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Comparison of CO2 and O2 fluxes demonstrate retention of respired CO2 in tree stems from a range of tree species

MPS-Authors
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Muhr,  Jan
Tree Reserve Carbon Pools, Dr. J. Muhr, Department Biogeochemical Processes, Prof. S. E. Trumbore, Max Planck Institute for Biogeochemistry, Max Planck Society;

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Trumbore,  Susan E.
Department Biogeochemical Processes, Prof. S. E. Trumbore, Max Planck Institute for Biogeochemistry, Max Planck Society;

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Kunert,  Norbert
Department Biogeochemical Processes, Prof. S. E. Trumbore, Max Planck Institute for Biogeochemistry, Max Planck Society;

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Pérez‑Priego,  Oscar
Biosphere-Atmosphere Interactions and Experimentation, Dr. M. Migliavacca, Department Biogeochemical Integration, Dr. M. Reichstein, Max Planck Institute for Biogeochemistry, Max Planck Society;

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Migliavacca,  Mirco
Biosphere-Atmosphere Interactions and Experimentation, Dr. M. Migliavacca, Department Biogeochemical Integration, Dr. M. Reichstein, Max Planck Institute for Biogeochemistry, Max Planck Society;

External Resource
Fulltext (public)

BGC2876.pdf
(Publisher version), 4MB

Supplementary Material (public)

BGC2876s1.zip
(Supplementary material), 459KB

Citation

Hilman, B., Muhr, J., Trumbore, S. E., Kunert, N., Carbone, M. S., Yuval, P., et al. (2017). Comparison of CO2 and O2 fluxes demonstrate retention of respired CO2 in tree stems from a range of tree species. Biogeosciences, 16(1), 177-191. doi:10.5194/bg-16-177-2019.


Cite as: http://hdl.handle.net/21.11116/0000-0001-9941-9
Abstract
The ratio of CO2 efflux to O2 influx (ARQ, apparent respiratory quotient) in tree stems is expected to be 1.0 for carbohydrates, the main substrate supporting stem respiration. In previous studies of stem fluxes, ARQ values below 1.0 were observed and hypothesized to indicate retention of respired carbon within the stem. Here, we demonstrate that stem ARQ<1.0 values are common across 85 tropical, temperate, and Mediterranean forest trees from 9 different species. Mean ARQ values per species per site ranged from 0.39 to 0.78, with an overall mean of 0.59. Assuming that O2 uptake provides a measure of in situ stem respiration (due to the low solubility of O2), the overall mean indicates that on average 41% of CO2 respired in stems is not emitted from the local stem surface. The instantaneous ARQ did not vary with sap flow. ARQ values of incubated stem cores were similar to those measured in stem chambers on intact trees. We therefore conclude that dissolution of CO2 in the xylem sap and transport away from the site of respiration cannot explain the low ARQ values. We suggest to examine refixation of respired CO2 in biosynthesis reactions as possible mechanism for low ARQ values.