Programme

• 09.30 – 09.40: Welcome and introduction by Toke T. Høye, Aarhus University, Denmark
  
  
• 09.40 – 10.25: 'Dissecting an Arctic interaction web' by Tomas Roslin, University of Helsinki, Finland
  Abstract
  No species is an island. Recent work emphasizes the importance of biotic interactions in even the harsh Arctic climate. Quantitative interaction webs offer a key tool for measuring, describing and understanding how communities are built and work. To make sense of them, we need to accurately resolve both the nodes (species) and links (interactions) of the web. The species-poor communities of the high Arctic are particularly amenable to such analyses.  Our ambitious aim is to use observations and molecular tools to describe the structure of full interaction webs, and to then challenge the understanding gained by controlled experiments testing dynamic predictions. For this purpose, we have already developed DNA barcodes for some 90% of the terrestrial flora and fauna of Zackenberg. These markers are now being applied for detecting species- and community-level dynamics in the unique monitoring data collected by the Basis programmes. When linked with insights from a set of experiments linking community structure to function, we hope to forecast functional consequences of observed and predicted changes in high-arctic communities.
  
  
• 10.25 – 11.10: 'Arctic terrestrial ecosystem in a changing world. Simple rules drive species interactions in the tundra' by Pierre Legagneux, University of Québec, Rimouski, Canada
  Abstract
  Determining the manner in which food webs will respond to environmental change is difficult because it largely depends on the relative importance of top-down vs. bottom-up forces. Determining how Arctic ecosystems will respond to climate change is crucial in the Arctic. In this region, global warming is most pronounced and it is also the most important threat to biodiversity. The effects of climate change on ecosystems can be investigated using either long-term datasets or by comparing food webs along a latitudinal gradient. We used both approaches to examine the impact of climate change on ecosystem structure and functioning. Based on a 20 year study of the terrestrial wildlife on Bylot Island, Nunavut, Canada, we first developed trophic mass balance models to assess the extent to which this tundra food web is dominated by plant–herbivore (bottom-up) or predator–prey (top-down) interactions and if the ecosystem functioning has switched over time due to global warming. Our results indicated that herbivores are not limited by primary production on Bylot Island. In contrast, we detected strong predator–prey interactions, supporting the hypothesis that top-down forces primarily control this food web. The results are interesting because the major increase in primary production that we have observed over the last 20 years has had no cascading effects on higher trophic levels. Secondly, we used the same approach to compare food-web structure and species interaction strengths for seven terrestrial sites spread over a wide range of latitudes (1,500km) and climates across the circumpolar world. We found that the intensity of predation on lower trophic levels has increased significantly with temperature through an indirect effect on food-web structure. Herbivore body size was a major determinant of predator–prey interactions. Interaction strengths were positively related to the predator–prey size ratio, with large herbivores mostly escaping predation. This result is very similar to the patterns that have been reported from work on the African savanna. This opens up the possibility that most terrestrial ecosystems may be governed by simple rules. These allometric relationships combined with climatic scenarios and species niche projections could be used to map the vulnerability of Arctic terrestrial ecosystems.
  
  
• 11.10 – 11.55: 'COAT: A plan for adaptive monitoring of terrestrial food webs in the age of rapid climate in Arctic Norway' by Rolf Ims, University of Tromsø, Norway
  Abstract
  In connection with the opening of Fram –High north centre for climate and the environment in Tromsø, the centre was tasked to develop a science plan for Climate ecological Observatory for Arctic Tundra (COAT). Over a period of two years a consortium of 23 ecologist and climatologists developed the plan, that according to the paradigm of adaptive monitoring, is to be implemented on Svalbard in the high arctic and on the Varanger Peninsula in the Norwegian low arctic. In the talk I will give an overview of the plan with emphasis on the key characteristics of the ecosystems that will be targeted as well as on the approaches and methods that will be used.

The presentations form part of a workshop on ”Arctic Ecosystems and Climate Change” organized by researchers from the Aarhus Institute of Advanced Studies and Department of Bioscience at Aarhus University. Each of the distinguished international speakers have been asked to give their perspective on Arctic ecosystem monitoring and research in a climate change context.

The lectures are held in English and open to the public. Registration is not necessary, and you are welcome to attend only one of the three lectures.