What happens in a Carpathian catchment after the sudden abandonment of cultivation?

Changes in land use induced by human activity trigger a number of processes in river catchments. These processes are particularly evident in the mountains, where wild vegetation overtakes abandoned arable land, stabilizing slopes and reducing sediment delivery to rivers. The energy of under-loaded rivers then makes incisions into their beds, which results in lower water levels. What is the rate of environmental changes induced by farmland abandonment, and does the environment restore its primary characteristics through a certain inertia? To answer these questions, we analyzed changes in land use in the Jasiołka River catchment located in the Carpathians, based on topographic maps from three periods covering more than 60 years. We also compared data on land use change with changes in the water levels in the Jasiołka River using regression models and principal component analysis. In the period analyzed, substantial transformations of the landscape were evident, mainly caused by dislocation of the population during and after World War II and, to a lesser extent, by changes in the political system in Poland after 1989. All these events led to the reduction of the arable land area, along with the enlargement of forest areas. Before World War II, arable land was the prevailing form of land use, taking up an area almost twice as large as the forest. Currently, the area of arable and forest land combined in the catchment area analyzed is similar, at approximately 42%. The response of the river to the changes in land use in its upper course, the location of the greatest extent of changes in landscape, is triggered almost immediately, decreasing the mean water level. In the mouth of the river, these processes occurred over a different period of time: The river incision was not as intensive and ended nearly 30 years later. The investigations strongly correlated the changes in almost all landscape elements with processes occurring in the river channel. Therefore, even small landscape components such as settlements or gullies that can exert a significant effect on catchment functioning should not be disregarded in this type of analysis. Together with large areas of forest, they regulate processes occurring on the slope and in the river channel. [ABSTRACT FROM AUTHOR]