Soil carbon and climate warming in tropical forests: using experimentation and elevation to reveal responses across space and time

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Climate change is predicted to release carbon stored in terrestrial ecosystems, causing a major acceleration of future climate change. This carbon release is predicted to occur through increased rates of decomposition and respiration by plants and soil microorganisms under warming. However, the acceleration could be constrained in the long-term if microorganisms adjust their community-wide physiology to metabolise less carbon under higher temperatures. Despite the significance of this potential feedback, we have little information on the magnitude and mechanisms by which it occurs in tropical forests, which contain two-thirds of global terrestrial plant biomass and a third of global soil carbon. I address this uncertainty, by combining a unique tropical forest soil warming experiment with a series of 'natural' experiments along tropical forest elevation/temperature gradients. I will use cutting-edge techniques in soil biogeochemistry and microbiology to determine the magnitude and mechanisms of carbon release from these soils under warming, and the mechanisms by which it may be constrained, particularly by the physiological and community-wide changes in microbial communities. By combining experimental study of short-term microbial responses and observational study of long-term responses across elevation gradients, I will gain unique integrated insights, enabling the extrapolation of findings to landscape scales, and providing key information urgently needed by Earth-system models. In summary, this project will directly address what has been identified as the most significant cause of uncertainty in predicting the feedbacks between climate change and terrestrial ecosystems: the magnitude and mechanisms for tropical forest soil carbon release under climate warming, and the role of microbial communities in constraining this release.