Climate variations and tree growth between 1961 and 1995 in Austria

Using clim ate records from 20 weather stations, we investigated the changes in temperature, rainfall, and length of the growing season between 1961 and 1995. To establish a link between changes in climate and tree growth, we analyzed radial increment rates from tree rings over the same period. Our results indicate: (1) no change in precipitation over the period; (2) a highly significant increase (ct=0.01) in average annual temperature (1.13°C), minimum temperature (1.23°C), winter temperature (2.70° C) as well as a significant (a=0.05) increase in the length of the growing season (14 days) since 1961. For the early 1990s, lower radial increment rates as well as a decrease in the temperature related climate parameters are detectable. To understand the importance of climate on tree growth we use the ecosystem model FOREST-BGC and predict the annual net primary production (NPP). The trends in NPP are consistent with observed diameter increment rates determined from 1179 increment cores for Norway spmce from all over Austria.