Die Artmächtigkeitsschwankungen in Einem Nordwestdeutschen Enzian- Zwenkenrasen II

Summary

A permanent quadrat of 3 sq metres was laid down in a Gentiano-Koelerietum stand located in the Beckumer mountains (Westphalia) in 1957 (cf.Vegetatio, Vol. XI, 1963, Fasc. 4; 237–40). The relevés made each year from 1957–61 as also from 1962–66 (see table) gave the following results:

Many species, especially the perennials, fluctuate little in their quantity over the years. Some plants continuously decrease or increase in number. An example of this isBrachypodium pinnatum which continuously decreased from 1957 to 1966. This decrease is most probably the result of an increase in the rabbit population after the Myxomatosis epidemic of 1956. Other species, especially the annuals, fluctuate irregularly in abundance. These fluctuations depend on fluctuations of climatic factors. In this wayGentiana germanica andLinum catharticum decrease enormously after dry periods during the spring or summer. They increase again after wet summers.