Earthcasting is the projection of Earth’s near surface fluxes (e.g., water, solutes and sediments) and architecture (e.g., regolith thickness and hydrologic properties). It provides a lens to examine how human and climatic perturbations will drive the evolution of the Critical Zone—the thin layer of earth located between the top of the canopy and the lower depths of circulating groundwater. To accomplish this goal we use a cascade modeling approach linking together meteorological forcing (NLDAS-2), land-surface hydrologic models (Flux-PIHM), and geochemical box models (WITCH). We explore two earthcasting scenarios centered on the response of solute fluxes and weathering rates to changing climatic and land cover conditions. The first is the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO), a temperate forested watershed overlying shale, where we use aspect-controlled differences in radiation to explore the impact of differing temperature and hydrologic regimes on solute fluxes and clay weathering kinetics. The second focuses on the grassland to temperate forest ecotone boundary of eastern-central Kansas, which is underlain by repeating couplets of shale and limestone, and represented by the Konza Prairie Long Term Ecological Research (LTER) Program and the University of Kansas Field Station. In this region differences in burning regimes support the coexistence of grasslands, shrublands and temperate forests, and provide the opportunity to examine the hydrologic and biogeochemical impacts of various vegetation communities on weathering rates and solute fluxes. Modeling results demonstrate that aspect-controlled radiation can influence soil profile weathering. Compared to the baseline model, moister, cooler, shaded hillslopes exhibited a 2% decline in weathering, while drier, warmer sun-facing slopes exhibited a 3% increase. Vegetation water and nutrient cycling at SSHCZO appears to induce a net reduction in mineral dissolution rates. Preliminary modeling results of the Kansan systems suggest that rooting depth may play a dominant role in controlling mineral weathering rates.

Earthcasting solute fluxes and soil development in the critical zone

253rd National Meeting (2017)

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