This determination of changes in forest sites is based on the comparison of well documented phytosociologieal surveys made by various authors in the 30's to 60's with new surveys of the same sites conducted 1984–1988. In evaluating floristic changes emphasis was placed on the ecologieal plant indicator values of ELLENBERG (1974, 1979) and LANDOLT (1977).
In the northern eentral Plateau and the Geneva Basin, in forests previously managed as sprout seedling forests or coppices, a drastic decrease in species number and shifts in species composition occurred, nitrogen indicators increasing in frequency as light figures sank. Possible causes may have been changes in forest management and/or deposition of nitrogen from the atmosphere.
Changes in 257 stands in the Alps were found to be due to natural and silviculturally initiated processes of regeneration. Merocenotie sampling, however, revealed a decrease in light, nitrogen, and reaction figures in remnants of old stands.
In over 60 stands in the lower Fricktal, intensive thinning and regeneration operations were reflected in increased illumination values. On the other hand, soil pH measurements revealed a trend towards acidification of the upper soil, which was corroborated by a decrease in phosphorus (P), calcium (Ca), magnesium (Mg), and heavy metals (Co, Ni, Zn).
The heterogeneity of the results shows that a system of long-term observation is essential for the precise determination of processes within the forest ecosystem.