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Australian savannas

Australian savannas

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Australian savannas

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

  2. 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

  3. 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

  4. 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

  5. Rainfall and Australian savannas • Rainfall is a major savanna determinant • Savannas may be either: • Wet >900mm/year • Semi-arid 300-900mm/year Australian savannas

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. Influence of Fire on Australian savannas Fire frequencies in northern Australia 1997-2005 as detected by NOAA satellites (Landgate) Australian savannas

  14. 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

  15. 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

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

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

  18. 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

  19. Site Locations Site 1 Site 2 Australian savannas

  20. 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 Australian savannas

  21. Contact Us Phone: 1300 363 400 or +61 3 9545 2176 Email: enquiries@csiro.au Web: www.csiro.au CSIRO Sustainable Ecosystems Aroon Edgar

  22. References • Australian Government, Department of Environment, Water, Heritage and the Arts: http://www.environment.gov.au/ • Australian Natural Resources Atlas: http://www.anra.gov.au • Dyer, R., Jacklyn, P., Partridge, I., Russell-Smith, J. and Williams, D. 2001. Tropical Savanna CRC: Savanna Burning: Understanding and using fire in northern Australia. Darwin • EPA website: • www.epa.qld.gov.au/ • www.epa.wa.gov.au/ • Google Maps: http://maps.google.com.au/ • Groves, R.H. 1981. Australian Vegetation. Cambridge University, Cambridge • Rangelands: http://www.rangelands-australia.com.au/ • Tropical Savanna CRC: http://savanna.ntu.edu.au/ Australian savannas