Evaluation of carbon flux responses to physical and chemical control strategies of Spartina alterniflora in the Yangtze River Delta

Aims: China has initiated nationwide management projects targeting the invasive plant Spartina alterniflora in coastal zones. while the impact of different S. alterniflora eradication strategies on carbon fluxes remains unclear. Methods: This study investigated the effects of different strategies (application of Haloxyfop-R-methyl (HPEM) and repeated mowing (Mowing)) on the efficiency in eradicating S. alterniflora and the difference in carbon fluxes (CO₂、CH₄) through field experiments, futher analyzing the relationship between sediment physicochemical properties, and microbial communities and their relationship with carbon fluxes over a one-year period. Results: Compared to Mowing, HPEM is more effective in eradicating S. alterniflora. Moreover, HPEM initially acted as a CO₂ source before the growing season, while repeated mowing sites consistently functioned as CO₂ sinks. Methane emissions at the HPEM site were significantly higher than those at Mowing and S. alterniflora sites during the non-growing season. Temperature and plant biomass were the main factors influencing carbon fluxes. Furthermore, we found that different eradication strategies significantly altered the soil microbial community structure, and these changes in microbial communities further influenced ecosystem respiration (ER), but had no significant impact on CH₄ emissions. Therefore, we assumed that the elevated CH₄ emissions at the HPEM site are primarily driven by the decomposition of dead plant material. Conclusions: Overall, we recommend repeated mowing as an effective long-term management strategy for controlling S. alterniflora. In areas requiring rapid and thorough removal of S. alterniflora, Haloxyfop-R-methyl can be employed, but vegetation should be promptly cut down after treatment to minimize the negative environmental impact of methane emissions.