Geografie 1961, 66, 193-225
The Vegetation of the Gullied Badland Near Polerady
The gullied land in the neighbourhood of the village Polerady (in the district of Žatec, Northwestern Bohemia) is, at this time, developing due to the process of bank erosion. Contrary to the bottom erosion, the bank erosion is explained by the author as a process caused more by sheet washing of the gully banks than by undercuting of themselves by a concentrated water stream. The occurance of this type of erosion is, nowadays, in Bohemia not frequent, but with regard to the scientifical and economic importance of the erosion problem a physically-geographical, geological and geobotanical analysis of the locality concerned has been carried out. The primary factors affecting the genesis and development of the bank erosion near Polerady are as follows: 1) the occurance of heavy tufaceous clays near the surface of the land; 2) the southern slope of the Borovec Hill, the foot of which was affected by a Pleistocene stream; 3) the subcontinental character of the climate in the region of Žatec with subnormal averages of precipitation. The subcontinental macroclimate emphasized by the dry and warm southern slope and heavy soil retarded the development of a contineous vegetation cover in the warm periods of the Postglacial Age and caused the establishment of herbaceous steppes and open woodland, which could not protect the soil against erosion. We can consider the gullies near Polerady a remainder of an older eroded land, where the soil washing was recently increased by human interference (destroying of woody-plants and overgrazing). The present-time gullies in Polerady do not increase rapidly in the direction of the neighbouring agricultural area (the head of the gullies being covered with grass vegetation!) and their seemingly dangerous aspect of absolutely bare banks is connected more with the insufficient ecesis of the plants than with the speed of the soil washing on the gully banks. The assymetrical profil (cf. fig. 5) of the gullies has been affected by the prevailing western winds, which increase the rain-wash on the windward banks. A striking sod-cornice edges the boundary between the primary land and the western windward banks and is considered a product of accelerated erosion and simultaneous resistance of the steppe-grass root systems against desiccation and decay. The eastern and southeastern banks present a gradual transition of the steppe sad and the gully bank. The bottom of the gullies is narrow and mostly covered by vegetation sod. Different cases of creeping down of the plant tussocks on the banks and the changes of floristic composition in the vegetation in the process of erosion are described. The gullied land in the neighbourhood of Polerady is a suitable place for the study of plant succession, of the ecology of the steppe vegetation and of the variability of plants in the course of succession.
