Study sites and sampling
We designated ten study sites in October 2019 when the soil disturbance made by the cranes are the most apparent on the sites. We used the following criteria for site selection: 1, the sites were situated at least 1 km from each other, 2, the sites were characterised by dry alkaline grassland vegetation (Achilleo setaceae – Festucetum pseudovinae ); 3, all the sites were managed by extensive grazing, 4) within each site vegetation patches disturbed by cranes as well as undisturbed areas occurred within a distance of 0.5 km in alkaline dry grasslands and 5) the disturbed and intact areas were at least 50 m2 large.
Within each site we designated two 30 m2-sized permanent plots; one in disturbed area and one in intact grassland. In October 2020 we re-visited all the sites to record whether the areas disturbed in 2019 were disturbed again in 2020 and whether the areas undisturbed in 2019 remained intact also in 2020. In each plot, we designated ten 1m × 1m sized quadrats, which were precisely marked with metal sticks placed underground so we could precisely re-visit the quadrats with the help of a metal detector. In total there were 100 ploughed and 100 undisturbed quadrats.
We recorded the species list and percentage cover of vascular plant species in each quadrat at four sampling dates: early April 2020, mid-June 2020, early April 2021 and mid-June 2021. This resulted in 800 observations in total. Nomenclature of vascular plants followed the work of Király (2009). We also recorded the total cover of vascular plants and that of cryptogams (i.e., the summed cover of mosses, lichens andNostoc cyanobacteria).