Poster Presentation Australian Society for Limnology Congress 2013

Mapping the Moira Grass: the decline of Pseudoraphis spinescens grasslands at Barmah Forest (#207)

Lyndsey Vivian 1 , Robert Godfree 1
  1. CSIRO, Canberra, ACT, Australia

Floodplain grasslands are highly dynamic, diverse and productive ecosystems. However, many floodplain grasslands are degraded because of changes to natural flood regimes. In southern Australia, one of the largest floodplain grasslands occurs at Barmah Forest, a ca. 30,000 ha floodplain on the Murray River. These grasslands, dominated by Pseudoraphis spinescens (Moira grass), have been declining in extent since river regulation in the 1930s. Current management focuses on using environmental flows to provide more natural flood regimes. However, there is no current estimate of the remaining extent of the grasslands following the Millennium Drought and the subsequent flooding from 2010-12, and little is known about the seed bank. To address these knowledge gaps, we conducted surveys to map and quantify the current distribution of P. spinescens grasslands in treeless plains and lakes across Barmah Forest, and investigated the seed bank dynamics. We also gathered evidence from photographs, historical observations and monitoring data to determine how P. spinescens grasslands have changed over time. Our results suggest there is currently less than 44 ha of P. spinescens grassland patches remaining in treeless areas in the forest, with an additional 105 ha containing lower cover. The seed bank also appears to be depleted. Pseudoraphis spinescens grasslands have declined at different times in different parts of the forest. A range of factors may be causing this decline, including altered flood regimes, drought, and grazing. Further research into understanding these drivers is crucial for improved conservation and management of this important floodplain ecosystem.