Higher temperatures increase nutrient availability in the High Arctic, causing elevated competitive pressure and a decline in Papaver radicatum

Abstract: Linking changes in the vegetation cover with factors that can moderate the effects of climate change is central to our understanding of Arctic ecosystems and their susceptibility to change. The aim of this study has been to investigate the moderating effects of soil conditions. A High Arctic population of Papaver radicatum was studied in relation to the prevailing surface temperature, active layer depth, soil moisture and soil water variables such as pH and conductivity at the site. Data was collected between 2004 and 2013 in the Zackenberg valley in NE Greenland. A negative trend over time was found in the number of P. radicatum flowers, as well as correlations between P. radicatum and conductivity, Ca2+ and dissolved total nitrogen (DTN). Surface temperatures increased, causing a deeper active layer and intensified weathering. The intensified weathering resulted in higher concentrations of ions in the soil water. No ion reached toxic levels, and the release of cations improved the nutrient status of the acidic soil. Together with warmer temperatures, this made the site more favourable for biological activity, elevating the competitive pressure. DTN decreased in correlation with dissolved organic carbon (DOC), since decomposition rates did not increase rapidly enough to meet the amplified demand on nitrogen and organic carbon. Due to P. radicatum’s high susceptibility to competition, the elevated competitive pressure is the most plausible reason for its decline. Previous studies have found that P. radicatum responds to warmer temperatures with increased growth. The results of this study contradict those of the previous studies, which were performed with open top chambers or over an altitudinal gradient instead of over time. This stresses the importance of integrating the plants’ full ecological context and allowing for complex feedback mechanisms to develop when studying the responses of Arctic plants to climate change.