Changes in the plant cover of the dune hill in Folusz near Szubin (NW Poland) between 1959 and 2012: the problem of preservation of xerothermic grasslands in the agricultural landscape

The dune hill in Folusz is one of the most interesting sites with xerothermic vegetation in the Polish lowland. It is different from other sites by the fact that xerothermic vegetation covers a single dune located amidst large areas of Molinia meadows rather than slopes of river valleys. Vegetation occurring on the hill represents a cold Stipa steppe with rare species of floodplain meadows and has long aroused the interest of botanists. In the 19th century and in the early 20th century, observations in this area were carried out by German botanists (L. Kühling, F. Spribille, H. Miller, W. Bock). In the 1930s, the investigation was continued by botanists from the University in Poznań. After World War II, it was one of the main research sites for botanists and ecologists from the University in Toruń, and recently also from the universities in Bydgoszcz. Floristic lists were compiled by all the aforementioned researchers, which describe the state of flora in the subsequent periods, and when collated in tables, they help to determine the directions of changes occurring in the area over a hundred years. Not all the materials obtained in the past were published. A lot of interesting data were preserved in the Toruń centre in the form of actual vegetation maps and relevés. This paper presents the comparison of vegetation from 1959, plotted on the unpublished vegetation map by J. Wilkoń-Michalska, with the vegetation in 2013. Changes in the land cover were also analysed through a series of aerial photographs from 1961, 1975, 1986 and 2005. The GIS and GPS technology was used in the spatial analysis. Furthermore, the analysis of flora changes was performed, including the comparison of data presented in ecological literature with unpublished data collected by J. Wilkoń-Michalska in 1956-1964. In addition, numerical analysis of relevés from both these periods and from 2012 was performed. The objective of all the analyses was to determine how the changes were affected by spontaneous development of oak trees on the dune and destructive human activity related to exploitation of the sand, afforestation of the dune with pine, birch and oak, and planting of common lilac. An effort was also made to assess the importance of including the Folusz dune hill within the Natura 2000 site − PLH040027 „Molinia meadows in Folusz” − for preventing further degradation of xerothermic vegetation