primarily a function of HA or FA. The significant relationship between Al and hue (−0.46; p = 0.025) and the strong correlation between Al and both HA and FA (0.87 and 0.86; p < 0.001) suggest a possible interaction between Al and the humic substances resulting in redder hues. We found more than twice as much HA in the spodic horizons as FA and concluded that FA is the precursor of HA in US Northeast spodic horizons.
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Soil Color and US Northeast Aquods
Soil Science Society of America Journal, 2016Co-Authors: Mark H Stolt, Martin C Rabenhorst, Elham A. Ghabbour, Geoffrey DaviesAbstract:Aquods commonly occur in wetland settings across a range of temperature regimes. Understanding their morphologies is critical to developing effective Hydric Soil indicators. In this study, we examined a range of wet Spodosols of the northeastern United States. We tested whether the red hues associated with wet spodic horizons are a function of humic (HA) and fulvic acids (FA) or Fe, and addressed questions related to Hydric Soil indicators, horizon designation, and Soil classification. Only two of the 11 seasonally saturated Spodosols met current criteria for Aquods. Almost all of the 24 Bh, Bhs, or Bhsm horizons had 3 to 10 times more ammonium oxalate extractable Al than Fe (mean Fe was
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Hydric Soil field indicators for use in mid atlantic barrier island landscapes
Soil Science Society of America Journal, 2015Co-Authors: Ann M. Rossi, Martin C RabenhorstAbstract:Hydric Soils in Holocene-aged barrier island landscapes in the Mid-Atlantic region of North America lack morphologies typically associated with saturated and reducing conditions. Furthermore, many better drained (nonHydric) Soils have low chroma colors due to parent material effects, making identification and delineation of wetlands problematic. Our objective was to develop field indicators that could be used to effectively recognize Hydric Soils in these environments. Soils along 10 topographic transects were evaluated at Assateague Island National Seashore, Maryland. Transects spanned a gradient of topographic positions from dune crests to interdunal swales. Water tables and reducing conditions were monitored to determine Hydric status. Soil descriptions along each transect were used to identify morphological features indicative of Soil wetness. Of 16 monitored and documented Hydric Soils, only five met recognized field indicators. Hydric Soils were best identified by the presence of matrix colors with chromas less than 2 in mineral Soils or the presence of at least 1 cm of muck (Oa horizon). On the basis these characteristics, we propose two new indicators restricted for use in Holocene-aged barrier island landscapes in the Mid-Atlantic region. These indicators will allow identification of Hydric Soils, improving the accuracy and ease of delineation of wetlands.