Linking Microscale Processes with the Macro World: Microbes & Moisture through the Soil Profile

Microbes control planet Earth. Yet, integrating microbial information into large scale-perspectives and models remains difficult. Classical biogeochemical models assume that microbes are in equilibrium with their environment; hence as long as conditions remain “quasi-steady state” such models work. However, the world is increasingly in a non-steady state. Particularly, the hydrological cycle is in increasing disarray. At least 1/3 Earth’s land experiences regular drought, and climate models suggest this will increase. However, the biological processes occurring during the dry season have only been studied by inference from what happens when the rains return. Important dry soil phenomena remain unexplained, such as the "Birch Effect"—the pulse of respiration on rewetting a dry soil. Where does the carbon come from? These processes appear to result from a combination of microbial drought survival physiology and disconnections in soil water films that limit substrate diffusion. A focus of the talk will be about how we bridge the scales from the micro- to the ecosystem: How can we capture key microbial dynamics in models that are parameterizable at ecosystem to global scales?