Abstract:
In terms of species richness, arthropods may represent as much as 85% of the
soil fauna. They comprise a large proportion of the meso- and macrofauna of the soil.
Within the litter/soil system, five groups are chiefly represented: Isopoda, Myriapoda,
Insecta, Acari, and Collembola, the latter two being by far the most abundant and diverse.
Arthropods function on two of the three broad levels of organization of the soil food web:
they are plant litter transformers or ecosystem engineers. Litter transformers fragment, or
comminute, and humidify ingested plant debris, which is deposited in feces for further
decomposition by micro-organisms, and foster the growth and dispersal of microbial
populations. Large quantities of annual litter input may be processed (e.g., up to 60% by
termites). The comminuted plant matter in feces presents an increased surface area to
attack by micro-organisms, which, through the process of mineralization, convert its
organic nutrients into simpler, inorganic compounds available to plants. Ecosystem
engineers alter soil structure, mineral and organic matter composition, and hydrology. The
burrowing by arthropods, particularly the subterranean network of tunnels and galleries
that comprise termite and ant nests, improves soil porosity to provide adequate aeration and
water-holding capacity below ground, facilitate root penetration, and prevent surface
crusting and erosion of topsoil. Also, the movement of particles from lower horizons to the
surface by ants and termites aids in mixing the organic and mineral fractions of the soil.
The feces of arthropods are the basis for the formation of soil aggregates and humus, which
physically stabilize the soil and increase its capacity to store nutrients.
