Tree-grass dominated savanna ecosystems are one of the most spatially distributed forms of terrestrial vegetation on the planet. They occur on all major continents, excluding Antarctica, and can dominate tropical, sub-tropical and temperate climatic areas. Their sheer diversity results in them having an immense effect on the global climate. It is therefore imperative to understand the dynamics of the tree and grass interactions within savanna ecosystems in order to understand how these ecosystems may react to future global change.
This research will aim to build upon previous research in tropical Australian savanna by understanding how the grass component of the savanna contributes to annual gross primary productivity (GPP). In order to achieve this, remote sensing techniques will be employed and supplemented with daily temporal frequency in situ sampling to understand how the grasses affect GPP during their strongly seasonal (wet season) dominance. Addressing the limitation of moderate resolution satellites (i.e. MODIS) to easily partition the contribution of grasses and woody overstory in the estimation of savanna greenness, the temporal in situ measurements will assist in quantifying these fractional changes over time.
The critical greenness observations will be related to ecosystem GPP, derived using eddy covariance techniques and light use efficiency estimates of GPP at the MODIS scale. This approach will provide a more complete understanding of the land-atmosphere processes occurring above tree-grass savanna in tropical north Australia.