Hydrogen apparent fractionation between source water and epicuticular waxes of Pinus sylvestris in North East Finland

Hydrogen isotopic composition of plant biomass provides crucial information about plant ecophysiology and local hydrology. Little is known about the apparent fractionation between hydrogen in source water and epicuticular leaf waxes of coniferous tree species that dominate the boreal forest ecosystem exposed to prolonged periods of sunlight during the growing season. In this study, single rope canopy access techniques were used to harvest needle and twig material from the upper, middle and lower crown of north and south facing branches of Pinus sylvestris within the subarctic forest of North East Finland. Samples were collected towards the beginning of the growing season in July and repeated in late September 2010. Leaf and twig waters were extracted cryogenically and analysed for D-enrichment. Individual n-alkanes are currently being quantified and analyzed for 13C/12C and D/H compositions. The molecular and isotopic data are supplemented by long-term in-situ cuvette photosynthetic assimilation measurements as well as relative humidity (RH), air temperature, precipitation and wind speed data collected by Helsinki University (SMEAR I). In addition RH, air temperature, wind speed and incoming solar radiation measurements were made at each individual sample point at the time of harvesting to quantify meteorological and microclimatological variation within individual trees. The outcome of this investigation will provide important insights into plant biochemistry and physiology of a crucial climate sensitive higher plant species subjected to continuous low light throughout the season. Furthermore, this work will expand our understanding of modern and palaeo-hydrology not only in northern Finland but also in other boreal forests around the world.