Vegetationskartierung
Dry calcareous grasslands are among the most species-rich habitats in Central Europe, harbouring numerous threatened species. Because of their strong decline, they are being protected under the European Habitats Directive. However, apart from this general decline, new grasslands developed after the abandonment of arable fields on marginal land over the course of the last few centuries or even decades.
The main question of this study was which species may indicate the age of a dry calcareous grassland habitat in the Franconian Jurassic mountains near Kallmünz. Furthermore, we asked if there is a general pattern of indicator species among available studies on ancient (i.e. those continuously used as pastures at least since 1830) and recent (i.e. those temporarily farmed as arable fields after 1830) calcareous grasslands. We compared the diversity parameters and nature conservation value of both grassland types. Additionally, we searched for differences in habitat and soil parameters.
We compiled a list of indicator species of both ancient and recent grasslands in the study region. Comparison with other studies leads to the conclusion that there are not many species that clearly indicate grassland age across different regions (the best indicators are Carex caryophyllea, Cirsium acaule and Hippocrepis comosa for ancient grasslands, and Agrimonia eupatoria and Astragalus glyciplyllos for recent grasslands).
Ancient grasslands harbour a somewhat greater number of threatened species than recent grasslands. Many species of the ancient grasslands under study can be considered relict species of steppic grasslands or open pine forests (e.g. Hippocrepis comosa, Pulsatilla vulgaris, Teucrium chamaedrys, Teucrium montanum and Thymus praecox). Recent grasslands also harbour rare and endangered species, especially disturbance-tolerant relicts of former arable use (e.g. Melampyrum arvense) and may therefore be of high conservation value, too.
The average number of species per plot is greater in ancient grasslands. However, the most species-rich plot (46 species of vascular plants within a 4-m2 quadrat) was found in a 60 years old grassland.
Arable cultivation in the past has altered the physical and chemical properties of the soil of recent grasslands. In general, ancient grasslands occur on nutrient-poorer and less calcium-rich soils with high water holding capacity. High water holding capacity is connected with high humus content, which increases the importance of ancient grasslands for carbon storage.
The challenges and benefits of differentiating grasslands of different age in the management of protected areas and landscape planning (e.g. the identification of High Nature Value farmland) are discussed.