Transformations of Vascular Flora of a Medieval Settlement Site: A Case Study of a Fortified Settlement in Giecz (Wielkopolska Region, Western Poland)

Exceptional components of the cultural landscape of Central Europe include archaeological sites, e.g., castle ruins, prehistoric or medieval fortified settlements, other settlements and burial mounds. The plants associated with them help us explain the processes of species persistence on habitat islands as well as the process of naturalization of crop species, which escape from fields or are abandoned. This study describes the flora of a medieval fortified settlement in Giecz (Wielkopolska region, western Poland), presents plant indicators of former settlements (relics of cultivation), species of high conservation value, and transformations of the vascular flora of this settlement over a few decades. Field research was conducted in 1993–1994, 1998–1999, and 2019. At the study site, 298 species of vascular plant species were recorded, and nearly 70% of them (201 species) have persisted there over the last 20 years. The flora includes seven relics of cultivation (Artemisia absinthium, Leonurus cardiaca, Lycium barbarum, Malva alcea, Pastinaca sativa, Saponaria officinalis, and Viola odorata), 5 species threatened with extinction in Poland and/or Wielkopolska, and 53 species of least concern (LC) according to the European red list. We have attempted to explain the floristic changes. The archaeological site in Giecz is of high conservation value, very distinct from the surrounding cultural landscape because of its specific flora, and composed of species from various habitats (e.g., dry grasslands, wooded patches, meadows, aquatic and ruderal habitats), including threatened, protected, and relic species.