Oral Presentation Australian Society for Limnology Congress 2013

Just add water? Lessons from Pillicawarrina (#102)

Samantha Dawson 1 , Richard Kingsford 1 , Peter Berney 2
  1. Australian Wetlands, Rivers and Landscapes Centre, University of New South Wales, Sydney, NSW, Australia
  2. NSW National Parks and Wildlife Services, Sydney, Australia

River regulation and agricultural activities have degraded many wetlands in the Murray-Darling Basin. To aid restoration, State and Commonwealth water management agencies are increasing environmental flows through infrastructure efficiencies, water buyback (>$8 billion) and purchasing agricultural land to increase protected area estates (Yanga, Toorale, Macquarie Marshes). My study site is the Macquarie Marshes in northern NSW, on the recently purchased Pillicawarrina property, which had been grazed and was cropped (irrigated and dryland) from the 1980s onwards. Part of this property was purchased in 2009, with the goal of returning the floodplain to pre-existing wetland vegetation. Initial restoration involved breaching levee banks to re-establish river-floodplain linkages. This approach (indirect restoration) is common in semi-arid wetlands, whereby wetland plant communities recolonise by natural processes, assisted through flooding and environmental flows. We aimed to investigate the likely success of indirect restoration by examining the composition of the soil seed bank and the extant plant community in cropped and uncropped areas.

We sampled soil seed banks on Pillicawarrina across eight types of extant vegetation and past cropping regimes. Seeds from sieved samples were identified and tested for viability and then compared among vegetation types and disturbance gradients.  Additionally, we surveyed previously cropped sites, comparing plant community composition to the adjacent wetland vegetation communities in the Macquarie Marshes Northern Reserve. Preliminary results suggest increased river-floodplain connectivity and flooding drive restoration of floodplain plant communities but this is mediated by the amount of disturbance, with the most highly disturbed areas taking longer to recover.