Dynamics of mountain birch treelines in the Scandes mountain chain, and effects of climate warming

Abstract

In Fennoscandia, the upper treelines most commonly consist of mountain birch (Betula pubescens ssp. czerepanovii [Orlova] Hämet-Ahti) (Hämet-Ahti 1987; Aas and Faarlund 1996; Moen 1998). In this thesis dynamics and potential responses to climate change of mountain birch trees and saplings in the upper part of the forest-tundra/alpine ecotone along the Scandinavian Mountain Chain are investigated through a combination of analytical and experimental studies. Present treeline trees and saplings above treelines constitute the basis for further development of the ecotone, in addition to being evidence of past and present dynamics. Hence, they are investigated in terms of their spatial distribution in relation to environmental factors, and their existence and development on a temporal scale. Further, potential responses to future climate change are investigated through experimental warming of naturally occurring mountain birch saplings in the same study areas. A latitudinal gradient of the study areas provides grounds for comparisons, and allows for broader conclusions across sites. A critical evaluation of the experimental method is necessary for assessing the results.