Improving Hydric Soil Identification in Areas Containing Problematic Red Parent Materials: a Nationwide Collaborative Mapping Approach

Sara C Mack,Martin C Rabenhorst,Jacob F Berkowitz

doi:10.1007/s13157-018-1114-6

Sara C Mack, Martin C Rabenhorst + Show 1 more

Open Access

https://doi.org/10.1007/s13157-018-1114-6

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Abstract

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.

Highlights

Hydric Soil Morphology and Problematic Hydric SoilsThe United States Army Corps of Engineers (USACE) wetland delineation manual and associated regional supplements provide technical guidance and procedures for identifying and Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.delineating wetlands (Environmental Laboratory 1987; Wakeley 2002)
The F21 - Red Parent Material hydric soil field indicator is approved for use in portions of the mid-Atlantic, New England, and Appalachian mountains including Major Land Resource Area (MLRA) 127 of Land Resource Region (LRR) N, MLRA 145 of LRR R, and MLRAs 147 and 148 of LRR S
51% of soils were characterized by CCPI values consistent with problematic red parent materials (RPM) properties, 19% displayed some resistance to color change, and 30% consisted of soils were identified as non-problematic RPM (CCPI >40)

Summary

Introduction

Each of these factors are identified using readily applicable field indicators (Environmnetal Laboratory 1987; Berkowitz 2011a; USACE 2012; Tiner 2016). Hydric soils are defined as Bsoils that have formed under conditions of saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions in the upper part^ (Federal Register 1994). These periods of saturation, when combined with soil-microbial activity and the depletion of oxygen, promote biogeochemical processes that result in morphological features useful for wetland identification during both wet and dry periods (Craft 2000; USDA-NRCS 2017). Common hydric soil morphologic features include: 1) the accumulation of organic matter from reduced rates of microbial decomposition under anaerobic conditions; and 2) the reduction and dissolution of ferric iron

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