Work

Ecosystem context modulates salinization impacts on diffusive greenhouse gas fluxes in coastal wetland soils

Year: 2026

Type: article

Study designs: Systematic Review, Meta-Analysis

Abstract: Saltwater intrusion is accelerating salinization in coastal wetlands, altering soil ionic strength and sulfate availability with potential consequences for soil diffusive greenhouse gas (GHG) fluxes. Despite numerous local studies, large-scale response patterns and associated mechanisms remain insufficiently resolved. Here, we combined a global meta -analysis of chamber-based soil diffusive GHG fluxes (76 studies; 813 paired observations) with a year-long mesocosm experiment to quantify salinization effects on soil diffusive CO 2 , CH 4 , and N 2 O fluxes. In tidal marshes, salinization suppressed CO 2 and CH 4 fluxes more strongly than in mangroves, by 31% and 42%, respectively, whereas N 2 O declined modestly by 14%. In mangroves, suppression was dominated by N 2 O, which declined by 38%, with smaller reductions in CO 2 (7%) and CH 4 (10%). Across studies, CO 2 and CH 4 responses were associated mainly with ambient salinity and temperature seasonality, whereas N 2 O responses were more closely associated with tidal range. By contrast, Δsalinity, the magnitude of salinity change, showed weaker explanatory power for soil diffusive GHG responses. The mesocosm experiment provided process-related support for these patterns. In Cyperus -planted mesocosms, salinization reduced labile carbon pools and acetate availability and was associated with lower functional potential for organic matter breakdown ( cex , cdh , xylA ) and methanogenesis ( mcrA , acsB ), consistent with lower soil diffusive CO 2 and CH 4 fluxes. In Kandelia -planted mesocosms, salinization reduced dissolved inorganic nitrogen availability, increased C:N ratios, and was associated with lower functional potential for nitrogen fixation, nitrification, and denitrification ( nifH, amoA, narG, nirS ), consistent with stronger N 2 O suppression. These findings suggest that salinization effects on coastal-wetland soil diffusive GHG fluxes are shaped by environmental gradients and soil biogeochemical conditions rather than by Δsalinity alone. Incorporating ecosystem context into process-based models may improve predictions of short- to medium-term GHG responses to salinization in coastal wetland soils.

Source: Geoderma

DOI: 10.1016/j.geoderma.2026.117941