Alpine Wetland Soils, Niwot Ridge, Front Range, Colorado

Alpine wetland soils differ significantly from lowland wetland soils because they typically do not exhibit extreme reducing conditions even when flooded throughout the growing season and producing wetland vegetation. Lack of reducing conditions leads to their classification as Oxyaquic Cryepts and Gelepts rather than Cryaquepts. Groundwater flow is impeded in areas where solifluction causes buried soils, which then fosters reducing conditions. Soil profiles were excavated and plants were surveyed at 26 locations in wet alpine tundra on Niwot Ridge, Colorado (40 degrees 3' North and 105 degrees 35' West). Ten soil subgroups were identified. Statistical analyses show positive but weak correlation between plant communities and underlying soil classification and characteristics. Bare ground indicates Entisols, and Pedicularis groenlandica is a strong indicator for Terric Cryofibrists. Soils have an acidic pH (A:4.1-5.1; B:4.6-6.0) and mainly a skeletal loam texture in the subhorizons. O horizons are mainly fibric. No clay films were identified. Alpine wetland development is strongly influenced by topographically driven micro-climate and disturbance factors. This study proposes a development sequence for alpine wetland soils from Gelorthent to Oxyaquic Humicryept to Cryofibrist in stable areas. On solifluction landforms this sequence may branch from Oxyaquic Humicryepts to Fluvaquentic Humicryepts and Fluvaquentic Cryaquepts. On north-facing slopes soil temperatures may remain cold enough to remain in the Gelic temperature regime resulting in Georthent to Oxyaquic Dystrogelept development sequence. In some respects this is a temporal sequence; in other respects it is a spatial series.