In the 2^nd forest district of the Canton Aargau (Jura mountains, Switzerland) with a forested area of 9000 ha, we investigated the relationship between vegetation and forest growth. lt represents a synthesis of three separate investigations.
Based on the site map established between 1976 and 1990, 140 representative sample plots were selected. Between 1992 and 2002, on each plot, a floristic relevé was made and the site was classified based on both stand age and top height.
The site index data collected in the 2^nd forest district of the Canton Aargau show that site and site index are not constant but do change over time, for instance, due to changes in climatic conditions. In order to correct these data we used plots of former yield experiments carried out by WSL between 1888 and 1981, comparing their site index with the ones collected 1990-1993 in the succeeding stands.
After correction, the site index data were linked with (a) phytosociological units, (b) indicator values according to Landolt (1977), (c) a newly calculated species-specific site-index-value (B-value) and (d) the results of a canonical correspondence analysis.
The results show that it is possible to reliably estimate the site index based on the composition of the field layer, provided the studied stand is located in the lower ranges of the Jura mountains.