How do soil arthropods help form humus from dead leaves and wood?

Soil arthropods play a critical role in the formation of humus by processing dead leaves and wood into a state that facilitates further decomposition.

When leaves fall, they are initially too tough for most animals to consume. After water-soluble components leach out, fungi and other microflora soften the plant structure, making the litter palatable to invertebrates. Soil arthropods—such as mites, springtails, millipedes, and wood lice—then fragment this material into a mulch.12

While these arthropods do not significantly alter the organic chemistry of the litter themselves, they create a suitable substrate for primary decomposers to break the material into simpler chemical compounds. In some soil formations, such as "moder," arthropods contribute directly to soil structure by producing fecal pellets that bind plant debris and mineral particles together into a netlike structure. Through these actions, arthropods help convert complex plant tissues into the finely divided organic matter known as humus, which is essential for soil fertility and nutrient cycling.13