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Methane (CH4) emissions from a peatland are a balance between CH4-producing and consuming processes in the peat.Certain graminoid and other herbaceous plant species provide a pathway for CH4 to escape from the peat profile without becoming available to CH4-consuming microbes (eg. Riutta et al. 2020). Whether also shrubs such as Betula nana and trees such as B. pubescens that are abundant in peatlands provide such a pathway is at least partly an open question.We measured CH4 fluxes of B. nana shoots both at a field site on a north boreal fen and in a climate-controlled (temperature, PAR) cabinet setup. In the field, sporadic measurements were made with manual chambers. Both chamber setups enclosed one shoot of the plant. In the climate-controlled setup, flux was measured multiple times per hour with an automated chamber system, and CH4 concentration in the soil was monitored with gas samples. PAR and temperature were monitored by the automated setup. 13C-labelled CH4 was injected into the soil in the climate-controlled setup to confirm that the source of the CH4 in the chamber was the soil and not possible aerobic CH4 production in the shoot, nor external contamination. Potential microbial CH4 production within B. nana is evaluated through PCR detection and sequencing of the methanogenic mcrA gene (in progress). In the climate-controlled setup, fluxes were measured similarly also from saplings of B. pubescens and B. pendula – a related species that does not grow in peatlands. A computerized tomography (CT) scan of the plants was performed to assess the presence or absence of aerenchymatic tissues, which could act as a pathway for the CH4 in the plant. CH4 emission from B. nana shoots was observed both in the field and in the climate-controlled setup. No PAR dependence of the emission was found, excluding the possibility of aerobic production of CH4 in the shoot. Further, the labelling experiment confirmed that B. nana acted as a conduit for CH4 originating from the soil. B. pubescens showed little flux and B. pendula no flux, even though CH4 was present in the soil. The CT scan confirmed presence of aerenchymatic tissue in the shoots B. nana and to a lesser extent in B. pubescens but not in B. pendula. ReferencesRiutta, T., Korrensalo, A., Laine, A.M., Laine, J., Tuittila, E.-S., 2020. Interacting effects of vegetation components and water level on methane dynamics in a boreal fen. Biogeosciences 17, 727–740. |
