Measurement guidelines for forest carbon sequestration were developed to support reporting by public and private entities to greenhouse gas registries. Although developed primarily for reporting about forestry "activities"-the categories of actions comprising forestry-rather than "projects," which are specifi c carbon management undertakings, the guidelines are based on experience with methods for the latter and thus are broadly useful for carbon estimation. The national greenhouse gas registry, known as 1605(b) in reference to the original authorizing language contained in the Energy Policy Act of 1992, accepts reports by entities about their forestry activities as a bundle (Birdsey 2006). Other greenhouse gas registries, such as that maintained by the state of California, accept reports about specific forestry projects.