Book Review: Soil Carbon Dynamics A Review of Soil Carbon Dynamics, An Integrated Methodology edited by W.L. Kutsch, M. Bahn and A. Heinemeyer (Cambridge University Press 2009) Reviewed by Rattan Lal This book describes methods to assess a vital natural resource: soil organic carbon (SOC) in natural and managed ecosystems. More than a billion people depend on the SOC pool to sustain their food supplies. Even so, certain areas have excess SOC that might help buffer and mitigate abrupt climate change. The significance of this book is heightened by its relevance to biodiversity, economic development, energy use, pollution abatement, and water quality. The top meter of soil contains about 2500 gigatons (Gt) of SOC, roughly four times the biotic pool (620 Gt) and three times the atmospheric pool (800 Gt). Soil organic carbon is an important component of the global carbon cycle because it is a source and sink of trace gases and it moderates C-bearing atmospheric species. Concentrations of SOC vary in response to natural processes, but its recent and rapid variability results from agricultural management to optimize the soil nutrient pool and crop/biomass yields. Keep in mind that many details of how agriculture affects SOC are incompletely understood.