Study on Methane Emissions Induced by Leaf Litter Accumulation in a Forest-Influenced Reservoir Ecosystem

Lakes are significant sources of CH₄ (methane) emissions and thus contribute to global greenhouse gas fluxes. This study investigated CH₄ emissions in Lake A, a forested reservoir in South Korea, by integrating water quality and sediment investigations with underwater bubble emission monitoring, which was conducted from August to November 2024. The study aimed to examine the impact of forest-derived detritus on eutrophication and CH₄ emissions within the lake. During the study period, a mesotrophic state (Korean Trophic State Index of 30.4–31.2) was maintained, with total organic carbon from leaf litter as the primary driver of eutrophication. Sediment surveys indicated that leaf litter accumulation shifted from upstream in 2010 to midstream areas (where CH₄ production is most active) in 2024. Horizontal distribution analysis confirmed a strong correlation between leaf litter deposition and CH₄ ebullition, particularly in shallow regions with reduced water flow. CH₄ emission monitoring showed that the average CH₄ flux in Lake A was 212.17 mg/m²/day, representing a moderate level compared to that of domestic and international lakes and wetlands. Higher CH₄ emissions were observed in midstream regions with active anaerobic decomposition, while lower emissions were observed in deeper downstream areas due to CH₄ oxidation. These findings underscore the role of leaf litter accumulation in CH₄ emissions and water quality in forested reservoirs. Continuous monitoring is essential for understanding CH₄ dynamics and developing effective lake and greenhouse gas management strategies.