Assessing soil fluxes of carbonyl sulfide to aid in ecosystem estimates of GPP

Friday, 19 December 2014
Mary Whelan1, Robert C Rhew2, J Elliott Campbell1, Timothy W Hilton1, Max B Berkelhammer3, Andrew Lee Zumkehr1 and Joseph A Berry4, (1)University of California Merced, Merced, CA, United States, (2)University of California Berkeley, Berkeley, CA, United States, (3)University of Illinois at Chicago, Chicago, IL, United States, (4)Carnegie Inst Washington, Washington, DC, United States
Measuring the draw down of carbonyl sulfide (chemical formula: COS) over ecosystems can provide a new tool for estimating gross primary production (GPP) at important temporal and spatial scales. COS is a gas ubiquitous in the atmosphere that shares many characteristics with CO2: both are taken up by enzymes in plant leaves at a predictable ratio and in proportion to their ambient concentrations. While CO2 is simultaneously respired by soil and plant roots, the dominant flux of COS is foliar absorption. Previously, ecosystem soil fluxes of COS were thought to be negligible in the application of this COS-GPP proxy. Here we present new data describing controls on soil fluxes as a way to anticipate COS soil exchange over heterogeneous landscapes. Using soil samples from two agricultural sites in the Great Plains and one site in the Colorado Desert, we captured data from the extremes of ecosystem GPP in the United States. We then built a model describing COS soil fluxes with inputs of soil temperature and soil water content based on characterized soil behavior. This study provides an essential refinement in applying COS-GPP estimates over the continents.