| Summary: | Climate change is predicted to accelerate the closer you get to the poles. And in contrast to more southern regions, which is forecasted to receive increased temperatures and drought, the Arctic is predicted to get both higher temperatures and an increase in precipitation. This means that in the study site for this paper, Adventdalen, on the high arctic island of Spitsbergen, Svalbard, the plant communities, will most likely experience an increase in both temperature and precipitation. This study looks at how three somewhat different plant communities in Adventdalen might respond to an increase in rainfall. The different plant communities are dominated by Cassiope tetragona, Dryas octopetala and Salix polaris, respectively. We aim to see if an experimental increase in precipitation will influence plant senescence in the autumn in the high arctic. In order to be able to see an effect within the realm of possibilities for the future, we chose to increase the amount of precipitation by 90 mm over a period of 6 weeks in the summer, capturing the peak of the growing period and the beginning of the senescence stages for the chosen plant communities. The results of this study show that an increase in precipitation will prolong the growing season and plant senescence in the study area. The magnitude of the NDVI response to increased soil moisture is plant species specific. The percent decline for NDVI measurements show that the biggest effect was achieved at the Cassiope site, where the watered plot had a change in NDVI values of - 22.9%, whereas the ambient plot had a change of – 51.3%. For the Dryas site the change in NDVI was for the watered plot – 31.0% and for the ambient plot the change was – 49.4%. For the Dryas site the change in NDVI values were the smallest, but still significant, with changes in NDVI for the watered plot at – 37.8% and the ambient plot at – 51.0%. An elongation of the growing period might give some species an advantage in productivity compared to others, while other species might suffer ...
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