A Catchment Scale Analysis of Interactions Between Hydrologic Flowpaths and Soil Development.

Order 2 soil survey and previous investigations in the upland headwater catchments at the Hubbard Brook Experimental Forest characterized soils as well drained Spodosols. However recent hydrologic monitoring documented transient water table development that was persistent during the non-growing season, and occasionally developed during storm events in certain landscape positions during the growing season. Detailed soil sampling revealed a range in spodic expression, including inclusions of Inceptisols with umbric epipedons. Variation in landform along hydrologic pathways, including breaks in slope, slope curvature, and variation in depth to confining layers (bedrock or densipan) explained much of the variability in soil development as well as soil chemical characteristics such as exchangeable acidity and carbon accumulation in mineral horizons. The height and duration of transient water saturation in the soil profile, as well as position along hydrologic flowpaths explain variation in soil development and soil chemistry. Several topographic indices, particularly distance to stream were statistically significant predictors of pedon morphology and chemistry. Hydrologic control of these processes within upland headwater catchments has implications for how watersheds will respond to climate change, and to predicting spatial patterns in soil properties, important to forest productivity and species suitability.