Carbon fluxes in Arctic plant species: photosynthetic performances, isotopic signature and VOCs emissions

One of the most important effect of global warming, in Arctic regions, is the permafrost degradation with consequent increase of soil active layer. A possible consequence of such degradation can be an increase in soil respiration with release of organic carbon stored in permafrost soils. On the other hand, climate change and, in particular, increasing temperature and CO2 concentration, may have, in those regions, positive feedbacks on photosynthetic activity. Not only the balance between photosynthesis and respiration, but also the monitoring of the different components of C flux is of great interest. The goal of the experimental campaign carried out in Ny-Ålesund during summer 2013 has been to study C fluxes on target plant species. We focused our attention on the most representative species at the site near the Amundsen-Nobile Climate Change Tower (CCT), characterized by a significant level of permafrost degradation. Photosynthetic performances at different CO2 concentration, incident light and temperature were measured on Salix Polaris, Dryas octopetala, Saxifraga oppositifolia, Carex rupestris. On the same species, Volatile Organic Compounds (VOCs) emitted from leaves were sampled and analyzed for their content, since quantitative determination of these compounds is considered to estimate the percentage of C lost by the system. Plant and soil samples have been collected to analyze 13C isotope composition, to obtain an overview of the carbon isotope signature along the continuum plant-soil. Measurements have been carried out manipulating temperature, CO2 concentration and light conditions to monitor the response of those arctic species to climate and atmospheric variations. Measurements of C assimilation and VOC emission will be compared between sites with different level of permafrost degradation and associated to soil respiration and C isotope signature. This, together with C flux measurements at plot level and with C data at large scale from the CCT, will allow to follow the fate of C under global warming conditions and will be the basis for long-term monitoring in this tundra ecosystem.