Soil Microbial Controls on CO2 Fluxes in a Tropical Dry Forest

Identifying key mechanisms underlying carbon cycling dynamics in a vulnerable, highly seasonal tropical dry forest ecosystem.

The Science

In dry or semiarid ecosystems, most soil respiration [carbon dioxide (CO2) production by microorganisms] can occur in large “pulses” immediately following rainfall events. An in situ rainfall manipulation experiment was combined with a simulation modeling approach to identify the dominant belowground controls on these important CO2 fluxes.

The Impact

Dissolved organic carbon availability to microbes was identified as a key controller of soil CO2 pulses following rainfall events. This relationship can be captured in simple ecosystem models, allowing a better prediction of how the ecosystem carbon balance will respond to ongoing changes in precipitation regime.


An in situ precipitation manipulation experiment was conducted in a tropical dry forest in Guanacaste, Costa Rica, to better understand the processes underlying rainfall-induced pulses of soil respiration. (Re)-wetting dry soil produced an immediate, substantial pulse of CO2, accompanied by rapid immobilization of nitrogen into the microbial biomass. The size of the CO2 pulse following simulated rainfall events was linked to dissolved organic carbon (DOC) availability to microbes. The relationships among soil moisture, DOC, and CO2 fluxes were then integrated into simple biogeochemical models, which could accurately predict observed patterns of CO2 flux in response to rainfall. Together, these data demonstrate that explicitly representing microbial processes in such models can improve predictions of carbon cycling under changing rainfall regimes.

Principal Investigator(s)

Jennifer Powers
University of Minnesota


The Terrestrial Ecosystem Science (TES) program of the Office of Biological and Environmental Research, within the U.S. Department of Energy Office of Science, (award number DESC0014363) and the National Science Foundation (CAREER grant DEB 1053237 to JSP).


Waring, B.G., and Powers, J.S. “Unraveling the mechanisms underlying pulse dynamics of soil respiration in tropical dry forests.” Environmental Research Letters 11(10), 105005 (2016). [DOI:10.1088/1748-9326/11/10/105005].