Effects of Changing Climate on the Alpine Tree Line and Mountain Forest Carbon Pools Along 1500 km N-S and Elevation Gradients

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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) expansion of the for est by colonization of non-forested areas and migration of the alpine tree line; (2) increased growth of existing trees which will have an impact on carbon sequestration and future carbon pools. The mountain forests and forest-alpine transition zone const itute a large proportion of Norway's land surface. This ecotone can be found along the entire mountain chain, from south to the north of the country. Little information is available about the current status and the consequences of future changes likely to take place in these areas because they are not covered by any official monitoring programs and they have also been neglected in official carbon reporting. The focus of this proposal 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 reasona ble cost. The methods will be demonstrated on a 1500 km N-S gradient. The LiDAR transect encompasses hundreds of elevation gradients, and changes in tree line and biomass stores in the mountain forest will, for the first time, be provided. Such changes ar e relevant for reporting on climate conventions, and experience gained may provide vital input to design of future monitoring programs. Experiments will be set up to gain a basic understanding of climatic effects on biological processes regulating recruit ment and growth of 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 changes in these climate-sensitive ecosystems