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

0518441 - ÚVGZ 2020 US eng A - Abstrakt
Mander, Ü. - Schindler, T. - Krasnova, A. - Macháčová, Kateřina - Pärn, J. - Soosaar, K.
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]
Institucionální podpora: RVO:86652079
Klíčová slova: methane * nitrous oxide * carbon dioxide * ch4 * n2o * co2 * nitrogen * carbon * emitter * source * sink * greenhouse gas budget * riparian alder forest * tree stems * soil * canopy * chamber * eddy covariance * losses
Obor OECD: Forestry

Riparian forests sequester carbon dioxide (CO2 ) but little is known about the methane (CH4 ) 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. Grey alder (Alnus incana) is a fast-growing tree with potential for short rotation forestry. Grey alder stands are considered as accumulators of carbon (C). Their symbiotic dinitrogen fixation ability makes alders important regulators of the nitrogen (N) cycle. 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 (eddy covariance technique). Water level and soil temperature and moisture were measured automatically, and composite soil samples were taken for physico-chemical analysis. 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 CH4 emitter. N2O fluxes from the soil and stems were low during the dry periods and peaked during the wet periods and the freezing-thawing. The forest was a net annual source of both CH4 and N2O (6.33±0.29 kg CH4 ha-1 and 3.42±0.12 kg N2O ha-1, mean±SE) and a net annual sink of CO2 (-21,025±158 kg CO2 ha-1). Estimated average annual losses of total organic C and total N in groundwater were 7.5 kg C ha-1 and 1.8 kg N ha-1, thus the forest was a net annual C sink (-5,224 kg C ha-1). The total GHG budget shows that grey alder forests as pioneer communities, regardless of the CH4 fluxes, sequester large amounts C and improve soil-nutrient conditions.
Trvalý link: http://hdl.handle.net/11104/0303574