This book is unique in providing a comprehensive, up-to-date synthesis of what is known about soil biodiversity and the factors that regulate its distribution, as well as the functional significance of below-ground biodiversity for ecosystem form and function. It describes the vast diversity of biota that live in the soil environment - the most complex habitat on earth - and discusses the factors that act as determinants of this diversity across different spacial and temporal scales. The Biology of Soil also considers how biotic interactions in soil influence the important soil processes of decomposition and nutrient cycling. It demonstrates how interactions and feedbacks between diverse plant and soil communities act as important drivers of ecosystem form and function. The importance of these relationships for understanding how ecosystems respond to global change phenomena, including climate change, is discussed in depth. Much is still to be learned about the soil biota and their roles in ecosystems, and the author highlights some of the many challenges that face ecologists in the exploration of soil.