Quaternary and the Czech landscape

1. What is the Quaternary?

The Quaternary is the youngest geological period. It started 2.6 million of years ago and it last till now. It has two parts, the older - Pleistocene (from 2.6 mil. years till 11.5 thousands before present), and younger - Holocene (11.5 thousands before present till now). In the Quaternary evolution of the human was under way and the anthropogenic impact on the Earth started.

The period of the late Tertiary and the Quaternary are characterised by significant climate oscillation with the displays of the alternation of cold and dry glacial periods and warm and humid interglacial periods. The Pleistocene was characterised by the global distinct climate oscillations (more than 100 cold and warm events). On contrary, the Holocene is climatically more stable and generally a warm period. The glacials were longer than interglacials, the erosion events were shorter than the periods of accumulation.

2. Pleistocene

In the Pleistocene, the character of geological, especially exogenous processes was affected by the existence of vast ice sheets that covered considerable part of northern Europe.

Read the Chapter 3.3 from Hradecký, J., Brázdil, R. Climate in the Past and Present in the Czech Lands in the Central European Context In Pánek, T. , Hradecký, J. (Eds.) 2016. Landscapes and Landforms of the Czech Republic. Cham: Springer. P. 19-28.

Task:

1. What is the Quaternary climate and sediment model?

2. How can be the phases of the climate cycle described?

3. During which phase the pedogenesis occurrs and when the sedimentation of the loess?

4. What is "loess"?

3. Holocene

The Holocene started with higher temperatures and higher precipitation and this led to the evolution of vegetation and changes in landform evolution. The Holocene stratigraphy recognize periods of the Preboreal, Boreal, Atlantic, Subboreal and Subatlantic in the Central Europe.

Preboreal and Boreal (ca 11,500–8000 cal. yr BP) correspond to the Mesolithic in archaeological stratigraphy. These periods are characterized by a continuous spread of forest in response to climate warming at the Pleistocene/Holocene boundary. Open forests of birch (Betula pendula) and pine (Pinus sylvestris) extended their area at the expense of late-glacial open steppe and tundra. The spread of broad-leaved temperate trees such as Acer, Fraxinus, Quercus and Tilia at low altitudes and Picea abies at mid-altitudes and in the mountains followed. The dense canopy of broad-leaved trees decreased the light available to the herb layer, leading to a decline in light demanding species typical of the herb layer of birch-pine forests and probably also to a decline in overall herb-layer species richness.

Atlantic (ca 8000–4500 cal. yr BP) is considered as the Holocene climatic optimum, with mean temperature estimated to have been 2–3 °C higher than today, and high precipitation. Low-altitude areas were dominated by forests of oak (Quercus) and noble hardwoods (Acer, Fraxinus, Tilia and Ulmus). The Atlantic was a period of maximum extent of forest at the expense of open land, and consequently it was a bottleneck for survival of late-glacial and early Holocene steppe flora and vegetation in the Czech lowlands. In the Boreal and early Atlantic, areas of open land may have been maintained by Mesolithic hunter-gatherers, large herbivores or a natural water deficit in dry areas and habitats. At about 7500 cal. yr BP Neolithic farming began in Moravian and Bohemian lowlands, especially in loess areas, and crop planting and livestock grazing led to significant extension of the area of open land at the expense of forest. However, forest dominated the landscape until the Bronze Age and only in the Iron Age did the open cultural landscape become established in the Czech lowlands.

Subboreal (ca 4500–2500 cal. yr BP) was probably cooler than the Atlantic and during the later stage after 3400 cal. yr BP, it was also drier. It corresponds to the latest stage of the Late Neolithic (Copper Age, Eneolithic), Bronze Age and early Iron Age. Density of prehistoric human habitation peaked in the Bronze Age, when new areas were settled in basins and river valleys in western and southern Bohemia The Subboreal was characterized by the spread at low altitudes of Carpinus betulus from the north-east and of Fagus sylvatica and Abies alba at mid-altitudes. At higher altitudes they spread into forests of Picea abies, forming mixed spruce-fir-beech forests.

Subatlantic (ca 2500 cal. yr BP to present) is a period with a climate roughly corresponding to the present, although with some fluctuations such as the cold period of the Little Ice Age (16–19th century AD). It corresponds to the late Iron Age, Roman, Migration, Medieval and Modern Periods. Around 2000 cal. yr BP, lowland areas in Bohemia and Moravia were dominated by forests of Quercus and Carpinus betulus, with a significant presence of Abies alba and Fagus sylvatica. Mid-altitudes were covered by forests of Fagus sylvatica and Abies alba. Picea abies was common in mixed forests in the mountains. Human population density was high in the Iron Age, which resulted in a large-scale deforestation in low-altitude areas. However, the human population decreased in the Roman Period and especially in the Migration Period (5–6th century AD). Until the 12th century AD human settlements were concentrated in the lowlands and upland fringes, however, localized human activity is supposed even in areas above 1000 m in some of the periods between the Iron Age and Early Medieval. Nevertheless, large-scale colonization of mid-altitude areas occurred only in the High Medieval, mainly in the 13–14th centuries. The settlement and associated deforestation of upland areas proceeded more or less continuously. Higher mountain areas were colonized only in the 16–17th centuries, when chalets were built in the Krkonoše Mts and deforested areas on the Carpathian summits were extended by the Wallachian colonists.

Further reading:

Chytrý, M. 2012. Vegetation of the Czech Republic: diversity, ecology, history and dynamics. Preslia 84: 427-504.