Science of TROBIT

Rainforest and savanna constitute the dominant two biomes of the tropical zone accounting for over 70% of the world’s plant species. With massive areas and high rates of latent and sensible heat exchange, they exert large yet different effects on the global climate. We have a limited understanding of their contemporary and future responses to global change. Tropical forests and savannas are very large carbon stores and are currently estimated to account for more than half of the global terrestrial carbon sink.

Although rainfall is a key determinant affecting the relative distributions of savanna and rainforest, other factors such as soil conditions, fire and disturbances such as grazing and human influence are also involved. Our knowledge of these factors and how they interact in influencing vegetation type is still poor - all global vegetation models currently misspecify the distributions of these biomes. Such knowledge is fundamental for understanding and predicting transitions in tropical vegetation at local, regional and global scales. For example, a drying of the Amazon Basin in coming decades could lead to the irreversible replacement of tropical forest with savanna, this then feeding back on the climate system as a consequence of changes in surface energy and mass balances - thereby accelerating global warming and tropical drying. One of the key motivations for this consortium is to reduce the recognised uncertainties in this model-based prediction of “Amazonian forest dieback.

Significant transitions centered on the gain or loss of savanna vegetation are not restricted to South America. Improved predictions of the factors causing forest / savanna transitions are fundamental to understanding future climate change and will depend on a significantly improved understanding of the environmental and edaphic determinants of the distribution of tropical vegetation at a global scale. To improve our understanding of these transition and improve predictions of change, we are establishing research sites in five countries across the tropics, Ghana, Cameroon, Brazil, Bolivia and Australia and are working to answer the following questions:

1) Functional Biogeography of Tropical Vegetation
2) Energy exchange and photosynthesis
3) Climate and Climate Change implications
4) Diversity of tropical biome structure and function

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