Numerical methods to recognize the soil types in the forest steppe

The authors generalized and summarized original and literature data with the view of studying the gray and dark-gray soils in the Volga-Kama forest steppe. The methods of multidimensional statistics permitted to determine the position of these soils in the available soil classification system. A great number of soils described by different researchers within the framework of Russian soil classification system (1977) were formalized in conformity with that published in 2004. In the latest classification system of soils in Russia the reliable differences in the humus horizon of gray and dark-gray soils are shown in the content of humus, exchangeable bases, clay fraction, acidity and thickness as well as in the thickness of the leached layer (up to the C horizon) and the humus storage within the one meter of soil (t/ha). The methods of numerical classification allowed determining discriminated functions and classify more exactly the studied soils in the Volga-Kama forest steppe. Based upon statistic processing of the obtained data the limits for properties of the humus horizon are suggested to distinguish the gray and dark-gray soils. The visual imagination widely adopted now to recognize the types of gray and dark-gray soils should be added by limits of their varying properties. The obtained results presented in this paper may be useful to improve the idea on properties of gray forest soils. The suggested criteria to recognize the studied soils may be applicable for studying and systematizing these soils as well as for purposes of land use, elaboration of regional database and in projects of ecological territory optimization.