 |
| Titel |
Tree CH4 fluxes in forestry drained peatland in southern Finland |
| VerfasserIn |
Iikka Haikarainen, Anuliina Putkinen, Petteri Pyykkö, Elisa Halmeenmäki, Mari Pihlatie |
| Konferenz |
EGU General Assembly 2017
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250148178
|
| Publikation (Nr.) |
 EGU/EGU2017-12412.pdf |
|
|
|
|
|
| Zusammenfassung |
| Methane (CH4) is among the most important greenhouse gases and its atmospheric
concentration is increasing. Boreal forests are commonly considered a net sink of
atmospheric CH4 due to CH4 consuming bacteria in aerated soil layers. Recent studies
have, however, demonstrated that trees are capable of emitting CH4 from their
stems and shoots by transporting anaerobically produced CH4 from deeper soil
layers to the atmosphere. Furthermore, trees may act as independent sources of
CH4.
We have measured tree stem CH4 exchange of boreal tree species at Lettosuo, a nutrient
rich peatland forest in Tammela, southern Finland (60˚ 38’ N, 23˚ 57’ E), using the static
chamber technique. Three species, downy birch (Betula pubescens), Norway spruce (Picea
abies) and Scots pine (Pinus sylvestris), were selected under investigation as they
represent common boreal tree species. Fluxes of CH4 were measured during 7.6.2016 –
17.10.2016 from in total 25 sample trees growing on two different plots: a treatment
plot where all the pines were removed to raise the water table level (WTL) and a
control plot. Three birches from the treatment plot were selected to measure CH4 flux
variation within vertical profile of the trees. Characterization of microbial communities,
quantification of methanogenic and methanotrophic functional genes, and measurements of
potential CH4 production and consumption from peat profile and forest floor moss
samples were also carried out to obtain insight to the CH4 flux dynamics at the studied
sites.
The pine removal treatment did not markedly change the average WTL, but it made the
WTL more variable with frequently 10–15 cm closer to soil surface compared to the WTL on
the control plot. We found small and variable CH4 emissions from the stems of trees on both
of the plots, while occasional consumption of CH4 was also present. Generally the CH4
emissions were higher and more dominant at the treatment plot compared to the control plot,
and the fluxes were significantly different between the plots (p < 0.001). The CH4 emission
rates from the birches at the treatment plot decreased exponentially in the stem vertical
profile. Clear seasonal flux dynamics or significant differences in the CH4 flux
between the species were not found at either of the plots. Microbial experiments
showed that anaerobic CH4 production, CH4 oxidation potential (under 1000 ppm
CH4) and the amount of methanogens were higher in the peat of the treatment
site.
The difference in the CH4 flux rates between the plots indicates that the WTL is a major
regulator of tree CH4 emissions on forestry drained peatlands, supporting our hypothesis that
the stem emitted CH4 originates from anaerobic soil conditions. This hypothesis is further
supported by the results of the microbial analysis and by the observation that more
CH4 is emitting from the lower parts of the stems compared to the upper stem. |
|
|
|
|
|
|