Holocene evolution of closed depressions and its relation to landscape dynamics in the loess areas of Poland

摘要

Past Pleistocene topography of the loess uplands is rich in local sinks (closed depressions (CDs)) influencing sediment fluxes. Soil-sediment sequences from CDs constituting geoarchives where landscape changes under natural and anthropogenic conditions have been recorded. Pedo-sedimentary archives from 10 CDs in the Polish loess belt and human settlements were analysed. Phases of the Holocene evolution of the CDs were correlated with landscape dynamics in loess areas in Poland and Central Europe. Phases of infilling of CDs occurring (2) from the late Boreal/early Atlantic Period until the (middle) late Bronze Age/early Iron Age and (4) since the early Middle Ages until today were documented. These were phases of long-term soil erosion and colluviation corresponding to the increasing agricultural land use of Polish loess uplands. Phases of soil formation related to geomorphic stabilization of CDs occurred (1) from the late Vistulian until the late Boreal/early Atlantic Period and (3) from the late Bronze Age/early Iron Age until the early/high Middle Ages. These were phases of decreased soil erosion and landform conservation in a considerable part of Poland's loess areas. Pedo-sedimentary archives from the CDs have recorded soil erosion strongly related with human-induced land-use changes. The mean soil erosion rate in the catchment of CDs was 0.33 t center dot ha(-1)center dot yr(-1) during prehistory and 4.0 t center dot ha(-1)center dot yr(-1) during the last approximately 1000 years. Phases of CD evolution are representative for the main phases of sediment and landscape dynamics in Poland's loess areas recorded in various archives, and are not synchronous with some of these phases in Central Europe.