Seasonally exposed shorelines of China's Three Gorges Reservoir host dense vegetation stands that accumulate nutrients and emit greenhouse gases (GHGs). This study tested whether an annual, zone-wide plant biomass removal could simultaneously reduce GHG emissions and prevent nutrient mobilization from soils into adjacent waters. We hypothesized that removing aboveground vegetation prior to re-inundation would reduce methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O) fluxes without significantly elevating soil or water nutrient levels. Across upstream, mid-reservoir, and downstream reaches, we monitored soil chemistry, near-shore water quality, and surface fluxes of CH₄, CO₂, and N₂O for four weeks following plant biomass removal. Harvesting reduced median soil CH₄ emissions by 67 %, CO₂ emissions by 40 %, and N₂O emissions by approximately 20 %, resulting in a total net benefit of 0.8 kg CO₂ equivalents per square meter. Key soil nutrients including total nitrogen (TN), total phosphorus (TP), Olsen-extractable phosphorus (Olsen-P), ammonium nitrogen (NH₄-N), and nitrate nitrogen (NO₃-N), as well as eleven monitored water-quality indicators, showed no statistically significant changes, indicating minimal nutrient mobilization. Mean standing biomass (652 ± 239 g m−2) contained 16.2 g nitrogen per kilogram and 4.2 g phosphorus per kilogram. Scaled to the 284.65 km2 drawdown zone, an annual harvest could remove approximately 3.0 kt of nitrogen and 0.8 kt of phosphorus, comparable to inputs from several tributaries. Mechanized vegetation harvesting therefore provides a feasible management practice offering both climate and water quality benefits for the Three Gorges Reservoir.
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