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Contribution of soil respiration in tropical, temperate, and boreal forests to the 18 O enrichment of atmospheric O 2
Author(s) -
Angert Alon,
Barkan Eugeni,
Barnett Bruce,
Brugnoli Enrico,
Davidson Eric A.,
Fessenden Julianna,
Maneepong Somsak,
Panapitukkul Nipa,
Randerson James T.,
Savage Kathleen,
Yakir Dan,
Luz Boaz
Publication year - 2003
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2003gb002056
Subject(s) - temperate climate , boreal , soil respiration , respiration , environmental chemistry , environmental science , taiga , temperate forest , ecosystem , terrestrial ecosystem , atmospheric sciences , tropics , ecology , soil water , chemistry , botany , soil science , biology , geology
The 18 O content of atmospheric O 2 is an important tracer for past changes in the biosphere. Its quantitative use depends on knowledge of the discrimination against 18 O associated with the various O 2 consumption processes. Here we evaluated, for the first time, the in situ 18 O discrimination associated with soil respiration in natural ecosystems. The discrimination was estimated from the measured [O 2 ] and δ 18 O of O 2 in the soil‐air. The discriminations that were found are 10.1 ± 1.5‰, 17.8 ± 1.0‰, and 22.5 ± 3.6‰, for tropical, temperate, and boreal forests, respectively, 17.9 ± 2.5‰ for Mediterranean woodland, and 15.4 ± 1.6‰ for tropical shrub land. Current understanding of the isotopic composition of atmospheric O 2 is based on the assumption that the magnitude of the fractionation in soil respiration is identical to that of dark respiration through the cytochrome pathway alone (∼18‰). The discrimination we found in the tropical sites is significantly lower, and is explained by slow diffusion in soil aggregates and root tissues that limits the O 2 concentration in the consumption sites. The high discrimination in the boreal sites may be the result of high engagement of the alternative oxidase pathway (AOX), which has high discrimination associated with it (∼27‰). The intermediate discrimination (∼18‰) in the temperate and Mediterranean sites can be explained by the opposing effects of AOX and diffusion limitation that cancel out. Since soil respiration is a major component of the global oxygen uptake, the contribution of large variations in the discrimination, observed here, to the global Dole Effect should be considered in global scale studies.