Rapid changes are expected in the mountain forest and the forest-alpine transition zone due to global warming. Since steep temperature-productivity gradients characterize these marginal areas, two fundamental effects are expected: (1) an expansion of the forest by colonization of non-forested areas and migration of the alpine tree line; (2) increased growth of existing trees which will have a significant impact on carbon sequestration and future carbon pools. The mountain forests and forest alpine transition zone constitute a large proportion of Norway’s land surface, and this ecotone can be found along the entire mountain chain from the southern part of the country and up to the north. However, there are no official monitoring programs covering these areas. Thus, little information is available about the current status and the consequences of future changes likely to take place and thus, so far these areas have been neglected in the official carbon reporting.

Position of small trees with GPS (Måling av små trær ) Foto: Erik Næsset

The main focus of this project is on development of efficient methods for detection of alpine tree line migration and biomass accumulation in the mountain forest based on LiDAR (Light Detection And Ranging) remote sensing. This technology is the most sensitive available to detect local and rapid change over short time periods and extensive areas at reasonable cost. The methods will be demonstrated on a 1,500 km N-S gradient established in 2006. The airborne LiDAR transect encompasses hundreds of elevation gradients and will be remeasured in 2011. This unique data set will document changes in tree line and biomass stores in the mountain forest. To document such changes are relevant for reporting on climate conventions, and experience gained may provide vital input to design of future monitoring programs. We have also set up experiments to gain a basic understanding of climatic effects on biological processes regulating recruitment and growth of new trees along the alpine tree line. By doing so, we will be able to provide estimates with respect to the remeasurement period needed to reliably detect significant changes in these climate-sensitive ecosystems.

Project title:

Effects of changing climate on the alpine tree line and mountain forest carbon pools along 1500 km N-S and elevation gradients

Principle investigator at UMB:

Prof. Erik Næsset


Prof Terje Gobakken (UMB)
Dr Ross F. Nelson (NASA),
Prof. Mikael Ohlson (UMB)
Dr Annika Hofgaard (NINA)
Dr Ole Martin Bollandsås (UMB)
Dr Nadja Stumberg (UMB)

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