title: Seasonal fluxes of carbonyl sulfide in a midlatitude forest.
abstract: Carbonyl sulfide (OCS), the most abundant sulfur gas in the atmosphere, has a summer minimum associated with uptake by vegetation and soils, closely correlated with CO2. We report the first direct measurements to our knowledge of the ecosystem flux of OCS throughout an annual cycle, at a mixed temperate forest. The forest took up OCS during most of the growing season with an overall uptake of 1.36 ± 0.01 mol OCS per ha (43.5 ± 0.5 g S per ha, 95% confidence intervals) for the year. Daytime fluxes accounted for 72% of total uptake. Both soils and incompletely closed stomata in the canopy contributed to nighttime fluxes. Unexpected net OCS emission occurred during the warmest weeks in summer. Many requirements necessary to use fluxes of OCS as a simple estimate of photosynthesis were not met because OCS fluxes did not have a constant relationship with photosynthesis throughout an entire day or over the entire year. However, OCS fluxes provide a direct measure of ecosystem-scale stomatal conductance and mesophyll function, without relying on measures of soil evaporation or leaf temperature, and reveal previously unseen heterogeneity of forest canopy processes. Observations of OCS flux provide powerful, independent means to test and refine land surface and carbon cycle models at the ecosystem scale.
authors.affiliation: Harvard School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138; Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138; rcommane@seas.harvard.edu.
authors.forename: Róisín
authors.identifier: http://orcid.org/0000-0003-1373-1550
authors.initials: R
authors.lastname: Commane
authors.affiliation: Department of Earth, Atmospheric & Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139;
authors.forename: Laura K
authors.initials: LK
authors.lastname: Meredith
authors.affiliation: Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523;
authors.forename: Ian T
authors.initials: IT
authors.lastname: Baker
authors.affiliation: Department of Global Ecology, Carnegie Institution, Stanford, CA 94305;
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Berry
authors.affiliation: Harvard School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138; Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138;
authors.forename: J William
authors.initials: JW
authors.lastname: Munger
authors.affiliation: Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305;
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Montzka
authors.affiliation: Department of Biology, Boston University, Boston, MA 02215;
authors.forename: Pamela H
authors.initials: PH
authors.lastname: Templer
authors.affiliation: Department of Biology, Boston University, Boston, MA 02215;
authors.forename: Stephanie M
authors.initials: SM
authors.lastname: Juice
authors.affiliation: Center for Atmospheric and Environmental Chemistry, Aerodyne Research Inc., Billerica, MA 01821.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Zahniser
authors.affiliation: Harvard School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138; Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138;
authors.forename: Steven C
authors.initials: SC
authors.lastname: Wofsy
mesh_terms: D065928:Forests; D008954:Models, Biological; D010788:Photosynthesis; D012621:Seasons; D013461:Sulfur Oxides / Q000378:metabolism*
chemical_list: D013461:Sulfur Oxides; C010063:carbonyl sulfide
keywords: carbon cycle; carbonyl sulfide; stomatal conductance; sulfur cycle