Combining a quantum cascade laser spectrometer with an automated closed-chamber system for δ13C measurements of forest soil, tree stem and tree root CO2 fluxess

Research output: Contribution to journalJournal article – Annual report year: 2019Researchpeer-review

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Combining a quantum cascade laser spectrometer with an automated closed-chamber system for δ13C measurements of forest soil, tree stem and tree root CO2 fluxess. / Brændholt, Andreas; Ibrom, Andreas; Ambus, Per; Larsen, Klaus Steenberg; Pilegaard, Kim.

In: Forests, Vol. 10, No. 5, 432, 2019.

Research output: Contribution to journalJournal article – Annual report year: 2019Researchpeer-review

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@article{4438e7fe587f47ad957b87fa78cb0615,
title = "Combining a quantum cascade laser spectrometer with an automated closed-chamber system for δ13C measurements of forest soil, tree stem and tree root CO2 fluxess",
abstract = "Recent advances in laser spectroscopy have allowed for real-time measurements of the 13C/12C isotopic ratio in CO2, thereby providing new ways to investigate carbon cycling in natural ecosystems. In this study, we combined an Aerodyne quantum cascade laser spectrometer for CO2 isotopes with a LI-COR LI-8100A/8150 automated chamber system to measure the δ13C of CO2 during automated closed-chamber measurements. The isotopic composition of the CO2 flux was determined for each chamber measurement by applying the Keeling plot method. We found that the δ13C measured by the laser spectrometer was influenced by water vapour and CO2 concentration of the sample air and we developed a method to correct for these effects to yield accurate measurements of δ13C. Overall, correcting for the CO2 concentration increased the δ13C determined from the Keeling plots by 3.4{\%}‰ compared to 2.1{\%}‰ for the water vapour correction. We used the combined system to measure δ13C of the CO2 fluxes automatically every two hours from intact soil, trenched soil, tree stems and coarse roots during a two-month campaign in a Danish beech forest. The mean δ13C was -29.8 ± 0.32{\%}‰ for the intact soil plots, which was similar to the mean δ13C of -29.8 ± 1.2{\%}‰ for the trenched soil plots. The lowest δ13C was found for the root plots with a mean of -32.6 ± 0.78{\%}‰. The mean δ13C of the stems was -30.2 ± 0.74{\%}‰, similar to the mean δ13C of the soil plots. In conclusion, the study showed the potential of using a quantum cascade laser spectrometer to measure δ13C of CO2 during automated closed-chamber measurements, thereby allowing for measurements of isotopic ecosystem CO2 fluxes at a high temporal resolution. It also highlighted the importance of proper correction for cross-sensitivity with water vapour and CO2 concentration of the sample air to get accurate measurements of δ13C.",
keywords = "Ecology and Ecosystems, Soils and Soil Mechanics, Automatic Control Principles and Applications, Optical Devices and Systems, Lasers, General, Inorganic Compounds, Automated closed-chambers, Forest carbon cycling, Isotope laser spectroscopy, Stable isotopes, δ13C of forest CO2 fluxes, Automation, Ecosystems, Forestry, Isotopes, Laser spectroscopy, Quantum cascade lasers, Soils, Spectrometers, Water vapor, Accurate measurement, Automated chamber systems, Closed chambers, CO2 fluxes, Forest carbons, High temporal resolution, Real time measurements, Carbon dioxide",
author = "Andreas Br{\ae}ndholt and Andreas Ibrom and Per Ambus and Larsen, {Klaus Steenberg} and Kim Pilegaard",
year = "2019",
doi = "10.3390/f10050432",
language = "English",
volume = "10",
journal = "Forests",
issn = "1999-4907",
publisher = "M D P I AG",
number = "5",

}

RIS

TY - JOUR

T1 - Combining a quantum cascade laser spectrometer with an automated closed-chamber system for δ13C measurements of forest soil, tree stem and tree root CO2 fluxess

AU - Brændholt, Andreas

AU - Ibrom, Andreas

AU - Ambus, Per

AU - Larsen, Klaus Steenberg

AU - Pilegaard, Kim

PY - 2019

Y1 - 2019

N2 - Recent advances in laser spectroscopy have allowed for real-time measurements of the 13C/12C isotopic ratio in CO2, thereby providing new ways to investigate carbon cycling in natural ecosystems. In this study, we combined an Aerodyne quantum cascade laser spectrometer for CO2 isotopes with a LI-COR LI-8100A/8150 automated chamber system to measure the δ13C of CO2 during automated closed-chamber measurements. The isotopic composition of the CO2 flux was determined for each chamber measurement by applying the Keeling plot method. We found that the δ13C measured by the laser spectrometer was influenced by water vapour and CO2 concentration of the sample air and we developed a method to correct for these effects to yield accurate measurements of δ13C. Overall, correcting for the CO2 concentration increased the δ13C determined from the Keeling plots by 3.4%‰ compared to 2.1%‰ for the water vapour correction. We used the combined system to measure δ13C of the CO2 fluxes automatically every two hours from intact soil, trenched soil, tree stems and coarse roots during a two-month campaign in a Danish beech forest. The mean δ13C was -29.8 ± 0.32%‰ for the intact soil plots, which was similar to the mean δ13C of -29.8 ± 1.2%‰ for the trenched soil plots. The lowest δ13C was found for the root plots with a mean of -32.6 ± 0.78%‰. The mean δ13C of the stems was -30.2 ± 0.74%‰, similar to the mean δ13C of the soil plots. In conclusion, the study showed the potential of using a quantum cascade laser spectrometer to measure δ13C of CO2 during automated closed-chamber measurements, thereby allowing for measurements of isotopic ecosystem CO2 fluxes at a high temporal resolution. It also highlighted the importance of proper correction for cross-sensitivity with water vapour and CO2 concentration of the sample air to get accurate measurements of δ13C.

AB - Recent advances in laser spectroscopy have allowed for real-time measurements of the 13C/12C isotopic ratio in CO2, thereby providing new ways to investigate carbon cycling in natural ecosystems. In this study, we combined an Aerodyne quantum cascade laser spectrometer for CO2 isotopes with a LI-COR LI-8100A/8150 automated chamber system to measure the δ13C of CO2 during automated closed-chamber measurements. The isotopic composition of the CO2 flux was determined for each chamber measurement by applying the Keeling plot method. We found that the δ13C measured by the laser spectrometer was influenced by water vapour and CO2 concentration of the sample air and we developed a method to correct for these effects to yield accurate measurements of δ13C. Overall, correcting for the CO2 concentration increased the δ13C determined from the Keeling plots by 3.4%‰ compared to 2.1%‰ for the water vapour correction. We used the combined system to measure δ13C of the CO2 fluxes automatically every two hours from intact soil, trenched soil, tree stems and coarse roots during a two-month campaign in a Danish beech forest. The mean δ13C was -29.8 ± 0.32%‰ for the intact soil plots, which was similar to the mean δ13C of -29.8 ± 1.2%‰ for the trenched soil plots. The lowest δ13C was found for the root plots with a mean of -32.6 ± 0.78%‰. The mean δ13C of the stems was -30.2 ± 0.74%‰, similar to the mean δ13C of the soil plots. In conclusion, the study showed the potential of using a quantum cascade laser spectrometer to measure δ13C of CO2 during automated closed-chamber measurements, thereby allowing for measurements of isotopic ecosystem CO2 fluxes at a high temporal resolution. It also highlighted the importance of proper correction for cross-sensitivity with water vapour and CO2 concentration of the sample air to get accurate measurements of δ13C.

KW - Ecology and Ecosystems

KW - Soils and Soil Mechanics

KW - Automatic Control Principles and Applications

KW - Optical Devices and Systems

KW - Lasers, General

KW - Inorganic Compounds

KW - Automated closed-chambers

KW - Forest carbon cycling

KW - Isotope laser spectroscopy

KW - Stable isotopes

KW - δ13C of forest CO2 fluxes

KW - Automation

KW - Ecosystems

KW - Forestry

KW - Isotopes

KW - Laser spectroscopy

KW - Quantum cascade lasers

KW - Soils

KW - Spectrometers

KW - Water vapor

KW - Accurate measurement

KW - Automated chamber systems

KW - Closed chambers

KW - CO2 fluxes

KW - Forest carbons

KW - High temporal resolution

KW - Real time measurements

KW - Carbon dioxide

U2 - 10.3390/f10050432

DO - 10.3390/f10050432

M3 - Journal article

VL - 10

JO - Forests

JF - Forests

SN - 1999-4907

IS - 5

M1 - 432

ER -