Limitations to Redoximorphic Feature Development in Highly Calcareous Hydric Soils

Abstract

Core Ideas Soil morphology in highly calcareous wetlands does not reflect current hydrology. Despite anaerobic conditions, redox features do not form in carbonatic soils. Problematic hydric soils in the arid west need to be investigated. Alternative indicators must be used to identify problematic hydric soils. Given the correct conditions, redox features will form in carbonatic soils. Wetlands in arid climates are particularly important to understand and conserve given, their low spatial extent and high rate of delivering ecosystem services. Hydromorphic soils formed in calcareous geologic materials in western Wyoming present challenges related to wetland delineation. Despite the presence of hydrophytic vegetation and wetland hydrology, these soils have not developed the traditional redoximorphic features required to identify hydric soils. To determine the limiting factor responsible for the lack of redoximorphic feature expression, a mesocosm study was conducted with cores extracted from the field. Fifteen intact soil cores were treated with Fe, organic C (OC), a combination of Fe + OC, or no amendment and inundated for 18 wk. Oxidation–reduction potential and pH were measured weekly and after 18 wk, the barrels were drained, the soil cores were dissected, and the redoximorphic features were described. The mesocosms treated with Fe and Fe + OC generated the greatest amount of redoximorphic features (21.9 and 23.0%, respectively). In contrast, the OC‐treated and control mesocosms produced minimal redoximorphic features (0.16 and 0.08%, respectively). According to the results of this study, the addition of Fe and the accompanying acidifying conditions allowed for the development of redoximorphic features and therefore is responsible for their absence in situ. The field identification of carbonatic hydric soils will require the use of an alternative field indicator beyond soil morphological indicators.