Session

Colchicum autumnale is a highly toxic plant species, which can be found in species-rich grasslands in the southern parts of Central Europe. In Austria it is typical for sites with a changing water supply. Although poisoning of small animals like rabbits and even of humans occur quite frequently, problems with farm animals like cattle, sheep and horses are recorded rather seldom. There seem to be mechanisms about animals learning not to eat this plant, neither on pastures, nor in the hay. Nevertheless, the plant has become a main problem for grassland farmers in some parts of eastern Austria, especially in the Wienerwald region, where they have become highly dependent on selling hay to horse keepers. As a result, in some parts of Lower Austria high densities of C. autumnale may endanger the management of species-rich grasslands. In the time around 2010, studies on population biology of C. autumnale were carried out by a team from the University of Natural Resources and Life Sciences, Vienna (BOKU). They suggested a strong effect of additional early mowing against the population of the species. From 2018 to 2022 we conducted a practical test of this method together with 12 farmers from the region. On 18 plots with high densities of C. autumnale regulation was carried out in a practical way, mostly either by mowing with a typical mower or with a flail shredder, usually in late April or early May. There were also reference plots without the regulation nearby. The density of C. autumnale was counted on plots with a radius of 3 m within the meadows. Additionally, 12 permanent plots with species lists and coverage were applied. During the project, changing densities of the populations of C. autumnale could be found for different reasons, mainly because of changing weather conditions from year to year. There was only one plot with a clear decline of density, where probably also other factors of the management were changed. Although there were no clear scientific results on effects of regulation, it showed the importance of integration farmers knowledge and their practical possibilities in the development of suggestions for grassland management. At least the resampling of the permanent plots showed a clear result. The biodiversity of the grasslands was not reduced by the regulation.