ИСТИНА

The first part of this study presents the moisture dependence of soil thermal diffusivity for Lammelic Arenosols of the East European Plain. The undisturbed soil cores 7 cm in height and 5 cm in diameter were studied using the unsteady-state method. Thermal diffusivity of capillary moistened soils was from 6.2E-7 to 7.6E-7 m2s-1; that of air-dry soils was about 2E-7 m2s-1, and the peak values were almost 10E-7 m2s-1 for soils with organic carbon content less than 0.3%, and didn’t exceed 8.5E-7 m2s-1 for soils with organic carbon content from 0.5 to 0.9%. At the next step hierarchical pedotransfer functions (PTFs) to estimate soil thermal diffusivity (k) at different volumetric water contents (Q) from available soil data were developed from the data set of 17 samples. The ranges of sand, silt, and clay within the data set were 87–97, 0–8, and 1–6%; organic carbon content ranged from 0.1 to 0.9%. The first-level PTF is a set of parameters of the average k(Q) curve for sands obtained by approximation of all observed data points with a 4 parameter function: k(Q) = k0 + a*exp[–0.5*(ln(Q/Q0)/b)^2], where k0 is the thermal diffusivity of dry soil, a is the difference between the highest thermal diffusivity and the thermal diffusivity of dry soil, Q0 and b are shape parameters. The PTFs of next levels are sets of regression equations to estimate the parameters k0, a, Q0, and b from available data on soil texture, bulk density, and organic carbon content.