The cycling of carbon and nitrogen in soils is controlled by microorganisms. How such microbial communities respond to novel climates regimes in the future will thus affect carbon and nitrogen fluxes, which in turn can change greenhouse-gas fluxes, soil fertilities, and other aspects of ecosystem functioning. Current models are limited in accurately predicting biogeochemical pulses during large rainfall events after droughts. As future climate regimes are expected to be characterized by an increased frequency of droughts and floods, overcoming this limitation, by better understanding the underlying microbial mechanisms, is important for predicting future ecosystem dynamics. Specifically, sudden changes in soil moisture resulting from droughts and floods induce moisture stress on microorganisms, which is bound to influence the distribution of microbial functional groups and traits. Changes in soil moisture also affect physical processes, like the diffusion of substrate, enzymes, and microbial cells, which must be in contact for microbial metabolism and many gas fluxes to proceed. Methodological challenges hinder investigating these mechanisms experimentally, leaving much unexplained variability in current biogeochemical models. In this project, we use an individual-based model of soil microbial communities developed at IIASA to examine how droughts and floods affect enzyme activity and the distribution of microbial traits, and how changes in these factors affect carbon and nitrogen cycling at larger scales. This work will inform efforts to more accurately predict biogeochemical fluxes under future rainfall regimes, as well as improve our understanding of the role of soil microorganisms in larger-scale ecosystem dynamics.
Last edited: 24 March 2016
International Institute for Applied Systems Analysis (IIASA)
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