Abstract:
The spatial and temporal dynamics of stream net density (SND) within the Central and Southern parts of the Russian Plain during the last two centuries are studied by comparison of historical cartographic sources. A significant decrease of SND is observed in the forest-steppe and steppe zones. The maximum SND decrease is detected at the northern edge of the steppe zone, where SND values in the middle of the 20th century were only 50-60% of those at the beginning of the 19th century. Two stages of permanent stream disappearance were found within the study area: (1) The end of the 18th century to the first half of the 19th century, where the SND decrease was associated with a high frequency of droughts, that coincided with an expansion of the area of arable land, and (2) the last quarter of the 19th century, where the SND decrease can be explained by the extreme erosion rates resulting from the expansion of cultivation over steep slopes during the expansion of arable cultivation after the 1861 land reform. The roles of regional climate dynamics and land use change are confirmed by hydrological and meteorological data coupled with data on anthropogenic gully formation. Detailed studies of SND dynamics in a number of key basins provide a basis for understanding the mechanisms of SND reduction. © 2005 Elsevier B.V. All rights reserved.
