Tracing the history of synanthropic flora and vegetation in the Czech Republic (original) (raw)

2017, PhD thesis, Charles University in Prague

Plant macro remains from archaeological situations were studied in order to trace the history of gradual formation of today’s synanthropic vegetation. Synanthropic plants represent a heterogeneous group of species with various qualities and strategies, as well as with various immigration histories. In general, the synanthropic flora is rich in aliens, so it is important to know, when exactly these species immigrated to our territory (to know their residence time). Besides the determination of the residence time of alien plants, also the dynamics of formation of urban flora and vegetation was studied. Special attention was paid to the Medieval Period, when the urbanisation process started. The emergence of urban agglomeration may have been the cause of the emergence of new habitats, followed by formation of new plant associations - the predecessors of the today’s ones. In general, towns represent a special case of anthropogenic environment with many various synanthropic habitats, causing their species richness. Questions 1. When exactly the synanthropic flora of medieval towns emerged? Was the transition from the Prehistory to the Medieval Period rather gradual or sudden? 2. What particular species took place in the medieval change of synanthropic vegetation? Where did these species come from? Was the emergence of medieval towns right the main cause of the observed change in species composition? 3. In which way was the local diversity of synanthropic flora influenced by medieval urbanisation? Did rather the new species emerge or, contrarily, the previously common ones extinct? 4. What factors influenced the spread of new species during the Medieval Period? Materials and Methods The data were based on the analyses of plant macroremains, sometimes in combination with other methods (mainly the pollen analysis). The case studies were focused on particular localities in Central Bohemia, tracing gradual changes taking place in each locality. To trace general trends and to answer the questions, the Archaeobotanical Database of the CR was used, covering the time span since the Neolithic to the High Middle Ages. Results and Discussion 218 archaeophytes were found in macro-remain material from high medieval towns, representing ca. 90% of unintentionally introduced alien plants. The majority of them have been present in our territory since the Prehistory; forty new aliens immigrated during the Early Medieval Period (EM). On the contrary, only several new aliens were introduced in High Medieval (HM). It means that the main wave of immigration took place in EM, which implies that the medieval immigration couldn’t be connected with the urbanisation process. Medieval urbanisation influenced plant diversity in the similar way as present processes connected with urban enlargement. The diversity of semi-natural vegetation in the suburbs drops as a result of vanishing of suitable habitats, whereas the abundance of common ruderal species increases. The increase of diversity via immigration of new alien species is connected mainly with the intensity of long-distance trade (mediated by increased propagule preasure). The frequency of alien species in medieval towns was also influenced by their residence time. The comparison of the OLD (present since the Prehistory) and NEW (since the Middle Ages) alien plants shows similar pattern as today’s comparison of archaeophytes vs. neophytes.