TY  - JOUR
A1  - Wohlfahrt, Georg
A1  - Brilli, Federico
A1  - Hörtnagl, Lukas
A1  - Xu, Xiaobin
A1  - Bingemer, Heinz
A1  - Hansel, Armin
A1  - Loreto, Francesco
T1  - Carbonyl sulfide (COS) as a tracer for canopy photosynthesis, transpiration and stomatal conductance : potential and limitations
T2  - Plant, cell & environment
N2  - The theoretical basis for the link between the leaf exchange of carbonyl sulfide (COS), carbon dioxide (CO2) and water vapour (H2O) and the assumptions that need to be made in order to use COS as a tracer for canopy net photosynthesis, transpiration and stomatal conductance, are reviewed. The ratios of COS to CO2 and H2O deposition velocities used to this end are shown to vary with the ratio of the internal to ambient CO2 and H2O mole fractions and the relative limitations by boundary layer, stomatal and internal conductance for COS. It is suggested that these deposition velocity ratios exhibit considerable variability, a finding that challenges current parameterizations, which treat these as vegetation-specific constants. COS is shown to represent a better tracer for CO2 than H2O. Using COS as a tracer for stomatal conductance is hampered by our present poor understanding of the leaf internal conductance to COS. Estimating canopy level CO2 and H2O fluxes requires disentangling leaf COS exchange from other ecosystem sources/sinks of COS. We conclude that future priorities for COS research should be to improve the quantitative understanding of the variability in the ratios of COS to CO2 and H2O deposition velocities and the controlling factors, and to develop operational methods for disentangling ecosystem COS exchange into contributions by leaves and other sources/sinks. To this end, integrated studies, which concurrently quantify the ecosystem-scale CO2, H2O and COS exchange and the corresponding component fluxes, are urgently needed.

We investigate the potential of carbonyl sulfide (COS) for being used as a tracer for canopy net photosynthesis, transpiration and stomatal conductance by examining the theoretical basis of the link between leaf COS, carbon dioxide (CO2) and water vapour (H2O) exchange. Our analysis identifies several limitations that need to be overcome to this end, however at present we lack appropriate ecosystem-scale field measurements for assessing their practical significance. It however appears that COS represents a better tracer for CO2 than H2O. Concurrent measurements of ecosystem scale COS, CO2 and H2O exchange are advocated.
KW  - carbon dioxide
KW  - gross photosynthesis
KW  - internal conductance
KW  - net photosynthesis
KW  - water vapour
Y1  - 2012
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/25787
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-257879
SN  - 1365-3040
SN  - 0140-7791
N1  - Copyright © 2011 Blackwell Publishing Ltd. Re-use of this article is permitted in accordance with the Creative Commons Deed, Attribution 2.5, which does not permit commercial exploitation.
VL  - 35
SP  - 657
EP  - 667
PB  - Wiley-Blackwell
CY  - Oxford [u.a.]
ER  -