On a question of non-constant thermal diffusivity of soils

Abstract

The general heat conductivity equation includes time- and depth-dependent soil properties (soil heat capacity and thermal conductivity). The simplified form of the heat conductivity equation contains only the soil thermal diffusivity parameter. Numerical solutions of the general and simplified equations were compared to quantify the possibility of equation reduction. Two test runs for soils with different compositions were done. The thermal regime for both peat soil and dark chestnut soil does not change significantly after using a simplified heat equation according to model estimations. The maximal soil temperature discrepancy was about 0.5 °C for peat soil and 2.2-3.3 °C for dark chestnut soil, which results in 4-6% error in methane efflux estimations.