History or abiotic filter: which is more important in determining the species composition of calcareous grasslands?

Dry calcareous grassland is one of the most species-rich and endangered ecosystem in Central Europe. Despite the dramatic loss of grassland in the second half of the 20th century due to abandonment of agricultural land or afforestation, new grasslands developed on former arable land. The main objective of this studywas to assess the effect of age on the vegetation and habitat properties of calcareous grasslands. We found that the history (former land use, age of habitats) of grassland localities has had a fundamental effect both on the species composition of the vegetation and habitat properties. Significant differences were found, especially in soil reaction and water-holding capacity. Therefore, we can state that both history and habitat properties determine the recent species composition pattern. Consequently, it was possible to identify species indicating the historical status of the grasslands. Indicators of ancient grassland (i.e., patches continuously used as pastures at least since 1830) could be assigned to typical Festuco-Brometea species but also more widespread grassland species such as Carex flacca, Buphthalmum salicifolium, Carlina vulgaris, Cirsium acaule, Hippocrepis comosa and Scabiosa columbaria. Indicators of recent grasslands (i.e., patches temporarily farmed as arable fields after 1830) belong to different phytosociological classes: Festuco-Brometea, Molinio-Arrhenatheretea, Trifolio-Geranietea sanguinei and Secalietea cerealis. Festuco-Brometea species restricted to recent grasslands were e.g. Thymus pulegioides subsp. carniolicus, Stachys alpina, Rhinanthus alectorolophus and Onobrychis viciifolia. The two latter species are survivors from the former arable cultivation, the first was an arable weed and the second a widespread fodder plant, but are now considered to be characteristic species of calcareous grasslands. Therefore, we claim that the occurrence of these species indicate calcareous grasslands that were previously arable fields and that recent grasslands are a monument to historical land use. Rare and/or endangered species were not only found in ancient but also in recent grasslands. Furthermore, recent grasslands have a high species diversity. Thus both, ancient and recent calcareous grasslands should be considered equally valuable from a nature-conservation point of view.