Preface

Soil has played a major role in human history. The literature of ancient Middle Eastern, Mediterranean, Chinese and Indian civilizations highlight the importance given to soil management and soil fertility. John Steinbeck's famous novel, Grapes of Wrath (1939), is one of numerous literary examples describing the dependency of human welfare on soil fertility. Set during the Great Depression Steinbeck focuses on a poor family of tenant farmers driven from their home by the Dust Bowl, droughts, economic turmoil and changes in agriculture practices. Despite this historical and literary context, our scientific understanding of soil and soil-associated processes, particularly the more biotic components, has remained limited. It is only in the last few decades that we have started to understand, in detail, the complex nature of soil biological communities and their environment, and soil biota's functional significance for ecosystem processes. We are now also considerably more aware of the role of soils, and soil biota, in regulating and determining the response of ecosystems to global environmental change. Excluding carbonate rocks, soils represent the largest terrestrial stock of carbon, holding approximately 1,500 Pg (10 15 g) C in the top metre. This is approximately twice the amount held in the atmosphere and thrice the amount held in terrestrial vegetation. Soils, and soil organic carbon in particular, currently receive much attention in terms of the role they can play in mitigating the effects of elevated atmospheric carbon dioxide (CO 2 ) and associated global warming.