Successful seminar on vegetation changes in tree line

The seminar, hosted at the Norwegian Research Council, Lysaker, gathered about 25 participants. The seminar marked the conclusion of a large research project funded by the Research Council’s NORKLIMA program. Petter Nilsen and Brita Slettemark from the Research Council welcomed everyone and told us about various research programs, such as BIONÆR and KLIMAFORSK. Erik Næsset then presented the background for the seminar and offered some insight into the use of laser technology for measurements of vegetation and monitoring of changes. Leif Kullman (Umeå University) spoke about various findings of “megafossils” of both spruce, pine and birch that appear as glaciers recede. Carbon dating of these fossils shows that after the last ice age, the tree line was found at higher altitudes than previously thought. Nadja Stumberg (NMBU, Østfold County Council) presented the results of her doctoral dissertation in which she has used ALS data for detection of pioneer trees in the tree line. Trees that are over a meter high could be detected with great certainty. Furthermore, Annika Hofgaard (NINA) spoke about her research showing that the climate models used today, probably estimate too rapid and extensive advancement of the tree line as a response to a warmer climate. Then James Speed ​​and Gunnar Austrheim (both NTNU) told us that it is not only the climate that controls the position of – and species distribution in the tree line and the distribution of stored carbon and ecosystem services related to the tree line. Grazing sheep also has an effect. We also heard from Jane Uhd Jepsen (NINA) that the arctic tree line is affected by grazing reindeer, and that the degree of grazing largely determines the structure of the vegetation which in turn influences the albedo, for example. Furthermore, she showed that large outbreaks of different moths has great effect on the Arctic tree line ecotones by that large areas of birch forest are defoliated. Lise Tingstad (UiB) asked then the question of whether in the future we will have forested mountains. The question of course was brought to a head, but the results she showed from seeding experiments conducted along precipitation and temperature gradients indicated that the germination capacity of spruce was not hampered by low temperatures. Furthermore, she showed that vascular plants had different responses when the competition was taken away on boreal sites (increased growth) vs. alpine sites (reduced growth). Finally Marius Hauglin and Ole Martin Bollandsås (both NMBU) talked about estimation of changes using ALS data. Hauglin showed that better results probably will be achieved by using an area-based approach to estimate changes in the tree line rather than having each tree as the basic unit. Bollandsås then showed results from a large-scale estimation of four year biomass changes in mountain forests along a 1,500-kilometer transect from south to north in Norway, where a significant increase in biomass was found.

Presentations from the seminar:

Leif Kullman (Professor emeritus, University of Umeå)
Title: Glacier recession reveals past treelines at unprecedented high elevations in the Swedish Scandes
Annika Hofgaard (Senior researcher, NINA Trondheim)
Title: Rate of forest advance and tundra disappearance – empirical evidence vs. model prediction
Gunnar Austrheim (Professor, NTNU) 
Title: Application of the ecosystem services framework to a sheep grazing experiment in the treeline ecotone
Jane Jepsen (Senior researcher, NINA Tromsø)
Title: Drivers of woody vegetation change in the low-arctic forest-tundra ecotone
James Speed (Researcher,NTNU)
Title: The impact of herbivores at the treeline ecotone
Lise Tingstad (PhD-student, University of Bergen)
Title: A forested future in the alpine? Climate, biotic interactions and plant population dynamics across the tree line ecotone
Nadja Stumberg (Østfold fylkeskommune)
Title: Detection of pioneer trees in the forest tundera ecotone using airborne laser scanning
Marius Hauglin  (Researcher, NMBU)
Title: Estimation of changes in the tree line using airborne laser scanner
Ole Martin Bollandsås (Researcher, NMBU)
Title: Large scale estimaton of biomass changes


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