Oral Presentation Australian Society for Limnology Conference 2016

Does floodplain watering improve understorey vegetation response to natural flooding? (#29)

Jason M Nicol 1 , Susan L Gehrig 1
  1. SARDI Aquatic Sciences, Henley Beach, SA, Australia

Watering areas of floodplain has become a widely adopted management intervention during periods without flooding. The aims of these interventions are to improve overstorey condition, provide conditions suitable for recruitment of flood dependent species and maintain floodplain condition so that it will respond to flooding. There is considerable evidence that watering improves overstorey condition and provides conditions suitable for recruitment of flood dependent species; however, how watering influences the response of floodplain vegetation to flooding it is not well understood. We proposed that the response of the understorey vegetation to flooding would be more positive on a watered floodplain compared to an unwatered floodplain. To test this hypothesis we compared the understorey vegetation before and after the 2010-11 flood on two floodplains on the lower River Murray: the Chowilla Floodplain which received 27.5 Gl of environmental water between 2004 and 2010 and the Pike Floodplain which received no environmental water. Vegetation surveys were undertaken in February 2010 on both floodplains and the vegetation was dominated by terrestrial and salt tolerant species with large areas devoid of vegetation; however, two temporary wetlands on the Chowilla Floodplain were watered in spring 2009 and those areas were dominated by flood dependent species. Species richness for Chowilla and Pike was 42 and 17 respectively in February 2010. The same sites were surveyed after the 2010-11 flood and the vegetation in areas that were flooded was dominated by flood dependent species on both floodplains and the species richness at Chowilla and Pike was 66 and 68 respectively. Data collected in this study did not show that there was a more positive response of the understorey vegetation on the watered floodplain and there is no evidence that watering maintains areas of floodplain so that they respond to flooding.