Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

Boreal and subarctic peatlands have been extensively studied for their major role in the global carbon balance. However, study efforts have so far neglected the contribution of these ecosystems to the non-methane biogenic volatile organic compound (BVOC) emissions, which are important in the atmospheric chemistry and feedbacks on climate change. We aimed at estimating the BVOC emissions from a subarctic peatland in northern Finland. Furthermore, our aim was to assess how these emissions are affected by enhanced UV-B radiation, the amount of which has increased especially at high latitudes as a result of stratospheric ozone depletion. The contribution of BVOC emissions to the total net carbon exchange and correlations between the emission of different BVOCs and net ecosystem CO2 exchange, CH4 emission, total green leaf area, and abiotic factors were also studied. The UV-B exposure, simulating a 20% depletion of stratospheric ozone, was started in 2003, and measurements were per- formed during the growing seasons of 2006 and 2008. The subarctic peatland proved to be a small source of BVOCs and the dominant moss, Warnstorfla exannulata, emitted a diverse compound spectrum. The water table level exerted a major influence on the BVOC emissions surpassing the effect of enhanced UV-B. In fact, no overall UV-B effect was established on the BVOC emissions, apart from toluene and 1-octene, emissions of which were doubled and tripled by enhanced UV-B in 2008, respectively. The contribution of BVOCs to the total net carbon exchange was below 1 %.