Thermal diffusivity of typical Chernozems in the Kamennaya Steppe reserve

The thermal diffusivity of medium-deep light clayey typical chernozems (Voronic Chernozems (Pachic, Clayic)) has been studied, which varies with the soil water content in the ranges of (0.77-2.88) x 10(-7) m(2)/s for the Ap horizon, (0.82-2.60) x 10(-7) m(2)/s for the Ad horizon, (0.86-2.58) x 10(-7) m(2)/s for the A1 horizon, (0.78-2.31) x 10(-7) m(2)/s for the A1' horizon, (0.81-2.87) x 10(-7) m(2)/s for the AB horizon, (1.01-3.33) x 10(-7) m(2)/s for the B horizon, and (0.98-3.26) x 10(-7) m(2)/s for the Bca horizon. The dependences of the thermal diffusivity on the water content are described by S-shaped curves with a long gently sloped segment in the region of volumetric water content below 0.15 cm(3)/cm(3), a region of pronounced increase of thermal diffusivity in the water content range from 0.15 to 0.30-0.35 cm(3)/cm(3), and the cessation of the increase or even some decrease in the water content range above 0.30-0.35 cm(3)/cm(3). The approximation of the experimental curves has allowed developing a set of pedotransfer functions, which reflect the differences between the horizons and can be used for the quantification of the thermal diffusivity of the studied horizons at any water content.