Short-term effects of disturbance and nitrogen deposition onAlternanthera philoxeroidesinvading wetland plant communities

ObjectiveDisturbance 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 philoxeroidesare relatively lacking. This study was to explore the short-term effects of disturbance, nitrogen deposition and wetland plant communities on A. philoxeroidesinvasion, which established a strong theoretical support and practical foundation for the physical control of A. philoxeroidesand the restoration and reconstruction of wetland vegetation.

MethodIn this study, invasive plant A. philoxeroidesand four wetland plant communities, including Myriophyllum aquaticum, Scirpus validus, Iris wilsoniiand Lythrum salicariawere 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. philoxeroidesmodes, and A. philoxeroidesand wetland plant communities composed by 4 plant species).

ResultSimulated 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. philoxeroideswas negative under mowing, the compensation index of biomass, stem length and ramet numbers of A. philoxeroideswas 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. philoxeroidesbranching. 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.

ConclusionSimulated herbivory and mowing are not conducive to the invasion of A. philoxeroidesto a certain extent, and have a strong inhibitory effect on the growth and recovery of A. philoxeroideswith 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. philoxeroidesto 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.