Regeneration potential of different Scots pine and Norway spruce provenances under variable drought Rising temperatures will lead to extended periods of summer drought, which may challenge the persistence of Scots pine and Norway spruce in dry alpine valleys where these species play an important role in the protection against natural hazards. We tested whether the natural regeneration of the two species in the Rhine valley near Chur, Switzerland, might be limited under future climatic conditions and we compared the performance of autochthonous provenances with that of seedlings originating from regions with already drier summer climate such as the Rhone valley, continental Eastern Europe or the Mediterranean basin. Seeds of Scots pine and Norway spruce were sown repeatedly in forest clearings at three south-exposed sites in the Rhine valley near Chur, Switzerland. Soil moisture was manipulated to a minor extent with throughfall reduction roofs. In both species, regeneration success was primarily driven by the weather conditions during the three months following seed sowing: the seedlings having emerged in the rainy spring of 2013 had a higher survival rate and accumulated up to five times more aboveground biomass than the seedlings emerging in the dry spring of 2011. In years with an average or even positive water balance, Scots pine seedlings were able to establish at all sites. In Norway spruce, by contrast, establishment rate exceeded 10% of viable seeds only at the site with the highest water retention capacity. In years with a positive water balance during spring, the seedlings from the Rhine and Rhone valleys outperformed those from most Mediterranean and Eastern European provenances, while no differences between provenances were found in the dry spring of 2011. We suggest that periodical regeneration of Scots pine will be likely in the Rhine valley even under future climatic conditions, whereas the establishment of Norway spruce may remain an exceptional event in dry, south-exposed clearings.