Physical properties of the mor layer in a Scots pine stand III. Thermal conductivity

Thermal conductivity was measured with thermal probes in undisturbed mor samples subjected to water desorption and sorption. The volumetric water content was determined simultaneously with time domain reflectometry. The thermal conductivity increased from 0.06 to 0.24 W m−1 K−1, when the water content increased from 0.10 to 0.40 m3 m−3. There was little spatial variation in the mor layer. The results were similar to those found in the literature for peat and humus materials. The thermal conductivity of the mor layer could be predicted with the de Vries model with good accuracy if the humus and air particles were assumed to be of lamellae shape and latent heat transport in air-filled pores was neglected. Key words: humus, thermal probe, thermal properties, time domain reflectometry