Exotic plant invaders as ecosystem engineers: Impacts on blue carbon accumulation by altering carbon emissions and thermal responses

Exotic plant invaders frequently function as ecosystem engineers, significantly influencing carbon cycling within native ecosystems. However, the impact of invasive species on carbon emissions and the thermal response of belowground soil organic carbon (SOC) decomposition has not been thoroughly examined. This gap in knowledge poses challenges for managing blue carbon sequestration in coastal salt marshes threatened by invasive plants. Here, we conducted both field investigations and microcosm experiments to assess the effects of a decade‐long invasion by Sporobolus alterniflorus on soil CO2 emissions, SOC decomposition rates, and their sensitivity to temperature variation (Q10). Our results showed that the CO2 emission and its Q10 from invaded soils were generally lower compared to native soils. Changes in soil pH, soil water content, and the ratio of dissolved organic carbon (DOC) to SOC attributable to plant invasion greatly affected CO2 emission, SOC decomposition, and Q10. Microcosm experiments verified the reduced SOC decomposition rates and Q10 values in invaded soils. Additionally, Q10 showed a significant negative correlation with the proportion of labile carbon in soils, supporting the carbon‐quality temperature hypothesis to explain the observed changes in Q10 after plant invasions. Overall, our findings suggest that decreased CO2 emissions and SOC decomposition rates are critical processes driving rapid SOC accumulation in coastal salt marshes following the invasion of S. alterniflorus. These results enhance our understanding of SOC sequestration dynamics in coastal blue carbon ecosystems in the context of exotic plant invasions.