Temperature sensitivity of willow dwarf shrub growth from two distinct High Arctic sites

The High Arcticregion has experienced marked climate fluctuations within the past decades strongly affecting tundra shrubgrowth. However, the spatial variability in dwarf shrubgrowth responses in this remote region remains largely unknown. This study characterizes temperature sensitivity of radial growth of two willow dwarf shrubspecies from two distinct High Arcticsites. The dwarf shrub Salix arcticafrom Northern Greenland (82°N), which has a dry continental High Arctic climate, is linked with Salix polarisfrom central Svalbard (78° N), which experiences a more oceanic High Arctic climatewith relatively mild winters. We found similar positive and significant relationships between annual growthof both Salix dwarf shrubspecies and July–August air temperatures (1960–2010), despite different temperature regimes and shrubgrowth rates at the two sites. Also, Salix dwarf shrubgrowth was significantly negatively correlated with Arcticand North Atlantic Oscillation(AO/NAO) indices; S. arctica from Northern Greenland was negatively correlated with previous autumn (AO index) and current summer AO and NAO indices, and S. polariswith the summer NAO index. The results highlight the importance of both local and regional climatic drivers for dwarf willow shrubgrowth in harsh polar deserthabitats and are a step in the direction of identifying and scaling changes in plant growth across the High Arctic.