Assessment of light and soil conditions in ancient and recent woodlands by Ellenberg indicator values.
The system of Ellenberg indicator species is widely accepted and used to characterize climate, light and soil conditions in central Europe and beyond. The aim of this study was to examine the extent to which Ellenberg indicator values can be used to characterize environmental conditions in ancient and recent woodlands. The study was based on data from 264 plots in ancient deciduous woodlands and adjacent 70-year-old recent woodlands located on the same soils in the Carpathian foothills. Vegetation data were related to information on light intensity and a range of soil variables. Despite a similar number of species on the plots in the ancient and recent woodlands, the correlations between the mean indicator values for light (mL), reaction (mR) and nitrogen (mN) and measured light intensity, soil pH and cation exchange capacity, respectively, were significantly lower in the recent woodlands than in the ancient woodlands. Due to a very slow and differentiated regeneration rate of the field layer, the species with the lowest indicator values for reaction and nitrogen were significantly less abundant in the recent woodlands than in the ancient woodlands, while the species with higher values of these indicators were more frequent. The change of the reaction of many species to light conditions was the main reason for poor prediction of light intensity in the recent woodlands by the mean indicator values for light. The mean Ellenberg indicator values for light, reaction and nitrogen were relatively good predictors of the environmental conditions in the ancient woodlands, with stabilized species composition determined mainly by the environmental regime. They were, however, much weaker indicators in the recent woodlands. This implies that the mean indicator values for secondary woodlands should be interpreted with caution and verified by measurements of environmental variables.