Processes within pasture and crop ecosystems: The fauna of grassland soils with special reference to Acari and Collembola

[First paragraphs...]
Soil animals may be classified into various categories depending on size (Fenton 1947; van der Drift 1951), degree of dependence on the soil (Jacot 1940), mode of locomotion (Kiihnelt 1955) or life form (Gisin 1943; Klima 1956). The first is the most widely used and a simple division is into micro-fauna (0.001mm-0.1mm), meio-or meso-fauna (0.1mm-10mm) and macro-fauna (over 10mm). The micro-fauna includes protozoa, nematodes, tardigrades; the meso-fauna, mites, collemboles, enchytraeids; and the macro-fauna, earthworms, molluscs and many insects, myriapods and spiders. This classification is obviously arbitrary, and some groups (e g. spiders) have representatives in more than one category.
Grassland soils contain many individuals and many species from each of these groups. Acari and Collembola are generally the most abundant arthropods, and in this paper their ecology will be considered with particular reference to their population density, communities and role in certain soil processes.