Estuarine wetlands are crucial in mitigating eutrophication in estuarine waters through plant uptake and microbial transformation. Nitrogen is one of the main nutrients removed. However, without proper plant harvesting, the nitrogen absorbed by plants can return to the water as litter during autumn and winter, potentially causing secondary pollution. This issue has been underexplored in natural estuarine wetlands. To address this, we conducted an in-situ survey at Chongming Dongtan to examine how nitrogen removal processes respond to different harvesting seasons and frequencies over time. The study found that the response of soil nitrification and denitrification to plant harvesting on tidal flats varied by time scales and harvesting patterns. Short-term responses of soil nitrification and denitrification depended on the harvesting season. Annually, combining plant uptake and soil denitrification, autumn and winter harvesting both improved nitrogen removal, with autumn being the most effective, boosting it by 73.0% and 61.7%, respectively, compared to no harvesting. While harvesting twice in summer and autumn significantly increased plant nitrogen uptake (p <
0.05), the overall removal (316.76 g N m