Three-year dynamics of N2O fluxes from soil, stem and canopy in a hemiboreal forest: Impacts of floods and droughts.

0544620 - ÚVGZ 2022 DE eng A - Abstract
Mander, Ülo - Schindler, Thomas - Macháčová, Kateřina - Krasnova, A. - Escuer-Gatius, J. - Maddison, M. - Pärn, J. - Veber, G. - Krasnov, D. - Soosaar, Kaido
Three-year dynamics of N2O fluxes from soil, stem and canopy in a hemiboreal forest: Impacts of floods and droughts.
EGU General Assembly 2020. on line: European Geosciences Union, 2020.
[EGU General Assembly 2020. 04.05.2020-08.05.2020, online]
Institutional support: RVO:86652079
Keywords : nitrous oxide * hemiboreal forest * tree stem * canopy * eddy covariance * chamber * flux * exchange * dynamics * nitrogen
OECD category: Plant sciences, botany
https://www.egu2020.eu/

Forests are important regulators of carbon dioxide fluxes, whereas overall greenhouse gas (GHG) budgets, in particular, nitrous oxide (N2O), are still largely unknown. No studies on ecosystem-level N2O budgets (soil and tree stem fluxes with eddy covariance (EC) measurements above the canopy) are found. During the period of August 2017 to December 2019, we measured the N2O budget of a 40-yr old hemiboreal grey alder (Alnus incana) forest stand in Estonia considering fluxes from the soil, tree stems and whole ecosystem. We measured the N2O budget considering fluxes from the soil surface (12 automated chambers, Picarro 2508), tree stems (60 manual sampling campaigns from 12 model trees with chambers at 0.1, 0.8 and 1.7 m, gas chromatographic analysis in lab) and whole ecosystem (EC technique: Aerodyne TILDAS). Simultaneously, soil water level, temperature and moisture were measured automatically, and composite soil samples were taken for physico-chemical analysis. Potential N2 flux in intact soil cores was measured in the lab using the He-O incubation method. Average N2O fluxes from the soil and tree stems varied from 1.2 to 3.0 and 0.01 to 0.03 kg N2O-N ha–1 yr–1, respectively, being the highest during the wet periods, peaking during the freezingthawing, and being the lowest in dry periods. The average annual potential N2 flux in the soil was 140 kg N2 ha–1 yr–1 which made the average N2:N2O-N ratio in the soil about 60. According to the EC measurements, the forest was a net annual source of N2O (3.4 kg N2O ha–1). Thus, the main gaseous nitrogen flux in this forest was N2 emission. Our carbon (C) budget showed that the forest was a significant net annual C sink. Results of our long-term study underline the high N and C buffering capacity of riparian alder forests.
Permanent Link: http://hdl.handle.net/11104/0321455