Methane and carbon dioxide fluxes above a boreal forest observed by true eddy accumulation and eddy covariance

0512059 - ÚVGZ 2020 AT eng A - Abstrakt
Siebicke, L. - Emad, A. - Macháčová, Kateřina - Mammarella, I. - Paulmann, D. - Peltola, O. - Pihlatie, M. - Rannik, Ü.
Methane and carbon dioxide fluxes above a boreal forest observed by true eddy accumulation and eddy covariance.
Geophysical Research Abstracts. Vol. 21. European geoscience union, 2019.
[EGU General Assembly Conference 2019. 07.04.2019-12.04.2019, Vídeň]
Institucionální podpora: RVO:86652079
Klíčová slova: true eddy accumulation * ch4 * co2 * boreal forest * ch4 sink
Obor OECD: Forestry

Forests play an important role in the exchange of greenhouse gases between the land surface and the atmosphere. While the soils of upland forests generally act as methane (CH4) sinks, there is recent evidence that trees can mediate CH4 emissions to the atmosphere. However, the net ecosystem exchange of CH4 and therefore the impact of forests on the atmospheric methane budget remains uncertain. The current study quantified the net ecosystem exchange of CH4 and carbon dioxide (CO2) continuously at 30-min resolution above a boreal forest at Hyytiälä, Finland, from July to December 2017 using two micrometeorological methods.We deployed a new implementation of the true eddy accumulation method, which is perceived to be particularly suitable for detecting small trace gas fluxes due to long signal integration times side-by-side to eddy covariance. To validate the new method, we compared true eddy accumulation CO2 flux measurements to the conventional eddy covariance CO2 flux measurements. Results showed that true eddy accumulation CO2 fluxes matched eddy covariance CO2 fluxes with R2 values of up to 0.96. The forest was most frequently a net sink of CH4 with shorter periods of net emissions of similar magnitude as the sink strength. In contrast to net CO2 fluxes, which declined over the period from July to December due to declining assimilation and respiration, the CH4 fluxes maintained significant magnitude and variance throughout the same period. The true eddy accumulation CH4 flux estimates showed significantly lower variance and noise compared to closed-path eddy covariance, suggesting a superior signal-to-noise ratio of true eddy accumulation when detecting the small net ecosystem exchange of CH4 and other trace gases over forests.
Trvalý link: http://hdl.handle.net/11104/0302264