![]() ![]() The results showed that the relative importance of the two factors and the direction of the effects are highly species-specific, while both factors tend to have consistent effects on both germination and early seedling survival within each species. The early establishment of these trees at the alpine treeline was limited either by temperature or by moisture, the sensitivity to one factor often depending on the intensity of the other. ![]() In addition, we monitored the germination response of three of these species to low temperatures under controlled conditions in growth chambers. Five European treeline tree species were studied: Larix decidua, Picea abies, Pinus cembra, Pinus uncinata and Sorbus aucuparia. We investigated the effect of soil temperature and moisture on germination and early seedling survival in a field experiment in the French Alps near the local treeline (2100 m a.s.l.) using passive temperature manipulations and two watering regimes. These earliest life stages may be major bottlenecks for treeline tree populations and will depend differently on climatic conditions than adult trees. For treelines to advance poleward or uphill, the first steps are germination and seedling establishment. However on a local scale, treeline form and position vary considerably due to other climatic factors, tree species ecology and life-stage-dependent responses. On a global scale, temperature is the main determinant of arctic and alpine treeline position. ![]()
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