Soil development on a topo-climosequence of late Pleistocene moraines, western Wind River mountains, Wyoming (USA)

Physical and chemical processes involved with soil development in dry mountain regions are underexplored. This study, therefore, compares soils developed on fifteen LGM-to-Late Glacial (∼20–15 kyrs) moraines located along a topo-climosequence in the Wind River Mountains (Wyoming) within three geomorphic regions separated by elevation: the Piedmont , Erosion Surface and Alpine regions. We investigated soil formation, soil erosion, organic matter formation and eolian influx to quantify the morphodynamic processes that determine the evolutionary trajectories of these soils. Soils on the alpine moraines that received higher levels of precipitation and had increased percolation rates showed stronger developmental characteristics than the soils of the lowest geomorphic regions. The porosity and weathering severity of the soils also increased, as did pedogenic oxyhydroxides of Fe and Al. Weathering indices such as the CIA index or the (Ca + K)/Ti ratio indicated that soils on the moraines of the Piedmont region exhibited lower weathering states than their counterparts on moraines of the sequentially-higher geomorphic regions ( Erosion Surface and Alpine ). The soil depth trend of these two indices showed that weathering intensity generally decreased with soil depth, beneath the relatively unweathered surface horizons, indicating the influence of eolian influx. The influence of eolian influx was highest at the piedmont sites, as indicated by the highest amounts of pedogenic silt+clay. Stocks of organic carbon were highest close to timberline and the hydrophobicity and immaturity of soil organic matter clearly increased with elevation. However, organic C stocks were relatively modest (in the range of 5–13 kg m −2 ), when compared to other mountain regions with moister conditions. In contrast to our expectations, weathering intensity was not highest beneath the forest of the Erosion Surface , but at the high-alpine sites. Climate had a measurable influence on the geochemical conditions. Significant levels of eolian influx co-determined the soil evolutional trajectories of these moraine soils.