Headwater stream networks are significant aquatic ecosystems, as they constitute the majority of river miles and are prominent carriers of biogeochemical signals from the surrounding terrestrial environment. Despite their importance, organic matter dynamics remain understudied in humid, low-relief headwater networks in the Gulf Coastal Plain of the Southeastern United States (US). To explore organic matter dynamics in an understudied region, we intensively sampled 20 subcatchments nested within the forested and actively managed South Sandy Watershed (125 km2) in the Talladega National Forest of central Alabama, US. Using samples collected monthly from September 2025 to January 2026, we evaluated the properties of dissolved organic matter (DOM) and particulate organic matter (POM) pools at each site. We characterized samples using optical properties, including specific ultraviolet absorbance at 254 (SUVA254), Fluorescence Index (FI), Humification Index (HI), and Biological Index (BIX). Collectively, these indices reflect the source, quality, and complexity of organic matter in each water sample. Notably, our seasonal sampling period encompassed organic matter dynamics before, during, and after leaf-off. We hypothesize that: 1) POM will experience a sharper increase in complexity during leaf-off and decrease afterward relative to DOM, 2) Both DOM and POM will have a strong allochthonous signal during leaf-off, followed by a more autochthonous signal, and 3) DOM and POM properties of each subcatchment will be correlated with vegetation cover. Results from our study will improve understanding of the contributions of headwater networks to the global carbon cycle, which is crucial for sustainable land management.