Soil-alluvial dynamics, landscape evolution and human activity in the Thaya river floodplain (Czech Republic) from the Late Pleistocene to the Holocene

Abstract

The development of the Thaya River floodplain has been shaped by interactions between fluvial dynamics, soil formation, and human activity. To better understand these processes, we conducted geoarchaeological research, including sedimentological, micromorphological, geochemical, palynological and chronological analyses of soil-alluvial sequence at Pohansko site spanning from the Late Pleistocene to the present. We identified four distinct soils, each formed during periods of relative landscape stability. Fluvisol 4 developed in the Mesolithic (Early Holocene), when the Thaya River floodplain was dominated by oak-lime-hornbeam forests, showing no evidence of deforestation. Fluvisol 3 formed in the later phase of the Neolithic (Middle Holocene), when the increasing presence of cereals and ruderal taxa suggests agricultural expansion. From the Young/Late Bronze Age to the Early Medieval period (Late Holocene), Fluvisol 2 developed, with a significant reduction of synanthropic plants and an increasing presence of pioneer species during the Bronze Age, indicating limited human activity. A peak in deforestation in the soil corresponds with expansion of the Great Moravian Empire, which is also linked with significant increase in nitrogen-loving herbs. The pollen spectra indicate decline in softwood, pines, ferns, hygrophilous and aquatic plants, while an increase in meadow areas. Geoarchaeological evidence further reveals that the modification of a channel near fortification probably in the same period, potentially serving both as a defensive feature and a source of construction material. While soil development was primarily driven by natural processes outside sandy elevation, further analyses are needed to clarify the relative influence of climate and human activity on floodplain dynamics.