Coastal marsh conversion to paddy fields leads to a more pronounced stimulation of temperature sensitivity of soil microbial respiration in higher-latitude regions.

Converting coastal wetlands to rice paddies can substantially impact soil CO₂ emissions. However, the impact of such conversion on the temperature sensitivity of soil microbial respiration (Q10) remains poorly understood. We used a space-for-time substitution approach to examine the variation characteristics and key influencing factors of Q10 in natural marshes and adjacent paddy fields across five Chinese eastern coastal wetlands. Linear mixed-effects model revealed that Q10 increased significantly by 14.4% after conversion. Interestingly, the difference in Q10 before and after conversion (△Q10) exhibits a clear latitudinal pattern, increasing as latitude rises. Structural equation model showed that conversion affected Q10 through altering contents of soil organic carbon, dissolved organic carbon, NO3-, water content, bulk density, and pH. LASSO regression identified pH changes and conversion year significantly affected △Q10. Future scenarios project a rise in CO2 emissions with conversion year, suggesting a positive feedback that exacerbates climate change, especially in higher-latitude regions.