Redistribution and emission of forest carbon by planned burning in Eucalyptus obliqua (L. Herit.) forest of south-eastern Australia

Abstract

We applied standard forest inventory and soil sampling techniques to estimate carbon stocks in aboveground forest components and belowground in soil and fine roots to 30cm depth before, and immediately after, low intensity planned burning. Three areas within Eucalyptus obliqua forest that had not been burnt for more than 20years were sampled and, based on the calculated mass of components prior to and immediately following burning, the redistribution of carbon within the forest and carbon emission from the forest to the atmosphere were estimated. Of the 165Mg C ha−1 in aboveground components, about 7.8Mg C ha−1 was redistributed through accession of tree components to the forest floor and deposition of incompletely combusted plant structures and litter on the soil surface. A further 6.7Mg C ha−1 was emitted to the atmosphere, mostly from the on-ground and near surface components of litter, coarse woody debris and understorey. Overall, these E. obliqua forests sequester around 244Mg C ha−1 to 30cm soil depth (excluding woody roots) and planned burning transferred about 3% of this C to the atmosphere and a further 3% was transformed to charred and fragmented organic matter and deposited on the soil surface. Estimating long term C balance of burnt forests will require a much better understanding of the decay characteristics of these charred organic materials and good measures of post-fire aboveground carbon accumulation. The more intense a fire becomes the greater will be C emission from coarse woody debris and understorey, indicating the importance of quantifying these components in emission estimates for more intense planned burns and for wildfires.