Global warming in high-latitude regions is significantly stronger than the global average. During the past decade, numerous researchers have reported trends of shrub expansion under warmer conditions. However, this Arctic greening trend seems to have halted during the past years, the causes of which are unknown. Simultaneously, increasing mention is made of abrupt permafrost thaw throughout the Arctic region, creating thaw ponds in which vegetation drowns. We propose that this provides a likely cause for this shift away from Arctic greening. Moreover, we hypothesize that extreme summer precipitation may trigger abrupt permafrost collapse due to increased heat transport to the permafrost. Combining satellite image analysis, dendrochronological analysis, field manipulation experiments and field monitoring will help us assess shrub dynamics and elucidate its drivers in lowland tundra ecosystems. Using time-series of satellite imagery we will assess the spatio-temporal dynamics of shrub decline/expansion on a landscape scale, aided by ground point observations and monitoring. To assess to what extent climatic events trigger thaw pond formation, we will perform dendrochronological analysis on drowned shrubs in thaw ponds of various age to assess time of drowning in relation to climate. Lastly, we will determine experimentally whether extreme summer precipitation triggers permafrost collapse using an irrigation set-up. A mechanistic understanding of shrub dynamics and permafrost degradation is vital for assessing future development of this ecosystem under global change and its implications for greenhouse gas balance. We expect that this research project in an understudied Arctic region will shed a new light on Arctic landscapes.
We provide a disciplinary and multidisciplinary research programme aimed at advanced understanding of environmental problems and advanced training of PhD candidates in this field.