Lowland forests in the eastern part of Austria are characterised by high temperatures and limited precipitation in summer. The frequent occurrence of drought periods is a limiting factor for tree growth. Due to global warming, temperature-induced droughts may even increase in frequency and severity and become a serious problem for forestry. Different broad leaf tree species as well as conifers are growing in this area. Norway spruce is of high economic importance here, but also most affected by drought periods. In previous studies, x-ray densitometry has often been used to investigate the relationship between maximum density and summer temperature at sites where temperature is a limiting variable (i.e. northern and elevation timberline). In this study, the analysis of the density profiles of 404 Norway spruce trees (808 cores) revealed interesting differences in the density level itself as well as in the reaction of the trees to drought. The sampled trees originated from a provenance trial and had been collected from three replicate sites of which each represents a different precipitation regime. The most prominent drought year in Europe 2003 did not show as strong reactions as other years (for example 1992). During two analysed drought periods, the mean ring density increased due to higher latewood percentage. However, an increase in earlywood density could be observed, too. First analyses showed differences in the reaction during drought of trees from various different provenances, suggesting that selection for drought resistance could help to prevent negative impacts of drought on wood quality.
