Soils

In accordance with the diverse geological substratum and articulated ground relief, characterized by both plateaux and steep slopes and outcrops of fresh rocks, the Prague area is characterized by a mosaic of various soil types and variants. With reference to pedology the location of Prague near the southern boundary of the Bohemian chernozem enclave, richly articulated here thanks to variable ground relief and climatic gradient between the warm, dry northwest and the colder, moister southeast, is of primary significance.

Pedological map of Prague (according to M. Tomášek, 1997).

Along the southern margin considerable areas are covered by typical chernozem on loesses covering the plateaux. In the west to southwest degraded chernozems grade into brown earths with symptoms of illimerization of different intensity appear on higher plateaux in the direction of Rudná.
The south and the southeast are characterized by brown forest soils (kambisols) in the widest meaning of the term. If loess covers crop up, the brown earths prevail on top of them. This applies also to the southwestern boundary zone of the plateaux bordering the Radotín Valley. In the Prague basin proper, its marginal hills and valleys, the soil conditions are far more complex, as the soils are influenced significantly by diverse substrates. The same applies also to minor enclaves and islands within the integral chernozem and brown earth areas.
On top of the Bohemian Karst limestones a whole series of humus-carbonate soils - rendzinas - can be found. These soils are mostly connected with slopes with full application of limestone substrate and its detritus. On the rocks and stony slopes shallow protorendzinas and moder rendzinas prevail, while the deeper detritus on milder slopes is covered with more mature mull rendzinas, and in the areas where moisture can collect, with brown rendzinas. Only on small areas, where the soil development could proceed for a long time, without being disturbed either by erosion or by new sedimentation, it is possible to find also fully decalcified weathered soils of the terra fusca type. In the framework of this basic scale there are numerous variants influenced by the properties of limestones. For instance, on top of the Lochkov limestones with intercalations of dark shales the soil is heavily influenced by the disintegration of these shales. The soil on top of the calcareous Dalej shales can be denominated as pararendzinas. From the number of other carbonate substrates mention should be made of Turonian sandy marlites which give rise to typical pararendzinas, showing strong tendency to decalcification at the western margin.
Another substrate cropping out on large areas and forming extensive plateaux are clayey shales of the Ordovician and partly the Upper Proterozoic. They are characteristic of the eastern part of Prague area where they gave rise to heavy gleyfied brown earths and locally to pelitic black earths. On the flat surfaces in depressions the gleyfication is due to the impermeability of these substrates. Lighter soils with a higher skeleton content are provided by flysh formations, such as the Letná strata, on top of which mostly weakly saturated brown soils - cambisoils - can be found, characteristic of most rock substrates of Pre-Cretaceous age with the exception of limestone.
A place apart is occupied by Paleozoic diabases which crop out only in small areas, usually in considerably sloping strata. Shallow soils are of the character of nutritive rankers (humus-silicate soils) with a high quota of coarse grained disintegrated diabase. Locally they can acquire even the character of pararendzinas.
On some sites the soils are only weekly developed and have remained in initial stages. An example of such a state are Hemrovy Skály (Hemr Rocks) near Butovice. Where diabase detritus collects, e.g. in some places in thermophilous oak forest on the Chuchle Wood slopes, the nutritive eubasic cambisoils of dark brown hues have developed. This protected area is a typical example of a mosaic of different soil types on a small site. In the cut of the horizontal forest road it is possible to see brown earths on top of loesses, poor oligobasic cambisoils on top of Kosov quartzites, the afore mentioned eubasic cambisoils on top of diabases and rendzinas on top of limestones. Similar conditions can be found also elsewhere in this area with fast alternations of mother rocks. Another example are the slopes in the Barrandov Rocks area.
Another soil group is characteristic of sandy substrates, on the one hand the Cenomanian thick-bedded sandstones, occupying a relatively large area in the Klánovice Wood, on the other hand the gravelsand terraces of the Vltava or the gravelsands of Tertiary age. The soils on these substrates can be described generally as light arenic cambisoils showing the tendency to podzolization due to the absence of bivalent bases and substrate permeability.
A significant place in Prague area is occupied by rankers on the rocky steep slopes of the Vltava canyon and in the valleys of some of its tributaries. In the majority of cases they include shales and graywackes, possibly some acid igneous Proterozoic rocks. According to the presence of the bases in the substrate it is possible to find a whole scale of ranker soils of different nutritiveness, ranging from poor acid varieties, often overgrown with thermophilous heaths, to mezotrophic, exceptionally euthrophic nutritive rankers with rich rocky steppe communities.
In the wide floodplains of the Vltava and particularly its confluence with the Berounka medium-nutritive brown soils of vega type prevail, discontinued by gley soils in earthfilled old river arms here and there. This soil association covers the largest area in the wide floodplain of the lowest Berounka. Different situation reigns in major lateral valleys. While on top of the Proterozoic and Ordovician in the SE non-carbonate medium-nutritive floodplain soils prevail, in the valleys of the Bohemian Karst and in the lower Vltava valley below Prague the floodplains are often calcareous with layers of calcareous tufa in lower strata. Various types of gley soils commonly occur in the fluvial plains.
Generally very small areas are occupied by shallow fen soils, mostly only of anmoor type, exceptionally also shallow fens. They can be found on top of the Ordovician and in the south side of the Motol basin, in Klánovice Wood and its neighbourhood.
The diverse soil mosaic occurs also in the area of lydite konobs such as the Ládví, some rocks in the Šárka gorge, the High Rock above Troja, and particularly the Kozí Hřbety and the Holý Vrch. While the lydite outcrops are covered with shallow, poor rankers with heaths, only a few metres lower there are heavily calcareous surf sediments of the Cretaceous with basic pararendzinas to rendzinas grading into the surrounding chernozems on loess.
The soil conditions are heavily complicated by the presence of mixed deluvia and minor slides, e.g. on the slopes of the Petřín hill, minor loess islands, which can occur also on the slopes formed by quartzites or the poor Ordovician rocks (Krč Wood) and old subtropical or tropical weathering products preserved in the form of pipes in various rocks. For instance in the middle of limestone grounds above Hlubočepy, in Bílá Rokle, there is a kaolinite fill of an enormous weathering depression with very poor soils indicated by heather islands in the middle of otherwise calciphilous vegetation. Characteristic of some depressions in Ordovician shales is mild salinification manifested e.g. by the occurrence of stawberry-headed clover (Trifolium fragiferum). Within the settlements major areas are covered also with secondary soils on top of made-up ground, garden soils (hortisoils) and the soils heavily contamined by Prague fall-out and industrial and transport products.

Erosion phenomena in Cihelna (PP) in the Bažantnice.

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