PhD Theses at SCIENCE – University of Copenhagen

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Methane and Root Dynamics in Arctic Soil: Responses to Experimental Summer Warming and Winter Snow Accumulation

Publication: ResearchPh.D. thesis

The projections for the end of the century across regions indicate that the Arctic will experience the largest increases in air temperature, especially during winter and spring time. As a consequence, the carbon (C) balance of the Arctic may be altered potentially leading to a positive feedback on the global climate.
We investigated two aspects of arctic ecosystem dynamics which are not well represented in climatic models: i) soil methane (CH4) oxidation in dry heath tundra and barren soils and ii) root dynamics in wetlands. Field measurements were carried out during the growing season in Disko Island, West Greenland, and CH4 and root dynamics were assessed in response to experimentally increased winter snow precipitation, summer warming and their interaction to better understand their contribution to the C balance of the Arctic.
Our results indicate that both the dry heath and barren soils have a large capacity to oxidize CH4 which seems mainly controlled by soil moisture. Short-term responses to climatic manipulations (1-2 years) suggest that increased winter snow precipitation may reduce CH4 oxidation rates due to increased soil moisture after thawing. On the other hand, increased summer air temperature may enhance soil CH4 oxidation rates as a consequence of increased soil temperature and evapotranspiration. Bearing in mind the large distribution of dry tundra soils over the Arctic and their strong potential to oxidize CH4, these ecosystems could play a central role in offsetting CH4 emissions from wetlands in a future warmer climate.
At the wet fen increased winter snow precipitation delayed the onset of the growing season of about a week and reduced the relative fine root production. The use of minirhizotrons improved our understanding of root growth and phenology. Total root number, length and maximum growth positively responded to experimental air warming, especially in the deeper soil layers; possibly due to an indirect effect of increased canopy temperature on the above-ground biomass. These initial below-ground responses to changes in climatic regimes suggest that future summer warming could potentially increase below-ground C allocation. Though, long-term observations will be necessary to address the effects that shifts in plant community composition and roots depth will have on the net C balance of the Arctic.
Original languageEnglish
PublisherDepartment of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen
Number of pages224
StatePublished - 2016

ID: 164423335