Contact: Robyn Cowley - Senior Rangeland Scientist
Reference to the DPIF Industry Development Plan 2013-2017:
2.1 Develop and promote more efficient and environmentally sound production systems.
2.1.3 Continue work to optimise sustainable and productive use of NT rangelands.
Project Status: Continuing.
The long-term Kidman Springs Fire Trial (established in 1993), assessed the impact of fire management on woody cover and pasture condition. The trial is replicated on red and black soil sites, with grazed experimental plots burnt early or later in the dry season every two, four and six years, as well as unburnt control plots. A bio-economic modelling of the fire trial results was applied to a Victoria River District (VRD) representative property to assess production and economic implications of fire management. A GIS analysis of fire frequency in the VRD for different land types and land uses was used to interpret the management implications of project results in the context of current fire regimes and potential opportunities in a carbon economy. In addition to work by DPIF at the site, external research agencies (CSIRO and Qld DERM) with expertise in soil carbon, soil respiration and above-ground carbon storage, have recently collected data to enhance our understanding of the carbon implications of fire management in a grazed savanna. Trial results were reviewed at a fire session at the Australian Rangeland Society conference in Kununurra in September 2012.
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Below: An aerial view of VRRS fire trial treatments on the red earth site, June 2013. More densely-treed plots have been burned less frequently over the last 20 years (blue outline –unburned, black outline – six yearly burns). More open plots have been burnt more frequently (red outline - two and four yearly late burnt)
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22Results
Late season fires were required every four years on the red earth soil to manage woody cover, whereas on cracking clay, early fires every four years were adequate to manage woody cover.
Fires every two years or early dry season fires increased annual grass yield, but decreased total yield on the cracking clay; on the red earths, fires suppressed the increase of Heteropogon contortus yield through time and increased the proportion of dicots. Aristida latifolia yield was lowest on two and four yearly fires on cracking clay sites.
Bio-economic modelling of a commercial cattle station found that fires every four years improved animal production and enterprise profits, with late season fire providing the greatest benefits. There was an opportunity cost for early season fires (as recommended for carbon and biodiversity outcomes) of $85/km2 compared with burning later in the year.
GIS analysis of fire frequency in the VRD found that fire frequency on pastoral land was currently less than required to manage woody cover for the moderate and high productivity land types. However, for the
non-productive pastoral land types, fire frequency was higher than recommended and there may be the potential to reduce fire frequency and reduce carbon emissions in these situations.
A review of the project found that woody cover change through time should be determined by analysis of aerial imagery.
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