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| Titel |
Annual fluxes of nitrous oxide (N2O) in boreal trees |
| VerfasserIn |
Katerina Machacova, Elisa Halmeenmäki, Otmar Urban, Mari Pihlatie |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250143755
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| Publikation (Nr.) |
 EGU/EGU2017-7508.pdf |
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| Zusammenfassung |
| Boreal forests covering almost one-third of the global forest area are considered to be a
natural source of nitrous oxide (N2O), an important greenhouse gas produced in soils. The
forest ecosystems exchange of N2O has so far been calculated based on N2O flux
measurements at the soil-atmosphere interface excluding other possible natural sources of
N2O. Scarce studies revealed that trees can emit N2O; however, only under conditions with
high N2O production in the soil due to e.g. fertilisation or flooding treatment. Unfortunately,
information about the N2O exchange of mature trees under natural field conditions is almost
non-existent.
We determined N2O fluxes from common boreal tree species: Scots pine (Pinus
sylvestris), Norway spruce (Picea abies), and downy and silver birch (Betula pubescens, B.
pendula). We aimed to investigate (1) whether these tree species exchange N2O with the
atmosphere, (2) whether these fluxes show seasonal cycle, (3) how the tree N2O fluxes
contribute to the forest floor N2O exchange, and (4) whether soil water content affects the
N2O exchange of trees.
The measurements were performed on mature trees in the boreal forest around the
SMEAR II station at Hyytiälä in southern Finland. Fluxes of N2O at stem and forest floor
level were simultaneously measured from June 2014 until May 2015 using static chamber
systems and quantified by gas chromatography.
All trees studied emitted N2O from their stems during the vegetation season. The
emission rates of all tree species decreased from October onwards. In winter, the tree fluxes
remained low (mostly weak uptake by birch and pine, weak uptake or emission by spruce)
and increased again in March. The forest floor mostly emitted N2O during the whole year
without significant seasonal variation.
At the annual scale, all species studied were sources of N2O. Spruce was the strongest
emitter of N2O with total emission of 0.91 mg N2O m−2 stem area and 2.4 g N2O ha−1
ground area per year, followed by pine (0.41 mg m−2 and 1.9 g ha−1 per year)
and birch (total emission of both sub-species was 0.38 mg m−2 and 0.71 g ha−1
per year). The forest floor emitted in total 7.1 mg N2O m−2 soil area and 70.7 g
ha−1 per year. These emissions were not significantly modulated by soil water
content.
Boreal tree species, as newly identified emitters of N2O, considerably contribute to total
N2O emissions of boreal forests and their emission potential has to be included in the forest
N2O emission inventories.
Acknowledgement
This research was supported by the Czech Science Foundation (17-18112Y), the National
Programme for Sustainability I (LO1415), EU FP7 project ExpeER (Grant Agreement
262060), Emil Aaltonen Foundation, Academy of Finland Research Fellow projects
(292699, 263858, 288494), The Academy of Finland Centre of Excellence (projects
1118615, 272041), and ICOS-Finland (281255).We thank Marian Pavelka, Jiří
Dušek, Stanislav Stellner, Jiří Mikula and Marek Jakubík for technical support. |
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