Integrated and comprehensive estimation of greenhouse gas emissions from land systems

Exchanges of carbon and nitrogen between the atmosphere and terrestrial ecosystems involve a complex set of interactions affected by both natural and management processes. Understanding these processes is important for managing ecosystem productivity and sustainability. Management processes also affect the net outcome of exchanges of greenhouse gases between terrestrial ecosystems and the atmosphere. In developing a national carbon accounting system (NCAS) for Australia to account for emissions and removal of greenhouse gases to and from the atmosphere, a carbon:nitrogen mass balance ecosystem model (FullCAM) was developed. The FullCAM model is a hybrid of empirical and process modelling. The approach enables application to a wide range of natural resource management issues, because it is at land-management-relevant spatial and temporal resolution and captures the main process and management drivers. The scenario-prediction capability can be used to determine the emissions consequences of different management activities. Because, in Australia, emissions of greenhouse gases are closely related to the retention of dead organic matter and the availability of nitrogen for plant growth, the carbon and nitrogen cycling as modelled are good indicators of ecosystem productivity and condition. The NCAS also emphasizes the advantages of a comprehensive and integrated approach to developing a continental scale ecosystem-modelling system that has relevance both to estimation of greenhouse gas emissions and sustainable management of natural resources.