Contemporary Trend in Erosion of Arable Ordinary Chernozems (Haplic Chernozems (Pachic)) within the Volga Upland (Saratov Oblast, Russia)статья
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Аннотация:The current trend in erosion rate of ordinary chernozems in Saratov oblast has been assessed.
Detailed studies have been performed in a small catchment area of the Bolshoi Kolyshley River (Medveditsa
River basin) using the radiocesium and soil-morphological methods. Data of long-term hydrometeorological
observations in the region, reported results of observations of water runoff and soil loss on the runoff plots of
the South-Eastern Research Institute of Agriculture (Saratov oblast), results of analysis of the grain size and
mineral composition of stratozems developed on the catchment valley bottom were also used for analysis. The
quantification of sedimentation rate in the valley bottom during two time windows (1963–1986 and 1986–
2017) based on the sediment dating using 137Cs as a chronomarker indicates their decrease at least in 4–
6 times after 1986, which points to a proportional reduction in erosion rate on the plowed slopes of the catchment
area. The analysis of the temporal variability of suspended loads in the regional rivers (Medveditsa and
Khopyor) during the period from 1940 to the present time allows drawing an analogous conclusion for the
Volga Upland within Saratov oblast. The decrease in the erosion rate of ordinary chernozems could be mainly
due to the reduction in water runoff from slopes during the spring snowmelt because of reduction in soil freezing
depth against the background of rising air temperature in winter and spring. This decrease in erosion rate
during the snowmelt period was not balanced by the regional increase in rainfall erosion related to some
increase in the rate of runoff-forming rainfalls. In the part of Saratov oblast, located within the Volga Upland,
where the studied catchment is situated, on the contrary, even a reduction in the frequency of rains with a
rainfall depth of more than 30 mm occurred over the last decades. The reduction in cultivated land area since
the late 1980s due to the abandonment of plowlands on the steepest slopes also contributes to the decrease in
total soil loss by erosion at the river basin scale. Within the studied small catchment, the share of perennial
grasses in crop rotations increased after 1986, which also promote to reduction in degradation rate of ordinary
chernozem by erosion.