Forest line changes after 1960 in a Norwegian mountain region – implications for the future

Abstract

Mountain treelines can be seen as boundaries between two vegetation zones – the alpine and subalpine zones – and function as an indicator of ecosystem change. Interpreting factors leading to changes in mountains includes disturbance from human resource use and climate as important factors. The article shows that forest line changes in eastern Jotunheimen, a mountain region in southern Norway, can be related to changes in livestock grazing pressure between the 1960s and 2002. In contrast to other European mountain regions, highly relevant climate variables such as the triterm (the summer months) have not changed in the studied region. Therefore, land-use change is considered the main driver for the forest line shifts observed in the region. However, the predicted climate warming, together with continued trends of decreasing and abandoned free-range grazing of livestock will cause further forest expansion above the present forest lines also in the eastern Jotunheimen mountain range.

Keywords:

• climate
• ecosystem change
• human resource use
• land use changes
• livestock grazing pressure

Acknowledgements

The study was performed within the EU 5th framework programme, project BioScene, EU Research 5th FRP, contract no. EVK2-CT-2002-00167. Additional funding was provided by Queen Maud University College. Additional GIS-based data were provided by A. Ekrem and S.N. Grenne. Valuable and improving comments on the article were given by J. Bolliger, P.S. Karlsson, J. Moen, U. Molau, C. Nilsson, H. Tømmervik, Anders Lundberg, and two anonymous reviewers, all of whom are gratefully acknowledged.