ABSTRACT
This chapter reviews the essential functions of the soil biota, i.e., the life in the soil, and its multiple roles in maintaining soil fertility. It considers the soil as a habitat for organisms, identifying what the important sources of energy and nutrients are for the soil biota and describing the flow of energy and the cycling of materials from above- to belowground. Linkages between above- and belowground processes are highlighted to illustrate their interconnectedness and to show how soil is not an inert medium. Instead, the soil is host to a wide variety and sizes of organisms that collectively perform numerous essential ecosystem services. Soil systems are among the most complex and variable habitats on earth. Any organism that makes its home in soil must devise multiple mechanisms to cope with its high variability in moisture and temperature and its continuous chemical changes so as to survive, function, and reproduce.
