RICHARD D. BARDGETT is Professor of Ecology at Lancaster University and has published widely on plant-soil interactions, nutrient cycling, and soil ecology. He is especially interested in studying linkages between plant and soil biological communities, and examining how these links are affected by herbivores. MICHAEL B. USHER is retired. For more than 40 years he has had a research interest in the soil biota, especially the Collembola (springtails), Isoptera (termites) and Mesostigmata (mostly predatory mites). He also has a strong interest in nature conservation, and is currently working on a number of aspects of the conservation of biodiversity. DAVID W. HOPKINS is Professor of Environmental Science at the University of Stirling and has research expertise in soils science and ecology, especially the biology and biochemistry of nutrient cycling. His research involves ecological, environmental and archaeological projects.