Soil fauna: occurrence, biodiversity, and roles in ecosystem function

The biodiversity of soil animals (fauna) is large, and fauna critically affect soil processes by feeding and fragmenting plant materials and organic substrates. Soil fauna exist in food webs, with a range of feeding modes (trophic levels). Soil faunal biodiversity involves degrees of functional specialization. Soil fauna body size affects soil processes across a broad spatial range: (1) “micro-food webs” with microbes and their protist and nematode predators; (2) microarthropods and enchytraeids, fragmenting decomposing litter; and (3) “ecosystem engineers,” e.g., earthworms, termites, and ants, which alter soil physical structure and influence rates of nutrient flows. We consider the conjoint action of the major faunal groups and discuss their roles in ecosystem function worldwide and in the context of ongoing global climate change.