Temporal dynamics of the ground vegetation in a Danish beech forest

Abstract

A Danish beech (Fagus sylvatica) forest was studied during a period of five years, to reveal temporal and spatial patterns in the ground vegetation within a year and between years. In 1994, twenty stations were established in commercially managed forests south of Aarhus, and the frequency of the vascular plants was recorded in 40 stratified random Raunkiær circles (0.1m2). The sampling was repeated in 1995, 1997 and 1998. The seasonal variation in species frequencies was furthermore studied in nine of the permanent stations. The findings were summarised in terms of species richness and averaged Ellenberg ecological values, and analysed with clustering analysis and ordination. We applied Steinhaus similarity index and detrended correspondence analysis to detect fluctuation and succession. To test for significant vegetation changes, a non-parametric Mantel test was used. The species richness and Ellenberg's indicator values were unchanged during the five years. The classification results, however, differed between the years. In particular, changes in the quantitative similarity between years were high (12-23%), and this was supported by ordination. We conclude that the vegetation in the study area, at least in the studied 5-years period, did not how signs of clear successional trends, but merely changes in species abundance, which we associate with short-term fluctuation. Further studies, on different time scales, of vegetation dynamics in forests should be initiated, in order to make better descriptions of plant communities, and to detect possible successional trends. We suggest that such studies also include long term monitoring of environmental parameters in a nested, permanent sampling design.