%0 Articles %T Growth limitation of trees and carbon balance of the vegetation in the treeline zone in north eastern Lapland %A Susiluoto, Sannamaija %D 2013 %J Dissertationes Forestales %V 2013 %N 161 %R doi:10.14214/df.161 %U http://dissertationesforestales.fi/article/1943 %X The aim of the thesis was to study the factors limiting tree growth at treeline in Värriö and to investigate how reindeer grazing affects the vegetation and carbon balance of the treeline environment. The factors limiting Tree growth in the treeline ecotone were studied based on two hypotheses, the sink limitation hypothesis and the resource limitation hypothesis. Resource limitation included both carbon and nitrogen limitation. Three different manipulation treatments; debudding, defoliation and fertilization; were performed on treeline trees in Värriö to test the hypotheses. According to the results tree growth in Värriö is clearly restricted by resources. The factors supporting the resource limitation hypothesis were increased growth due to fertilization and debudding treatments and decreased stem diameter growth due to the defoliation treatment. Also, sapflow was not down-regulated due to debudding treatment. There was some increase (p=0.054) due to fertilization treatment in carbon isotope ratio, which furthermore supports the resource limitation hypothesis. Grazing did have an effect on the amount of carbon bind to vegetation, as the biomass of lichens was decreased due to grazing by 85 %. There were also changes in species composition due to grazing. Net carbon exchange correlated with the dwarf shrub cover, but the dwarf shrub cover did not change due to grazing. Overall, grazing did not affect the carbon fluxes on the area. Overall, the results showed that the tree growth in the study site is restricted by resources. Grazing affects the species composition and vegetation carbon stocks, but not on productivity or soil carbon stocks. Both treeline rise and increase in the abundance of the trees in the treeline would affect significantly on the carbons stocks of these ecosystems. Since reindeers might affect the regeneration of treeline, future research on the interactions between grazing and treeline progression would be important.