Dry calcareous grasslands are among the most species-rich and endangered ecosystems in the Central- European landscape. They are of anthropogenic origin and mainly a result of grazing by domestic animals. Due to land-use changes in the last century, particularly in the 1960s, they were often abandoned or afforested. Therefore, in 1975 long-term experiments were started in the southwestern Germany (Baden-Württemberg) to determine the effectiveness of alternative management treatments in maintaining grasslands and their species composition. The aim of this study was to assess the effect of grazing (reference management treatment), mowing once a year, mulching twice a year, mulching every second year, burning once a year and succession (abandonment) on the population structure (in terms of density, age structure, reproduction mode) and seasonal germination niche of a dwarf shrub, Helianthemum nummularium, and a herbaceous plant, Lotus corniculatus. To study the age structure, annual ring analyses were applied. The classification of the reproduction mode, either by seed or vegetatively, was carried out by differentiating the central under-ground organ either as a root (in this case the individual has established from seed) or rhizome (the individual has developed from clonal multiplication). The seasonal germination niche was derived from the age structure. Management clearly affected population density and age structure. Highest density of individuals was found in the grazing and the lowest in the succession treatment. In the mulching every second year and succession treatments populations were senescent. Management also affected reproduction mode in H. nummularium. Regeneration by seed was especially enhanced by mowing and burning but was inhibited by mulching twice and succession. In the latter treatments H. nummularium reproduced only clonally. Helianthemum nummularium germinated mainly in autumn but burning by breaking the dormancy of seeds initiated germination in spring. A similar pattern was detected in L. corniculatus: burning increased germination rate in spring. Comparing population characters (density, age, reproduction mode) to the traditionally used grazing treatment, mowing was most similar and for L. corniculatus additionally burning. This is in contrast to the assessment of the vegetation of the management treatments where mowing and mulching twice per year maintain a similar floristic composition. Finally, the analysis of the population structure revealed important mechanisms behind population and vegetation dynamics.
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.
Urbanization is one of the most extreme forms of land transformation. It is supposed to change the frequencies of species trait states in species assemblages. We hypothesize that the flora of urban and rural areas differs in the frequency of trait states and ask which traits enable a plant to cope with the urban environment. We tested our hypothesis in Germany, which was divided into grid-cells of ca 130 km2. We distinguished urbanized (with more than 33% urban land use; n = 59), agricultural (with more than 50% agricultural land use; n = 1365) and semi-natural (with more than 50% forest and semi-natural land use; n = 312) grid-cells and calculated the proportions of plant species per trait state in each grid-cell. Multiple linear regressions explained the log-transformed ratio of one proportion to another with land use (urban, agricultural, semi-natural) and the environmental parameters (climate, topography, soils and geology). Additionally, linear mixed effect models accounted for the effects of land use and biogeography and differences in sample size of the three grid-cell types. Urbanized and rural areas showed clear differences in the proportion of trait states. Urbanized grid-cells had e.g., higher proportions of wind-pollinated plants, plants with scleromorphic leaves or plants dispersed by animals, and lower proportions of insect-pollinated plants, plants with hygromorphic leaves or plants dispersed by wind than other grid-cells. Our study shows that shifts in land use can change the trait state composition of plant assemblages. Far-reaching urbanization might consequently homogenize our flora with respect to trait state frequency.