In the morning, Eirik gave a trial lecture, entitled “Vegetation-climate interaction at the global scale”. He gave a very good overview of this topic, which has been central in EMERALD. In the afternoon, he defended his thesis “On the role of lichens in vegetation-climate interactions” for the degree of Philosophiae Doctor. The opponents, Professor Bente Jessen Graae, Department of Biology, NTNU, and Professor Gareth Rees, Scott Polar Research Institute, University of Cambridge, complimented him for his very interesting thesis work, and noticed his rather broad research scope on bright, ground-covering lichens and their function in land-climate interactions.
Below you will find Eirik’s popular science summary of his work:
Current climate change is amplified over northern high latitudes, affecting the biogeochemical interactions between vegetation and the climate. However, the role of lichens, bryophytes and soil crust communities in these interactions are not well understood. This doctoral thesis focuses on bright, ground-covering lichens and their function in land-climate interactions, changes to their distribution, and responses to winter climate change.
In this study we find that land surfaces covered by bright types of lichens have the highest albedo effect of all naturally occurring vegetation. The high albedo effect is especially important for vegetation-climate interactions at high latitudes, as carbon sequestration is much lower than in warmer biomes. Over the latest 40 years the volume of lichen have declined across the pan-Arctic. From previously being mainly limited by increased grazing pressure from reindeer and caribou, and now higher competition from trees and shrubs under climate change is taking over as the major factor for limiting lichen.
While herbivory, increase in wildfires, and summer warming benefit herbs and shrubs at the expense of lichens, winter heatwaves represent an opposite effect. Lichens prove to be much more robust against the stress of ice encapsulation and midwinter thaw-and-refreezing cycles than vascular plants and bryophytes. Thus, lichens will still be able to compete successfully against vascular vegetation in areas where unstable winter conditions drive vegetation dynamics.
We congratulate Eirik for all the hard work and dedication. We wish him all the best in his future endeavors.