Abstract ID: 322

Using experimental drought to understand rain forest carbon cycling at seasonal to interannual timescales

Drought strongly affects rain forest functioning at seasonal, interannual and potentially longer timescales. The mechanisms underlying the effects of drought on the cycling of water and carbon by rain forest represent an increasing focus for the research community, not least because some representations of these processes in large scale models can misguide understanding. We performed an artificial through-fall exclusion experiment in eastern Amazonia, excluding water from the soil over 1 ha of forest. The aim was to probe the mechanisms underlying the response by rain forest to drought. We completed a detailed three year measurement and modelling analysis of the impact of soil moisture reductions on photosynthesis, respiration and other components of productivity. The rainfall exclusion process was also extended over additional years, with a less intensive measurement program considering longer-term ecological processes. The results of our analysis provide the first detailed measurement-driven quantification of the impacts of large scale experimental drought on both photosynthesis and respiration. They not only demonstrate some expected reductions in both processes, but also differences in the response in respiration by different components of the ecosystem. These differences (e.g. between soil and leaves) have a significant impact on the change in NEP under drought. We consider these effects in the context of carbon exchange in the Amazon at larger geographical scales, and particularly at the seasonal-interannual timescale.

Session:  Carbon - The role of seasonality in carbon and water balance.

Presentation Type:  Oral