ALPINE WETLAND SOIL DEVELOPMENT, NIWOT RIDGE, COLORADO

Soil profiles were excavated at 26 locations in wet alpine tundra on Niwot Ridge, Colorado (40^o3’N, 105^o35’W). 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. Statistical analyses show positive but weak correlation between plant communities and underlying soil classifications. Soils have acidic pH (A:4.1-5.1; B: 4.6-6.0) and mainly skeletal loam texture in the subhorizons. O horizons are mainly fibric. 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 Gelorthent to Oxyaquic Dystrogelept development sequence. This project proposes adding Oxyaquic and Histic modifiers to the Gelept suborder. We also propose a new term, Fluxaquentic, to describe profiles that include buried soils resulting from solifluction rather than flood deposition.