Estimation of soil thermal properties using conduction and conduction–convection heat transfer equations in the Brazilian Pampa biome

•We used models of heat transfer by conduction and convection to estimate soil thermal properties.•We used 1.5 years of experimental data on a natural pasture area in the Pampa biome in southern Brazil.•We consider the effects of soil heterogeneity and thermal convection due to the vertical movement of water in the soil, W.•Soil thermal diffusivity (k) showed an inverse seasonal variation with soil temperature.•Increasing values of W led to an increase in the variability of k with depth.