The effect of inundation and salinity on the germination of seed banks from wetlands in South Australia

Abstract

Three wetlands from the Upper South East of South Australia were chosen to investigate how a past history of drought (dry since 2002, 2004 and 2005) and salinity (2800 to >20,000 mg L −1) influenced the response of the seed bank to two water regimes (drained and flooded) and four salinities (500, 1000, 3000 and 5000 mg L −1). The maximum number of germinants (1270 ± 850 m −2) and species richness (7 ± 2.4) was greatest under the fresher drained treatment compared with the flooded more saline treatment under which there was no germination at one site. There were significant interactions between water regime and wetland previous history for two wetlands, but not the third which was the most saline and had experienced the longest drought. This indicated that the previous drought and salinity conditions experienced by a wetland affected seedling emergence but in the two less impacted wetlands the imposition of fresher drained conditions mitigated against these impacts. This suggests that if drought conditions continued with repeated exposure to elevated salinities the number of seeds and the species diversity of the seed banks would continue to decline.