Leaf‐out in northern ecotypes of wide‐ranging trees requires less spring warming, enhancing the risk of spring frost damage at cold range limits

Aim Trees need to avoid frost damage to their young leaves by leafing out after the occurrence of the last frost, yet they also need to start photosynthesis early in the season to achieve sufficient growth. This trade‐off leads to the hypothesis that ‘safety margins’ against spring frost should become shorter, the longer the winter duration, perhaps reaching an asymptotic limit where frost damage would occur in most years. Physiologically,...