Innovative Findings in Northern Savannah Fire Management

Dr Dionne Walsh using a drip torch to light an experimental burn at the Kidman Springs fire experiment. Image: NT DAF.

SPELLING northern savannah country post-burn could extend the intervals between controlled burns from four years to six, according to Australia’s only long-term study into grazing land savannah burning.

A combination of burning and post-burn spelling promoted palatable grasses while effectively managing the tree-grass balance, as revealed by a 30-year study at Victoria River Research Station, located 400km south of Darwin.

Research Initiatives

The study, spearheaded by NT’s Department of Agriculture and Fisheries, evaluated the impact of fire on vegetation across various frequencies and fire seasons. The research team investigated different woody cover effects with early burns (June) versus late burns (October) conducted at intervals of two, four, and six years on both eucalypt woodlands and grasslands.

Dr Robyn Cowley

Key Insights

Lead researcher and senior rangeland scientist Dr Robyn Cowley noted that, given suitable fuel loads, a six-yearly, late-season fire may maintain the tree-grass balance effectively in woodlands.

“Early dry season fires had little impact on woody plants in the woodland. However, on the grassland, early six-yearly fires were just as effective as late fires,” said Dr Cowley.

Since 2013, the research team has implemented a wet-season spelling approach on designated fire-experiment plots, effectively reducing the average stocking rate by one-quarter compared to continuously grazed sites. This method is endorsed for promoting pasture recovery post-fire.

“Before we introduced post-fire spelling, burnt areas often suffered from heavy grazing, leading to a concerning decline in preferred pasture species in the grassland,” Dr Cowley explained.

Drone footage of controlled burns in October 2019 at the Kidman Springs grassland site.

Dr Cowley explained that the experiment aimed to examine how controlled burns affect vegetation structure and productivity. “The semi-arid tropical savannas of northern Australia have evolved with fire; however, traditional Aboriginal burning practices have diminished, resulting in increased wildfire control and reduced fire incidence in grazing areas. This shift can disrupt the ecological balance,” she noted.

Conclusions

Fluctuating rainfall and drought influence woody cover, but the study revealed that grass understorey growth exhibited remarkable resilience, with perennial grasses remaining largely unaffected. The findings suggest that post-fire grassland diversity significantly improves.

“Without fire, the native woody encroachment into productive grasslands can convert them into open woodlands, negatively impacting livestock carrying capacity,” Dr Cowley warned.

Other key researchers involved in the study include Dr Rodd Dyer and Dr Mark Hearnden.

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