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Biomes and Regions of Northern Eurasia

Steppe and Forest-steppe

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Anthropogenic Transformation of Steppe and Forest-steppe

Steppe is the main agricultural region of Northern Eurasia and 57 per cent of the area occupied by chernozems is arable land (Table 11.2).

Table 11.2 Environmental characteristics and land use in the steppe biome

The agricultural development of steppes has a very long history and three major phases in the transformation of steppe soils are distinguished: development, degradation, and cultivation (Kovda, 1974). In the early stages of agricultural use of steppe and forest-steppe soils (the first few years after ploughing), yields are usually high. However, at this stage cycling of minerals is transformed, and a decline in the contents of organic matter, nitrogen, and phosphorus and degradation of the physical and moisture properties of the soil occur. If no organic fertilizers are applied, soils degrade. The fertility of chernozems starts to decline, followed by a changing morphology (compaction) of the soil, a sharp decline in yields, and their subsequent stabilization at a much lower level. Cultivation of chernozems refers to its rational and sustainable use which is only possible if fertilizers are used in order to compensate for the loss of natural fertility. The maintenance of the optimal balance of organic matter and other nutrients makes its possible to obtain high yields while preserving or even improving chernozem fertility.

Farming over a long period has considerably altered the properties of chernozems and particularly their organic matter content. In the 1980s, data were published illustrating the loss of organic matter, which occurred during the last hundred years since Vasily Dokuchaev began studying chernozems (Rozanov, 1983). Thus in 1881, the humus content in the uppermost 30 cm layer varied between 10 per cent and 13 per cent in the typical chernozems of the Voronezh region in Central Russia while its humus reserve was estimated as 30-39 thousand t km^-2. By 1981, these values had decreased to 7-10 per cent and 21-30 thousand t km^-2. The total loss of organic matter over the last hundred years was, therefore, 9000 t km^-2 in all or 90 t km^-2 each year. In the Stavropol region, organic matter declined at the rate of 70-80 t km^-2 a^-1, in the Orenburg region at the rate of 90 t km^-2 a^-1, and in the leached chernozems of the Ulyanovsk region at the rate of 270 t km^-2 a^-1. On average, the loss of organic matter over the last hundred years is estimated as 20-35 per cent in the Black Soils region of Central Russia, Northern Caucasus, and the Orenburg region, and as 56-69 per cent in the forest-steppe of the Volga region (Chesnyak et. al., 1983).

Soils of the European steppe and forest-steppe are highly susceptible to the formation of gullies and erosion which in turn contribute towards the intensive loss of organic matter from soils. The physical geography of the southern East European plain (e.g., parent rocks are mainly loess and chalk; the high intensity of summer rainfall; and freeze-thaw effects) predetermines the naturally high erosion rates. However, the major cause of landscape degradation is anthropogenic and the most important is the removal of natural vegetation and the cultivation of land. The elimination of shrubs and tall grasses, which delayed snow melt in spring, minimized surface runoff and maintained high ground water levels, resulted in less moisture accumulation in soils, thereby increasing their credibility. In addition, traditional agricultural techniques (emphasis on grain cultures in the three-field system, shallow ploughing) favoured the development of erosion. The origin and history of soil erosion in the southern East European plain have been studied by many scientists and Stebelsky (1974, 1983) provides a good summary.

Although the chernozems of the East European plain have been cultivated since the Neolithic, there is little evidence for early land degradation. The 14th-century chronicles only occasionally mention dust storms, and there are no reports of these in the forest-steppe zone. However, land inventories compiled in the 16th century mention the occurrence of gullies, both active and stabilized and wooded, in what is now the Tula region, thus testifying to earlier periods of soil erosion (Stebelsky, 1983). During the 16th and 17th centuries, the forest-steppe and steppe were rapidly settled and extensive lands were cultivated, but it was in the 19th century when most of the expansion took place. During that century, the rural population more than doubled from 6 to 12.8 million people in what is now the Black Soils region (Stebelsky, 1974). With no growth in industrial employment and improvements to agricultural techniques, the agrarian development placed increasing pressure on land resources. By the end of the 19th century, about two-thirds of the land were cultivated in the Black Soils region and the pressing need for land caused river terraces and slopes to be ploughed. Much of the rich farmland was lost to the formation of gullies and landscapes of forest-steppe and steppe zones were permanently altered (Stebelsky, 1983).

As often happens, environmental change was accompanied by growing poverty, conflict, and eventually social crisis. In 1890, the Eighth Congress of Russian Naturalists and Physicians approached the Ministry of State Property with a request to fund research on gullying and soil erosion in forest-steppes and steppes. This study, completed by Masalsky (1897), revealed widespread gullying in Bessarabia (now Moldova), Podolya, the Dnieper and the Donetsk uplands, and particularly in the Central Russian (Srednerusskaya) and the Volga uplands. The percentage of land occupied by gullies ranged between 0.5 per cent to 25 per cent with 3-5 per cent of the area being most commonly reported (The highest figures were later proved to have been overstated since not only active gullies but also ravines were included). Landowners and peasants were encouraged to take action against soil erosion. However, most did not see a connection between land use and gullies and considered soil erosion unavoidable and conservation measures too expensive (Stebelsky, 1983).

The work by Masalsky provided a considerable amount of descriptive material; the first detailed maps of the level of soil erosion and gully density appeared a few decades later. A large expedition through the European part of the FSU was conducted between 1939 and 1941 and provided data for the first general comprehensive map of soil erosion in the European FSU. The Black Soils region of southern European Russia experienced the most extensive soil erosion. By the middle of the 20th century, only 10 per cent of land was not affected by gully erosion here, a medium network of gullies (0.2-0.4 km of gully per km²) covered about 30 per cent of land, and a dense network (0.5-1.2 km of gully per km²) covered another 35 per cent (Sobolev, 1948; Guzhevaya, 1948).

At present, landscapes of the steppe and forest-steppe biome are at different stages of anthropogenic transformation. The following categories can be distinguished: pristine landscapes; lands used for grazing with intermittent arable agriculture (this land use corresponds to nomadic livestock breeding); arable lands with extensive agriculture; and arable lands with modern agriculture (Krupennikov, 1983). There are very few regions where virgin steppes occur, and possibly only steppes protected in nature reserves fall into this category. Nomadic land use was typical of the European steppe until the beginning of the 19th century, in northern Kazakhstan it existed until the 1950s and at present is practised in the Altay steppes. The most typical example of extensive agricultural land use was the infamous Virgin Land project of the 1950s, which aimed at the expansion of arable agriculture into the steppes of northern Kazakhstan and Southern Siberia. Intensive agriculture is practised in the forest-steppe and steppe of the Ukraine, Northern Caucasus, the Black Soils region of Central Russia and the Volga region. The scale of transformation of the steppe and forest-steppe biomes is illustrated in Tables 11.2 and 11.3.

Table 11.3 Environmental characteristics and land use in the forest-steppe zone

Thus, in the Ukraine, the Black Soils region of Central Russia, the Volga region, and Kazakhstan between 74 per cent and 91 per cent of flat, well-drained plains with chernozem soils is occupied by arable fields. The remaining 10-20 per cent is usually not a natural steppe or forest-steppe but, on the contrary, an anthropogenic landscape.

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