Understanding COS Fluxes in a Boreal Forest: Towards COS-Based GPP Estimates.

Thursday, 17 December 2015
Poster Hall (Moscone South)
Linda Kooijmans1, Huilin Chen2, Franchin Alessandro3, Helmi Keskinen3, Janne Levula3, Ivan Mammarella3, Kadmiel S Maseyk4, Mari Pihlatie5, Arnaud P Praplan6, Ulrike H Seibt7, Wu Sun8 and Timo Vesala3, (1)University of Groningen, Groningen, Netherlands, (2)Centre for Isotope Research, Groningen, Netherlands, (3)University of Helsinki, Helsinki, Finland, (4)Open University, Milton Keynes, United Kingdom, (5)University of Helsinki, Physics, Helsinki, Finland, (6)Finnish Meteorological Institute, Helsinki, Finland, (7)University of California Los Angeles, Los Angeles, CA, United States, (8)University of California Los Angeles, Atmospheric and Oceanic Sciences, Los Angeles, CA, United States
Carbonyl Sulfide (COS) is a promising new tracer that can be used to partition the Net Ecosystem Exchange into gross primary production (GPP) and respiration. COS and CO2 vegetation fluxes are closely related as these gases share the same diffusion pathway into stomata, which makes COS a potentially powerful tracer for GPP. While vegetative uptake is the largest sink of COS, the environmental drivers are poorly understood, and soil fluxes represent an important but relatively unconstrained component. Therefore, the realization of the COS tracer method requires proper characterization of both soil and ecosystem fluxes. A campaign to provide better constrained soil and ecosystem COS flux data for boreal forests took place in the summer of 2015 at the SMEAR II site in Hyytiälä, Finland. Eddy covariance flux measurements were made above the forest canopy on an Aerodyne continuous-wave quantum cascade laser (QCL) system that is capable of measuring COS, CO2, CO and H2O. Soil COS fluxes were obtained using modified LI-COR LI-8100 chambers together with high accuracy concentration measurements from another Aerodyne QCL instrument. The same instrument alternately measured concentrations in and above the canopy on a cycle through 4 heights, which will be used to calculate ecosystem fluxes using the Radon-tracer method, providing ecosystem fluxes under low-turbulent conditions. We will compare ecosystem fluxes from both eddy covariance and profile measurements and show estimates of the fraction of ecosystem fluxes attributed to the soil component. With the better understanding of ecosystem and soil COS fluxes, as obtained with this dataset, we will be able to derive COS-based GPP estimates for the Hyytiälä site.