EFFECT OE ANCIENT TERRACING ON SOIL BALANCE IN MOUNTING ZONE OF DAGESTAN (EASTERN CAUCASUS, RUSSIA)

ABSTRACT

Mountainous Dagestan (Eastern Caucasus, Russia) is one of the world centers of terraced arable farming. Long history of agricultural development of the region led to significant changes in the soil forming conditions and resulted to increase in the volumes of the soil layer. As an example of the effects of terraced farming on the soils ballance, we investigated a set of agricultural terraces near the Jaba village (41.423614, 47.776390) in the Dagestan Republic of Russian Federation (Eastern Caucasus). The terraced slope area is 4.0 km2, the steepness is approximately 25-350. Soil-forming rocks are clay-slates. This area is isolated by the river Samur on one side and by landslides from two sides and represents the agricultural zone of the Jaba village. The time of the appearance of the village and, consequently, beginning of the terracing of the slopes belong to the Middle Ages (11-14 centuries AD). Taking into consideration, that thickness of the soil layer on the non-terraced plots on slopes of the same steepness is about 0.3 m, before the beginning of terracing, the total volume of soil on the slope was 1.2 million m3. At present, on the slope there are 55 terraces with an average length of 2000 m. The drilling all terraces along the catena through the entire slope and topographical survey were carried out. It was established that the steepness of terraces surface is 3-10º, the width is 3-4 m, average height of the terraces edge is about 7 m. Average thickness of the soil layer at the lower border of the terrace surface is 2.5 m. In the area of upper border of the terrace, soil cover is often absent and soil-forming rocks are cropped up. Accordingly, the volume of soil in all the terraces on the slope is at least 2 million m3. Considering that terrace edge is 45-60º, the total volume of soil on terracing slope is 2.7 million m3. Thus, terracing of the slope led to an increase in the volume of the soil by more than two times for the 600-800 years. The formation of additional volumes of soil occurred due to anthropogenic destruction of soil-forming rocks in the area of the upper border of the terraces.

Keywords: Eastern Caucasus, ancient terraces, plowing, soil, erosion, accumulation