How are patterns of arctic plant communities affected by climate and the ongoing climate change?

Ph.D. defence, Friday 7 April 2017. Lærke Stewart.

2017.04.07 | Steffi Hjerrild Iversen

Lærke Søndergaard Stewart

Maps showing the modelled distribution of vegetation types along a mountain slope in Northeast Greenland (present conditions are shown in the centre of the top row (0;0)). Changing temperature and soil moisture scenarios are modelled for altered vegetation patterns. With rising temperatures, the potential habitat for heath types dominated by dwarf-shrubs (Empetrum heath and Vaccinium heath) increases at the expense of more open habitats dominated by forbs and grasses. The relative distribution of these two types is largely determined by the degree of soil moisture.

During her PhD, Lærke Stewart has researched the importance of climate for plant distributions in the Arctic.

Terrestrial plants and plant communities provide important resources for animals and humans worldwide and play a key role in global biochemical cycles with feedbacks to the freshwater and marine systems, as well as to the atmosphere and climate. Climate change has the potential to reshuffle plant species and communities, and through that ultimately to affect the structure and functioning of ecosystems. During the past decades, ongoing climate change has been particularly severe in the Arctic, and predictions for the future suggest warming to amplify. Studying the distribution of arctic species and plant communities, as well as their drivers is imperative, if we are to make predictions of the future conditions of vegetation.

By means of fieldwork and subsequent modelling, Lærke Stewart’s PhD has contributed to an increased understanding of the effects of climate and other factors on the distribution of arctic plants, both at local and more global (whole Arctic) scales. This understanding forms the basis for predictions of the future distributions of arctic plant communities.

The PhD degree was completed at Arctic Ecosystem Ecology and Ecoinformatics and Biodiversity, Department of Bioscience, Science and Technology, Aarhus University.

This résumé was prepared by the PhD student.

Time: Friday 7 April 2017 at 13.00.
Place: Niels Bohr Auditorium RI B112, Department of Bioscience, Aarhus University Roskilde, Frederiksborgvej 399, 4000 Roskilde.
Title of dissertation: Arctic Plant Communities: Past, Present and Future.
Contact information: Lærke Stewart, e-mail:, tel.: +45 25580686
Members of the assessment committee:
Professor Tord Snäll, Swedish University of Agricultural Sciences, Sweden.
Professor Christer Nilsson, Umeå University, Department of Ecology and Environmental Science, Sweden.
Senior Researcher Dr. Morten Frederiksen (chair), Department of Bioscience, University of Aarhus, Denmark.

Main supervisor:
Senior Researcher Dr. Niels Martin Schmidt, Arctic Ecosystem Ecology and Arctic Research Centre, Department of Bioscience, Aarhus University, Denmark.
Professor Dr. Loïc Pellissier, Landscape Ecology, Institute of Terrestrial Ecosystems, ETH Zürich, Zürich, Switzerland and Swiss Federal Research Institute WSL, 8903 Birmensdorf, Switzerland.
Professor Jens-Christian Svenning, Ecoinformatics and Biodiversity, Department of Bioscience, Aarhus University, Denmark.
Language: The PhD dissertation will be defended in English

The defence is public.
The dissertation is available for reading at the Graduate School of Science and Technology/GSST, Ny Munkegade 120, building 1520, rooms 128-134, 8000 Aarhus C.

PhD defence
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Revised 23.02.2018