Methane emissions from plants in northern boreal peatlands

• Main Author: Ge, Mengyu
• Other Authors: University of Helsinki, Faculty of Agriculture and Forestry, Doctoral Programme in Sustainable Use of Renewable Natural Resources, Helsingin yliopisto, maatalous-metsätieteellinen tiedekunta, Uusiutuvien luonnonvarojen kestävän käytön tohtoriohjelma, Helsingfors universitet, agrikultur-forstvetenskapliga fakulteten, Doktorandprogrammet i hållbart utnyttjande av förnybara naturresurser, Brix, Hans, Koskinen, Markku, Pihlatie, Mari, Lohila, Annalea, Mäkiranta, Päivi
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Helsingin yliopisto 2023
• Subjects: environmental Science; Betula nana
• Online Access: http://hdl.handle.net/10138/565683

Northern peatlands emit about 36 Tg CH4-C per year, which is approximately 11% of global CH4 emission (Wuebbles & Hayhoe, 2002). In northern peatlands, CH4 transport through aerenchymatous plants is an important pathway for soil-produced CH4 to escape into the atmosphere. Yet, the magnitude, drivers, and processes of plant-mediated CH4 transport remain unclear. This thesis aims to 1) evaluate CH4 flux, transport efficiency, and seasonality of common herbs (Carex rostrata and Menyanthes trifoliata) and shrubs (Betula nana and Salix lapponum) in boreal peatlands; 2) determine the key variables affecting plant-mediated CH4 flux; 3) determine the main CH4 release site of herb C. rostrata, one of the most abundant herb species in northern peatlands; and 4) determine whether plant-mediated CH4 exchange processes include within-plant CH4 production and oxidation. The field and climate-controlled measurements were conducted throughout the growing seasons in 2020 and 2021 to quantify species-specific plant-mediated CH4 fluxes, and their environmental drivers (water-table level, peat temperature, and porewater CH4 concentration ([CH4]pw)). To reveal plant-mediated CH4 exchange processes, a 13C-labelling measurement was conducted and plant CH4 cycling microbes were examined. The sedge C. rostrata showed the highest CH4 flux, greatest transport efficiency, and strongest seasonality. Phenology affected CH4 flux from all investigated species, whereas the opposite was true for the effects of photosynthetically active radiation (PAR). A higher air temperature only and significantly reduced fluxes from C. rostrata, whereas it did not affect CH4 fluxes from the other three species. [CH4]pw positively affected CH4 fluxes from all investigated species but B. nana. Leaves were shown to play a minor role in CH4 release from C. rostrata. Both CH4 production and oxidation can potentially occur in the shoots of M. trifoliata and S. lapponum, and oxidation in B. nana, while no CH4 cycling microbes were found in C. rostrata suggesting ...