Biennial GHG budget of a riparian forest: From soil and tree-stem to ecosystem level

0544639 - ÚVGZ 2022 US eng A - Abstract
Mander, Ülo - Schindler, Thomas - Krasnova, A. - Macháčová, Kateřina - Pärn, J. - Soosaar, Kaido
Biennial GHG budget of a riparian forest: From soil and tree-stem to ecosystem level.
AGU Fall Meeting. Washington: American Geophysical Union, 2019.
[AGU Fall Meeting 2019. 09.12.2019-13.12.2019, San Francisco]
Institutional support: RVO:86652079
Keywords : greenhouse gas * nitrous oxide * methane * alder tree * stem * canopy * soil * riparian forest * eddy covariance
OECD category: Plant sciences, botany
www.agu.org/Fall-Meeting-2019

Riparian forests sequester carbon dioxide (CO2) but little is known about the methane (CH ) and nitrous oxide (N2O) balance in the forests. Trees themselves can emit CH4 and the vegetation can be a significant CH4 source. Few studies show that drained nitrogen-rich organic soils under deciduous forests can be significant N2O sources with significant emissions in winter. No ecosystem-level N2O budget (fluxes in the soil, tree stems and shoots, and above the canopy) is available. Grey alder (Alnus incana) stands are considered as accumulators of carbon (C). From July 2017 to July 2019 we measured budgets of CO2, CH4 and N2O of a 40-yr old riparian grey alder forest stand in Estonia using continuous measurements from the soil surface, samples from tree-stem chambers and continuous whole-ecosystem measurements (the eddy covariance (EC) technique). In the wet periods, stem flux of CH4 was the main source for ecosystem exchange, whereas in the dry periods, unexpectedly, ecosystem flux was significantly higher than fluxes from soil and tree stems. Most likely, canopy was the main CH emitter. N2O fluxes from the soil and stems were low during the dry periods and peaked during the wet periods and the freezingthawing. The forest was a net annual source of both CH4 and N2O (6.33±0.29 kg CH4 ha and 3.42±0.12 kg N2O ha , mean±SE) and a net annual sink of CO2 (-21,025±158 kg CO ha ). Estimated average annual losses of total organic C and total N in groundwater were 7.5 kg C ha and 1.8 kg N ha , thus the forest was a net annual C sink (-5,224 kg C ha ). The total GHG budget shows that grey alder forests as pioneer communities, regardless of the CH fluxes, sequester large amounts C and improve soil-nutrient conditions.
Permanent Link: http://hdl.handle.net/11104/0321470