Toward the Understanding of Biogeochemical Functions of the Future Floodplain
Authors
Peter S. Nico1*, Vincent Noël2 (noel@slac.stanford.edu), Tristan Babey3, Sam Pierce3, Chris Francis3, Patricia Fox1, Dipankar Dwivedi1, Nicola Falco1, Rosemary Carroll4, Bhavna Arora1, Michelle Newcomer1, Kristin Boye2, Eoin Brodie1 (elbrodie@lbl.gov)
Institutions
1Lawrence Berkeley National Laboratory, Berkeley, CA; 2SLAC National Accelerator Laboratory, Menlo Park, CA; 3School of Earth, Energy, and Environmental Sciences, Stanford University, Stanford, CA; 4Desert Research Institute, Reno, NV
URLs
Abstract
Floodplains act as critical buffer zones between mountain hillslopes and rivers, regulating water and element (e.g., nutrients, colloids) exports to rivers. Concurrent temperature changes and increased hydrologic pulse disturbances will change the function of floodplains in the future. As floodplains physically and biologically rearrange in response to these drivers, there will be concomitant changes in floodplain hydrologic partitioning and biogeochemical functioning. Yet, the consequences of interacting hydrological and ecological impacts of disturbances on element retention capacity of future floodplains are still unknown.
The hydrologic connectivity between hillslopes, floodplains, and rivers drives biogeochemical processes and exchange fluxes. Through a series of lab, field, and modeling experiments, the team recently demonstrated that disturbances in hydrologic connectivity and water chemistry impacted floodplain biogeochemical processes in previously unpredicted ways; fine-scale sediment heterogeneities and colloidal transport had orders of magnitude larger impacts than what was predicted by “traditional” modeling/theory. Furthermore, modeling and field observations suggest that hydrologic regime changes will drive changes in vegetation (e.g., grasses replacing willows) of future floodplains with implications for water/nutrient retention capacity. For example, DNRA tends to decrease in absence of willows, likely leading to increased nitrification and decreased nitrate retention.
Researchers expect future natural and managed adaptations (e.g., beaver dams, forest management) to mitigate the impacts of hydrological dynamic changes. The recent studies show that beaver dams overshadow climatic hydrologic extremes in their effects on water residence time and nitrogen fluxes in riparian zones.
Going forward, the team will instrument and sample floodplains that exhibit recent hydrological and vegetation changes corresponding to various scenarios predicted for a future climate and planned management experiments (e.g., beaver dam analogs, forest management). These test sets will help researchers understand the changes that can be expected in the future and prepare useful and actionable predictions of future floodplain functioning.