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Biomass of the Arctic Birch in Fennoscandia. MSc Dissertation.

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The change in biomass and extent of trees can be an indication of the effects of climate change. Higher latitudes and elevations have been identified as regions which are particularly sensitive to changes in global temperature. The Arctic birch which occupies the ecotone between tundra and forest has been increasing in extent and biomass toward higher latitudes and elevations. This could results in a net release of carbon from the soil to the atmosphere, but also the locking of atmospheric carbon in the biomass of these trees. We have proposed new methods that could be used to estimate and monitor the change in extent and biomass of Arctic birch. The first relies on tree crown extraction techniques from true colour aerial images and lidar tree heights taken over Abisko, Sweden. The second uses tree shadow length extraction on snow using template matching from IKONOS-2 images over Kevo, Finland. Tree characteristic have been sampled at both sites and biomass calculated using allometric relations. The third uses the biomass modelled using the previous methods as independent variable and MODIS summer EVI or the difference between summer and winter EVI as dependent variable in a non-linear regression based model to estimate biomass over Fennoscandia. A MODIS percentage tree cover mask was used to remove soil and vegetation background signal influences. Results have been validated at every stage and compared with NFI data at country and regional level. Results are comparable if not better than previous research.
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