Abstract: Elevated nitrogen levels in the environment enhance the adaptability and invasive ability of Spartina alterniflora. However, there is limited research on reducing soil nitrogen content by carbon addition to control Spartina alterniflora. In this study, under simulated tidal conditions, we used carbon addition to reduce available soil nitrogen. We set up an experiment with two types of carbon sources (glucose and sodium acetate), two carbon addition levels (400 and 800 g C·m^-2), and a control (CK) to analyze the effects of carbon addition on S. alterniflora biomass and root and leaf morphological traits. The results showed that carbon addition significantly decreased soil nitrate nitrogen and the biomass of roots, stems, and leaves of S. alterniflora (P<0.05). When the rate of carbon addition reached 800 g C·m^-2, it significantly reduced lateral root length, adventitious root length, root surface area, specific root length, leaf length, leaf width, leaf perimeter, leaf area, and specific leaf area, and significantly increased the ratio of lateral root length to adventitious root length and root tissue density (P<0.05). However, carbon addition treatments had no significant effect on stem-to-leaf ratio and leaf length-width ratio of S. alterniflora (P>0.05). S. alterniflora biomass was significantly negatively correlated with carbon addition level, while root tissue density and the ratio of lateral root length to adventitious root length were significantly positively correlated with carbon addition level (P<0.05). Overall, carbon addition reduced soil nitrate nitrogen content and significantly inhibited the biomass of S. alterniflora as well as the biomass of roots and leaves. Our findings could contribute to predicting the response of invasive plants to nutrient management measures and provide new insights for the management of invasive S. alterniflora.

Key words: Spartina alterniflora, carbon addition, nitrate nitrogen, root morphological trait, leaf morphological trait, biomass