The impacts of burrowing activities of introduced rattus norvegicus on plant communities and moisture content and salinity of topsoil in Jiuduansha Wetland, Shanghai

Jiuduansha, currently in the succession stage of herbaceous plant community, are newly emerged islands in the Yangtze River estuary, and it was confirmed in 2008 that Rattus norvegicus had colonized the Jiuduansha Wetland. In order to know the effects of burrowing activities of introduced Rattus norvegicus on plant communities and soil in the Jiuduansha Wetland, we measured plant coverage, plant density, plant height, plant species importance value, plant species richness, plant species evenness, plant species diversity, moisture content and electroconductibility of topsoil between burrowing and non-burrowing areas. We also investigated the spatial relationship of burrowing locations and tidal creeks to explore the habitat selection strategy of Rattus norvegicus. The results showed that the burrowing activities of Rattus norvegicus reduced the coverage and height of Phragmites australis within Phragmites australis monoculture communities; and reduced the density, relative density, community coverage and importance value of Phragmites australis while increasing the density, coverage, relative density, relative height and importance value of Scirpus mariqueter in Phragmites australis-Scirpus mariqueter mixed communities; and increased the relative density, relative coverage and importance value of Tripolium vulgare and community species diversity while reducing the density and coverage of Spartina alterniflora and community coverage in Tripolium vulgare and Spartina alterniflora dominated communities. The burrowing activities of Rattus norvegicus reduced moisture content and electroconductibility of topsoil. Rattus norvegicus prefer to burrow near the edge of tidal creeks, which may contribute to its fitness. Introduced Rattus norvegicus could affect vegetation structure and succession of Jiuduansha by burrowing.