Hydric soils identification is a key component of wetland delineation and management in the United States. However, some hydric soils fail to exhibit characteristic morphologies (i.e., Field Indicators of Hydric Soils - FIHS) used in wetland delineation despite the presence of anaerobic conditions, wetland hydrology, and hydrophytic vegetation. Soils in semi-arid and arid riparian areas remain particularly challenging, where unpredictable patterns of wetland hydrology, salt accumulation, and periodic sediment deposition hinder the development of common hydric soil morphological features. In response, this study (1) applied the Hydric Soils Technical Standard (HSTS) in problematic soils in western Nebraska and (2) assessed the occurrence of iron monosulfide (FeS) features that only form under anaerobic conditions. Results confirmed the presence of hydric soils, despite the absence of FIHS, and documented 2–7% FeS concentrations within the upper 28 cm of the soil surface. Notably, deployed Indicator of Reduction in Soils (IRIS) devices also displayed evidence of FeS-precipitation. These findings suggest that opportunities exist to improve hydric soils identification and wetland delineation in arid and semi-arid regions by incorporating visual observations of FeS into the Field Indicators of Hydric Soils and other approaches to document anaerobic conditions in soils.

含水土壤识别是美国湿地划定和管理的关键组成部分。然而，尽管存在厌氧条件、湿地水文和水生植被，但一些含水土壤未能表现出用于湿地划定的特征形态（即，含水土壤的田间指标 - FIHS）。半干旱和干旱河岸地区的土壤仍然特别具有挑战性，湿地水文、盐分积累和周期性沉积物沉积的不可预测模式阻碍了常见的含水土壤形态特征的发展。作为回应，本研究 (1) 在内布拉斯加州西部有问题的土壤中应用了水合土壤技术标准 (HSTS)，并且 (2) 评估了仅在厌氧条件下形成的一硫化铁 (FeS) 特征的发生情况。结果证实了含水土壤的存在，尽管没有 FIHS，并记录了土壤表面上部 28 厘米内 2–7% 的 FeS 浓度。值得注意的是，部署的土壤减少指标 (IRIS) 设备也显示出 FeS 沉淀的证据。这些发现表明，通过将 FeS 的目视观察纳入含水土壤的田间指标和记录土壤厌氧条件的其他方法，存在改善干旱和半干旱地区含水土壤识别和湿地划定的机会。