Australia's vegetation has evolved with fire over recent and geological time where the combination of fire interval, intensity, timing and species response has created the grassy ecosystems of the Eastern Mount Lofty Ranges. Having an understorey dominated by grasses, seasonal herbaceous species and few woody shrubs.
Species found in grassy ecosystems have survived and thrived with fire through a number of mechanisms that either protect the core of the plant from the heat of the fire allowing it to re-shoot or through having a positive regeneration response from seed. The following are some examples of how particular types of plants survive fire.-
- Native Grasses re-grow from root stock that is protected below soil.
Xanthorrhoea sp. re-shooting
one week after fire
Photo: Bill New [NCSSA 2006]
- Lilies, orchids and other bulbs are generally Spring growing and will re-grow from bulbs protected below the soil.
- Tussocks such as iron grass, grass trees and sedges can re-shoot from the base of the plant and root stock.
- Wattles and other pea species have a hard seed coat that can be cracked by the heat of the fire, promoting germination with the next suitable conditions.
- Species such as sheoak, banksia and hakea have seed encapsulated in woody pods that protect the seed from fire and release the seed following a fire.
- Eucalyptus and Melaleuca species regenerate from epicormic buds protected under the bark and in the lignotuber at the base of the tree. And seed is released from woody capsules following a fire.
- The seed of many species can be stimulated out of dormancy by chemicals leached into the soil seed bank following fire and rains.
So the species of grassy ecosystems have various mechanisms to respond to fire, and sites that have a base of native vegetation will successfully regenerate. And indeed grassy ecosystems need some disturbance to refresh the system and to allow all species to regenerate every now and then. Fire has historically provided such disturbance however burning regularly and or too often can be counter productive and can promote weed invasion and will select for species that favour the timing and conditions of the event.
Weed invasion and vermin pose threats to the success of regeneration and in turn the long term health of grassy ecosystem vegetation. Weeds can take hold in burnt and disturbed areas where the soil is laid bare by the burning of the vegetation and surface humus. Rabbits, hares and too many kangaroos will impact on regeneration by browsing the green pick available from re-shooting plants and germinating seedlings. Stock accessing remnant vegetation through damaged fences will disturb the soil and browse on regenerating plants.
Burning of a grassy remnant provides an opportunity to assist the regeneration of native plant species through weed and vermin control. Fire will open up the area and perhaps make it easier to see weedy individuals and also to access them. The spot spraying of fresh growth of perennial weed grasses such as Phalaris sp. (phalaris grass), Ehrhata calycina (perennial veldt grass) and Pentameris pallida (pussy tail grass) can reduce the dominance of these species and allow native species to regenerate. Briar rose and other woody weeds will re-shoot following fire and can be managed by spraying the re-growth or through cut and swab removal. Newly germinating woody weeds such as African daisy are relatively easy to hand pull and cotton bush can be grubbed and removed from site when mature seed pods are present.
The reduced vegetation cover provided by the burn can also be used to advantage in controlling vermin. Vermin may be easier to see with shooting providing effective removal of hares, cats and foxes. The location of warrens and access for destruction may be made easier through the opening of the vegetation directly following a fire.
Planned and controlled burning is the preferred mechanism for using fire to manage grassy ecosystems. Deliberately lit fires are dangerous to the community and risk life and assets including remnant grass lands. These unfortunate occurrences of burning should still however be made use of to carry out weed and vermin control where required.
Burning of grasslands is considered as vegetation clearance under the Native Vegetation Act however the use of burning as a management tool can be given permission where the burning activity is part of a well developed vegetation management plan and approval is given by the Native Vegetation Council NVC). Further information about the NVC Guidelines for clearance through ecological prescribed burning is available here.