Vojen Ložek

Mid-Holocene bottleneck for central European dry grasslands: Did steppe survive the forest optimum in northern Bohemia, Czech Republic?

Revisiting the classical Gradmann’s ‘steppe theory’ for central Europe, we examine whether the early Holocene steppe habitats survived the critical period of maximum Holocene afforestation: the mid-Holocene bottleneck. Despite the undisputable fact that afforestation was a dominant ecological factor in this period, our parallel analyses of pollen and molluscs from sedimentary sequences discovered in the dry lowland area of northern Bohemia, Czech Republic (Zahájí and Suchý potok sites, lower Ohře area) provide strong evidence for uninterrupted local occurrence of steppe grasslands throughout the Holocene. At the onset of the Neolithic agriculture, this area was covered by forest-steppe. Analogously to the present forest-steppe landscapes of eastern Europe and south-western Siberia, dry areas of northern Bohemia were dominated by open-canopy pine–birch forests that enabled continuous survival of many light-demanding plant species from the late Glacial and early Holocene to the Neolithic. Later on, anthropogenic deforestation and livestock grazing created a semi-natural steppe. Our data suggest that this secondary steppe can be viewed as a direct continuation of the late Pleistocene and early Holocene natural steppe rather than a purely cultural steppe developed only after deforestation of a continuously forested mid-Holocene landscape by humans. At the same time, we provide evidence supporting Gradmann’s ‘steppe theory’, assuming that in central Europe, Neolithic farming started in those areas that were not completely forested but contained remnants of natural steppes. This finding has important implications for the interpretation of present biodiversity patterns in central Europe.

Mollusc succession of a prehistoric settlement area during the Holocene: A case study of the České středohoří Mountains (Czech Republic)

Some Central European areas were attractive for the first agricultural settlements due to their suitable natural conditions. The Holocene development of such areas was thus under long-term human pressure, whose impact on the whole landscape is still poorly understood. One of such areas is the České středohoří Mountains. While pollen analyses can provide the general pattern of the landscape development, the analyses of mollusc succession provide landscape details, which are important primarily in landscapes with high habitat diversity. Based on the study of 11 mollusc successions situated at the České středohoří Mountains, we describe the postglacial development of the area and show the moderate fluctuation of woodland, wetland and open country habitats without any distinct succession peaks of particular habitat types during the whole Holocene. However, a detailed look of species exchange has provided additional information of succession pattern. The impoverishment of woodland communities is probably caused by human pressure, not natural processes, because fully developed woodland assemblages had occurred there during the past interglacials. It seems for now that humans had affected the whole landscape of the prehistoric settlement area, including hard-to-access sites, not only the nearby surroundings of their settlement.

Early postglacial recolonisation, refugial dynamics and the origin of a major biodiversity hotspot. A case study from the Malá Fatra mountains, Western Carpathians, Slovakia

While general trends in Central European postglacial recolonisation dynamics are relatively well known, we often lack studies on intermediate (meta-population, landscape) scales. Such studies are needed to increase our understanding of, for example, the location of refugia; emergence of endemism, rates and trajectories of postglacial migrations; and anthropogenic landscape changes. Here, we focused on the outer Western Carpathian mountain chain Malá Fatra, which is currently characterised by high biodiversity and endemism and is thus considered a likely refugium of the Last Glacial period for the temperate biota of Eastern–Central Europe. We used molluscs and vascular plants as reference taxonomic groups and supported palaeoenvironmental interpretations of their (sub)fossil assemblages using high-resolution geochemical data. Generally, postglacial biotic successions from the study region fit the standard developmental pattern well in Middle and Eastern European uplands. Nevertheless, we found important biogeographically based peculiarities. In total, more than 50 species per (sub)fossil community at the reference site Valča, including 30 woodland species and 11 Carpathian endemites, make site of the highest known Holocene mollusc species diversity in Europe. Our palaeoecological analysis of this long-term biodiversity hotspot suggests that the Western Carpathians were likely an important source of the postglacial recolonisation of Central Europe by forest biota and, at the same time, an area of refugium-based endemism.