Fire In The Landscape
This article was published in the Autumn 2012 edition of Fire Australia magazine.
Perched 30 metres above the ground atop an outstretched former-MFB crane, Mana Gharun is carefully measuring the moisture content of the eucalyptus leaves in the tree canopy. The 2009 Black Saturday fires burned extremely hot in these mountain forests, just south of Beechworth in the Victorian Alps. Mana, a researcher from the University of Sydney, is part of a collaborative group trying to find out how these forests are recovering from such a severe bushfire.
Twenty kilometres south, down a winding dirt fire track, Dr Gary Sheridan from the University of Melbourne is on firm ground, measuring the impact of the same fire on water run-off. In a steep gully, Gary and his colleagues have built a water trap to measure how fast and furious rainwater flows over the badly burned landscape.
This research on severely bushfire-damaged landscapes is helping to predict future fire behaviour – both prescribed fire and bushfire – and the potential adverse impacts on water and carbon. The Bushfire Cooperative Research Centre has commissioned this research through the University of Sydney and the University of Melbourne to measure fire impacts on water resources, erosion and carbon emissions.
Fire and land management agencies across southeastern Australia are supporting this research including ACT Parks, Conservation and Lands, whose Fire Management Unit Manager, Neil Cooper, is the lead end user of the projects. Other agencies involved are the Victorian Department of Sustainability and Environment, Parks Victoria, Country Fire Authority, CSIRO, New South Wales National Parks and Wildlife Service, State Forests NSW, NSW Rural Fire Service, Murray– Darling Basin Authority, and ActewAGL.
In four separate projects grouped under the name Fire in the Landscape, researchers are investigating above and below-ground carbon and water quality and quantity. The projects aim to gain knowledge for fire and land managers, to reduce the risk of large bushfires while delivering more high-quality water and an improved carbon balance.
Project leader Dr Tina Bell, from the University of Sydney’s Faculty of Agriculture and Environment, said the Fire in the Landscape research is addressing complex issues through the projects.
“This research involves two very important aspects of the environment: carbon and water. Or to put it more simply, the air we breathe and the water we drink,” she said.
One part of the field-based research is tackling questions such as how fire influences forest carbon storage and carbon dioxide emissions to the atmosphere.
“The immediate effects of fire in a forest or woodland, whether planned or unplanned, are to kill the vegetation and to convert the carbon stored in the vegetation into gases such as carbon dioxide, carbon monoxide and methane, as well as ash and charcoal.”
The University of Sydney’s investigations on carbon emissions from fire is linked to the work at the University of Melbourne, which is looking at carbon storage in soils and leaves and wood on the forest floor.
“In the months and years following a fire, the vegetation recovers but the amount of water the regenerating vegetation uses changes the amount of water available for run-off into catchments. We know the risk of erosion is highest when the vegetation has been removed and has not yet fully recovered, but one of the main aims of these research projects is to gain a better understanding of patterns of post-fire erosion events.”
The regeneration of the forest is not only important to protect the land from erosion but as Dr Bell explained, “as the forest or woodland regenerates, carbon is stored in leaves and bark, as litter on the forest floor and humus in the soil, as well as in fallen logs and branches. Recovering forest and woodlands change in water use and carbon storage capacity for many years after a fire.”
Dr Tarryn Turnbull, also from the University of Sydney’s Faculty of Agriculture and Environment, noted that the 2009 fires in Victoria mainly burned in mixed-species foothill forests.
“This forest type makes up much of the watersheds for catchments for Victoria and New South Wales and can be quite diverse, with up to 10 species of eucalyptus per hectare. You can compare this with other forest types, such as open jarrah forests in south Western Australia, which are dominated by only one or two species,” she said. “It is well known that water yield from catchment areas is coupled with water use by trees. Older, more established trees have a relatively lower water requirement than young, regenerating trees growing after a disturbance such as wildfire. As an example, a five per cent change in water use of the vegetation is equivalent to a 20 per cent reduction in the return of water to stream flow.
“There is no doubt that the fires in 2009 in mixed species forest have caused a change in hydrological cycles and therefore water yield. The question we are asking is, how big will that change be?”
The water use in wet ash-type forests has been studied extensively but mixed-species forests differ from ash-type forests in that they regenerate via sprouting shoots rather than from seed. Previous research has shown that juvenile leaves on epicormic sprouts are physiologically and phenologically different to mature leaves, but little is known about the water use of resprouting eucalypts and how this varies over time among species, topography and age.
This part of the research studying water has chosen four pairs of sites in north-eastern Victoria that have been selected according to time since fire (2006-07 and 2009) and elevation (300 metres and 900m above sea level).
The impact of fire upon water supply is also being studied by a PhD scholar from the University of Sydney, Jessica Heath. “This is an important issue as bushfires have a considerable impact on the environment, causing loss of vegetation and litter, a decline in soil organic matter and changes in soil properties. This, in effect, has an impact on the catchments’ hydrological processes.”
University of Melbourne’s Dr Gary Sheridan, from the Department of Forest and Ecosystem Science, is leading the project researching bushfire threats to hydrology and soil.
“Our work is focused around developing a model that will allow fire managers to predict the change in risk to water quality as a function of the frequency of prescribed burning,” he said.
“As part of this work we are investigating major erosion events after the 2009 Black Saturday fires in Victoria. The fires were stopped on the boundary of the water supply catchments that supply 80 per cent of Melbourne’s water. After the fires, more than 600km of firebreaks were constructed or upgraded to protect them from future fires and similar catchment protection efforts have taken place in other states.
“Given these substantial efforts and resources assigned to catchment protection it is important that fire managers have a clear understanding of what is at risk from bushfire and how this could be reduced with prescribed fire. Our aim is to develop a model for fire and land managers to predict how the probability of extreme impacts on water quality may be modified by prescribed fire.”
Dr Sheridan’s colleague at the University of Melbourne, Petter Nyman, said the risk of water quality impacts can be assessed in different contexts.
“From an operational perspective, the fire and land management activities influence risk through erosion mitigation works, the timing of prescribed fire and the pattern of burn in relation to drainages. Yet at a strategic level, the risk is influenced by climate change, resources allocated towards fire suppression, annual prescribed fire targets, strategic fuel reduction burns and other regional fire management strategies,” he said.
These two different views are having a great impact on the way the research is being interpreted.
“In terms of operational aspects, research can address changes in risk in response to erosion control works, burn patterns and the connectivity between streams and drainages. And from a strategic stance, research can address questions relating to the change in risk as a result of more frequent fire.”
Benefits for fire and land managers
The benefits that will come from the Bushfire CRC’s Fire in the Landscape research are extensive.
University of Sydney’s Dr Bell said that once the research is complete there will be a better understanding across the industry of water use and carbon storage capacity of forests and woodlands, the patterns of post-fire erosion events and emissions from bushfires and prescribed burning.
“If we can measure the processes involved we can better predict the risks associated with the effects of fire in the landscape,” she said. Lead end user Neil Cooper said he has great expectations for the outcome of the projects.
“I see this research developing operational tools that will help solve some of the major issues faced by land managers across the world: how to predict the likely erosion responses and carbon and water impacts to different fire regimes and weather patterns over a period of time. This type of information is critical for rapid-assessment team surveys as it will identify ‘hot spots’ for immediate treatment in an effort to prevent major adverse damage to water quality, infrastructure and human life,” he said.
“Of even more importance will be the application of these tools in the planning stages of prescribed burning, where sensitive areas can be identified before placing planned fire into the landscape,” he said.
Research Director of the Bushfire CRC, Dr Richard Thornton, said the ability to determine the fire-related effects on hydrology, erosion and carbon storage and emissions will be a major benefit to the community.
“The knowledge gained from the Fire in the Landscape research will ensure our land can be managed better before and after fire, our water resources are preserved and maintained, our air is fresh and clean and our personal safety and assets are secured for years to come,” he said.
“By improving our knowledge on how to manage fires in the landscape we will better our chances of coping with our changing environment. This Bushfire CRC research will give future generations the tools to be more resilient to bushfires.
“The knowledge gathered from such research will allow for better planning of strategies in fire management and post-fire regeneration of the landscape, which will reassure the community in the event of a fire.”