Nutrient Dynamics along a Planar Hillslope in a Small, Forested Catchment, Central Pennsylvania.

Understanding subsurface heterogeneity and topography and their relation to spatial and temporal nutrient patterns is fundamental to ecosystem dynamics and biogeochemical pathways. Center of this complexity is soils, which play an important role is coupling hydrologic flow and nutrient transformation and transport. Here, we investigated soil nutrient patterns along a steep, planar hillslope in the Shale Hills Catchment, a Critical Zone Observatory recently established in USA. Measurements of carbon, nitrogen, and phosphorus content were carried out in soil cores taken along the hillslope. As well, weekly soil water samples collected from nested lysimeters along this hillslope were analyzed for inorganic and organic forms of carbon, nitrogen and phosphorus. Preliminary results indicate that carbon, nitrogen, and phosphorus content in soil cores decreased with depth at each hillslope position (ridge top, mid slope and bottom slope). Additionally, the concentration of carbon, nitrogen, and phosphorus in the soil cores were found to be highest at the ridge top and lowest at mid slope, with bottom slope concentrations similar to those at the ridge top. In this study, it appears that both spatial and temporal nutrient patterns are influenced by topography and soil depth, as well as soil water flux and storage. As such, a better elucidation of how water flow pathways influence nutrient dynamics is essential for understanding the coupling of local hydrologic and biogeochemical processes. Future work also includes characterization of soil gas chemistry and quantification of soil organic matter turnover time.