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Impacts of forest fires on soil dissolved organic matter biogeochemistry

Wildfires, soil organic carbon, biomarkers, carbon cycling, environmental quality

Theme 2: Geobiology of Modern Habitable Earth > Session 2a: Microbe-mediated Carbon Cycling on Modern Earth

Dissolved organic matter (DOM) is the most reactive and mobile fraction of forest soil organic matter, and it is increasingly impacted by wildfires worldwide. However, the changes in the dynamics, influencing factors, and environmental impacts of soil DOM following fire events remain insufficiently explored. In this study, carbon quantification and various spectroscopy and spectrometry techniques were applied to analyze DOM contents and characteristics in wildfire cases and laboratory-controlled burning experiments. The results showed that DOM exhibited significantly higher temporal variations compared to bulk soil organic matter (SOM) after fire, with carboxyl-rich compounds rapidly diminishing, while nitrogen-rich condensed aromatics persisted for an extended period. Heating temperature, fuel type, and oxygen availability were identified as key factors controlling the chemistry of pyrogenic DOM. Moreover, pyrogenic DOM was found to influence sulfamethoxazole degradation through different pathways, suggesting that fire can alter environmental quality. This study enhances the understanding of the temporal variations in the effects of fire on different soil DOM components, which can help inform future post-fire environmental management strategies.