Agriculture 2013, 3, 629-659; doi:10.3390/agriculture3040629 OPEN ACCESS agriculture ISSN 2077-0472 www.mdpi.com/journal/agriculture Review Role of Arthropods in Maintaining Soil Fertility Thomas W. Culliney Plant Epidemiology and Risk Analysis Laboratory, Plant Protection and Quarantine, Center for Plant Health Science and Technology, USDA-APHIS, 1730 Varsity Drive, Suite 300, Raleigh, NC 27606, USA; E-Mail:
[email protected]; Tel.: +1-919-855-7506; Fax: +1-919-855-7595 Received: 6 August 2013; in revised form: 31 August 2013 / Accepted: 3 September 2013 / Published: 25 September 2013 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.