Local variability in growth and reproduction of Salix arctica in the High Arctic

Arctic terrestrial ecosystemsare heterogeneous because of the strong influences of microtopography, soil moisture and snow accumulation on vegetation distribution. The interaction between local biotic and abiotic factors and global climate patternswill influence species responses to climate change. Salix arctica(Arctic willow) is a structuring species, ubiquitous and widespread, and as such is one of the most important shrub species in the High Arctic. In this study, we measured S. arctica reproductive effort, early establishment, survival and growth in the Zackenberg valley, north-east Greenland. We sampled four plant communities that varied with respect to snow conditions, soil moisture, nutrient content and plant composition. We found large variability in reproductive effort and success with total catkindensity ranging from 0.6 to 66 catkins/m 2 and seedling density from <1 to 101 seedlings/m 2 . There were also major differences in crown area increment (4–23 cm 2 /year) and stem radial growth (40–74 µm/year). The snowbed community, which experienced a recent reduction in snow cover, supported young populations with high reproductive effort, establishment and growth. Soil nutrient content and herbivore activity apparently did not strongly constrain plant reproductionand growth, but competition by Cassiope tetragonaand low soil moisture may inhibit performance. Our results show that local environmental factors, such as snow accumulation, have a significant impact on tundraplant response to climate change and will affect the understanding of regional vegetation response to climate change. Keywords: Herbivory; nutrient; plant colonization; vegetation; shrub; water availability. (Published: 27 June 2016) To access the supplementary material for this article, please see the supplementary files in the column to the right (under Article Tools). Citation: Polar Research 2016, 35 , 24126, http://dx.doi.org/10.3402/polar.v35.24126