Seasonal fluxes of carbonyl sulfide in a midlatitude forest

  • Sites: US-Ha1
  • Commane, R.C., Meredith, L. K., Baker, I. T., Berry, J. A., Munger, J. W, Montzka, S. A, Templer, P. H., Juice, S. M., Zahniser, M. S., Wofsy, S. C. (2015/11/2) Seasonal fluxes of carbonyl sulfide in a midlatitude forest, PNAS, (), 1-7.
  • Funding Agency: DOE, NOAA, NSF

  • 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 CO 2 . 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 sto-
    mata 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 evapora-
    tion or leaf temperature, and reveal previously unseen heteroge-
    neity 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.