The impact of soil microorganisms on the global budget of delta18O in atmospheric CO2.
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%.
Wingate
Lisa
L
School of GeoSciences, University of Edinburgh, Edinburgh EH9 3JN, United Kingdom. l.wingate@ed.ac.uk
Ogée
Jérôme
J
Cuntz
Matthias
M
Genty
Bernard
B
Reiter
Ilja
I
Seibt
Ulli
U
Yakir
Dan
D
Maseyk
Kadmiel
K
Pendall
Elise G
EG
Barbour
Margaret M
MM
Mortazavi
Behzad
B
Burlett
Régis
R
Peylin
Philippe
P
Miller
John
J
Mencuccini
Maurizio
M
Shim
Jee H
JH
Hunt
John
J
Grace
John
J
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
D010103:Oxygen Isotopes; D002245:Carbon Dioxide; D002256:Carbonic Anhydrases