PhD defence: Ludovica D'Imperio

Ludovica D'Imperio defends her thesis,

Methane and root dynamics in artic soil.
Responses and experimental summer warming and winter snow accumulation.

Supervisors:
Professor Inger Kappel Schmidt, IGN
Professor Bo Elberling, IGN

Assessment Committee:
Professor Kai Finster, Aarhus University
Associate Professor Roberg Björg, University of Gothenburg
Professor Per Ambus (chair), IGN

Summary:
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.

The thesis is available from the PhD administration office at Øster Voldgade 10: 04.1.409