DEVELOPING WATERSHED-SCALE WILDFIRE EXPERIMENTATION: WILDFIRE SEVERITY AND POST-FIRE PRECIPITATION INFLUENCE ON FATE AND TRANSPORT OF PYROGENIC ORGANIC MATTER IN TERRESTRIAL-AQUATIC INTERFACES

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 and nitrogen. Wildfire severity may also alter: (1) the varying proportion of labile/soluble black carbon (BC) to recalcitrant/insoluble BC, (2) surface hydrodynamics of infiltration, and (3) known microbial community structure. Furthermore, post-wildfire precipitation behavior may further impact the distribution of PyOM at the watershed scale.

Prescribed forest fires, or controlled burns, are common practices to aid in the preservation and health of forested ecosystems. These watershed-scale fire manipulations also provide the opportunity to serve as a proxy to study how widespread fire events alter hydro-biogeochemical processes in the natural environment. However, many environmental and societal considerations (i.e., atmospheric mixing, smoke production, wind patterns, soil moisture, fuels, etc.) must be accounted for to successfully conduct high-intensity prescribed fires.

Wildfire simulations at the watershed scale (~ 150 acres) were conducted within the Clemson Experimental Forest (Clemson, SC - Fall 2023) and Savannah River Site (New Ellenton, SC - April 2024) to produce an experimental design for high-intensity prescribed burn and comprehensively document the spatiotemporal influence of wildfire severity/post-fire precipitation on PyOM fate across the terrestrial-aquatic interface. Field sampling (water, soil, & fuels), laboratory analysis (FT-ICR-MS, NMR, CHNS/O EA, & TOC/TN), and modeling efforts (PFLOTRAN and ATS) are conducted pre-fire, post-fire, and post-fire rainfall event. The spatiotemporal field, laboratory, and modeling efforts identify fire/rainfall-induced variation in (1) PyOM characteristic/fate, (2) hydrodynamics, and (3) microbial community structure. The disturbance induced by the high-intensity prescribed fire experiments aims to not only provide a mechanistic understanding of the natural hydro-biogeochemical response to varying wildfire severity and post-fire precipitation, but also create a blueprint for future high-intensity prescribed fire experiments with the advancement of wildland fire research.