Fire and vegetation management in pasture lands of the Victoria River District, Northern Territory

Dyer, Rodd MacGregor (2003). Fire and vegetation management in pasture lands of the Victoria River District, Northern Territory Master's Thesis, School of Land, Crop and Food Sciences, The University of Queensland.

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Author Dyer, Rodd MacGregor
Thesis Title Fire and vegetation management in pasture lands of the Victoria River District, Northern Territory
School, Centre or Institute School of Land, Crop and Food Sciences
Institution The University of Queensland
Publication date 2003
Thesis type Master's Thesis
Open Access Status Not Open Access
Supervisor John Mott
Total pages 194
Language eng
Subjects 07 Agricultural and Veterinary Sciences
Formatted abstract
Anecdotal and scientific evidence suggests that tree and shrub thickening is occurring throughout savanna woodlands in the Victoria River District (VRD) of the Northern Territory. A likely contributing factor is thought to be changes to fire regimes, primarily a reduction in the incidence, extent and intensity of burning, resulting from both direct and indirect impacts of grazing and pastoral land-use. A program of long-term fire research was established in late 1993 on Victoria River Research Station (Kidman Springs). This work investigated the impact of fire frequency, fire season, fuel loads and fire intensity on woody plants and pasture condition in arid short grass (ASG) and ribbon-blue grass (RBG) communities in the VRD. 

Woody plant height and pasture community, but not fuel load or burning season, significantly influenced woody plant mortality. Mortality rates following burning averaged 2% in RBG and 5% in ASG. Smaller plants had higher mortality rates. Mortality rates for Lysiphyllum cunninghamii (bauhinia) and Carissa lanceolata (conkerberry) were 3% and 5% respectively, and higher compared to 1% for Terminalia volucris (rosewood). Despite low plant mortality, fire induced top kill can be used to manipulate canopy cover and plant height in both pasture communities. Top kill occurs following the death of aerial branches and is related to plant height and factors that influence fire intensity. Intense fires have the most impact on top kill and plant structure. Although top kill was greater following latedry burns, season of burn had no impact on average canopy cover. Increasing burning frequency did result in significant reductions in canopy cover for both pasture types. Once woody plants exceed 2.0 -2.5 meters in height they become more difficult to control with fire. Implementing a prescribed bum every 5-6 years will maintain woody plants below this critical height. 

Fuel loads of at least 2000 kg DM/ha, fuel cover of at least 60%, as well as appropriate fire weather and fuel curing state are required to cause significant changes to woody plant structure. Grazing pressure on each pasture type needs to be managed prior to burning to ensure suitable fuel conditions.

Without burning, native woody plant growth/regrowth in both RBG and ASG pasture communities continues rapidly. Results indicated that woody plant growth and recovery in the absence of fire continues at the rate of between 10-20 cm per year for all species less than 200 cm. Obvious recovery of woody plant height was observed in plots unburnt for 5 years, but no increase in plant density was detected.  ........................................................
Keyword Vegetation management -- Northern Territory -- Victoria River District
Grassland fires -- Northern Territory -- Victoria River District

Document type: Thesis
Collection: UQ Theses (non-RHD) - UQ staff and students only
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