Between 1864 and 2000 spring and summer temperatures in Switzerland have increased by 0.8°C per 100 years. Climate models predict a more than doubling of this temperature rise by the middle of this century. Depending on the limiting factors for tree growth temperature increase may lead to different growth responses.
Tree provenance trials along elevation gradients were used to study the effect of future climate warming. With increasing elevation tree stem and height growth declines and needles become shorter. High elevation and northern provenances are optimally adapted to a short growing season, but cannot completely utilize the longer growing season when planted at low elevation. They may respond less to climate warming than low elevation trees if planted at high elevation.
Needle elongation pattern of European larch in the Engadin valley corresponds to an upward shift of 200 m over the past 20 years which is in agreement with the observed temperature increase in spring. During the extremely warm and dry summer 2003 tree stem growth has decreased at low elevation, but not at higher elevation. Thus an increase in summer drought may offset growth increases at low elevation in the future.