ALLUVIATION IN SMALL VALLEYS AS AN INDICATOR OF LAND USE CHANGES DURING THE LAST MILLENIUM, SUBCARPATHIAN LOESS PLATEAU, POLAND

The undulating Kanczuga Loess Plateau, 250-270 m a. s. l., is located in the temperate climatic zone of Central Europe, within the northern foreland of the Carpathians. It is dissected by a network of valleys from 30 to 60 m deep, filled by a several meters thick layer of mineral and organic deposits, which started to accumulate in the early Holocene. In one such valley, traces of human-induced environmental transformation from the Neolithic period have been found. Around 3500 years BP, however, conditions conducive to the accretion of organic matter prevailed, suggesting renaturalisation of the environment. Accretion of organic matter was interrupted by the deposition of organic silts. Transfer of eroded soils started first in the small tributary valley mouth areas as early as in the late Roman period – around 280 BC - 30 AD. In the upper reach of the main valley, which was the last area penetrated by people, traces of soil erosion have been recorded as a thin (10 cm) layer of silts with pollen of synanthropic plants, covering the peat younger than 1260±70 years BP (680-870 AD). Radiocarbon dating indicates that the process of alluviation of the small valleys dissecting the sides of the largest ones began only in the 11th century. Processes of soil erosion and sediment transfer during this period were caused by agricultural activity in the drainage basin and by valley side clearance and subsequently intensified in the 14th century, linked to the increase of cultivated area and the associated clearance. It is very probable that changes in the precipitation regime at the beginning of the Little Ice Age accelerated the soil erosion and sediment transfer processes initiated by human activity. This sequence of events was broadly similar to those found in the temperate climatic zone located further to the west, within the foreland of the Eastern Sudetes Mountain and in the Rhine Catchment.