Short-term effects of disturbance and nitrogen deposition on Alternanthera philoxeroides invading wetland plant communities

  Objective  Disturbance and nitrogen deposition are important environmental factors influencing plant invasion. At present, studies on the synergistic effects of disturbance and nitrogen deposition on plant communities in wetland invaded by Alternanthera philoxeroides are relatively lacking. This study was to explore the short-term effects of disturbance, nitrogen deposition and wetland plant communities on A. philoxeroides invasion, which established a strong theoretical support and practical foundation for the physical control of A. philoxeroides and the restoration and reconstruction of wetland vegetation.

  Method  In this study, invasive plant A. philoxeroides and four wetland plant communities, including Myriophyllum aquaticum, Scirpus validus, Iris wilsonii and Lythrum salicaria were selected as the subjects. And three-factor control experiments were designed for invasive plant disturbance (no disturbance, simulated herbivory, mowing), nitrogen deposition (no nitrogen addition and with nitrogen addition), and native plant competition or not (only A. philoxeroides modes, and A. philoxeroides and wetland plant communities composed by 4 plant species).

  Result  Simulated herbivory and mowing had significantly reduced the growth and reproduction traits, including the relative growth rate based on biomass, plant height and node number of A. philoxeroides. And mowing had a greater impact than simulated herbivory. The growth rate of biomass, stem length and internode numbers of A. philoxeroides was negative under mowing, the compensation index of biomass, stem length and ramet numbers of A. philoxeroides was significantly lower than those of simulated herbivory treatment, but there was insufficient compensation. Furthermore, the wetland plant community significantly reduced the indexes including root, leaf, total biomass, leaf number, stem length and branch number of A. philoxeroides. However, nitrogen deposition only significantly affected the compensation coefficient of A. philoxeroides branching. Except for leaf number and branching compensation coefficient, there was no significant interaction between disturbance and nitrogen deposition on plant communities in the wetland invaded by A. philoxeroides.

  Conclusion  Simulated herbivory and mowing are not conducive to the invasion of A. philoxeroides to a certain extent, and have a strong inhibitory effect on the growth and recovery of A. philoxeroides with the increase of interference intensity. Nitrogen deposition does not significantly affect the composite indicator of A. philoxeroides. The local wetland plant community can inhibit the invasion of A. philoxeroides to a certain extent. Combination of the disturbance and nitrogen deposition only has a significant effect on the compensation coefficient of number of leaves and number of ramets, but has no significant effect on the wetland plant community invaded by A. philoxeroides.