Country-wide estimates of forest biomass are the major driver for estimating and understanding carbon pools and flux, a critical component of global change research. Important determinants in making the estimates include the areal extend of forested lands and their associated biomass. Estimates for these parameters may be derived from surface-based data, photo interpretation or satellite remote sensing, with varying degrees of uncertainty. Ground data are typically aggregated by forest type, stand age, productivity level, and ownership. Survey priority is usually given to regions and forest types with timber of commercial value, such that information on understory biomass and forested lands of low commercial value is either absent or of limited reliability.