TS-CRC Student project - Aspects of the physiological and fire ecology of Gamba Grass

Nothern Territory University

Natalie Rossiter


Summary | Aims | Progress | Utilisation and application of research |

Natalie Rossiter in front of a stand of gamba grass. The tussocks can reach a height of 4 metres, and produce very high fuel loads for fires in the savannas

Natalie Rossiter in front of a stand of gamba grass. The tussocks can reach a height of 4 metres, and produce very high fuel loads for fires in the savannas


Gamba grass (Andropogon gayanus) is a vigorous perennial species that has been selected as a pasture species for its competitive abilities and growth rates. However, concern has been raised about its recent spread outside of pastoral systems, and its occurrence is increasing in upland savannas and along riparian habitats.

At present there is little information on what effect the replacement of native grasses by exotic species such as Gamba grass may have on ecosystem processes such as fire regime and water and carbon cycles. This project will examine three related aspects of gamba grass ecology (1) plant physiological characteristics, particularly assimilation rates; (2) above-ground biomass production (fuel load), and (3) fire regime characteristics.

Results obtained on gamba grass will be compared with the native grasses Sorghum intrans and Heteropogon contortus. The results of this study will contribute to a greater understanding of the consequences of altering the composition of the savanna grass understorey.


The aims of this study are to:

  1. To determine the physiological mechanisms that allow gamba grass to accumulate greater biomass than native vegetation.
  2. To describe the potential changes to fire regimes that may be caused by the greater biomass production of Gamba grass.


To compare physiological aspects of gamba grass, heteropogon, and sorghum, the photosynthesis rate, and transpiration rate have been measured monthly since March 2001.

To compare biomass production (fuel load) between gamba grass and native grasses, plant biomass has been measured once in the early dry season (the start of the fire season), and will be measured again in the mid-dry season.

To determine the effects of gamba grass invasion on fire regime, experimental fires have be lit in savannas with understoreys dominated by gamba grass. This work was undertaken at Wildman River Reserve, in conjunction with the Parks and Wildlife Commission Rangers. Fuel loads and other fire characteristics such as flame, scorch and char height, rate of spread and fire temperature were measured. This information is currently being analysed and will be used to determine fire intensities and compared with known values for native grasses.

Utilisation and application of research

  • The research findings of the project will be used in education units at NTU on fire ecology and weed management.
  • The outputs of the project will also be used in the 'Flames ' and 'Savannas' model.
  • The outcomes of this research will assist managers to prioritise the need for weed control.

Dr Samantha Setterfield
Dr Lindsay Hutley
Dr Michael Douglas


Dr Lynda Prior
Dr Dick Williams
Northern Territory Bushfires Council
Northern Territory Parks and Wildlife Commission

Natalie is currently working towards her PhD on the impact of gamba grass. You can read about her project and progress by clicking here>>