Water, energy and carbon fluxes from the world's tallest anigosperm (Eucalyptus regnans) at Wallaby Creek, south-eastern Australia

Australian temperate open forests cover an area of ~ 5.5 million ha of the continental landmass and have the potential to act as an important carbon sink. These forests also occupy many water catchments in the Victorian region, including Wallaby Creek (King Lake, Victoria), where the current site is located. The dominant canopy species in the catchment is Eucalyptus regnans (Mountain Ash), and is the world's tallest angiosperm (flowering plant). Old growth sites (200+ years) within the forest can reach heights of more than 100 metres, and their existence is crucial for the sustainable management and quality of Melbourne's drinking water. Previous estimates from temperate forests have generally shown that the net uptake of carbon (NEE) of ecosystem decreases with stand age, and in old growth forests carbon cycling has often been assumed to be in equilibrium. However, results from the Northern Hemisphere, using eddy covariance flux towers, indicate that old growth forests are a greater sink than first thought. The role of old growth open temperate forests in Australia is uncertain and this is the first such study of old growth forests in Australia. In order to advance our knowledge about carbon and water cycling in Australian temperate forests and reduce the uncertainty in carbon accounting of such forests, we have initiated a long term flux tower in the old growth Mountain Ash forest. We are using the Eddy Covariance method which will measure the carbon, water, energy fluxes. The tower itself is 110m high and is the tallest forest flux tower in the world. The site has been running since August 2005 and we present preliminary results from the site. Ultimately this approach will allow us to investigate, hourly, seasonal and interannual variability of water and carbon fluxes. It will aid in understanding how these ecosystems may respond to global change and how that in turn may affect water catchments.