Abstract: This research is based in far north-west Queensland at Boodjamulla National Park, a dryland savannah dominated by Eucalyptus and Melaleuca woodlands and floodplains. The interspaces between the perennial tussock grasses are dominated by cyanobacterial soil crusts. The wet season is governed by monsoonal troughs and in the dry season there is often no rain at all. This two-year project has focused on; establishing the diversity of the different crust ecosystems, net carbon uptake annually, and seasonal eco-physiological function. Crust communities can be divided into three main types: flood plain crusts dominated by Scytonema, Simploca and Nostoc, with abundant liverworts and some areas of moss; dry savannah and elevated crusts dominated by Scytonema and Stigonema with lichens and liverworts and; rock crusts dominated by cyanobacteria and cyanolichens. CO2 exchange is measured with an automated cuvette system that records the CO2 difference over three minutes on a thirty-minute cycle, continuously. Data from the first wet season has shown that CO2 uptake by cyanobacteria is tightly linked to light intensity but at a considerable temperature range, of 23-36°C. During the wet season, ground water levels were maintained for many weeks. Throughout this time net CO2 uptake peaked, significantly outweighing respiration. This translates to highly productive cyanobacterial crusts for almost the entire wet season. In contrast, during the dry season a series of tests showed that cyanobacterial crusts were completely inactive. At the commencement of the wet season new cyanobacterial soil crusts are formed at the expense of last season’s crusts. In the growth stage cyanobacteria reach extremely high net photosynthetic rates coupled with N2-fixation. This constitutes the first wide-ranging eco-physiological report on crust function of its kind. The information will provide a comprehensive daily database for the calculation net productivity on an annual basis for cyanobacterial crusts in these ecosystems.
Williams, W., Reichenberger, H., Rose, N., Büdel. B., 2010, Cyanobacteria highly active during the wet season: A longterm study at Boodjamulla National Park, north-west Queensland., Conference Paper, viewed 14 August 2022, https://www.nintione.com.au/?p=3559.