Oral Presentation Australian Society for Limnology Congress 2013

Examination of River Red Gum (Eucalyptus camaldulensis) condition in relation to river flow in Victoria, Australia (#40)

Aidan Kereopa 1 , Angus Webb 1 , Siobhan deLittle 1
  1. University of Melbourne, Parkville, VIC, Australia

Examining ecological responses to changes in river flow is important for appropriate management of river systems. This is particularly significant for regulated rivers as water extraction for human use can create a scenario where the biota is already in a state of water stress. This study examines the condition of River Red Gum (Eucalyptus camaldulensis) in Victoria at the end of a major drought period (2000-2010). We investigated the connection between antecedent hydrological conditions and health of this iconic eucalypt species. Remotely sensed data (LiDAR and Landsat TM 4-5) were used to quantify red gum condition. Plant area index (PAI) was extracted from LiDAR data, and riparian vegetation was stratified by tree height and overlayed with a normalised differenced vegetation index (NDVI). Previously acquired flow data was then correlated with tree condition using Bayesian hierarchical modelling. The analyses revealed a gradient of hydrologic stress across Victoria. A decline in tree condition from east to west in the state was related to reduced flooding. The study forms part of a wider assessment of the ecological benefit from public investment in purchasing and releasing environmental flows. The methods used allow for a review of evidence for the applicability of remote sensing data to landscape scale hydro-ecological investigations. Analysis also highlights the applicability of Bayesian hierarchical modelling to complex environmental problems. For river red gum, it highlights the importance of high flows and floods in maintaining tree condition. Whether such flows can be delivered by environmental flows programs is another matter.