2024 Abstracts

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


Gavin Gleasman1* ([email protected]), Alex Chow2, Donald Hagan1, Huan Chen3, Barbara Campbell4, Jeff W. Atkins5, Carl Trettin6, Scott Brooks7, Scott Painter7, Peijia Ku6, Russell Hardee1, Jesus Gomez Velez7, Fernanda Santos7, Dinuka Lakmali Jayasuriya Patabandige4, Yuhua Zheng1, Michael Langley5


1Department of Forestry and Environmental Conservation, Clemson University, Clemson SC; 2Earth and Environmental Sciences Program, The Chinese University–Hong Kong; 3Department of Environmental Engineering and Earth Science, Clemson University, Clemson SC; 4Department of Biological Science, Clemson University, Clemson SC; 5Southern Research Station, U.S. Forest Service, New Ellenton SC; 6Center for Watershed Research, U.S. Forest Service, Cordesville SC; 7Envrionmental Science Division, Oak Ridge National Laboratory, Oak Ridge TN


Wildfires vastly disturb forest environments by influencing local hydro-biogeochemical cycles. The severity of a wildfire modifies the composition, transport, and abundance of pyrogenic organic matter (PyOM) in the natural environment, including pyrogenic organic carbon (PyOC) and nitrogen (PyON). Wildfire severity alters (1) the varying proportion of labile and soluble black carbon (BC) to recalcitrant and insoluble BC; (2) surface hydrodynamics of infiltration; and (3) known microbial community structure. Along with wildfire severity, postwildfire precipitation behavior further impacts the distribution of PyOM. Wildfire simulations at the watershed scale was conducted within the Clemson Experimental Forest (SC; Fall 2023) and is planned for Savannah River Site (SC; April 2024) to comprehensively document the influence wildfire severity and postfire precipitation have on the fate of PyOM across the terrestrial–aquatic interface. The production, composition, and fluxes of PyOM will be quantified in soil (particulate and porewater) and surface water samples (stream and runoff). The PyOM will be quantified by collecting soil and water samples before and after the wildfire simulation, natural precipitation events, and simulated rainfall experiments in locations of varying wildfire severity. Perturbations to watershed hydrodynamics due to the wildfires will be quantified through infiltration tests and soil saturation measurements. The leachability, degradability, and mobility of PyOM from soil and water samples will be quantified using controlled experimental conditions. The assessment of microbial community structures will determine their spatial and temporal relation to varying PyOM and nutrient pools, as well as their resilience and resistance to wildfire severity. The dissolved and particulate PyOM, nutrient pools, microbial structure, and hydrodynamic data obtained during field and laboratory experiments will be applied to develop a reaction network model and a reactive- transport model by coupling PFLOTRAN and ATS code. The field, laboratory, and modelling results aim to provide a mechanistic understanding of the natural hydro-biogeochemical response to varying wildfire severity and postfire precipitation.