Soil Fluxes of Carbonyl Sulfide After Fall Senescence in a Mixed Hardwood Forest

Abstract:

In situ observations of carbonyl sulfide (OCS) are being used as a proxy for terrestrial gross primary productivity (GPP) on plot to continental scales. However, the strength of the OCS soil flux remains poorly constrained, leading to an uncertainty in GPP estimates in shoulder seasons when soil consumption of OCS may be similar to uptake by vegetation. Throughout the summer and winter of 2019, we measured OCS gradients at Harvard Forest, a mid-latitude mixed hardwood forest located in western Massachusetts. We calculated ecosystem and soil fluxes of OCS and found that OCS soil fluxes continue long after fall senescence, where soils continue to take up OCS and respire CO₂ until the first snowfall event. Our results highlight how the soil OCS sink must be considered when using OCS to constrain ecosystem GPP models.