Aroon Edgar, James Cook University, Townsville, Australia Michelle Waycott, James Cook University, Townsville, Australia Tony Grice, CSIRO Sustainable Ecosystems, Townsville, Australia Australian savannas

Australian savanna systems Savannas in an Australian context are referred to as ‘woodlands’ or ‘shrublands’ Variations in rainfall and soil determine structure and composition of savanna vegetation Broad Australian Vegetation Types

Australian savannas Australian tropical savannas Tropical savannas display a number of landforms: flat to hilly savanna woodlands sandstone country black soil plains Australian savannas tend to be <500 m above sea-level, with local relief generally <100 m. Australian sites are located along the eastern coast – Townsville and Charters Towers Extent of savannas throughout Northern Australia

Australian savannas Climate of Australian savannas Australian savannas lie within a tropical climatic zone Distinctive wet/dry seasons Variability in climate due to latitude, topography and distance from the coastline

Australian savannas Rainfall and Australian savannas Rainfall is a major savanna determinant Savannas may be either: Wet >900mm/year Semi-arid mm/year

Australian savannas Soils and Australian savannas The exact distribution of soil types in savannas is complicated Range of soil types found in savannas: Lithosols Lateritic soils Cracking clays Red/yellow earths Deep sands Alluvial soils Most notable feature of the soils that savanna vegetation grows upon is its low fertility Silver-leaved ironbark open-woodland on shallow soils that have low water-holding capacity and low fertility.

Australian savannas Vegetation Communities in Australian savannas Savanna communities range from: Open forests (coastal regions) Woodlands (semi-arid regions) Open woodlands (arid regions) Majority of savanna ecosystems in northern Australia are grassy landscapes. Classified in relation to the structure and composition of the vegetation

Australian savannas Vegetation structure in Australian savannas Savanna structure includes: a grassy component, and a woody plant component Tree height can range from 2-20 meters Canopy cover may vary between <1% and 60-70% Tree density can range up to 100/hectare Narrow-leaved ironbark and bloodwood woodland

Australian savannas Vegetation dominants in Australian savannas Australian savanna vegetation dominated by sclerophyllous taxa within: Eucalypts Acacia Other genera found within savannas: Eurphorbiaceae (Petalostigma) Combretaceae (Terminalia) Proteaceae (Grevillea) Bombacaceae (Adansonia) Casuarinaceae (Casuarina) Eucalypts dominate the savanna landscape

Australian savannas Understorey in Australian savannas Savanna understorey dominated by grass species Sorghum (coastal) Heteropogon (semi-arid) Themeda (semi-arid) Chryspogon (arid) Aristida (arid) Type of grassy understorey also varies with rainfall and soil texture Grass species used in Australian experiment Heteropogon contortus

Australian savannas Ecological distinctives of Australian savannas Australian Savannas have a number of ecological distinctives: Few large hard hoofed herbivores, soft footed macropods Large numbers of termites, and the Influence of fires

Australian savannas Influence of Fire on Australian savannas Fire has influenced the nature of Australian savannas over the course of their evolution It has shaped much of the vegetation and ecology of savannas and is an integral part of their management Aborigines have used fire since their arrival in Australia for a variety of reasons – communication, ‘cleaning’ the country and to maintain food sources Changes to traditional fire regimes has affected all aspects of the ecology of savannas – plants, animals, nutrients and water

Australian savannas Influence of Fire on Australian savannas Fire frequencies in northern Australia as detected by NOAA satellites (Landgate )

Australian savannas Biodiversity in Australian savannas Australian savannas are a refuge for biodiversity of world significance Savannas are home to a range of species of native plants, mammals, birds, reptiles and amphibians, and a great number of invertebrate species Many of the plants and animals found in Australian savannas are endemic

Australian savannas Biodiversity Issues in Australian savannas Extinction rates in Granivorous birds Savanna grasses are an important food source for a variety of Australian birds Small mammal decline Savannas act as a refuge for many of Australia’s smaller mammal species. Issues stemming from invasive grasses Invasive grasses have the potential to displace native vegetation, as well as increasing the fire fuel load

Australian savannas Land-use in Australian savannas Major land uses of Australian savannas include: Pastoralism Aboriginal Lands Conservation Reserves Military

Australian savannas Land-use in Australian savannas Land use in northern Australia

Australian savannas Australian Savanna Experiment Sites will be located at: Oak Valley (Site 1: ) 25km south of Townsville Average annual rainfall of 1120mm Grassland bordered by riparian area Fletcherview (Site 2: ) 100km southwest of Townsville Average annual rainfall of 600 mm Open savanna woodland combined with patches of dry rainforest or ‘vine thicket ’.

Australian savannas Site Locations Site 1 Site 2

Australian savannas Australian Species Tree Species: Wet Eucalyptus tessellaris Eucalyptus playtphylla Casuarina littoralis Melaleuca viridiflora Dry Eucalyptus erythropholia Eucalyptus creba Acacia shirleyi Petalostigma pubescens Grevillea pteridifolia Erythrina vespertillio Site 1: Humid Site

Contact Us Phone: or Web: CSIRO Sustainable Ecosystems Aroon Edgar

Australian savannas References Australian Government, Department of Environment, Water, Heritage and the Arts: Australian Natural Resources Atlas: Dyer, R., Jacklyn, P., Partridge, I., Russell-Smith, J. and Williams, D Tropical Savanna CRC: Savanna Burning: Understanding and using fire in northern Australia. Darwin EPA website: Google Maps: Groves, R.H Australian Vegetation. Cambridge University, Cambridge Rangelands: Tropical Savanna CRC: