Impact of the introduced grass Agrostis stolonifera on vegetation and soil fauna communities at Marion Island, sub-Antarctic.

摘要

Agrostis stolonifera is the most successful introduced vascular plant at sub-Antarctic Marion Island. Since its accidental introduction, probably in the 1950s, it has spread over the northern half of the island. It invades undisturbed native vegetation and reaches dominance in a range of habitats. It is most abundant on wet slopes and river banks, where it replaces the rosaceous dwarf shrub Acaena magellanica communities by dense grassland. These plant communities showed a reduction of 50% in the mean number of native plant species, although more macro-invertebrates and more mites [Acari] were found where A. stolonifera was dominant. The invasion by A. stolonifera did not pose an immediate threat to the survival of native species, but changes induced in the drainage line communities significantly reduce the value of the island from a conservation viewpoint and as a natural laboratory for fundamental ecological research.