Established in 1976 for use in the Forestry Commission's quinquennial forecast of production and valuation, use of the database has since been extended to other management areas. The data are held in three fields or groups: a) the key field, which provides location by Forest District, geographical block, compartment, subcompartment and component, b) the required data field, containing crop data including species, age, yield class and area, other land use data and nationally required information such as local authority area, c) the optional data field, containing details of site factors such as soil and windthrow hazard, and for codes that group up land units into treatment blocks.