The role of trees in the CH4 and N2O exchange in boreal forest

0544622 - ÚVGZ 2022 DE eng A - Abstract
Vainio, E. - Galeotti, L. - Ghasemi, H. - Haikarainen, I. - Macháčová, Kateřina - Patama, M. - Pyykkö, P. - Rauna, L. - Pihlatie, M.
The role of trees in the CH4 and N2O exchange in boreal forest.
EGU General Assembly 2020. on line: European Geosciences Union, 2020.
[EGU General Assembly 2020. 04.05.2020-08.05.2020, online]
R&D Projects: GA ČR(CZ) GJ17-18112Y
Institutional support: RVO:86652079
Keywords : boreal forest * soil moisture * methane * nitrous oxide * birch * spruce * pine * tree * soil * stem * shoot * flux * exchange * chamber
OECD category: Plant sciences, botany
https://www.egu2020.eu/

Boreal forests are considered a sink of CH4 due to predominant soil oxidation, but when CH4 is taken up by the tree roots, it bypasses the CH4-oxidation zone in the surface soil. The stem N2O fluxes at the boreal zone have been shown to follow seasonal physiological activity of trees. However, studies on tree CH4 and N2O fluxes are scarce in the boreal zone. We studied the tree stem CH4 and N2O exchange from the stems of Scots pine, downy birch, and Norway spruce – in total 47 trees, growing at six study plots with naturally different soil moisture and ground vegetation conditions (6–9 trees per plot). The measurements were performed during July–August 2017 at the Hyytiälä SMEAR II site, in southern Finland. In addition to the stems, we measured forest floor CH4 and N2O fluxes at all the plots, and shoot CH4 fluxes from birch and pine at one plot. The stem chambers were installed at the tree bases, ca. 30 cm above the soil surface. Additionally, from the trees with the shoot measurements, we measured the stem fluxes from several heights in order to study the flux variation in the stem vertical profile. All the flux measurements were conducted with closed chambers – the stem and forest floor measurements were performed by using manual sampling and gas chromatography, while a portable greenhouse gas analyser was used for the shoot measurements. The results show that all the studied tree species emit both CH4 and N2O from stems. Birches growing at one plot with waterlogging conditions stand out with the highest stem CH4 emissions. Concerning the N2O emissions, birch stems showed significantly higher emissions than pine stems. The results of the shoot measurements indicate that both birch and pine emit small amounts of CH4 from their shoots, but the driving factors of the emissions may be different for the two species.
Permanent Link: http://hdl.handle.net/11104/0321457