Abstract
Projections of future conditions within the critical zone—earthcasts—can be used to understand the potential effects of changes in climate on processes affecting landscapes. We are developing an approach to earthcast how weathering will change in the future using scenarios of climate change. As a first step here, we use the earthcasting approach to model aspect-related effects on soil water chemistry and weathering on hillsides in a well-studied east-west trending watershed (Shale Hills, Pennsylvania, USA). We completed model simulations of solute chemistry in soil water with and without the effect of aspect for comparison to catchment observations. With aspect included, aqueous weathering fluxes were higher on the sunny side of the catchment. But the effect of aspect on temperature (0.8 °C warmer soil on sunny side) and recharge (100 mm/year larger on shaded side) alone did not explain the magnitude of the observed higher weathering fluxes on the sunny side. Modeled aspect-related differences in weathering fluxes only approach field observations when we incorporated the measured differences in clay content observed in augered soils on the two hillslopes. We also had to include a biolifting module to accurately describe cation concentrations in soil water versus depth. Biolifting lowered some mineral dissolution rates while accelerating kaolinite precipitation. These short-duration simulations also highlighted that the inherited differences in particle size on the two sides of the catchment might in themselves be explained by weathering under different microclimates caused by aspect—over longer durations than simulated with our models.
| Original language | English |
|---|---|
| Pages (from-to) | 974-993 |
| Number of pages | 20 |
| Journal | Journal of Geophysical Research: Earth Surface |
| Volume | 124 |
| Issue number | 4 |
| DOIs | |
| State | Published - Apr 2019 |
Funding
This work was facilitated by NSF Critical Zone Observatory program grants to C. J. D. (EAR 07-25019) and S. L. B. (EAR 12-39285 and EAR 13-31726). The research was conducted in Penn State's Stone Valley Forest, which is supported and managed by Penn State's Forestland Management Office in the College of Agricultural Sciences. X. Gu was supported by DOE grant DE-FG02-05ER15675. Data and PIHM model output used to parameterize, calibrate, and validate the model can be found through the Critical Zone Observatory websites criticalzone.org and http://www.czo.psu.edu/data_geochemical_geophysical.html. We acknowledge conversations with N. West and would like to thank the reviewers, including C. Harman, for their thoughtful and insightful comments. This work was facilitated by NSF Critical Zone Observatory program grants to C. J. D. (EAR 07\u201025019) and S. L. B. (EAR 12\u201039285 and EAR 13\u2010 31726). The research was conducted in Penn State's Stone Valley Forest, which is supported and managed by Penn State's Forestland Management Office in the College of Agricultural Sciences. X. Gu was supported by DOE grant DE\u2010 FG02\u201005ER15675. Data and PIHM model output used to parameterize, calibrate, and validate the model can be found through the Critical Zone Observatory websites criticalzone.org and http://www.czo.psu.edu/data_ geochemical_geophysical.html. We acknowledge conversations with N. West and would like to thank the reviewers, including C. Harman, for their thoughtful and insightful comments.
Keywords
- geochemical modeling
- microclimate
- vegetation cycling