Timber soils involve a thin, moderately dark layer of partially decayed leaves, twigs, and fallen logs, which lie overtop lighter-colored soil. Timber soils result from trees shedding their leaves and twigs, which accumulate on the surface of a soil and decay over a long period of time. For this reason, timber soils have a thin, top layer of organic matter. While timber soils do not have as high of an organic matter content compared to prairie soils, they are known to have a moderate amount of organic matter.
Over time, as the timber soils have been worked, they have been mixed with the lighter soil underneath to produce a lighter-colored surface soil.