How Does Fuel Reduction Burning Influence Forest Carbon Storage And CO2 Emissions To The Atmosphere?

Presentation at Research Forum of the 2012 Bushfire CRC and AFAC Annual Conference.

Fuel reduction burning over large areas of forest is currently a key tool of management in reducing the risk of mega-fires to life and property and crucial regional assets such as water catchments. At both policy and management levels there is a poor basis for determining the impacts of fuel reduction burning on release of CO2, a major greenhouse gas, to the atmosphere. We measured forest carbon pre- and post-fire at a range of sites in south-eastern Australia to improve the basis for calculating the transfer of carbon, during fuel reduction burning, from forests to the atmosphere as CO2. Eucalyptus obliqua dominated forests in the Otway Ranges, Gippsland and north-east Tasmania were selected for measurements.

We used standard forest inventory to derive estimates of forest biomass (aboveground) and sampling to calculate forest floor (coarse woody debris and litter) and soil carbon stocks (to 30cm depth). We derived burn intensity rankings from flame height, changes in bark thickness and immediate post-fire changes in canopy cover (hemispherical photography). From these estimates of mass loss due to burning we calculated the mass of CO2 emitted to the atmosphere from published emission factors. Results to date show that most emitted carbon is lost from understorey, surface litter and bark. We discuss these results by contrasting CO2 emissions from repeated fuel reduction burns with estimates for emissions from occasional mega-fires such as those in Victoria in 1983, 2003, 2006/7 and 2009. Methods to minimize emission while maintaining the benefits of fuel reduction burning are discussed.