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Sediment type and nitrogen deposition influence the relationship between Alternanthera philoxeroides and experimental wetland plant communities
Wetlands are susceptible to invasions. Nutrient availability of wetland sediment is strongly influenced by both sediment type and nitrogen deposition. We performed a greenhouse experiment to investigate the main effects and interactions between presence of Alternanthera philoxeroides, sediment type and nitrogen deposition on biomass and evenness of experimental wetland plant communities. We established wetland plant communities without and with A. philoxeroides in two different sediment types crossed with two nitrogen deposition treatments. Experimental wetland plant communities consisted of four native or naturalized wetland species. Sediment type and nitrogen deposition significantly promoted A. philoxeroides growth. At the community level, presence of A. philoxeroides decreased the total biomass of wetland plant species and increased community evenness, while sediment type significantly decreased evenness. At the species level, presence of A. philoxeroides significantly decreased total biomass of Iris wilsonii and increased total biomass of Pontederia cordata. However, the interaction between invasion and nitrogen deposition significantly increased total biomass of Butomus umbellatus. These findings suggested both sediment type and nitrogen deposition promote A. philoxeroides growth and exacerbate A. philoxeroides invasion into wetland plant communities. However, presence of A. philoxeroides can increase the evenness of the wetland plant communities at a small scale by suppressing dominant species.
MF17335 Accepted 22 December 2017
© CSIRO 2017