The impact of a novel invasive species, Orbea variegata (African carrion flower), on the chenopod shrublands of South Australia

This study measured the impact of an introduced plant species, Orbea varieg ata (African carrion flower), upon the dominant shrub Atriplex vesicaria (b ladder saltbush) and the annual plant community in chenopod shrublands of S outh Australia. Shrubs with Orbea growing underneath were likely to be less healthy than shrubs without Orbea. Pre-dawn water potential and growth of saltbush decreased in the presence of Orbea. Orbea appears to limit water a vailability to saltbush either by direct competition, a decrease in rainfal l penetration through the soil, or a combination of both. Orbea also reduce d both the germinable soil seed bank and the biomass of annual plants. Our data suggest that Orbea has a severe detrimental effect on the native veget ation. We speculate that Orbea has the potential to spread further into the chenopod shrublands during years of particularly high summer rainfall. (C) 1999 Academic Press.