Thermal diffusivity/admittance and cultivation

Cultivation (without any associated addition of organic residues) leads to the decrease of soil organic matter, since cultivation helps aerate the soil, which in turn increases the activity of soil organisms. And soil organisms are responsible for the mineralization (ie decomposition) of organic residues.
In lecture on Feb 28 (ie lecture #20), Sandra showed you a photo of an Organic soil from Cloverdale, BC where due to about 50 years of cultivation those soils lost about 1m of organic horizon. In the photo, you can see grayish spots of mineral subsoil that are now at the surface, since all of the organic horizon that was originally above it, has been decomposed.

Thanks Maja.