Developing a savanna burning emissions abatement methodology for tussock grasslands in high rainfall regions of northern Australia

摘要

Fire-prone tropical savanna and grassland systems are a significant source of atmospheric emissions of greenhouse gases.  In recent years, substantial research has been directed towards developing accounting methodologies for savanna burning emissions to be applied in Australia’s National Greenhouse Gas Inventory, as well as for commercial carbon trading purposes.  That work has focused on woody savanna systems.  Here, we extend the methodological approach to include tussock grasslands and associated Melaleuca-dominated open woodlands (<10% foliage cover) in higher rainfall (>1,000 mm/annum) regions of northern Australia.  Field assessments under dry season conditions focused on deriving fuel accumulation, fire patchiness and combustion relationships for key fuel types: fine fuels − grass and litter; coarse woody fuels − twigs <6 mm diameter; heavy woody fuels − >6 mm diameter; and shrubs.  In contrast with previous savanna burning assessments, fire treatments undertaken under early dry season burning conditions resulted in negligible patchiness and very substantial consumption of fine fuels.  In effect, burning in the early dry season provides no benefits in greenhouse gas emissions and emissions reductions in tussock grasslands can be achieved only through reducing the extent of burning.  The practical implications of reduced burning in higher rainfall northern Australian grassland systems are discussed, indicating that there are significant constraints, including infrastructural, cultural and woody thickening issues.  Similar opportunities and constraints are observed in other international contexts, but especially project implementation challenges associated with legislative, political and governance issues.