title: The impact of soil microorganisms on the global budget of delta18O in atmospheric CO2.
abstract: Improved global estimates of terrestrial photosynthesis and respiration are critical for predicting the rate of change in atmospheric CO(2). The oxygen isotopic composition of atmospheric CO(2) can be used to estimate these fluxes because oxygen isotopic exchange between CO(2) and water creates distinct isotopic flux signatures. The enzyme carbonic anhydrase (CA) is known to accelerate this exchange in leaves, but the possibility of CA activity in soils is commonly neglected. Here, we report widespread accelerated soil CO(2) hydration. Exchange was 10-300 times faster than the uncatalyzed rate, consistent with typical population sizes for CA-containing soil microorganisms. Including accelerated soil hydration in global model simulations modifies contributions from soil and foliage to the global CO(18)O budget and eliminates persistent discrepancies existing between model and atmospheric observations. This enhanced soil hydration also increases the differences between the isotopic signatures of photosynthesis and respiration, particularly in the tropics, increasing the precision of CO(2) gross fluxes obtained by using the delta(18)O of atmospheric CO(2) by 50%.
authors.affiliation: School of GeoSciences, University of Edinburgh, Edinburgh EH9 3JN, United Kingdom. l.wingate@ed.ac.uk
authors.forename: Lisa
authors.initials: L
authors.lastname: Wingate
authors.forename: Jérôme
authors.initials: J
authors.lastname: Ogée
authors.forename: Matthias
authors.initials: M
authors.lastname: Cuntz
authors.forename: Bernard
authors.initials: B
authors.lastname: Genty
authors.forename: Ilja
authors.initials: I
authors.lastname: Reiter
authors.forename: Ulli
authors.initials: U
authors.lastname: Seibt
authors.forename: Dan
authors.initials: D
authors.lastname: Yakir
authors.forename: Kadmiel
authors.initials: K
authors.lastname: Maseyk
authors.forename: Elise G
authors.initials: EG
authors.lastname: Pendall
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Barbour
authors.forename: Behzad
authors.initials: B
authors.lastname: Mortazavi
authors.forename: Régis
authors.initials: R
authors.lastname: Burlett
authors.forename: Philippe
authors.initials: P
authors.lastname: Peylin
authors.forename: John
authors.initials: J
authors.lastname: Miller
authors.forename: Maurizio
authors.initials: M
authors.lastname: Mencuccini
authors.forename: Jee H
authors.initials: JH
authors.lastname: Shim
authors.forename: John
authors.initials: J
authors.lastname: Hunt
authors.forename: John
authors.initials: J
authors.lastname: Grace
mesh_terms: D001272:Atmosphere / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry*; D002256:Carbonic Anhydrases / Q000378:metabolism; D057231:Climate Change; D008954:Models, Biological; D010103:Oxygen Isotopes / Q000032:analysis*; D012621:Seasons; D012988:Soil Microbiology
chemical_list: D010103:Oxygen Isotopes; D002245:Carbon Dioxide; D002256:Carbonic Anhydrases