- Title:
-
The Distribution and Dynamics of Grass-Layer Plants in a Tropical Savanna: Results of the Territory Wildlife Park Fire Experiment in Northern Australia
- Date:
- September 2008
- Organisations
- AFAC 2008 Conference
- Authors:
- K.A Scott, S.A Setterfield, M.M Douglas, A.N Andersen.
- Location:
- Australia, Australia
Overview
The International Bushfire Research Conference 2008 - incorporating The 15th annual AFAC Conference, Adelaide, South Australia, Australia
The tropical savannas of northern Australia are undeniably Australia's most flammable ecosystem. Despite that acolade though, little is known of the role of fire in ecological processes, and the impact of different fire regimes on species abundance in Australian savannas.
To address the research gaps, a manipulative fire experiment was established by the Bushfire CRC and collaborators in 2004, in savanna near Darwin, Northern Territory. One component of the multidisciplinary research program investigated the role of fire regimes on the abundance of grass-layer plants (e.g. grasses and herbs) and their life cycle processes.
During a four year observation period, the species composition of grass-layer plants remained unchanged by different fire regime treatments, including the extremes of annual burning and fire-exclusion. Instead, their distribution in the landscape was strongly influenced by environmental factors such as soil moisture, shading from trees, and litter cover. Density increased progressively during the four year study, corresponding to increasing rainfall. Grass-layer plants were resilient to a high fire frequency because of their ability to sprout after fire and avoid heat-related mortality, as buried seeds in a soil seed bank. Adults of a dominant perennial grass had a similar survival rate within anually burnt and unburnt plots, after a three-year observation period.
Similarly, the density of germinable seeds in the soil seed bank was not significantly reduced by fire. In fact, laboratory heating promoted seed germination (especially native legumes), and exposure to ambient smoke increased the germination of a common annual grass. In contrast to short term fire regimes though, long term (15 year) fire exclusion may have a profoud effect on plant composition.
A comparison between a long unburnt and frequently burnt site revealed a significant difference in grass species composition, owing to the loss of common species such as Sarga intrans with fire exclusion.
