The dry year in 2003 affected the Swiss forest in different ways. Stem growth in trees at 15 out of the 17 LWF sites clearly reacted to the estimated drought stress. The drier it was between March and August 2003, the less stem growth there was in comparison with the previous year.  Aridity decreased, however, with altitude. At sites above 1300 metres a.s.l., trees even grew better. This had mostly to do with the higher temperatures in 2003, as climate analyses in Alpine regions and comparisons with satellite images were able to demonstrate. On most of these sites trees grew again normally in 2004. Unlike with growth, however, the condition of the tree crowns was different. In J uly and August 2003 no increase in crown defoliation was observed, although at the most arid sites some premature
colour change occurred and leaves were shed early in late summer and autumn. In summer 2004 a marked increase in crown defoliation was registered at many sites. Tree mortality does not appear to have risen markedly at any of the LWF sites apart from the Visp site in Canton Valais. It was expected that there would be similar losses among broadleaf trees to those that occurredafter the dry years in 1947 and 1949. Up until now, however, no marked increase in direct drought damage has been observed, nor in the root and stem diseases that thrive on lack of water. This shows once again the complexity of both the influences on the forest and the forest’s reactions to them.