How do Wildfire Severity and Post-Fire Precipitation Influence Fate and Transport of Pyrogenic Organic Carbon and Nitrogen in Terrestrial-Aquatic Interfaces?

Authors

Alex Chow¹* (achow@clemson.edu), Huan Chen², Barbara Campbell³, Jeff W. Atkins⁴, Carl Trettin⁵, Scott Brooks⁶, Scott Painter⁶, Peijia Ku⁶

Institutions

¹Department of Forestry and Environmental Conservation, Clemson University, SC; ²Department of Environmental Engineering and Earth Science, Clemson University, SC; ³Department of Biological Science, Clemson University, SC; ⁴Southern Research Station, U.S. Forest Service, New Ellenton, SC; ⁵Center for Watershed Research, U.S. Forest Service, Cordesville, SC; ⁶Environmental Science Division, Oak Ridge National Laboratory, TN

Abstract

Wildfire significantly changes the composition and quantity of forest biomass, converting lignin and polysaccharide rich and relatively degradable carbon pools to polycyclic aromatic and charcoal rich and recalcitrant black carbon. Abundance and distribution of these carbon pools are affected by the severity of a wildfire and the intensity and frequency of post-fire rainstorms. However, there is no comprehensive knowledge available about the impacts of both fires and post-fire rainstorms on the fates of pyrogenic organic carbon (PyOC) and nitrogen (PyON) in burned terrestrial and aquatic ecosystems. To address the knowledge gap, researchers will collaborate with scientists at U.S. Forest Service and Oak Ridge National Laboratory to conduct watershed-scale wildfire experiments in the DOE Savannah River Site, SC. Production, composition, fluxes, and temporal dynamics of PyOC and PyON in both soil and surface runoff under different severity of wildfires as well as intensity and frequency of post-fire rainstorms will be determined in the field conditions. Leachability, degradability, and mobility of PyOC and PyON will be quantified in controlled conditions. Microbial communities will also be assessed for resistance and resilience as well as function in relation to watershed perturbation and post-fire nutrient pools. Data obtained from the experiments will be used to develop, calibrate, and evaluate a reactive transport model of PyDOM and nutrients in burned landscapes. The results from field and laboratory experiments will be used to develop a reaction network accounting for dissolved and particulate BC and BN and production of carbon (C) and nitrogen (N) gases. The reaction network will be implemented in the PFLOTRAN software. Flow and transport of particulate and dissolved phases will be modeled with ATS, which uses the Alquimia interface to access PFLOTRAN’s reaction capability. Key parameters appearing in the flow and reactive transport model will be estimated by uncertainty-aware inverse modeling using the measured C and N fluxes. ATS-PFLOTRAN models of the plot and small watershed experiments will then be used to assess transferability of estimated parameters across scales.