[3][4] Moders are similar to mors as they are made up of partially to fully humified organic components accumulated on the mineral soil.
[2][7] "L" litter: A horizon is defined by accumulating primary leaves (and needles), twigs, and woody materials, with the original structures visible.
[2] "F" Fermentation: A horizon defined by the buildup of partially decomposed organic matter generated primarily from leaves, twigs, and woody materials.
Some of the original structures are difficult to identify, and materials may have been pounded into small pieces or particles in part by soil fauna, as in a "MODER".
[6] These layers are mostly made up of partially decomposed plant remains broken or comminuted by soil fauna and are loosely organized rather than matted like the Fq horizons.
A distinctive aspect of the Fa horizon and its loose nature is the abundance of soil fauna droppings, which can be seen with high magnification.
Bacteria, actinomycetes, and protozoa are progressively contributing to the breakdown process, although fungi continue to play an important role[2] Soil fauna break plant residues into non-compact, loose arrangements mainly constituted of faunal droppings, which make up friable Fz horizons in moders.