Identifying key mechanisms underlying C cycling dynamics in a vulnerable, highly seasonal tropical dry forest ecosystem.
In dry or semiarid ecosystems, most soil respiration (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.
Dissolved organic carbon available 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 us to better predict how 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 N 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 our predictions of C cycling under changing rainfall regimes.
Contacts (BER PM)
University of Minnesota
The US Department of Energy, Office of Science, Office of Biological and Environmental Research, Terrestrial Ecosystem Science (TES) Program (award number DESC0014363) and the National Science Foundation (CAREER grant DEB 1053237 to JSP).
Waring, B.G. and J.S. Powers. “Unraveling the mechanisms underlying pulse dynamics of soil respiration in tropical dry forests.” Environmental Research Letters 11(10):105005 (2016). [DOI: doi:10.1088/1748-9326/11/10/105005]
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