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

据预测，气候变化将释放储存在陆地生态系统中的碳，导致未来气候变化的大幅加速。预计这种碳释放是在变暖的情况下通过植物和土壤微生物的分解和呼吸速率增加而发生的。然而，如果微生物在更高的温度下调整其群落范围内的生理机能以代谢更少的碳，那么从长远来看，这种加速可能会受到限制。尽管这种潜在的反馈很重要，但我们对它在热带森林中发生的程度和机制知之甚少，而热带森林含有全球陆地植物生物量的三分之二和全球土壤碳的三分之一。我通过将独特的热带森林土壤变暖实验与沿着热带森林海拔/温度梯度进行的一系列“自然”实验相结合，解决了这种不确定性。我将使用土壤生物地球化学和微生物学的尖端技术来确定变暖下这些土壤碳释放的幅度和机制，以及它可能受到限制的机制，特别是微生物群落的生理和全群落变化。通过将微生物短期响应的实验研究与跨海拔梯度长期响应的观测研究相结合，我将获得独特的综合见解，使研究结果能够外推到景观尺度，并提供地球系统模型急需的关键信息。总之，该项目将直接解决预测气候变化与陆地生态系统之间反馈的最重要的不确定性原因：气候变暖下热带森林土壤碳释放的幅度和机制，以及微生物群落在限制这种释放中的作用。

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.