RESULTS OF A SOILS INVENTORY AND LANDFORM MAPPING AT MOUNT RAINIER NATIONAL PARK

Mount Rainer National Park (MORA), a 95,700 hectacre park centered on a 4,390 m tall stratovolcano in the Cascade Range of Washington State, is a challenging environment for a soil survey. A soils resource inventory was completed in 2016 by the National Resource Conservation Service (NRCS), in partnership with the National Park Service (NPS), using a landform base map created by the NPS using field and LiDAR mapping techniques. Studies in the North Cascades and the surrounding vicinity link pedogenic processes to soil-landscape relationships, providing insight to the links between landforms and soils. Landforms contain information on 3 of the 5 soil forming factors (topography, parent material and time). The landform map of the park, with a suite of 34 landforms, was used as a base map and correlation tool. Glacial erosion created the dominant landforms of the park; cirques (7%) and valley walls (51%). The most commonly occurring landforms are glacial moraines scattered at various elevations. A total of 116 debris avalanches were mapped; many of these are very old features, while others remain active today.

A total of 813 soil observations were made during the soil survey; Andisols and Spodosols compose a majority of the park with smaller areas of Inceptisols, Entisols, Histosols and Gelisols. This survey created 36 new soil series endemic to MORA. Soil classification within the park is largely determined by the presence or absence of tephra. Across landform type and elevation, volcanic glass is the dominant material comprising soils. The dominant process of soil formation at lower elevations is podsolization while melanization is dominant in sub-alpine parkland; however unstable landforms in all elevation zones (mass movements, floodplains, debris cones) interrupt this pattern. Soil profiles at lower elevations along valley walls and debris aprons were typically elluvial/illuvial sequences in volcanic ash over colluvium and residuum. Sub-alpine parklands were composed of organic-rich layers along with interbeds of numerous tephra deposits. Both the landform and soils map have application to land management within MORA, including but not limited to, road and trail management, native plant restoration, geological hazard analysis and habitat suitability for a variety of species.