779 / 2024-09-19 12:10:10

Tidal irrigation-based rice cultivation enhances coastal blue carbon and decreases GHG emissions in brackish mudflats

Sea rice; Carbon uptake; Saltwater tidal irrigation; Coastal wetlands; Coastal agriculture; Climate change

Coastal agriculture has been adopted to increase agricultural productivity, whereas its effects on blue carbon function and greenhouse gas (GHG) emissions are unclear. In this study, we investigated the effects of tidal saltwater on CO₂ uptake and CH₄/N₂O emissions from a coastal rice ecosystem, and as well as the associated greenhouse gas mitigation mechanisms. Here, sea rice enhanced net ecosystem CO₂ exchange (NEE) and gross primary productivity (GPP) after saltwater irrigation. This was accompanied by an increase in tillering number, shoot dry mass and grain yield. Furthermore, we observed a significant change in the mitigation of CH₄ and N₂O in the coastal rice system due to the tidal saltwater treatment. Specifically, an anticipated decrease in CH₄ was observed during the tillering stage. Additionally, the study highlighted a significant decrease in the sustained-flux global warming potential (SGWP) of the sum CO₂-eq of CO₂, CH₄, and N₂O throughout the tidal saltwater irrigation period, with reductions of 22.29%~39.06% for sea rice varieties, respectively. In the rhizosphere soil, functional genes involved in CO₂ fixation and CH₄ and N₂O oxidation were upregulated. Therefore, the simulation of tidal saltwater in a coastal rice system demonstrated its ability to increase carbon uptake and mitigate greenhouse gas emissions, particularly CH₄ and N₂O. We suggest that coastal rice cultivation using natural tidal irrigation is an effective approach to strengthen the ecological and economic benefits of coastal tidal mudflats by reducing greenhouse gas (GHG) emissions and enhancing rice yields.