Browsing by Author "Majamäki, Renata"

Nitrous oxide (N₂O) is a powerful greenhouse gas, and its global warming potential is almost 300 times more compared to carbon dioxide. In the soil ecosystem, N₂O is mainly released into the atmosphere in the microbiological process, denitrification. Subarctic tundra soils are important sources of N₂O and due to global warming, N₂O can be released an increasing amount from these soils in the future. Snow cover and ice layers influence to production of greenhouse gases during winter. In this master’s thesis, active microbial communities and their functional genes were studied from subarctic tundra soils across the five different vegetation types in northern Finland in early April. Additionally, various environmental factors (pH, soil temperature, soil organic matter, soil water content, and snow depth) and gas fluxes of nitrous oxide, methane, and carbon dioxide were studied together with metatranscriptomic data. The study focuses on the genes involved in denitrification, as it is the main process of releasing N₂O. This study showed that microbial activity was notable already in early April and indicated that microorganisms stayed active in these subarctic soils in winter and can continue producing greenhouse gases throughout the year. Kilpisjärvi tundra soils are complex systems, and various environmental factors shaped the abundance and diversity of active denitrifiers, their functional genes, and the production of N₂O. Transcripts of genes involved in denitrification were active and N₂O fluxes ranged from -4 to 21 μg m-2 d-1. Overall production of N₂O from these tundra soils was small, yet evident, and the soils can be notable sources of N₂O in winter.