Program C: Systems Modelling

An Overview of the 2001- 2002 Research Year and Prospects

The major highlight of Program C was the commencement of research involving analysis and inter-comparison of models producing estimates of NPP at the continental scale. NPP data for the Australian continent were obtained from a range of models and showed a wide range of estimates for continental NPP ranging from about 0.9Gt to about 3.5Gt carbon per year. The work by the CRC has shown that the NPP of Australia is much less well known than its climatic drivers, temperature, rainfall, runoff, and solar radiation. The largest relative variation of estimates in NPP appears to be in arid and semi-arid regions. These regions comprise much of the surface area of Australia and deserve more attention as small changes in carbon stocks over large areas can produce significant sinks or sources of carbon.

Systematic comparison of biological models and their outputs has to date been uncommon in Australia and until now we have lagged behind international efforts. Internationally inter-comparison of the soil vegetation atmosphere transfer type models has become more common in the last few years with inter-comparison studies on global estimates of NPP and of model subcomponents. The CRC research activities and workshops have for the first time drawn together the majority of continental scale biological modellers in Australia plus some international participants. Participation in model inter-comparisons improves the “credentials” of each of the participating models.

NPP is usually difficult to measure and few if any systems in Australia have comprehensive estimates of NPP covering the full range of climate variability. Most biological measurements are of components of the ecosystem system (i.e. standing biomass or litter fall) and hence the reliance of modelling for integrating the little data we have over time and space. Models are the only mechanism for estimating current and future CO2 and climate change impacts on carbon stocks of Kyoto and non-Kyoto lands.

Other highlights include refinement of the CenW model and its successful testing against carbon isotope data from tree rings, integration of NPP models into the Carbon Modelling Integration Shell (COINS) framework, assembly and documentation of useful datasets.